After being periodically surveyed by robotic spacecraft in recent years, did those astronomers that discovered the other moons of Jupiter years before got the accolades that they truly deserve?
By: Ringo Bones
I tend to have a rather rigid definition on the difference between space exploration and astronomy because to me, sending space probes to distant celestial bodies – in my point of view – is space exploration. While peering though an astronomical telescope via the eyepiece or via a high-resolution computer grade monitor in front of me is what I define as true astronomy. The Voyager and Galileo spacecraft flybys of Jupiter and the planet’s retinue of satellites may have gathered data previously unknown to late 19th and early 20th Century astronomers. But the astronomers themselves who discovered those excruciatingly tiny non-Galilean satellites decades before those robotic spacecraft flybys seem to have been largely forgotten in this day and age.
Before the Pioneer X and Voyagers I and II flybys, there are only 12 moons of Jupiter that can be seen from Earth using existing astronomical telescope technology prior to the 1960s. Set side-by-side to the relatively large four Galilean satellites: Io at 2,000 miles, Europa at 1,800 miles, Ganymede at 3,120 miles, and Callisto at 2,800 miles, the other moons of Jupiter look like grains of sands in comparison. With diameters that range from as large as 70 miles to as small as 10 to 12 miles, discovering these Jovian moons without resorting to optical interferometry is probably next to impossible.
The first one of these non-Galilean satellites to be discovered was discovered by an American astronomer named Edward Emerson Barnard of Barnard’s Star fame in 1892 and was called / designated as V. This tiny Jovian moon at just 70 miles in diameter in unique in many ways. V orbits just 110,000 miles from Jupiter allowing Jupiter’s strong gravitation to make the tiny moon hurtle through space at 1,000 miles a minute – 26 times faster than the Earth’s moon.
On average, Jupiter is 629 million kilometers from Earth, which makes Barnard’s discovery of V somewhat of a remarkable feat in astronomy back in 1892 because astronomical telescopes having at least a 4-meter diameter mirror is the minimum needed to see V from Earth due to the Rayleigh Criterion limitations. The smallest celestial object that a 4-meter mirrored astronomical reflecting telescope when the Rayleigh Criterion is taken into account is around 103.5 kilometers – a little under 70 miles - in diameter from 629 million kilometers away using the visible spectrum centered around 550 nanometers. And most important of all, use of optical interferometry in astronomy to bypass the inherent Rayleigh Criterion limitations of existing reflecting telescopes in 1892 was still several years away. Probably a few years after 1910 when Albert A. Michelson used an optical interferometer of his own design to accurately measure the diameters of those newly-discovered tiny satellites or moons of Jupiter.
Even the discovery of the next non-Galilean satellite designated as VI (diameter 50 miles) in 1904 and VII (diameter 20 miles) in 1905 by American astronomer Charles Dillon Perrine is also miraculous given that optical interferometry for astronomical use is still years away. Even back in 1908, when English astronomer Philbert Jaques Mellote discovered Jupiter’s moon designated as VIII with a diameter of 10 miles without an aid of optical interferometry is nothing short of a miracle.
In 1914, an American astronomer named Seth Barnes Nicholson discovered one of the last few moons of Jupiter whose diameter averages between 10 to 12 miles designated as IX, probably with the aid of Albert A. Michelson’s newfangled optical interferometer. Not only will Nicholson discover the last of the tiny moons of Jupiter that can be seen from Earth before the Pioneer X and Voyager spacecraft flybys, he also made remarkable theories that almost accurately predicted the actual climate of the planet Venus. Together with fellow astronomer Charles St. John, their hot and dry Venus climate hypothesis that they proposed back in 1922 was proven to be closer to reality. Compare that to the one proposed in 1918 by Swedish chemist Svante August Arrhenius – who also discovered the mechanism behind the greenhouse effect – depicted planet Venus as covered by hot steamy tropical swamps.
In 1938, Nicholson discovered another two of Jupiter’s very tiny non-Galilean satellites. Designated at the time as X and XI, X because Nicholson declined suggesting names for the new Jovian moons that he discovered orbits in a region 7,400,000 miles away from Jupiter while XI orbits in a region almost 15 million miles away from Jupiter. X is part of the other 4 of Jupiter’s outermost satellites that orbit in a retrograde direction. Two of these outer satellites even have “open” orbits that are never repeated from one circuit to the next. Probably due to the Sun’s much stronger gravitational influence in comparison to Jupiter’s at this distance.
The last of Jupiter’s satellites / moons that can be seen by Earth-based telescopes have to await discovery until 1951 when XII – now known as Ananke – was yet again discovered by Seth B. Nicholson. XII or Ananke was a difficult find not only because of the Jovian moon’s small size – 10 miles – but also because it shines no brighter than the light of a burning candle seen from 3,000 miles away at night. This is primarily due to the Jovian moon’s extremely low visual albedo or reflectivity, not to mention the Jovian moon’s relatively small size of 10 miles in diameter. Sadly, these amazing astronomers, especially Seth Barnes Nicholson, are largely forgotten given their amazing feats in the science of astronomy.
Thursday, February 25, 2010
Monday, February 22, 2010
Optical Interferometry: A Way Around the Rayleigh Criterion?
Invented by Albert A. Michelson during the 1870s, can optical interferometry be used effectively in circumventing the Rayleigh Criterion limitations of a typical reflecting telescope?
By: Ringo Bones
Albert A. Michelson was more famous for his work with Edward W. Morley in which they won the 1907 Nobel Prize in physics for proving that the mythical medium called the ether wind doesn’t exist, thus paving the way for Einstein’s theory of special relativity. Michelson invented the interferometer primarily as a way of accurately measuring the speed of light back in the 1870s. Albert A. Michelson also managed to earn the fame of being the first one to utilize optical interferometry as a very important astronomical instrument until 1920. It is this time when Michelson became the first ever person to measure a diameter of a star using an optical interferometer of his own design. He determined that Alpha Orion to be 260 million miles in diameter. A few years before, Michelson was also the first person to determine the diameter of Jupiter’s satellites. But how does optical interferometry works?
Optical interferometry depends on the light splitting and summing properties of an interferometer. An interferometer is an instrument that utilizes light interference phenomena for precise determinations of wavelength, fine structure of spectral lines, refractive indices of a given medium and very fine linear displacement of distant objects. By bringing together beams of starlight captured by two or more widely separated telescopes, a typical optical interferometer can achieve the equivalent resolving power of a single instrument equipped with a main mirror as large as the distance between the ganged telescopes.
When the starlight beams are combined, the light waves interfere with one another. Where the peak of one light wave meets the peak of another, they reinforce each other. When the peak of one light wave meets the through of another, they cancel out. An electronic detector or a video digital-to-analog-converter (video DAC) records the resulting pattern of dark and light areas – or interference fringes – which can then be analyzed by computer via digital signal processing to extract detailed information about the object being observed. If at least three telescopes are used, the fringes can be rendered into images hundreds of times crisper than even those obtained by the orbiting Hubble Space Telescope – at a much reduced expense, thus bypassing the Rayleigh Criterion limitations of constructing an ever bigger mirror of a typical astronomical telescope. Given its ability to improve reflecting telescope performance beyond their Rayleigh Criterion limitations, why is it that most astronomers are still mistrustful over optical interferometry?
There had been famous and amazing stargazing feats achieved by optical interferometry since the 1970s. In 1974, Kitt Peak National Observatory astronomers managed to penetrate the Earth’s atmospheric haze for the first time by discerning the features in the atmosphere of a star named Betelgeuse with the computer aided technique called speckle interferometry, while the Mark III Optical Interferometer on Mount Wilson Observatory in California had been in operation since 1986. Astronomers tend to be a conservative bunch and a lot of them consider optical interferometry to be “black magic” because even though they can measure the outlines of celestial objects millions – even billions - of miles away, optical interferometers cannot make true images of these objects.
If you remember the movie version of Tom Clancy’s Patriot Games when Langley analysts got a hard copy of a photo taken by a KH-11 reconnaissance satellite showing the cleavage of the female underwriters of the Ulster Liberation Army standing in the middle of the Libyan Desert. You’ll notice that it is monochromatic – i.e. black and white – yet managed to show features that according to Rayleigh Criterion on the KH-11 reconnaissance satellite’s mirror specifications cannot supposedly resolve that make it appear like a distinct black and white image of a woman’s cleavage seen from 160 miles up. That’s the power of optical interferometry put to use were the video signals are probably processed using the reconnaissance satellite’s built-in 10-bit video DAC that’s probably not more advanced than one’s found in a circa 1998 DVD player.
Image quality-wise, the resulting image is so “abstract” and “clinical” that free-spirited American under-aged teens who are frequent skinny-dippers have no fear having compromising photos taken by computer nerds who know how to re-task the US National Security Agency’s reconnaissance satellites - Largely because its image quality is far inferior in comparison to those photos taken by a typical paparazzi operating in the 90210 area code. Probably due to the fact that optical interferometry – a technique probably utilized by the KH-11 reconnaissance satellite to be able to read Soviet-era Pravda headlines and car license plates from 160 miles up - cannot make true images.
By: Ringo Bones
Albert A. Michelson was more famous for his work with Edward W. Morley in which they won the 1907 Nobel Prize in physics for proving that the mythical medium called the ether wind doesn’t exist, thus paving the way for Einstein’s theory of special relativity. Michelson invented the interferometer primarily as a way of accurately measuring the speed of light back in the 1870s. Albert A. Michelson also managed to earn the fame of being the first one to utilize optical interferometry as a very important astronomical instrument until 1920. It is this time when Michelson became the first ever person to measure a diameter of a star using an optical interferometer of his own design. He determined that Alpha Orion to be 260 million miles in diameter. A few years before, Michelson was also the first person to determine the diameter of Jupiter’s satellites. But how does optical interferometry works?
Optical interferometry depends on the light splitting and summing properties of an interferometer. An interferometer is an instrument that utilizes light interference phenomena for precise determinations of wavelength, fine structure of spectral lines, refractive indices of a given medium and very fine linear displacement of distant objects. By bringing together beams of starlight captured by two or more widely separated telescopes, a typical optical interferometer can achieve the equivalent resolving power of a single instrument equipped with a main mirror as large as the distance between the ganged telescopes.
When the starlight beams are combined, the light waves interfere with one another. Where the peak of one light wave meets the peak of another, they reinforce each other. When the peak of one light wave meets the through of another, they cancel out. An electronic detector or a video digital-to-analog-converter (video DAC) records the resulting pattern of dark and light areas – or interference fringes – which can then be analyzed by computer via digital signal processing to extract detailed information about the object being observed. If at least three telescopes are used, the fringes can be rendered into images hundreds of times crisper than even those obtained by the orbiting Hubble Space Telescope – at a much reduced expense, thus bypassing the Rayleigh Criterion limitations of constructing an ever bigger mirror of a typical astronomical telescope. Given its ability to improve reflecting telescope performance beyond their Rayleigh Criterion limitations, why is it that most astronomers are still mistrustful over optical interferometry?
There had been famous and amazing stargazing feats achieved by optical interferometry since the 1970s. In 1974, Kitt Peak National Observatory astronomers managed to penetrate the Earth’s atmospheric haze for the first time by discerning the features in the atmosphere of a star named Betelgeuse with the computer aided technique called speckle interferometry, while the Mark III Optical Interferometer on Mount Wilson Observatory in California had been in operation since 1986. Astronomers tend to be a conservative bunch and a lot of them consider optical interferometry to be “black magic” because even though they can measure the outlines of celestial objects millions – even billions - of miles away, optical interferometers cannot make true images of these objects.
If you remember the movie version of Tom Clancy’s Patriot Games when Langley analysts got a hard copy of a photo taken by a KH-11 reconnaissance satellite showing the cleavage of the female underwriters of the Ulster Liberation Army standing in the middle of the Libyan Desert. You’ll notice that it is monochromatic – i.e. black and white – yet managed to show features that according to Rayleigh Criterion on the KH-11 reconnaissance satellite’s mirror specifications cannot supposedly resolve that make it appear like a distinct black and white image of a woman’s cleavage seen from 160 miles up. That’s the power of optical interferometry put to use were the video signals are probably processed using the reconnaissance satellite’s built-in 10-bit video DAC that’s probably not more advanced than one’s found in a circa 1998 DVD player.
Image quality-wise, the resulting image is so “abstract” and “clinical” that free-spirited American under-aged teens who are frequent skinny-dippers have no fear having compromising photos taken by computer nerds who know how to re-task the US National Security Agency’s reconnaissance satellites - Largely because its image quality is far inferior in comparison to those photos taken by a typical paparazzi operating in the 90210 area code. Probably due to the fact that optical interferometry – a technique probably utilized by the KH-11 reconnaissance satellite to be able to read Soviet-era Pravda headlines and car license plates from 160 miles up - cannot make true images.
Thursday, February 11, 2010
The Rayleigh Criterion: The Bane of Mirrored Telescopes?
Named after a 19th Century English physicist, is the Rayleigh Criterion the true arbiter over press hype of the true capabilities of large mirrored telescopes and reconnaissance satellites?
By: Ringo Bones
I could have titled this blog entry as; “Is the KH-Series of American Reconnaissance Satellites’ Capability of Seeing Soviet-era Pravda headlines from 160 kilometers up Somewhat Overly Optimistic?” but that would only answer a part of a little understood concept of optics. And if the “hype” over the runaway success of adaptive optics were to be believed, would this imply that the best astronomical telescopes could soon be found here on Earth as opposed to orbital space? Though that too is only part of the story, but the point of this discussion is about how an oft-ignored, yet vital aspect, of advanced telescope design. Whether using a Hubble Space Telescope-sized 2.4-meter primary mirror or a 10-meter primary mirrored Earth-based astronomical telescope is ultimately diffraction limited. This means that the resolution of a large reflecting telescope – whether those on the KH-series reconnaissance satellites, the Hubble Space Telescope, or those very large astronomical telescopes found on top of Mauna Kea or in the Chilean desert – is limited by diffraction.
The first person to study the diffraction limitation problem of reflecting or mirrored astronomical – or other large - telescopes was a 19th Century English physicist / gentleman-scientist named John William Strutt, but he’s better known to the rest of the world as the 3rd Baron Rayleigh or Lord Rayleigh. Also more famous for his 1904 Nobel prize for Physics for the discovery of the element argon – which he isolated in cooperation with Sir William Ramsay – than his work / investigations in optics that lead to the criterion named after him. The Rayleigh Criterion defines the resolution capabilities of a reflecting telescope where two points are just resolved when their angular separation is equal to an angle designated as theta at which the first diffraction minimum occurs. As given in the equation theta = 1.22 multiplied by the wavelength of light of interest divided by the mirror diameter of the telescope. The number 1.22 is a constant derived by Lord Rayleigh when he used differential equations in tackling this problem. The angle theta can also be designated as dividing the linear separation of the characters of interest – like the headline of a Soviet-era Pravda newspaper at around an inch or 2.5 cm – with the orbital altitude of the reconnaissance satellite – often at 160 kilometers up.
If anyone – besides me – is really curious if a KH-11 like reconnaissance satellite is really capable of seeing clearly a Pravda newspaper headline from 160 kilometers from the Earth’s surface. One can use the Rayleigh Criterion to test to test whether the KH series of reconnaissance satellite’s capabilities are nothing more than cold War era media hype. Let’s just assume that the KH-11 reconnaissance satellite has a main mirror similar in size to that of the Hubble Space Telescope at 2.4 meters since the two are almost of similar dimensions. Assuming that it works in the visible light spectrum at 550 nanometers (smack down in the middle or the green portion of the visible light spectrum) as the wavelength of interest.
So to get the resolution limit of your typical reconnaissance satellite, just multiply 1.22 with the orbital altitude of the reconnaissance satellite – usually around 160 kilometers or 160,000 meters. Multiply this number with the quotient that resulted when the wavelength of interest – 550 nanometers (550 times 10 to the negative 9 meters) – is divided by the reconnaissance satellite’s main mirror diameter of 2.4 meters. The resulting figure is 4.47 centimeters, which makes the reflecting telescope of your typical reconnaissance satellite really have a hard time seeing a Pravda newspaper headline – even license plates – from 160 kilometers up. The letters and numbers may be 4.47 centimeters tall but if they are spaced closer than 4.47 centimeters, the resulting image will be a blur if taken from 160 kilometers up. Shifting to the longer infrared wavelengths worsen the resolution when looking at “small” objects, while the shorter ultraviolet wavelengths could face problems of increasing atmospheric opacity from going through more than 100 kilometers of air.
There might be truth to the rumors of the gripes of “civilian” optical technicians working on the Hubble Space Telescopes main mirror during the Reagan Administration being denied access to the mirror testing equipment primarily used to test the main mirrors on the KH-11 series of reconnaissance satellites. Citing national security concerns back when America was still engaged in a Cold War with the Soviet Union. Sadly, this resulted in the Hubble Space Telescope’s technicians not knowing that the telescope’s main mirror is ground a few millionths of an inch too much while still on the ground in the NASA clean room. Worse still, the astronomical community only knew of the Hubble’s misshapen mirror only after it has been launched 350 kilometers into orbital space when they tested it, hence the then famous press headline of the Hubble Space Telescope being a 1.2 billion dollar blunder.
Maybe, the end of the Cold War proved to be a blessing in disguise to the Hubble Space Telescope because there are rumors too that the potato chip-shaped “corrective lenses” that are retrofitted to the Hubble back in 1993 were borrowed from the KH series of reconnaissance satellites. Maybe this specially shaped lenses are the “magic wand” that allowed the NSA reconnaissance satellites to beat around the Rayleigh Criterion / diffraction limitations of space-based reflecting telescopes. Regardless whether they are used to look up and out into space or look down on Earth’s surface in search of WMDs.
By: Ringo Bones
I could have titled this blog entry as; “Is the KH-Series of American Reconnaissance Satellites’ Capability of Seeing Soviet-era Pravda headlines from 160 kilometers up Somewhat Overly Optimistic?” but that would only answer a part of a little understood concept of optics. And if the “hype” over the runaway success of adaptive optics were to be believed, would this imply that the best astronomical telescopes could soon be found here on Earth as opposed to orbital space? Though that too is only part of the story, but the point of this discussion is about how an oft-ignored, yet vital aspect, of advanced telescope design. Whether using a Hubble Space Telescope-sized 2.4-meter primary mirror or a 10-meter primary mirrored Earth-based astronomical telescope is ultimately diffraction limited. This means that the resolution of a large reflecting telescope – whether those on the KH-series reconnaissance satellites, the Hubble Space Telescope, or those very large astronomical telescopes found on top of Mauna Kea or in the Chilean desert – is limited by diffraction.
The first person to study the diffraction limitation problem of reflecting or mirrored astronomical – or other large - telescopes was a 19th Century English physicist / gentleman-scientist named John William Strutt, but he’s better known to the rest of the world as the 3rd Baron Rayleigh or Lord Rayleigh. Also more famous for his 1904 Nobel prize for Physics for the discovery of the element argon – which he isolated in cooperation with Sir William Ramsay – than his work / investigations in optics that lead to the criterion named after him. The Rayleigh Criterion defines the resolution capabilities of a reflecting telescope where two points are just resolved when their angular separation is equal to an angle designated as theta at which the first diffraction minimum occurs. As given in the equation theta = 1.22 multiplied by the wavelength of light of interest divided by the mirror diameter of the telescope. The number 1.22 is a constant derived by Lord Rayleigh when he used differential equations in tackling this problem. The angle theta can also be designated as dividing the linear separation of the characters of interest – like the headline of a Soviet-era Pravda newspaper at around an inch or 2.5 cm – with the orbital altitude of the reconnaissance satellite – often at 160 kilometers up.
If anyone – besides me – is really curious if a KH-11 like reconnaissance satellite is really capable of seeing clearly a Pravda newspaper headline from 160 kilometers from the Earth’s surface. One can use the Rayleigh Criterion to test to test whether the KH series of reconnaissance satellite’s capabilities are nothing more than cold War era media hype. Let’s just assume that the KH-11 reconnaissance satellite has a main mirror similar in size to that of the Hubble Space Telescope at 2.4 meters since the two are almost of similar dimensions. Assuming that it works in the visible light spectrum at 550 nanometers (smack down in the middle or the green portion of the visible light spectrum) as the wavelength of interest.
So to get the resolution limit of your typical reconnaissance satellite, just multiply 1.22 with the orbital altitude of the reconnaissance satellite – usually around 160 kilometers or 160,000 meters. Multiply this number with the quotient that resulted when the wavelength of interest – 550 nanometers (550 times 10 to the negative 9 meters) – is divided by the reconnaissance satellite’s main mirror diameter of 2.4 meters. The resulting figure is 4.47 centimeters, which makes the reflecting telescope of your typical reconnaissance satellite really have a hard time seeing a Pravda newspaper headline – even license plates – from 160 kilometers up. The letters and numbers may be 4.47 centimeters tall but if they are spaced closer than 4.47 centimeters, the resulting image will be a blur if taken from 160 kilometers up. Shifting to the longer infrared wavelengths worsen the resolution when looking at “small” objects, while the shorter ultraviolet wavelengths could face problems of increasing atmospheric opacity from going through more than 100 kilometers of air.
There might be truth to the rumors of the gripes of “civilian” optical technicians working on the Hubble Space Telescopes main mirror during the Reagan Administration being denied access to the mirror testing equipment primarily used to test the main mirrors on the KH-11 series of reconnaissance satellites. Citing national security concerns back when America was still engaged in a Cold War with the Soviet Union. Sadly, this resulted in the Hubble Space Telescope’s technicians not knowing that the telescope’s main mirror is ground a few millionths of an inch too much while still on the ground in the NASA clean room. Worse still, the astronomical community only knew of the Hubble’s misshapen mirror only after it has been launched 350 kilometers into orbital space when they tested it, hence the then famous press headline of the Hubble Space Telescope being a 1.2 billion dollar blunder.
Maybe, the end of the Cold War proved to be a blessing in disguise to the Hubble Space Telescope because there are rumors too that the potato chip-shaped “corrective lenses” that are retrofitted to the Hubble back in 1993 were borrowed from the KH series of reconnaissance satellites. Maybe this specially shaped lenses are the “magic wand” that allowed the NSA reconnaissance satellites to beat around the Rayleigh Criterion / diffraction limitations of space-based reflecting telescopes. Regardless whether they are used to look up and out into space or look down on Earth’s surface in search of WMDs.
Wednesday, December 23, 2009
Silent Skies for Radio Astronomers
With the ever-increasing expansion of radio-frequency mobile telecommunication chatter via cellular / mobile phones and other wireless devices, will our skies be “silent” enough for radio astronomy?
By: Ringo Bones
The International Astronomical Union and the International Dark Skies Association had made significant progress recently in stamping out the scourge of urban light pollution during the celebration of the UN sponsored 2009 International Year of Astronomy. Especially when the Galloway Forest Park in Scotland was established as a protected dark sky area for stargazers and amateur astronomers. Unfortunately, nothing has been done for radio astronomers when it comes to the “trivial” problem of the increasing radio-frequency traffic that denied a chatter-free silent sky condition for astronomers who explore the cosmos in the radio portion of the electromagnetic spectrum. Especially in radio frequencies of interest used in exploring our universe like galactic structure and evolution to signs of “extraterrestrial technology”.
As far back as the 1970s, astronomer Carl Sagan raised concerns over the US Department of Defense’s heavily encrypted DARPA Net “Hotline” operating so close a frequency to the hydroxyl radical radio frequency. In 1995, the Strasbourg-based European Science Foundation issued a warning that the rapid expansion of the mobile communications / mobile phone / cellular phone industry’s excessive “radio-frequency pollution” – a.k.a. RF pollution - was a serious threat to radio astronomers worldwide. Back then, Dr. James Cohen of Britain’s Jodrell Bank observatory decried the ongoing deployment of numerous low-Earth-orbit telecommunications satellites used to serve the mobile / cellular phone industry.
Around that time, Dr. James Cohen stated that even if the sideband emissions from satellite / mobile / cellular telephones were small, they would still devastate radio telescopes equipped with large dishes which are so sensitive they can detect extremely weak and distant RF signals on the sub-nanovolt level. Like urban light pollution plaguing astronomers who work in the optical portion of the electromagnetic spectrum, Dr. Cohen likened the problem to a professional photographer having a light shining into his or her lens every time he or she tried to snap a picture. Dr. Peter Napier of the US National Radio Astronomy Observatory concurred with Dr. Cohen, saying that the problems of excessive RF pollution in the radio spectrum of our skies were severe and getting worse as the years go by. Dr. Napier characterized common telecommunications engineering practices as “inadequate” to prevent severe disruption to radio astronomy.
Due to a lack of a legally binding international treaty designed to protect the world’s radio astronomers against excessive RF frequencies reaching into their astronomical instruments or radio frequency pollution. The International Telecommunications Union (ITU) had assigned a frequency of 1410MHz – previously the sole domain of the US DoD during the height of the Cold War to send heavily encrypted data streams – available for civilian use for satellite / mobile / cellular phone systems. Unfortunately, this radio frequency band is dangerously close to the 1412MHz signature of the hydroxyl radical – a hydrogen / oxygen molecular fragment widely distributed in space and is used by radio astronomers to map our universe.
In the time since the European Science Foundation issued its warning against excessive radio frequency traffic ruining radio astronomy, “celestial traffic” via telecommunications satellites around the Earth had increased tremendously. These now support an ever-growing market of dedicated ISDN modem / broadband modem lines / wi-fi / and mobile / cellular phones – not to mention an “experimental” system intended to prevent auto collisions. Not only do these satellites contribute to the RF frequency pollution that spoils radio astronomy - their highly reflective Teflon-coated antennae can also be a source of light pollution to astronomers working in the optical spectrum. These satellites – like the various Iridium satellites and the 24-satellite Global Positioning System in geosynchronous orbits - are probably the only “stars” visible in urban areas plagued by sodium-vapor street-lamp light pollution.
The radio frequency pollution problem shows no sign of abating. Mike Cousins, who runs the Stanford Research Institute’s radio-telescope research program, told the San Francisco Examiner that the problem is “constant, sometimes severe”. There is now a cellular phone tower just over the hill from Stanford’s 150-foot dish, Cousins told the San Francisco Examiner’s science writer Keay Davidson. “There is nothing we can do about it” Cousins says. The Stanford dish is sensitive enough to pick up radar reflections from ships in the Western Pacific and Citizen’s Band radio transmissions from as far away as Florida. Even Seth Shostak of the SETI Institute in Mountain View, California, characterized the radio frequency pollution problem in radio astronomy as “science versus heavy-duty commerce”. Scientists at Seth Shostak’s institute search for radio frequency signals from extraterrestrial civilizations.
Will the radio frequency pollution problem that plagues radio astronomers like urban light pollution problems plaguing astronomers using optical telescopes ever be solved? Most radio telescopes, like their optical counterparts, stand in once-remote and once-uninhabited locations that are now surrounded by highly urbanized civilization with their inherently light and RF polluting lifestyle. Even the International Dark Skies Association had failed to solve the increasing light pollution problem around Mount Wilson Observatory in Pasadena, California.
Recently, radio astronomers have developed a few techniques for separating the extraterrestrial radio signals of interest from the more mundane RF pollution noise. One is by computer correlation of signals received by two or more dishes spaced hundreds of miles apart. Using this technique, radio astronomers can filter out the transmissions of cellular phone “yakking yuppies” and concentrate on the spectrum of interest. The better – if not the best technique – for radio astronomers to beat radio frequency pollution is to build a radio astronomy dish as far away from the earthbound RF noise as possible – like on the dark side of the Moon. Sadly, this project won’t be getting any US Congressional funding anytime soon after the Bush-Cheney Consortium ran their “Global War on Terror in a malfeasant manner that left the US Government mired in a 12 trillion dollar debt burden. Some gifted scientist now smoking weed in Amsterdam could have built a faster-than-light capable spacecraft that carries a crew of 150 with that kind of money.
By: Ringo Bones
The International Astronomical Union and the International Dark Skies Association had made significant progress recently in stamping out the scourge of urban light pollution during the celebration of the UN sponsored 2009 International Year of Astronomy. Especially when the Galloway Forest Park in Scotland was established as a protected dark sky area for stargazers and amateur astronomers. Unfortunately, nothing has been done for radio astronomers when it comes to the “trivial” problem of the increasing radio-frequency traffic that denied a chatter-free silent sky condition for astronomers who explore the cosmos in the radio portion of the electromagnetic spectrum. Especially in radio frequencies of interest used in exploring our universe like galactic structure and evolution to signs of “extraterrestrial technology”.
As far back as the 1970s, astronomer Carl Sagan raised concerns over the US Department of Defense’s heavily encrypted DARPA Net “Hotline” operating so close a frequency to the hydroxyl radical radio frequency. In 1995, the Strasbourg-based European Science Foundation issued a warning that the rapid expansion of the mobile communications / mobile phone / cellular phone industry’s excessive “radio-frequency pollution” – a.k.a. RF pollution - was a serious threat to radio astronomers worldwide. Back then, Dr. James Cohen of Britain’s Jodrell Bank observatory decried the ongoing deployment of numerous low-Earth-orbit telecommunications satellites used to serve the mobile / cellular phone industry.
Around that time, Dr. James Cohen stated that even if the sideband emissions from satellite / mobile / cellular telephones were small, they would still devastate radio telescopes equipped with large dishes which are so sensitive they can detect extremely weak and distant RF signals on the sub-nanovolt level. Like urban light pollution plaguing astronomers who work in the optical portion of the electromagnetic spectrum, Dr. Cohen likened the problem to a professional photographer having a light shining into his or her lens every time he or she tried to snap a picture. Dr. Peter Napier of the US National Radio Astronomy Observatory concurred with Dr. Cohen, saying that the problems of excessive RF pollution in the radio spectrum of our skies were severe and getting worse as the years go by. Dr. Napier characterized common telecommunications engineering practices as “inadequate” to prevent severe disruption to radio astronomy.
Due to a lack of a legally binding international treaty designed to protect the world’s radio astronomers against excessive RF frequencies reaching into their astronomical instruments or radio frequency pollution. The International Telecommunications Union (ITU) had assigned a frequency of 1410MHz – previously the sole domain of the US DoD during the height of the Cold War to send heavily encrypted data streams – available for civilian use for satellite / mobile / cellular phone systems. Unfortunately, this radio frequency band is dangerously close to the 1412MHz signature of the hydroxyl radical – a hydrogen / oxygen molecular fragment widely distributed in space and is used by radio astronomers to map our universe.
In the time since the European Science Foundation issued its warning against excessive radio frequency traffic ruining radio astronomy, “celestial traffic” via telecommunications satellites around the Earth had increased tremendously. These now support an ever-growing market of dedicated ISDN modem / broadband modem lines / wi-fi / and mobile / cellular phones – not to mention an “experimental” system intended to prevent auto collisions. Not only do these satellites contribute to the RF frequency pollution that spoils radio astronomy - their highly reflective Teflon-coated antennae can also be a source of light pollution to astronomers working in the optical spectrum. These satellites – like the various Iridium satellites and the 24-satellite Global Positioning System in geosynchronous orbits - are probably the only “stars” visible in urban areas plagued by sodium-vapor street-lamp light pollution.
The radio frequency pollution problem shows no sign of abating. Mike Cousins, who runs the Stanford Research Institute’s radio-telescope research program, told the San Francisco Examiner that the problem is “constant, sometimes severe”. There is now a cellular phone tower just over the hill from Stanford’s 150-foot dish, Cousins told the San Francisco Examiner’s science writer Keay Davidson. “There is nothing we can do about it” Cousins says. The Stanford dish is sensitive enough to pick up radar reflections from ships in the Western Pacific and Citizen’s Band radio transmissions from as far away as Florida. Even Seth Shostak of the SETI Institute in Mountain View, California, characterized the radio frequency pollution problem in radio astronomy as “science versus heavy-duty commerce”. Scientists at Seth Shostak’s institute search for radio frequency signals from extraterrestrial civilizations.
Will the radio frequency pollution problem that plagues radio astronomers like urban light pollution problems plaguing astronomers using optical telescopes ever be solved? Most radio telescopes, like their optical counterparts, stand in once-remote and once-uninhabited locations that are now surrounded by highly urbanized civilization with their inherently light and RF polluting lifestyle. Even the International Dark Skies Association had failed to solve the increasing light pollution problem around Mount Wilson Observatory in Pasadena, California.
Recently, radio astronomers have developed a few techniques for separating the extraterrestrial radio signals of interest from the more mundane RF pollution noise. One is by computer correlation of signals received by two or more dishes spaced hundreds of miles apart. Using this technique, radio astronomers can filter out the transmissions of cellular phone “yakking yuppies” and concentrate on the spectrum of interest. The better – if not the best technique – for radio astronomers to beat radio frequency pollution is to build a radio astronomy dish as far away from the earthbound RF noise as possible – like on the dark side of the Moon. Sadly, this project won’t be getting any US Congressional funding anytime soon after the Bush-Cheney Consortium ran their “Global War on Terror in a malfeasant manner that left the US Government mired in a 12 trillion dollar debt burden. Some gifted scientist now smoking weed in Amsterdam could have built a faster-than-light capable spacecraft that carries a crew of 150 with that kind of money.
Monday, December 21, 2009
Can the International Astronomical Union Stop Urban Light Pollution?
As one of the major goals of the International Year of Astronomy 2009 (IYA 2009), does the International Astronomical Union or IAU hold enough clout to stop the scourge of light pollution?
By: Ringo Bones
As the only international astronomical body that has the power to downgrade Pluto from a bona fide planet to a “dwarf planet” status, the International Astronomical Union could have easily stopped urban light pollution. But as of late, many amateur astronomers have always been wondering why the International Astronomical Union had always been “very meek” when it comes to stamping out the scourge of urban light pollution. The question now is, can the IAU – using its political clout – really has the power to stamp out the scourge of urban light pollution? After all, those sodium-vapor lamps that radiate as much light upwards as well as lit our streets is pretty useless when it comes to stopping a 123-grain Lapua Scenar round travelling at 2,600 feet per second, doesn’t it?
When it comes to achieving the “bottom list” of the International Year of Astronomy 2009’s major goals – i.e. on facilitating the preservation and protection of the world’s cultural and natural heritage of dark skies in places such as urban oases, natural parks and astronomical sites. It did manage to score big points recently when the world’s astronomical community voted Galloway Forest Park in Scotland as one of the best stargazing sites on the planet. Galloway Forest Park was even awarded “dark skies” status and praised for accessibility to the general public. The park’s dark skies status accolade was probably due to the healthy tree cover filtering the distant glow of not-so-distant urban nighttime illumination.
Recently, the International Dark Skies Association had tested the levels of darkness in the Galloway Forest Park using a Sky Quality Meter – a method of darkness measurement that would rate a photographer’s darkroom (with the dim red light on?) a rating of 24, the highest reading possible. Galloway Forest Park got 23 out of 24, while the reading in cities such as Glasgow would be 15 or 16.
Despite of its relatively close proximity to major urban centers, it is a miracle that Galloway Forest Park managed to score very high marks on the Sky Quality Meter. But the park’s proximity to northern England, Central Scotland and Northern Ireland – not to mention the ferry port of Stranraer – allowed Galloway Forest Park to score high on the general public accessibility scale in comparison to some other famed but more remote stargazing sites in Britain. Let’s just hope that billionaire property developer Donald Trump doesn’t buy the park in order to turn it into an extremely well-lit casino and golf course. Noting that the full Moon can’t be seen anymore on a well lit nights of the Las Vegas Strip.
To the benefit of us amateur astronomers who live elsewhere on the planet. The International Astronomical Union should be urging governments around the world to redesign streetlights so that they only illuminate the pavement as opposed to our current ones that does double duty of shining a spotlight on four-engine World War II-era night-bombers flying at 25,000 feet. These overly bright streetlights that scatter their light everywhere can’t even make a 9-mm Parabellum round fall to the ground as soon as it leaves the muzzle of a Beretta 92-F – like those “newfangled” inertial dampening field devices. And lets not forget that they don’t even to do double duty either as a quantum-tunneling wormhole that allows our law enforcement personnel to “ miraculously materialize” at the scene of the crime in less than three seconds as far as I know. These overly-bright sodium-vapor lamps that scatter their lights all over the place – especially upwards – not only ruin amateur astronomer’s view of the night sky, they also produce unnecessary carbon dioxide that leads to global warming.
By: Ringo Bones
As the only international astronomical body that has the power to downgrade Pluto from a bona fide planet to a “dwarf planet” status, the International Astronomical Union could have easily stopped urban light pollution. But as of late, many amateur astronomers have always been wondering why the International Astronomical Union had always been “very meek” when it comes to stamping out the scourge of urban light pollution. The question now is, can the IAU – using its political clout – really has the power to stamp out the scourge of urban light pollution? After all, those sodium-vapor lamps that radiate as much light upwards as well as lit our streets is pretty useless when it comes to stopping a 123-grain Lapua Scenar round travelling at 2,600 feet per second, doesn’t it?
When it comes to achieving the “bottom list” of the International Year of Astronomy 2009’s major goals – i.e. on facilitating the preservation and protection of the world’s cultural and natural heritage of dark skies in places such as urban oases, natural parks and astronomical sites. It did manage to score big points recently when the world’s astronomical community voted Galloway Forest Park in Scotland as one of the best stargazing sites on the planet. Galloway Forest Park was even awarded “dark skies” status and praised for accessibility to the general public. The park’s dark skies status accolade was probably due to the healthy tree cover filtering the distant glow of not-so-distant urban nighttime illumination.
Recently, the International Dark Skies Association had tested the levels of darkness in the Galloway Forest Park using a Sky Quality Meter – a method of darkness measurement that would rate a photographer’s darkroom (with the dim red light on?) a rating of 24, the highest reading possible. Galloway Forest Park got 23 out of 24, while the reading in cities such as Glasgow would be 15 or 16.
Despite of its relatively close proximity to major urban centers, it is a miracle that Galloway Forest Park managed to score very high marks on the Sky Quality Meter. But the park’s proximity to northern England, Central Scotland and Northern Ireland – not to mention the ferry port of Stranraer – allowed Galloway Forest Park to score high on the general public accessibility scale in comparison to some other famed but more remote stargazing sites in Britain. Let’s just hope that billionaire property developer Donald Trump doesn’t buy the park in order to turn it into an extremely well-lit casino and golf course. Noting that the full Moon can’t be seen anymore on a well lit nights of the Las Vegas Strip.
To the benefit of us amateur astronomers who live elsewhere on the planet. The International Astronomical Union should be urging governments around the world to redesign streetlights so that they only illuminate the pavement as opposed to our current ones that does double duty of shining a spotlight on four-engine World War II-era night-bombers flying at 25,000 feet. These overly bright streetlights that scatter their light everywhere can’t even make a 9-mm Parabellum round fall to the ground as soon as it leaves the muzzle of a Beretta 92-F – like those “newfangled” inertial dampening field devices. And lets not forget that they don’t even to do double duty either as a quantum-tunneling wormhole that allows our law enforcement personnel to “ miraculously materialize” at the scene of the crime in less than three seconds as far as I know. These overly-bright sodium-vapor lamps that scatter their lights all over the place – especially upwards – not only ruin amateur astronomer’s view of the night sky, they also produce unnecessary carbon dioxide that leads to global warming.
Monday, November 30, 2009
Saturn’s Newly Discovered Ring System: A Curious Astronomical Oversight?
Inexplicably overlooked by the Cassini-Huygens space probe’s arrival into Saturn back in 2004 is the planet Saturn’s newly discovered ring system the greatest astronomical oversight history?
By: Ringo Bones
When a newly-discovered ring system of the planet Saturn was first seen and discovered by a space based – though still in Earth’s orbit – Spitzer Space Telescope at the NASA Jet Propulsion Laboratory back in October 2009. The first thought that came through my mind was how come the Cassini-Huygens space probe wasn’t the first one to “see” and discover this dust-based ring system of the planet Saturn when it entered into orbit there back in July 2004? You know, that controversial Cassini-Huygens space probe whose weapons grade plutonium-based thermal generator used to power its electronics was the subject of Professor Michio Kaku’s disdain during its launch back in 1997.
This somewhat curious and inexplicable astronomical oversight aside, the newly discovered ring system of the planet Saturn is a natural wonder of the cosmos to behold. Probably greater than that in comparison to the seven ring bands that we knew before. The new ring system lies 8 million miles from Saturn’s surface, compared to 85,000 miles of the outer reaches of the previously known ring system. If seen by the naked eye from the Earth’s surface, Saturn would appear as large as the full Moon instead of just a “bright-ish” star that is of no consequence to civilians clueless about navigating using star positions. Sadly, our eyes – normal human eyes that is – are not designed to see Saturn’s newly discovered ring system.
The NASA JPL Spitzer Space Telescope, which was the instrument used to discovered the new ring system back in October 2009, is primarily designed to “see” and find dim stars – i.e. brown dwarf stars that are believed to be the underlying explanation of the dark matter phenomena - that radiate most of their energy in the infrared region of the electromagnetic spectrum. Unlike the Hubble Space Telescope which can only reach the TV infrared remote / gallium arsenide-based night vision goggles section of the electromagnetic spectrum. The previously mysterious dust deposits on one hemisphere of Saturn’s moon Phoebe could now be safely blamed on the newly discovered ring system, which is made up mostly of ultrafine dust particles.
Given that the dust particles comprising the newly discovered ring system of Saturn has an average temperature of –300ºF, one needs specialized equipment to see it. Like a germanium bolometer, an instrument first developed by Professor Frank J. Low of the University of Arizona. A germanium bolometer is an instrument used to detect extremely weak infrared – make that thermal-range – radiation. Composed of a tiny crystal of germanium cooled by liquid helium to almost absolute zero, a germanium bolometer is able to detect a hundred-trillionth of a watt of infrared radiation - equivalent to sensing the glow of a lighted cigarette 10,000 miles away. The NASA JPL Spitzer Space Telescope was probably equipped with one.
To us amateur astronomers, being able to see the newly discovered ring system of Saturn from our hopefully light pollution free regular stargazing sites could be an almost impossible task. At an average temperature of –300ºF – which is probably 50ºF colder than the surface of Pluto – the dust that make up Saturn’s newly discovered ring system will be too cold to be visible with the more common gallium arsenide-based night vision goggles / image intensifiers. Even those Vietnam War era photomultiplier tube-based image intensifiers will probably still can’t see Saturn’s newly discovered rings. A 5,000 US dollar bolometer-on-a-chip equipped thermal camera similar to that mounted on a state of the art firefighter’s mask when placed behind the eyepiece of a Celestron reflecting telescope with an 8-inch mirror will probably work. If the telescope’s primary mirror is efficient enough in focusing in the thermal infrared range – though I haven’t tried this set up yet.
By: Ringo Bones
When a newly-discovered ring system of the planet Saturn was first seen and discovered by a space based – though still in Earth’s orbit – Spitzer Space Telescope at the NASA Jet Propulsion Laboratory back in October 2009. The first thought that came through my mind was how come the Cassini-Huygens space probe wasn’t the first one to “see” and discover this dust-based ring system of the planet Saturn when it entered into orbit there back in July 2004? You know, that controversial Cassini-Huygens space probe whose weapons grade plutonium-based thermal generator used to power its electronics was the subject of Professor Michio Kaku’s disdain during its launch back in 1997.
This somewhat curious and inexplicable astronomical oversight aside, the newly discovered ring system of the planet Saturn is a natural wonder of the cosmos to behold. Probably greater than that in comparison to the seven ring bands that we knew before. The new ring system lies 8 million miles from Saturn’s surface, compared to 85,000 miles of the outer reaches of the previously known ring system. If seen by the naked eye from the Earth’s surface, Saturn would appear as large as the full Moon instead of just a “bright-ish” star that is of no consequence to civilians clueless about navigating using star positions. Sadly, our eyes – normal human eyes that is – are not designed to see Saturn’s newly discovered ring system.
The NASA JPL Spitzer Space Telescope, which was the instrument used to discovered the new ring system back in October 2009, is primarily designed to “see” and find dim stars – i.e. brown dwarf stars that are believed to be the underlying explanation of the dark matter phenomena - that radiate most of their energy in the infrared region of the electromagnetic spectrum. Unlike the Hubble Space Telescope which can only reach the TV infrared remote / gallium arsenide-based night vision goggles section of the electromagnetic spectrum. The previously mysterious dust deposits on one hemisphere of Saturn’s moon Phoebe could now be safely blamed on the newly discovered ring system, which is made up mostly of ultrafine dust particles.
Given that the dust particles comprising the newly discovered ring system of Saturn has an average temperature of –300ºF, one needs specialized equipment to see it. Like a germanium bolometer, an instrument first developed by Professor Frank J. Low of the University of Arizona. A germanium bolometer is an instrument used to detect extremely weak infrared – make that thermal-range – radiation. Composed of a tiny crystal of germanium cooled by liquid helium to almost absolute zero, a germanium bolometer is able to detect a hundred-trillionth of a watt of infrared radiation - equivalent to sensing the glow of a lighted cigarette 10,000 miles away. The NASA JPL Spitzer Space Telescope was probably equipped with one.
To us amateur astronomers, being able to see the newly discovered ring system of Saturn from our hopefully light pollution free regular stargazing sites could be an almost impossible task. At an average temperature of –300ºF – which is probably 50ºF colder than the surface of Pluto – the dust that make up Saturn’s newly discovered ring system will be too cold to be visible with the more common gallium arsenide-based night vision goggles / image intensifiers. Even those Vietnam War era photomultiplier tube-based image intensifiers will probably still can’t see Saturn’s newly discovered rings. A 5,000 US dollar bolometer-on-a-chip equipped thermal camera similar to that mounted on a state of the art firefighter’s mask when placed behind the eyepiece of a Celestron reflecting telescope with an 8-inch mirror will probably work. If the telescope’s primary mirror is efficient enough in focusing in the thermal infrared range – though I haven’t tried this set up yet.
Sunday, April 12, 2009
Buying Your Own Starter Astronomical Telescope
From the elementary grade amateur to the tenured professional astronomer who decides to buy one, is buying your own astronomical telescope still a good investment?
By: Vanessa Uy
For the tenured professional whose significant other is understanding enough to allow him or her to own a “reasonably-sized” astronomy telescope – given that the one he or she uses on the job probably has a primary mirror taller than their two-story house. Owning a “portable” astronomy telescope surely has it’s own advantages. For the elementary grade amateur – or those in between – there’s nothing more satisfying than emulating the Golden Age of 17th Century Astronomy every time you use your telescope. But if you are looking for one, read on. Given that 2009 has been designated as the International Year of Astronomy, everyone should have the opportunity to experience first hand of using your very own astronomical telescope.
Even though there are very user-friendly astronomical telescopes that cost around 3,000 US dollars though the wisdom of shelling out with that sum of money can be questionable - especially if your funds doesn’t stretch that far. We should be looking for something more modest given that the world is currently in a recession. The second hand classifieds selling such items – like those on major astronomy magazines like Astronomy or Sky & Telescope - can be a good place to check out. But there are those brand-new priced between 150 to 500 US dollars that will do very well as starter telescopes. Even the ubiquitous 10 X 50 binocular telescope qualify as a very good starter refracting astronomical telescope. It can be used to see the major craters on the Moon and even has the magnifying power to see the planet Uranus.
There are two basic kinds of astronomical telescopes that you can choose: refractors and reflectors. A telescope’s primary function is to collect light and gather it to a focus. A refractor telescope uses a lens – called the objective lens – to refract or bend light to a focus. While a reflecting telescope uses a mirror – called the primary mirror – to reflect light to a focus. To know which type of astronomical telescope is best for you very much depends on what you will be looking at most of the time – or your specialty. Refractors are generally better for viewing small bright objects, like the Moon – if you consider the full Moon “small” – the planets, and double stars. Reflectors are generally suited for viewing large dim objects like the Milky Way, nebulae, other galaxies and star clusters.
When those in the know talk about a telescope’s “size” they are talking about its aperture. Aperture is the diameter of the telescope’s primary lens or mirror. For example, a 4-inch reflector doesn’t mean that the telescope is 4 inches long. It means that its primary mirror is 4 inches in diameter. For some weird reason, the aperture measurement of refractors or lens telescopes are usually given in millimeters, while the apertures of reflecting or mirror-type telescopes are usually given in inches. And remember an astronomical telescope’s job is to collect light. The larger the aperture, the more light it collects and the sharper the image it delivers. So chose the largest one you can afford because more than anything else, aperture determines what you will be able to see with the telescope.
Vibration can be an issue when it comes to starter astronomical telescopes. No matter which kind of telescope you choose, make sure it is attached to a good, sturdy mount. Telescopes mounted on long skinny legs that are held together with tiny screws are not worth the time and money. There is nothing worse than trying to use a telescope that makes the planet Jupiter look like that alien probe in the sci-fi TV series Threshold every time the cat walks by. Astronomical telescopes – especially the reflecting type – are prone to vibration. Even though my trusty but rusty Celestron 8-incher probably cost 1,500 US dollars when new, I can’t even play my stereo at a decent enough volume every time I use it because it vibrates wildly in time to the music. So listening to J.S. Bach’s organ cantatas or Iron Maiden’s Fear of the Dark while using a reflecting astronomical telescope is out of the question.
Speaking of astronomical telescope mounts, most beginners’ telescopes come with a simple alt-azimuth or equatorial mount. The “alt” means altitude and “azimuth” refers to horizontal movement. Which means an alt-azimuth mount allows the telescope to be moved or aimed up and down of left and right. An equatorial mount is set up so that one axis always points to the North Star. This type of mount moves in curves that match the movement of the celestial bodies in the night sky. Which can be an advantage if you want to use your telescope to capture long exposure photographs of a dim star using de rigueur 150 ASA 35mm photographic film.
There are advantages and disadvantages of each type of mount. Alt-azimuth mounts are mostly used in refractor or lens-type telescopes and are easier to use. And can be a boon if your telescope does double duty as a sniper’s spotting telescope. Especially if you are skilled enough to be a able to hit a bowling pin from 6,000 feet away using a rifle that fires the .50 caliber Browning Machine Gun cartridge. Although equatorial mounts – usually relegated to reflecting astronomical telescopes - are primarily designed to track celestial objects with ease. Plus the latitude and altitude readout on the equatorial mount can be very educational, especially if a seasoned astronomer ask you about the coordinates of the particular patch of night sky you are currently looking at. But most of all, it doesn’t matter which kind of mount you get, as long as it is sturdy enough for your telescope not to vibrate wildly every time the cat walks by.
By now, you’re probably asking how much magnification capability can I buy for my money. Sure enough, commercially manufactured astronomical telescopes’ power specification can be a contentious issue, especially since entry-level manufacturers tend to be too optimistic – even dubious - about the capabilities of their product lines. A telescope by itself doesn’t magnify anything because it doesn’t make objects look bigger it makes objects look brighter.
Making things look bigger is the job of the eyepieces you use with the telescope. Which – to the astronomical telescope’s manufacturers’ disdain – can allow you to use microscope magnification eyepieces as magnification eyepieces for your starter astronomical telescope. So it can be a boon if you also own a starter microscope. By changing eyepieces, you change the magnification. In most cases, the eyepiece will be marked with a number – usually in millimeters – that tells its focal length. The same eyepiece will deliver different magnifications in different telescopes. But in general, the lower the number on the eyepiece, the higher the magnification it delivers.
And believe it or not, you don’t even need a lot of magnification to see some interesting celestial vista. You can see Jupiter and the planet’s four biggest moons at a magnification of just 15 times (15X) – which is half that of the magnifying power of Galileo’s first astronomical telescope. While Saturn’s rings pop out at around 30X magnification. It is worth noting that most beginners’ astronomical telescopes – especially those with small apertures – can’t deliver a good image of anything at much over 150x. Either the result is an image that is too dark, since higher magnifications tend to darken the image, or is an overly distorted mush. Most entry-level astronomical telescopes – those priced between 150 to 300 US dollars – come with one or more eyepieces. You can also buy extra eyepieces separately or use ones from your microscope. Generally, it’s nice to have three sets of eyepieces: one for low power around 15X, one for medium power around 30X to 60X, and one for high power around 100X or greater.
For those beginners looking for an astronomical telescope on the cheap – which usually means second hand – avoid falling into the “long skinny trap”. I mean don’t discount a telescope just because it doesn’t looks like your typical astronomy telescope – i.e. long and skinny and mounted on a tripod. I’ve frequently encountered second-hand telescopes being offered on garage sales and swap meets that although very good, tend to look weird. Like the Astrocan, a round telescope that rotates on a short metal base. And Dobsonian reflectors – featured in the movie Roxanne – which have very stable box-shaped alt-azimuth mounts are often featured on Internet adverts being offered at prices too low to ignore. These two types are probably the most common second-hand astronomical telescopes being offered for sale. Although these types of astronomical telescopes have the disadvantage of not being so man-portable, unless of course your observation spot is accessible by car.
A good place to buy an astronomical telescope if you chose to buy one brand new are astronomy specialists shops – although some offer second-hand and “ex-dem” models at “very reasonable” prices. The clerks are more than likely to be able to help you choose a good scope within your budget, and you’ll also be able to test the telescope at the store. Also, you will be able to take the telescope back to the store if there are manufacturing defects. Or servicing within the warranty period since the shop is probably the telescope manufacturers authorized distributor / dealer. And the specialist shop carries a line of eyepieces and other accessories that you may want to buy later on. And believe it or not, specialist astronomy shops are probably the last place on the planet that sells 35mm photographic film. Given that - to my knowledge - everyday picture taking / photography has more-or-less gone completely digital since 2005.
By: Vanessa Uy
For the tenured professional whose significant other is understanding enough to allow him or her to own a “reasonably-sized” astronomy telescope – given that the one he or she uses on the job probably has a primary mirror taller than their two-story house. Owning a “portable” astronomy telescope surely has it’s own advantages. For the elementary grade amateur – or those in between – there’s nothing more satisfying than emulating the Golden Age of 17th Century Astronomy every time you use your telescope. But if you are looking for one, read on. Given that 2009 has been designated as the International Year of Astronomy, everyone should have the opportunity to experience first hand of using your very own astronomical telescope.
Even though there are very user-friendly astronomical telescopes that cost around 3,000 US dollars though the wisdom of shelling out with that sum of money can be questionable - especially if your funds doesn’t stretch that far. We should be looking for something more modest given that the world is currently in a recession. The second hand classifieds selling such items – like those on major astronomy magazines like Astronomy or Sky & Telescope - can be a good place to check out. But there are those brand-new priced between 150 to 500 US dollars that will do very well as starter telescopes. Even the ubiquitous 10 X 50 binocular telescope qualify as a very good starter refracting astronomical telescope. It can be used to see the major craters on the Moon and even has the magnifying power to see the planet Uranus.
There are two basic kinds of astronomical telescopes that you can choose: refractors and reflectors. A telescope’s primary function is to collect light and gather it to a focus. A refractor telescope uses a lens – called the objective lens – to refract or bend light to a focus. While a reflecting telescope uses a mirror – called the primary mirror – to reflect light to a focus. To know which type of astronomical telescope is best for you very much depends on what you will be looking at most of the time – or your specialty. Refractors are generally better for viewing small bright objects, like the Moon – if you consider the full Moon “small” – the planets, and double stars. Reflectors are generally suited for viewing large dim objects like the Milky Way, nebulae, other galaxies and star clusters.
When those in the know talk about a telescope’s “size” they are talking about its aperture. Aperture is the diameter of the telescope’s primary lens or mirror. For example, a 4-inch reflector doesn’t mean that the telescope is 4 inches long. It means that its primary mirror is 4 inches in diameter. For some weird reason, the aperture measurement of refractors or lens telescopes are usually given in millimeters, while the apertures of reflecting or mirror-type telescopes are usually given in inches. And remember an astronomical telescope’s job is to collect light. The larger the aperture, the more light it collects and the sharper the image it delivers. So chose the largest one you can afford because more than anything else, aperture determines what you will be able to see with the telescope.
Vibration can be an issue when it comes to starter astronomical telescopes. No matter which kind of telescope you choose, make sure it is attached to a good, sturdy mount. Telescopes mounted on long skinny legs that are held together with tiny screws are not worth the time and money. There is nothing worse than trying to use a telescope that makes the planet Jupiter look like that alien probe in the sci-fi TV series Threshold every time the cat walks by. Astronomical telescopes – especially the reflecting type – are prone to vibration. Even though my trusty but rusty Celestron 8-incher probably cost 1,500 US dollars when new, I can’t even play my stereo at a decent enough volume every time I use it because it vibrates wildly in time to the music. So listening to J.S. Bach’s organ cantatas or Iron Maiden’s Fear of the Dark while using a reflecting astronomical telescope is out of the question.
Speaking of astronomical telescope mounts, most beginners’ telescopes come with a simple alt-azimuth or equatorial mount. The “alt” means altitude and “azimuth” refers to horizontal movement. Which means an alt-azimuth mount allows the telescope to be moved or aimed up and down of left and right. An equatorial mount is set up so that one axis always points to the North Star. This type of mount moves in curves that match the movement of the celestial bodies in the night sky. Which can be an advantage if you want to use your telescope to capture long exposure photographs of a dim star using de rigueur 150 ASA 35mm photographic film.
There are advantages and disadvantages of each type of mount. Alt-azimuth mounts are mostly used in refractor or lens-type telescopes and are easier to use. And can be a boon if your telescope does double duty as a sniper’s spotting telescope. Especially if you are skilled enough to be a able to hit a bowling pin from 6,000 feet away using a rifle that fires the .50 caliber Browning Machine Gun cartridge. Although equatorial mounts – usually relegated to reflecting astronomical telescopes - are primarily designed to track celestial objects with ease. Plus the latitude and altitude readout on the equatorial mount can be very educational, especially if a seasoned astronomer ask you about the coordinates of the particular patch of night sky you are currently looking at. But most of all, it doesn’t matter which kind of mount you get, as long as it is sturdy enough for your telescope not to vibrate wildly every time the cat walks by.
By now, you’re probably asking how much magnification capability can I buy for my money. Sure enough, commercially manufactured astronomical telescopes’ power specification can be a contentious issue, especially since entry-level manufacturers tend to be too optimistic – even dubious - about the capabilities of their product lines. A telescope by itself doesn’t magnify anything because it doesn’t make objects look bigger it makes objects look brighter.
Making things look bigger is the job of the eyepieces you use with the telescope. Which – to the astronomical telescope’s manufacturers’ disdain – can allow you to use microscope magnification eyepieces as magnification eyepieces for your starter astronomical telescope. So it can be a boon if you also own a starter microscope. By changing eyepieces, you change the magnification. In most cases, the eyepiece will be marked with a number – usually in millimeters – that tells its focal length. The same eyepiece will deliver different magnifications in different telescopes. But in general, the lower the number on the eyepiece, the higher the magnification it delivers.
And believe it or not, you don’t even need a lot of magnification to see some interesting celestial vista. You can see Jupiter and the planet’s four biggest moons at a magnification of just 15 times (15X) – which is half that of the magnifying power of Galileo’s first astronomical telescope. While Saturn’s rings pop out at around 30X magnification. It is worth noting that most beginners’ astronomical telescopes – especially those with small apertures – can’t deliver a good image of anything at much over 150x. Either the result is an image that is too dark, since higher magnifications tend to darken the image, or is an overly distorted mush. Most entry-level astronomical telescopes – those priced between 150 to 300 US dollars – come with one or more eyepieces. You can also buy extra eyepieces separately or use ones from your microscope. Generally, it’s nice to have three sets of eyepieces: one for low power around 15X, one for medium power around 30X to 60X, and one for high power around 100X or greater.
For those beginners looking for an astronomical telescope on the cheap – which usually means second hand – avoid falling into the “long skinny trap”. I mean don’t discount a telescope just because it doesn’t looks like your typical astronomy telescope – i.e. long and skinny and mounted on a tripod. I’ve frequently encountered second-hand telescopes being offered on garage sales and swap meets that although very good, tend to look weird. Like the Astrocan, a round telescope that rotates on a short metal base. And Dobsonian reflectors – featured in the movie Roxanne – which have very stable box-shaped alt-azimuth mounts are often featured on Internet adverts being offered at prices too low to ignore. These two types are probably the most common second-hand astronomical telescopes being offered for sale. Although these types of astronomical telescopes have the disadvantage of not being so man-portable, unless of course your observation spot is accessible by car.
A good place to buy an astronomical telescope if you chose to buy one brand new are astronomy specialists shops – although some offer second-hand and “ex-dem” models at “very reasonable” prices. The clerks are more than likely to be able to help you choose a good scope within your budget, and you’ll also be able to test the telescope at the store. Also, you will be able to take the telescope back to the store if there are manufacturing defects. Or servicing within the warranty period since the shop is probably the telescope manufacturers authorized distributor / dealer. And the specialist shop carries a line of eyepieces and other accessories that you may want to buy later on. And believe it or not, specialist astronomy shops are probably the last place on the planet that sells 35mm photographic film. Given that - to my knowledge - everyday picture taking / photography has more-or-less gone completely digital since 2005.
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