Given the existing technology at the time, did Johannes Hevelius (1611-1687) able to know more about the Moon in comparison to his astronomy contemporaries?
By: Ringo Bones
Some astronomers think that we only managed to know more about the Moon than Johannes Hevelius did when we had the ability to send robotic spacecraft and manned exploration of the Moon, but is there some truth to this? Even though it was Galileo who first documented the Moon’s topography as seen from his first telescope back in 1610. It was Johannes Hevelius, a notable Polish astronomer born in January 28, 1611 that from his crowded rooftop in Danzig laden with his custom built telescopes – where he gained the fame as the pioneer of Lunar topography a few years later. Hevelius also studied distant celestial objects, but learned little because of dust and other disturbances in the atmosphere over Poland despite using an aerial telescope of his own design that’s 150 feet (46-meter) long – equal to the height of a modern 12-story building.
In collaboration with his wife Elizabeth, they charted the Lunar landscape then published their descriptions in Selenographia back in 1647. During his extensive studies of the Moon, Hevelius got curious of the fact that 59% of the Moon’s surface visible from Earth. During his time, the period between new Moons was already measured with a fair degree of accuracy. And the fact that the same face is always turned toward the Earth with only minor wobbling – the extra 9% of the Moon’s surface seen from Earth – was noted although not explained. The modern explanation is in part that the Moon is not a perfectly symmetrical spheroid. The Moon has a massive bulge, which the Earth’s gravitation attracts like a plumb bob, thus keeping the same hemisphere towards the Earth. With such detailed observations of the Moon, Johannes Hevelus’ contribution to modern selenology was indeed indispensable.
During his lifetime, Johannes Hevelius was also credited for discovering four comets and was noted for his suggestion that the comets revolved around the Sun in a parabola. And his observations on comets were published in Prodromus Commeticus in 1665 and Cometographia in 1688. Hevelius also listed 1,564 stars and in 1661 became the second person on Earth to witness the transit of Mercury – i.e. the planet Mercury moving across the face of the Sun as seen from Earth. Coincidentally, he passed away during his birthday on 1687.
Monday, July 19, 2010
Tuesday, March 30, 2010
Aperture Synthesis: Making Radio Telescopes “See”?
Developed by Sir Martin Ryle back in 1952, can aperture synthesis be used to make radio telescopes finally “see” celestial objects when before it can only “hear” them?
By: Ringo Bones
When the Rayleigh Criterion is taken into account, radio telescopes seem to “hear” rather than actually “see” the celestial objects of interest they are aimed at due to the much longer wavelengths of the radio spectrum in comparison to the optical / visible light part of the electromagnetic spectrum. This is the reason why RADAR or radio wave-based imagery of the universe has always been inferior in resolution terms in comparison to optical astronomy. The most obvious solution is to make ever-larger radio telescope dish antennas so that their resolution capabilities would equal that of optical telescopes, but that presents its own problems. Even the 1,000-foot diameter RADAR dish in Arecibo, Puerto Rico - in imaging terms - still cannot match the detail resolution of the human eye, and making ever bigger dishes presents its own problems.
Since radio astronomy began, astronomers had been constructing ever-larger dish antennas in an attempt to detect radio emissions from objects millions of light years away from Earth where the optical portion of the electromagnetic spectrum – i.e. visible light – cannot be picked up by optical telescopes. Radio astronomers knew, however, that to “see” into more distant objects would require the construction of antennas several miles wide. And it had taken awhile for radio astronomy to rival that of its optical sibling in resolution terms.
Ever since Albert A. Michelson used his interferometer in optical astronomy to bypass the inherent Rayleigh Criterion limitations of reflecting telescope with finite-sized mirrors, radio astronomers have adopted this technique in radio astronomy. The simplest kind of radio interferometer is based on the Michelson interferometer – which consists of two small reflectors. Radio waves arriving at an angle to the baseline of the reflectors reach each other slightly before the other, producing a multi-lobed antenna pattern similar to the fringe pattern in optical interferometers. The farther apart the reflectors, the narrower the width of the lobes – or beams – of the antenna’s radiation pattern, thus greatly increasing the radio telescope’s resolution.
A very example of this type of radio telescope is the California Institute of Technology twin-element interferometer, which consists of two 90-foot steel-mesh parabolic antennas. The antennas are mounted on special vehicles that move along special railroad tracks that can be separated by up to 1,600 feet in either east-west or north-south direction. With a beam-width or acceptance angle as narrow as 0.03 degrees, the telescope is used to record the 960-MHz radio noise in our Milky Way galaxy.
Another type of radio interferometer consists two linear arrays at right angles to each other that electronically compares the fan-shaped beams of the two arrays that result in a single pencil beam being produced that can accurately pinpoint radio sources. Developed in the early 1950s by the Australian radio astronomers W. N. Christiansen and B. Y. Mills. Each array may consist of many dipole antennas (Mills cross), parabolic antennas (Christiansen cross), or a parabolic cylinder.
The Mills cross near Sydney Australia was completed in 1952 and has legs 1,500 feet in length. Later upgraded to a version in 1957 with 3,500-foot legs, and a 1.6-kilometer version. The cross antenna at Stanford University consists of 16 steerable 10-foot parabolic reflectors in a row 375 feet long bisected by a similar row at right angles to it. This antenna is roughly equivalent to a single paraboloidal antenna 375 feet in diameter. Other cross radio telescopes include the Soviet Union’s 0.62-mile (1-kilometer) cross consisting of two parabolic cylinders, while a similar instrument is also found in the University of Bologna in Italy.
Radio interferometer resolution further improved when British astronomer Sir Martin Ryle developed a more effective method called aperture synthesis. He discovered that if he periodically varied the distances between a number of small radio telescopes, they would yield the resolving power of a single mammoth-sized radio telescope. Aperture synthesis was developed over two decades starting in 1952. This technique revolutionized radio astronomy by allowing radio astronomers to achieve an accuracy and resolution rivaling that of optical science. Together with Antony Hewish, Ryle won the Nobel Prize in physics in 1974. The first ever given to astronomers since it began in 1901. In fact, the long time-exposure of Ryle’s telescopes allow “viewing” with a definition so sharp that in the words of the Nobel selection committee: “it corresponds to an observer on Earth being able to see details of a postage stamp on the Moon.”
Years later, aperture synthesis even influenced the development of the US Navy’s Synthetic Aperture RADAR technology that allows their ship and plane based radar systems to achieve the same capabilities to that of the Distant Early Warning (DEW) Line base in Thule, Greenland. Many pundits claim that Synthetic Aperture RADAR is the main technology that made Operation Desert Storm a success in 1991.
By: Ringo Bones
When the Rayleigh Criterion is taken into account, radio telescopes seem to “hear” rather than actually “see” the celestial objects of interest they are aimed at due to the much longer wavelengths of the radio spectrum in comparison to the optical / visible light part of the electromagnetic spectrum. This is the reason why RADAR or radio wave-based imagery of the universe has always been inferior in resolution terms in comparison to optical astronomy. The most obvious solution is to make ever-larger radio telescope dish antennas so that their resolution capabilities would equal that of optical telescopes, but that presents its own problems. Even the 1,000-foot diameter RADAR dish in Arecibo, Puerto Rico - in imaging terms - still cannot match the detail resolution of the human eye, and making ever bigger dishes presents its own problems.
Since radio astronomy began, astronomers had been constructing ever-larger dish antennas in an attempt to detect radio emissions from objects millions of light years away from Earth where the optical portion of the electromagnetic spectrum – i.e. visible light – cannot be picked up by optical telescopes. Radio astronomers knew, however, that to “see” into more distant objects would require the construction of antennas several miles wide. And it had taken awhile for radio astronomy to rival that of its optical sibling in resolution terms.
Ever since Albert A. Michelson used his interferometer in optical astronomy to bypass the inherent Rayleigh Criterion limitations of reflecting telescope with finite-sized mirrors, radio astronomers have adopted this technique in radio astronomy. The simplest kind of radio interferometer is based on the Michelson interferometer – which consists of two small reflectors. Radio waves arriving at an angle to the baseline of the reflectors reach each other slightly before the other, producing a multi-lobed antenna pattern similar to the fringe pattern in optical interferometers. The farther apart the reflectors, the narrower the width of the lobes – or beams – of the antenna’s radiation pattern, thus greatly increasing the radio telescope’s resolution.
A very example of this type of radio telescope is the California Institute of Technology twin-element interferometer, which consists of two 90-foot steel-mesh parabolic antennas. The antennas are mounted on special vehicles that move along special railroad tracks that can be separated by up to 1,600 feet in either east-west or north-south direction. With a beam-width or acceptance angle as narrow as 0.03 degrees, the telescope is used to record the 960-MHz radio noise in our Milky Way galaxy.
Another type of radio interferometer consists two linear arrays at right angles to each other that electronically compares the fan-shaped beams of the two arrays that result in a single pencil beam being produced that can accurately pinpoint radio sources. Developed in the early 1950s by the Australian radio astronomers W. N. Christiansen and B. Y. Mills. Each array may consist of many dipole antennas (Mills cross), parabolic antennas (Christiansen cross), or a parabolic cylinder.
The Mills cross near Sydney Australia was completed in 1952 and has legs 1,500 feet in length. Later upgraded to a version in 1957 with 3,500-foot legs, and a 1.6-kilometer version. The cross antenna at Stanford University consists of 16 steerable 10-foot parabolic reflectors in a row 375 feet long bisected by a similar row at right angles to it. This antenna is roughly equivalent to a single paraboloidal antenna 375 feet in diameter. Other cross radio telescopes include the Soviet Union’s 0.62-mile (1-kilometer) cross consisting of two parabolic cylinders, while a similar instrument is also found in the University of Bologna in Italy.
Radio interferometer resolution further improved when British astronomer Sir Martin Ryle developed a more effective method called aperture synthesis. He discovered that if he periodically varied the distances between a number of small radio telescopes, they would yield the resolving power of a single mammoth-sized radio telescope. Aperture synthesis was developed over two decades starting in 1952. This technique revolutionized radio astronomy by allowing radio astronomers to achieve an accuracy and resolution rivaling that of optical science. Together with Antony Hewish, Ryle won the Nobel Prize in physics in 1974. The first ever given to astronomers since it began in 1901. In fact, the long time-exposure of Ryle’s telescopes allow “viewing” with a definition so sharp that in the words of the Nobel selection committee: “it corresponds to an observer on Earth being able to see details of a postage stamp on the Moon.”
Years later, aperture synthesis even influenced the development of the US Navy’s Synthetic Aperture RADAR technology that allows their ship and plane based radar systems to achieve the same capabilities to that of the Distant Early Warning (DEW) Line base in Thule, Greenland. Many pundits claim that Synthetic Aperture RADAR is the main technology that made Operation Desert Storm a success in 1991.
Thursday, February 25, 2010
Those Other Moons of Jupiter
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.
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.
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.
Subscribe to:
Posts (Atom)
