The work of today’s amateur astronomers goes far beyond peering through a telescope on a lonely mountaintop. Thanks to advances in solid-state imaging, software and inexpensive optics, they are collecting professional-quality data and making their own discoveries.
Jeff Hopkins, a retired electrical engineer, studies the brightness of variable stars from his own observatory near Phoenix, Ariz., U.S.A. He is organizing an observing campaign to study an unusual binary star over the next two years.
(See box at end of article.)
Tom Kaye is building an observatory dedicated to the search for planets outside our solar system. His team has finished grinding a 1.1-m mirror blank for the observatory’s telescope and is preparing to construct the building that will house the large instrument and its electronic camera equipment.
However, this is not the project of a large university or research organization. Kaye, who lives under the dark skies of southeastern Arizona, is an ex-entrepreneur who sold off two companies to pursue his scientific interests. He’s one of a growing number of amateur astronomers who collect data for, and collaborate with, professional astronomers.
Traditionally, professional-amateur collaboration has consisted of comet searches and meteor counting. Increasingly, however, stargazers collect their data with robotic telescopes that may be in their backyard or halfway around the world. “Most of the people I work with don’t have an eyepiece on their telescopes,” Kaye said.
One of the driving forces behind this shift is the wider commercial availability of large telescopes, CCD cameras, photometry software, robotic devices and spectrographs. The average amateur today can make observations that not all professionals could make a few decades ago, said Arne Henden, a professional astronomer who heads a group of 1,200 mostly amateur sky watchers, the American Association of Variable Star Observers (AAVSO).
According to Henden, four trends have changed the face of amateur astronomy over the past two decades. The first is the “GOTO mount,” a time-saving automated telescope mount that comes with software that can point the telescope to any desired sky object. The second is the widespread availability of high-quality optics, often manufactured outside the United States, which have made it easier for people to afford large apertures. “Very few people could afford 12-inch telescopes back in the 1970s,” he said.
Third, off-the-shelf CCD cameras have been available to the amateur market for at least a decade, leading to higher-precision photometry. Finally, companies, research organizations and talented individuals have made software packages for data analysis, photometry and spectrometry available at very low cost or even no cost.
History of amateur astronomy
Before the 19th century, astronomy didn’t draw a hard-and-fast line between “amateur” and “professional.” In the 19th century, rich Americans endowed several observatories (such as Yerkes in Illinois, Chamberlin in Colorado and Griffith in California), and a few of them got interested in looking through the telescopes themselves. For example, Percival Lowell (1855-1916), a descendant of wealthy Massachusetts industrialists, built his own observatory in Flagstaff, Ariz., in order to search for the purported “canals of Mars.”
During Lowell’s time, and increasingly afterward, astronomy, like other scientific disciplines, became more professionalized. Clyde W. Tombaugh, who discovered Pluto in 1930, had a career in astronomy without getting a Ph.D. However, as astronomical equipment became more costly and sophisticated, doctoral work became increasingly important for anyone who wanted to make a full-time living in astrophysical research.
By the early 20th century, amateur stargazers had few optical tools available, unless they wished to make their own—an option that some ambitious amateurs embraced. For example, an explorer and engineer named Russell W. Porter spearheaded the 20th-century amateur telescope-making movement. Shortly after World War I, he started a class in his home town of Springfield, Vt., and it became a club known as the Springfield Telescope Makers. A description of the group’s activities in Scientific American garnered so much public interest that the magazine came out with a regular “Back Yard Astronomer” column.
Companies started making commercially available amateur telescopes in the 1950s. Even then, many amateurs preferred to make their own telescopes because it was a lot less expensive. However, two developments stimulated the amateur market for larger-aperture reflectors.
First came the advent of Schmidt-Cassegrain telescopes for astrophotography. The compact Schmidt-Cassegrain design combines two spherical mirrors (a primary concave mirror and a secondary convex mirror) with an aspheric corrector plate, located at or close to the secondary mirror, to correct spherical aberration. Figuring the corrector plate by hand is tricky, but 40 years ago the discovery of a new automated figuring technique jump-started the high-volume production of Schmidt-Cassegrains.
At the same time, the rise of the Dobsonian telescope gave amateurs a chance to view fainter objects than ever before. In the late 1960s, John Dobson and a group calling itself the San Francisco Sidewalk Astronomers put a plain Newtonian telescope on a simple alt-azimuth mount and popularized it as a means of bringing astronomy to the masses. Though unsuitable for long-exposure astrophotography because of its lack of tracking availability, it provided a stable, inexpensive platform with good support for a large mirror.
The developments sparked “aperture fever” in the 1980s and 1990s, said amateur astronomer Steve Beckwith of Bolton, Mass. Amateurs started to build monster-sized Dobsonians with apertures of 12 to 16 inches, and manufacturers have responded with inexpensive “Dobs” of all sizes, plus Schmidt-Cassegrains and other compact reflectors.
Amateurs and data collecting
John Gross, a truck mechanic and heavy-equipment dealer in Tucson, Ariz., owns and maintains the Sonoita Research Observatory about 50 miles southwest of that city. The observatory’s telescope is automated, so it watches the skies remotely while Gross sleeps and allows him to analyze the data on his own schedule.
Gross admits to a childhood fascination with the stars and planets, dating back from the Apollo 11 lunar landing. He progressed to bigger and bigger scopes in his early adulthood. Then he discovered computers, GOTO automation and CCD imaging, in that order. Now he collaborates with Czech astronomer Petr Pravec on obtaining light curves of binary asteroids, and he makes one-third of the available time on his robotic observatory available to the AAVSO, which has resulted in several articles in professional journals.
“The automation interests me, and I like working with the equipment and making it work,” Gross said. For his primary telescope, he uses a 14-inch Schmidt-Cassegrain telescope on an automated mount with a CCD camera, interchangeable filters in standard astronomical bandpasses and an automatic focuser. The scheduling software has a safe mode in case of power outages, and a cloud sensor even recognizes when the sky is too overcast for observing and closes the observatory’s dome slit accordingly.
Gross collaborates with Walt Cooney, an amateur from Baton Rouge, La.; Dirk Terrell, an astrophysicist at the Southwest Research Institute in Boulder, Colo.; and Henden.
A team operating out of an amateur-owned observatory can follow the same star every night for years. Cooney has been following one particular star, called Z Ursa Minor, which exhibits a rare and peculiar type of variability. Sonoita has collected several years of data on it from almost every clear night.
Kaye’s automated observatory in southeastern Arizona features a robotic arm that opens and closes the dome slit as needed for observing. It saw “first light” in January.
That’s a perfect example of the kind of projects that amateurs can do for professionals, Gross said. With a large telescope at a professional site, time is limited for each observer, and smaller scopes (under 1 m in aperture) have been closed down over the years at the major observatories. However, there are many bright stars within the reach of amateur scopes that the professionals don’t have time to study.
Searching for extrasolar planets
Kaye said he got interested in astronomy fairly late in life. When he heard about the comet that crashed into Jupiter in 1994, he purchased his first telescope and attached it to a CCD camera, which was then new to the market. However, since he lived in Chicago—seven miles north of one of the world’s busiest airports—his ability to take interesting sky photographs was severely limited.
Inspired by a documentary about redshifts and the expanding universe, Kaye studied up on spectroscopy and fiber optics and eventually built his own fiber-fed spectrograph to use under the light-polluted skies of Chicago. The telescope needs to be at the same ambient temperature as the outside air, while the spectrograph requires absolute thermal stability for high precision. The only way you get that is through separating the spectrograph from the telescope enclosure and feeding the starlight to the spectrograph through fiber optics.
In a few months, Kaye taught himself how to measure the difference in velocity between two stars. He and his group eventually achieved a level of precision that allowed them to confirm the companion planet circling Tau Bootis, a relatively bright star some 15.6 parsecs from Earth.
In 1997, a professional team, led by the veteran planet-hunters R. Paul Butler (Carnegie Institution of Washington) and Geoff Marcy (University of California at Berkeley), discovered the Tau Bootis companion. However, in 2000, Kaye’s group proved that amateurs could detect the slight wobbles of a star as its orbiting planet tugged at it.
A 16-inch Schmidt-Cassegrain telescope is hoisted into its permanent home.
Kaye’s 16-inch Meade LX200 is the workhorse that he and his collaborators used to detect the Tau Bootis planet. Recently, Kaye set up the LX200 in its own “bubble dome” made inexpensively from a 500-gallon polyethylene water tank. Once he finishes setting up the robotic software, the telescope will run unattended all night long, looking for transits of stars that might have extrasolar planets.
To improve the precision of their radial velocity measurements, Marcy and Butler put an iodine-vapor cell in the light path of their spectrograph. Kaye is using a competing twin-fiber system developed by another planet-hunter, Michel Mayor of the University of Geneva, Switzerland. One fiber delivers light from a thorium-argon lamp to the spectrograph, and the other transfers starlight from the telescope.
Cindy and Jerry Foote are two other amateur astronomers who have contributed to extrasolar planet-hunting. Long interested in astronomy, Jerry Foote got involved more than a decade ago with the Center for Backyard Astrophysics (CBA), a group based out of Columbia University. At the time, CBA was looking for people to compile light curves of variable stars, which Jerry—a medical-device physicist by training—started taking.
Along the way Jerry dragged Cindy to many amateur-astronomy meetings, and one on the conferences, devoted to the search for extrasolar planets, piqued her interest. The Footes secured a 14-inch telescope at that 2006 meeting, and Cindy practiced taking light curves of transiting exoplanet candidates until she was able to get a good-quality data set. She has since been working with an international planet-hunting team called the XO Project, headed by Peter McCullough of the Space Telescope Science Institute.
The Footes work every clear night, and Cindy has taken more than 87,000 images over 1,200 hours of observing time and contributed to five Astrophysical Journal articles.
The couple lives in Kanab, Utah, where they now use home-built, equatorial-mounted 24- and 16-inch automated telescopes with fast f/3 focal ratios, equipped with CCD cameras and standard filters. Jerry has developed a home business designing custom telescope mounts and refurbishing old telescopes.
“We’re doing professional work, there’s no doubt about it,” Jerry Foote said. “There’s another really interesting distinction—owning our own telescopes, we can devote as much time to it as we want. If you’re a professional, you might get one week at Kitt Peak.”
So you want to be an amateur astronomer…
Like real estate, astronomy is about “location, location, location.” It’s no secret that the skies around most major cities are murky with light pollution. In the United States, many high-end amateur astronomers have relocated to rural western areas far from city lights, often with the added benefits of low humidity and high altitude.
However, amateurs who reside in populated areas can still make valuable contributions to science. For example, the AAVSO collects tens of thousands of visual observations per year from amateurs who do the best they can given their equipment and sky conditions. Beckwith, president of the Amateur Telescope Makers of Boston, knows one New England amateur who monitors 10 stars every clear night; he makes visual estimates of things he can see with his Dobsonian. People using CCD cameras can “go deeper” and get better accuracy thanks to software.
Most serious amateur astronomers either own their own backyard telescopes or are active in an amateur club with its own observatory, said Paula Szkody, a University of Washington scientist who compares AAVSO members’ measurements of cataclysmic variable stars with data she gets from the Hubble Space Telescope. “Some amateurs are just into the [telescope] building part,” Szkody said. “Some build because they like pictures of nebulae and galaxies, but AAVSO members are those who really want to contribute to the science.”
The state of the art…and what it costs
When using a CCD camera, the telescope’s drive has to track the sky object precisely. For a visual observation, it doesn’t matter if the star drifts across the telescope’s field of view.
Many amateurs use a Dobsonian telescope with an alt-azimuth manual mount, which is very inexpensive for the telescope size, Henden said. Many companies sell such scopes with 6- to 12-inch apertures for $300 to $1,200. They are entirely suitable for visual observations, but unsuited to CCD imaging, because the Earth’s rotation causes blur in exposures of more than a few seconds. Astrophotographers have traditionally used motor-driven equatorial mounts, but the computer-controlled alt-azimuth mounts developed for giant professional telescopes have been making their way down to the GOTO-equipped portable instruments.
Single-channel solid-state photometers have been around for couple of decades, and they yield a precise measurement without the need for flat-fielding or image processing. “If you’re interested in bright stars, these are excellent tools,” Henden said.
Artist’s interpretation of Epsilon Aurigae. (See box at end of article for additional information.)
Over the past few years, amateurs have been able to get their hands on near-infrared single-channel photometers that image in the J and H bands (1 to 1.6 µm) with an InGaAs detector designed for the communications industry. With such equipment, amateurs can study bright objects that would saturate the faint-object detectors on professional-class telescopes. And since they own the observatory and don’t have to deal with oversubscription and the telescope allocation committee, they can spend as much time collecting data as they would like.
GOTO systems have made observing more convenient for both casual and advanced observers. If you wanted to look at the Ring Nebula before the advent of GOTO systems, for example, you would have to bring out your sky charts, figure out approximately where to aim the telescope’s narrow field of view, and then work your way over to it in an iterative process known as “star-hopping.” If you are revisiting that field every night, you get accustomed to it; however, the first time you go there, you might spend 10 or 15 minutes tracking down the faint planetary nebula.
On the other hand, the GOTO device will automatically point the telescope within 1 arcminute of the desired object. The system even makes polar-alignment easier by honing in on a known reference star.
Doing CCD work requires an accurate telescope drive, and CCD cameras have small fields of view, so a GOTO system is almost essential. However, GOTOs are no longer pricey because of the mature microcontroller market, Henden said. Some GOTO mounts use Global Positioning System technology, so that the end user doesn’t even have to input the latitude, longitude, time and date.
Henden believes the quality of commercial amateur-telescope optics has improved over the past 20 or 30 years. With the mass-production techniques of today’s large telescope makers, the difference between one mirror and the next from the same company is small. Even for super-cheap telescopes marketed to absolute beginners, the mirrors are of decent quality; the eyepieces are usually the problem part of the instrument. “In general, you get what you pay for,” Henden said.
According to Henden, spectroscopy is an up-and-coming field for amateurs. With a device that retails for about $3,000, they can study bright objects that were observed back in the 1950s and haven’t been touched since. Amateurs can do long-term monitoring and see changes over periods of decades or longer that would be missed by professionals.
The world of amateur astronomy isn’t cheap, although serious amateurs can get by with something less than the budget of a professional astronomy department.
A single-channel optical photometer runs about $1,500, and a near-infrared version is about $2,500. The CCD camera can cost anywhere from a few hundred dollars to more than $10,000, depending on the size of sensor, the number of pixels and other technological details. A telescope of the 10- to 12-inch class can cost $2,000 to $4,000, and software costs from zero to a few hundred dollars.
The budget-minded observer, however, could get a small CCD camera from one of the major telescope manufacturers, attach it to a commercial digital camera lens and measure stellar brightnesses for less than $1,000.
High-end amateurs spend about as much money on an observatory as they would on a car, Henden said. In that respect, astronomy isn’t that much different from other expensive hobbies, such as sailing or scuba diving.
Blurring the lines between amateur and professional
The typical advanced amateur astronomer is between 40 and 60 years old, and is more likely to be male than female, Henden said. Typically these stargazers were passionate about astronomy in their youth, but then family life and careers got in the way. Once the children were grown up and out the door, they got back into their old hobby.
“For every professional astronomer, there are at least 10 amateurs,” said Anthony Moffat of the University of Montreal, Canada. “They’re clearly our friends.”
Szkody said she enjoys working with amateurs. “Sometimes professionals lose sight of the fun of looking through a telescope,” she said. “The amateurs haven’t lost that sense.” And, since they’ve spent a lot of their own time and money on their pursuit, they tend to feel more personally invested in it. Moreover, amateurs can often be available on a moment’s notice to observe a swiftly unfolding phenomenon—without having to apply for peer review or funding first.
The line between amateur and professional astronomers is certainly blurring. In some cases, the amateurs know more about their equipment and the sky than the professionals do, whereas the professional scientists know the theory and do the modeling. “The two together are very synergistic,” Henden said.
Patricia Daukantas is the senior writer/editor of Optics & Photonics News.
Leading an International Campaign
This year has been dubbed the International Year of Astronomy (www.astronomy2009.org), and, coincidentally, 2009 offers unprecedented opportunities for amateur and professional sky watchers to collaborate. One amateur from Phoenix is looking for help to study a rare stellar event.
Epsilon Aurigae, a mysterious binary-star system, goes through a two-year eclipse every 27.1 years, most recently in 1982-84. The next eclipse begins this summer. Veteran variable-star observer Jeff Hopkins has co-written a book with University of Denver astrophysicist Robert Stencel to explain what scientists still don’t know about the long-period system (www.hposoft.com/EAur09/Book.html).
Since the early 1980s, Hopkins, a retired computer engineer, has been doing photoelectric photometry with his home-built photon counter attached to his Celestron 8-inch telescope. He reports standard deviations approaching 0.001 magnitudes with this system. A few years ago, he acquired a 12-inch Meade LX200GPS telescope and, last year, a Lhires III spectrometer with a 2,400-lines/mm grating. He’s been taking high-resolution spectra of Epsilon Aurigae since August and hopes to present his findings at the next meeting of the Society for Astronomical Sciences.
Stencel got to know Hopkins in the early 1980s through their shared interest in the unusual binary star. At the time, he said, Hopkins was able to take advantage of the first generation of single-channel photometers. He then branched out to CCD photometry of several notable variable stars.
Epsilon Aurigae, a relatively bright third-magnitude star system, will begin dimming in August, remain dim through 2010, and climb out of its eclipse in the spring of 2011. The disk that may surround one of the stars, which astrophysicists think is causing the eclipse, exhibits some peculiar behavior that scientists don’t fully understand, according to Stencel.
You don’t have to wait until August to start studying Epsilon Aurigae—Hopkins and Stencel welcome out-of-eclipse observations to catch any unusual behavior. The pair welcomes both naked-eye observations and electronic photometry. To learn how to join the campaign, visit www.hposoft.com/Campaign09.html.
References and Resources
Some of the largest organizations for amateur astronomy (and for collaboration with professional scientists):
>> American Association of Variable Star Observers
>> American Meteor Society
>> Association of Lunar and Planetary Observers
>> Astronomical League
>> Astronomical Society of the Pacific
>> British Astronomical Association
>> Center for Backyard Astrophysics
>> International Dark-Sky Association
>> International Occultation Timing Association
>> The International Year of Astronomy
>> Royal Astronomical Society of Canada
>> Society for Astronomical Sciences
(Note: The observatories listed here are not open to the public unless specifically mentioned on their Web sites.)
Observatories of the amateur astronomers mentioned in the OPN article:
>> Hopkins Phoenix Observatory (Jeff Hopkins)
>> Sonoita Observatories (John Gross)
>> Spectrashift Extrasolar Planet Search Project (Tom Kaye)
>> Vermillion Cliffs Observatory, click on "Observatory" or "Current Observation" (Cindy and Jerry Foote)
>> Blackberry Observatory (Walt Cooney)
>> Amateur Telescope Makers of Boston (Steve Beckwith, 2009 club president)
Web sites of some other prominent amateur astronomers:
>> Tonny Vanmunster, CBA Belgium Observatory
>> Christian Buil, France: http://www.astrosurf.com/buil/index.htm
>> Sebastián Otero, Argentina: http://ar.geocities.com/varsao/
>> Jennie McCormick, Farm Cove Observatory, New Zealand
>> Antonio Garrigós—Sánchez, Spain: http://www.astrogea.org/agarrigos/index.html
>> Nyrölä Observatory, Finland
>> David H. Levy, Arizona, U.S.A.: http://www.jarnac.org/
>> Brian D. Warner, Colorado, U.S.A.: http://www.minorplanetobserver.com/PDO/PDOHome.htm
Some organizations that make it possible for amateurs to operate telescopes in remote locations around the world:
>> Global Rent-a-Scope
>> RAS Observatory
>> Rockbottom Observatory's robotic telescope
>> Share Your Sky
>> SLOOH LLC
>> AstroGea, a group based in Barcelona (Spain) that links amateurs with professional astronomy projects throughout Europe
"Star parties" are gatherings of amateur astronomers who set up their telescopes together to observe the night sky. Most parties welcome stargazers of all skill levels, from complete beginners to advanced amateurs. Some may charge admission fees or require reservations. Here are a few of the largest such gatherings:
>> Stellafane, Vermont, U.S.A.
>> Texas Star Party, Texas, U.S.A.
>> Winter Star Party, Florida, U.S.A.
>> Astrofest, Illinois, U.S.A.
>> Grand Canyon Star Party, Arizona, U.S.A.
>> Starfest, Ontario, Canada
>> Equinox Sky Camp, United Kingdom
>> Kielder Forest Star Camp, United Kingdom
>> Swiss Star Party, Switzerland
>> South Pacific Star Party, New South Wales, Australia
>> Queensland Astrofest, Queensland, Australia
>> Southern Skies Star Party, Bolivia
Other links of interest to amateur astronomers:
>> The International Dark-Sky Association fights light pollution worldwide.
>> The magazines Sky & Telescope and Astronomy provide links to astronomy clubs, events, space news and more.
>> Exoplanet Observing for Amateurs by Bruce L. Gary is a downloadable PDF book.
>> The spectroscopy section of the Amateur Astronomy Association (Germany) is running an observing campaign for a colliding-wind binary star called Wolf-Rayet 140.
>> The Minor Planet Bulletin provides invaluable information for observers of asteroids. Brian D. Warner also has posted a guide to minor planet photometry.