By Robert Bunge
Standing at a bus stop in Norfolk, Virginia, I was waiting to catch a bus from a mall back to the aircraft carrier I lived on. My Navy buddies and I had taken in a movie and some fast food - our escape from Navy chow for the evening. Outside, it was cold and my buddies were all huddled, out of the wind, in the bus shelter behind me.
I had stepped out of the shelter. Peering through the glare of a hundred mall parking lot lights, I looked at Orion. My target was Betelgeuse, the bright red star that forms Orion's left shoulder. Because I was in downtown Norfolk, I could perhaps, see a dozen stars across the entire sky.
Not exactly the conditions you might expect to be able to do some astronomy, let alone make a scientific astronomical observation! Yet, that is exactly was I was about to do.
Not too many amateurs know this, but Betelgeuse is a variable star. It changes in brightness over time. In Betel's case, it is over the course of 2070 days (5.5 years), where it ranges from 0.4 to 1.3 in magnitude.
I looked for the comparison stars I needed: Procyon, Castor, Pollux,
Rigel, Capella, and Aldebaran. I glanced quickly between Betel and
each of the other stars, one at a time, having committed the magnitudes
of these stars to memory. Ok, Betel was dimmer than Procyon (0.5
mag.). It was brighter than Pollux. Bt also brighter than Aldebaran
(1.1 mag). Betel seemed a little closer to Aldebaran, so after comparing
them for a couple of minutes, I decided Betel was at about 0.9 mag.
After I got back the ship, I'd record this in my logbook. At the end of the month, I'd fill out my monthly report and mail it to the headquarters of the American Association of Variable Star Observers (AAVSO).
A few nights later, my budget had been busted, so I was stuck on the ship for the evening. Come 10 p.m., I grabbed my observing kit and climbed to a walk way near the top of the ship, more than 10 stories above the pier the ship was tied up to. This walkway was shielded from lights on the ship and faced south. It had a commanding view of the Norfolk Naval Operating Base. Across the pier was another carrier. Again, only a few stars were visible in the sky because of the light pollution.
But this time, I pulled a pair of 10x50 binoculars from my observing
kit. I found the three belt stars of Orion in the bincs, and star
hopped down to see the faint glow of M-42, the great Orion Nebula.
I hopped back up to the belt stars. Using an AAVSO chart, I started
star hopping about five degrees west to the location of W Orionis, a long
period Mira-type variable star that ranges from 5.9-7.7 mag. over the
course of 200 days. Glancing from the bincs to the chart, I decided W was at 6.6 mag. tonight. Yet another entry in my logbook and yet another line in my report to AAVSO HQ.
These are two of several hundred variable star observations I made over the course of several years. Many of these observations were made with binoculars. Many were made with 4 and 6-inch short focus Newtonian reflectors. A number were made with the naked eye. Many were made from light polluted skies, many were made from dark as dark-can-be locations while the ship was at sea.
Variable star observing is a great way to observe, especially if you
are observing alone. It can be done from just about anywhere, using
just about any type of equipment, from the naked eye, to binoculars to
high-tech telescopes, computers and CCD cameras. All types are useful and have their place. And you contribute to science. Professional astronomers from around the world depend on AAVSO members to monitor and make long-term observations they can't make because of time, limited telescope time and budget constraints.
When variable stars suddenly outburst, or do something odd, AAVSO learns about it via their worldwide network of observers. AASVO then sends out alerts via email. Sometimes, professionals have turned the world's most powerful telescopes and spacecraft to a variable within hours of an amateur noticing the outburst.
NOVAC member Steve Robinson is a variable star observer that has taken the high tech-route. Steve learned about AAVSO and variables about four years ago and started collecting equipment required to use a CCD camera to electronically collect data. Using an 18-inch telescope, a CCD camera and a collection of computers, he mostly follows stars that are fainter than 14th mag. and had gone deeper than 18th magnitude.
And he does this all from his light polluted Rockville, Maryland driveway... he just rolls his equipment out from the garage and is up and running in a few minutes. Steve likes the CCD approach because he likes playing with the technology and the challenge of making good, consistent observations. He especially likes that a CCD is more accurate then our old Mk1 human eyeball/brain combination.
While the AAVSO likes CCD observations, they never turn away quality
observations no matter who made them. AAVSO was founded in 1911 through
a joining of amateur astronomers and Harvard Observatory Director Edward
Pickering who had been working together for years, but decided to more
formalize the process in order to encourage others to contribute. Housed for years at Harvard, in the 1980's, AAVSO moved into its own quarters. Under the leadership of Executive Director Janet Mattei it has slowly transformed into a modern information technology organization.
When I made the two observations noted above in 1982, it was an entirely
paper process. As a member, I sent in monthly reports. If I
had a question, I wrote a letter to Janet. If I wanted a star chart,
a letter (and included some money to cover costs). Once a year, I'd get a calendar and a copy of the "Journal of the AAVSO," a collection of papers written by members. Buried in the back where reports of
observations, broken down by state, country and observer. It was fun to see my name in print and to see how I stacked up against some big-time observers.
Today AAVSO has taken full advantage of the information age. Their very fine website (http://www.aavso.org) allows users to search a database of their charts (they have them for more than 3000 stars) and download them for local printing. You can also search a database of variable stars and real-time plot "light curves" - a plot of the star's magnitude against time - for specific stars. In 2000, 400,000 observations were submitted to AAVSO, putting the total number of observations since 1911 over 10 million. All of these observations - both paper and electronic have been entered into digital databases and are available via the AAVSO website.
When you plot a light curve on the website, you see a list of other observers who have contributed to the data. You can even plot the light curve with your own observations in plotted in a different color.
Finally, you can submit your observations electronically. When I made some recent observations of variables in Pegasus, I went the AAVSO website and was able to enter them with a few clicks. Setting up my account only took a few minutes (I had to wait one day for the account to be finalized) and was free. You can also use a computer program to enter your observations that creates a data file that you can upload to AAVSO. This allows you to upload many observations very quickly.
Indiana amateur Dan Kaiser is the President of the AAVSO. Dan says, "I personally observe eclipsing binaries, mostly. Using a CCD I am able to observe from my backyard which is moderately light polluted." Eclipsing binaries are very close double stars that past in front of one another during their orbit. Thus, from Earth, we see a change in brightness as one component moves in front of the other.
Dan points out that many professional astronomers rely on AAVSO for important data, including when to best schedule time for large observatory telescopes and spacecraft. "The director's report from 2000 lists 431 requests from astronomers, observers, educators, and students. These included data support for observations with ground-based telescopes (such as KPNO, VLBA, INT, SAAO) and satellites (FUSE, Chandra, Hubble Space Telescope, XMM, RXTE, ISO, GP-B, ASCA)," says Dan.
You don't have to be a member of AAVSO to contribute observations, but it is encouraged. Dues range from $15 to $100 depending on your age (under 20 years of age is cheaper) and how much you want to support the organization. Member dues, endowments, and grants, support AAVSO.
If you are a NOVAC member who can't - or can - get away to visit NOVAC's observing sites, are interested in contributing to science, don't have a lot of equipment (or do have a lot!), variable star observing might just be the ticket for you.
http://www.aavso.org - the website
of the American Association of
Variable Star Observers;
- AAVSO President Dan
Kaiser's website: see Dan's home observatory, light curves and a movie
of an eclipsing binary star;
- Steve Robinson's homepage.
Information on his projects, and CCD images he has taken.