|
Adventures With Your CCD by Robert Sandness I used to believe that asteroids were pretty boring objects in well defined orbits. Over the past year I have learned that asteroids are both interesting and an area where amateur observers can really contribute. After reading Dennis di Cicco article on asteroid hunting (CCD astronomy Spring 1996), I decided to try my luck. First I obtained a copy of the shareware program Astrometrica by Herbert Raab (http://mars.planet.co.at/lag/astrometric a/astrometrica.html). This program in conjunction with the Hubble Guide Star catalog allows you to measure the position of any object to better than 0.5". Even though my CCD camera pixels cover about 2' by 2.3' I can regularly obtain sub arc second measurements by using 3 to 10 Hubble guide stars . Next I imaged some bright, well known asteroids using my C14 / ST6 combination. By taking 100 second exposures 20-30 minutes apart and using the Astrometrica blink function, the motion of a asteroid is obvious. After using Astrometrica to calculate the asteroid's RA & Dec coordinates in these images, I sent the results off via Email to Brian Marsden who runs the Minor Planet Center as part of the Smithsonian Astrophysical observatory. ( http://cfa- www.harvard.edu/cfa/ps/info/Astrometry.html)
Within hours of my transmission Brian informed me that my measurements were of acceptable accuracy and assigned my observatory code number 763. This now enabled me to send in both asteroid and comet measurements on a regular basis and have them semi-automatically added to the overall database. Over the next month I sent in several measurements of fainter asteroids. Then it happened -- I found something that wasn't on the charts (Guide 4.0) and had the motion of a main belt asteroid. Unfortunately, to confirm a new 'discovery' you must image the object on 2 or more different nights. Clouds and business travel prevented this so my first find got away. In late August I found another new object on several nights which has been designated 1996 QQ1. Further observations of this 17th magnitude object allowed Brian Marsden to link my find with 2 nights of observations made in 1991 by observatory 590 -- better known as Mt. Palomar!. This was great news since it allowed Brian to develop a very solid orbit for this object . With further observations over the next few months this object could join the ranks of the numbered asteroids. Last October we had 3 nights of very clear, dark and transparent skies. Each night I was able to find an uncharted asteroid -- 1996 TM3, 1996 TN3, and 1996 TS6. I am now in the process of following each of these objects (18th to 20th magnitude) to further refine their orbits. It is also a thrill when your observations are cited in the official IAU/ MPEC circulars which announce new discoveries and associated observations. After I submitted observations on P/1996 N2 -- the asteroid that has a tail like a comet, I was surprised to see observatory 763 cited along with the 1.2 metre Siding Spring Observatory and DAO in Victoria. Currently there is an added incentive to observe asteroids. In June the Benson award was created to encourage searching for Near Earth Asteroids. Ten awards of $500 will be made. The first award went to friend of mine in Tucson. Roy Tucker found 1997MW1 after only 83 exposures. Nine prizes remain to be won. (For more details see http://www.skypub.com). Many NYAA members can participate in these activities. You need a telescope (8" or larger) and some sort of CCD system that can reach 15-18 magnitude with a 100-200 second exposure. A 386 or better computer is required to run one of a number of astrometric software programs. If anyone is interested in getting started, I'd be glad to help. When you want a change from taking pretty pictures, try asteroid hunting -- it's an adventure! |
Asteroid 3761 in motion. Images by Bob Sandness.