For asteroid occultations of relatively short duration, the event can be timed by allowing the star to trail in RA across the CCD. I have written a small application to aid with the planning of such observations and it had its first trial on the recent occultation of SAO 60107 by 516 Amherstia. This method has some limitations in magnitude limit and timing accuracy and resolution but is relatively simple, especially with a planning tool such as AsterOcc.
Since our system allows the telescope and CCD camera to be controlled by a VB application, I plan to extend this app to actually carry out the observation. The initial (RA drift) sequence will be:
Our telescope has variable rate drive in both RA and DEC and a more sofisticated routine would involve tracking at some varied rate rather than simply turning the RA drive off.
Here is my first attempt at an ADSO observation: It is the occultation of SAO 60107 by Amherstia (516) on January 14, 2002. It was taken through clouds that made the star invisible in a 35 second image taken just 15 minutes before the event.
The drift begins on the left. The preliminary reduction from my measured positions of the starting point, disappearance, reappearance, and end give a total length of the trail of 34.2 seconds (the exposure was 35 seconds), and a duration of the event of 5.4 seconds. The midpoint of the event was 00:19:02.5 UT. The starting point is a bit ambiguous due to clouds and more analysis is needed. This should not effect the observed duration.
Rosemary Hill Observatory, Bronson, Florida, U.S.A.
+82 35 13W, +29 24 03N
46 cm. f/10.7 telescope, ST-8E CCD
John P. Oliver
Details of this event can be found at http://lunar-occultations.com/iota/asteroids/0114amherstia.gif and http://www.oz.net/~stevepr/Asteroids/2002_01/0114_516.htm
IOTA (International Occultation Timing Association)
Steve Preston's Very Useful pages
May 1, 2002 10:37
