Make your own free website on
G11 Periodic Error Analysis
The G11 is a great mount for the money.  In general I have had good success with the ST4 autoguider but occasionally I would get apparent wild swings in the readings followed by a loss of the star.  I decided to determine what the error was in the tracking by using the CCDTRACK software from SBIG. 

I set up the software to track a star with the relays inactive.  After each exposure of 2 seconds the coordinate of the star was logged to a file.  This file was then loaded into excel and the following graphs made.




As can bee seen from the RA axis chart, there is a relatively smooth error with the mount showing about 18 arcsec peak to peak error over a period of 4 minutes.
The dec axis is more puzzling.  In particular there are two large spikes which do not seem to make sense.  In addition, when I was using CCDTRACK with the relays active, the ST4 lost the star and it was due to a large swing in the DEC value.
All images and contents are Copyright 2000 by Tom Blahovici. All rights reserved. The images and contents may not be reproduced, published, copied or transmitted in any form without written permission of the author.