Guiding Error Tests
The following are some tests I ran using my Atlas EQ/G mount to see if using the EQMOD new Periodic error correction while also using an autoguider would produce better results than using the autoguider alone.
The following were the
conditions of the test:
The same star was used for each test, as was the same settings for each camera. 31 Eta Ceti has a declination of -10 degrees 8 minutes. For the first two test the mount was almost perfectly balanced. For the third test the mount was made significantly heavier on the counterweight side while tracking in the Eastern sky. There was no wind and the sky conditions and seeing were fair with some haziness.
Test 1: EQMOD PEC +
Test 2: Autoguider
Test 3: Autoguider
only + Mount off balance
PEC + guiding and guiding alone seem to have about the same amount of error with almost 3 arc seconds plus or minus and an average error of almost 1 arc second. Shifting the weight on the mount so that it is not balanced, but lifting against gravity improves tracking performance by a factor of 3! This I found surprising and in the future in the field I will always adjust the balance accordingly.
Based on these three tests it is more important to have the mount out of balance than to have PEC while autoguiding. Further testing would be required to see if exposures over 1 second of the autoguider would be better with PEC than without. With a longer time between autoguider corrections PEC may become more significant in improving tracking accuracy. For autoguider exposures 0.2 seconds PEC provides no advantage at all over autoguiding alone.