[Geoff45 (Geoff)]

Originally Posted by White Rabbit

Thanks Merlin.

Am I correct in assuming then that you would not need to guide better than 3 arcseconds? If you are guiding better than 3 you would just be chasing atmospheric refraction.

Thanks

To avoid chasing the seeing, take longer guide exposures--6 to 10 seconds. This averages out the seeing variation and gives a better idea of the true guide error.
Geoff