[Aavso-photometry] Re: tau Boo Observations

[rbissinger at aol.com]

Since tau Boo is so bright I decided to try using an f/5 106mm refractor last night to include SAO 100751 (MV = 5.798) in the field as a comp star, about 1-1/2 degrees from tau Boo.  With an ST-10XME I used 15 second exposures with a V filter.  High clouds definitely introduced significant scatter into the photometry but for those periods of clear sky I was able to attain around 0.006 mag precision using 5 exposure bins (75 seconds), 0.005 mag precision using 10 exposure bins (150 seconds).  (By "precision" I mean one sigma standard deviation in the time series; I did not transform the data nor account for differential extinction as yet).
 
I'm curious as to how this precision level might compare to swinging away from tau Boo and doing photometry on a star not in the same field as tau Boo over an entire evening?  Might be easier to do for these bright targets if one has access to a wide field refractor...Ron Bissinger, Pleasanton, CA USA