[Aavso-photometry] Short-Exposure Photometry

[Dan Kaiser]

Arne wrote:

>I am surprised that your exposures are this short.  At 8th magnitude,
>the 1.0m saturates at about 0.5 seconds, which means you should be in
>the 5-6 second range at V for HD 209458.  

I base my thoughts on previous experience with OW Gem, at mag 8.2 V.  I
was saturating at 5-6 seconds and needed to defocus to reach 7 second V
exposures.  If the B filter will give 2-3 x that I will be happy.

>I don't think you need to worry about guide stars.  If the image wanders
>a bit on the CCD, that won't hurt, but guiding a 10-second exposure should
>not be necessary.

It has been my experience that my best photometry is when the stars stay
on the same pixels.  Thus my desire to guide.  However I may not have a
bright enough guide star in B, time will tell.  If not I will have to
deal with it.

>This is a good event for the USA.  It is difficult (total depth is 0.02mag),
>but if you can't do this one, you need to improve your techniques as all
>other potential eclipse systems are predicted to be even shallower. 

I'm sure Arne meant transit systems rather than eclipsing.

Dan