[Aavso-photometry] Scattered Light

[Michael Koppelman]

Lots of good advice, Gary. I'm not sure this one is necessary,  
though. You certainly want to go long enough to get rid of shutter  
effects, but for me those effects are gone by the time the exposures  
is over 3 seconds or so (which you can see here: http:// 
www.lolife.com/astronomy/lintest/lin5.jpg). I usually do flats that  
are 5s - 15s in length and then do separate darks for the flats.

The drawback with going long is just the time it takes, so if that is  
not an issue for you, that's great. For me, if I want 16 (or more)  
flat exposures, I don't want to be hanging around for an extra 30-60  
minutes at 5AM.

M.


On Jun 20, 2007, at 1:03 PM, bailyhill at aol.com wrote:

> 9.  Another tip--I used flats of the same exposure as the image-- 
> usually 120 seconds.  I adjust the light source to do this.  This  
> means that the same master dark can be used and there is no  
> scaling.  It also gets away from the Shutter Issues that Mike  
> talked about.  It might be that the flats in GRAS001 are very  
> short, and have some shutter exposure mixed with the signal.