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Help with strange data of a delta scuti star

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Help with strange data of a delta scuti star

Good afternoon,

I collected some data using a small refractor o YZ Boo (a delta scuti star). As you can see (below) the first part of the curve doesn't look right and I'm wondering why. 

I've tried different reference stars and I even tried to put a simulated gaussian star and I always get a scattered first hour. Looking at the images individually doesn't show anything special (no clouds or obvious noise in the background).  

I think I've narrowed it down to a CCD problem, some sort of noise that is non-uniform.  Two nearby stars magnitude difference will vary by ~0.2 and are uncorrelated. 

One more thing to note, I used 2x2 binning and the seeing was so good that stars sometimes fell within a single pixel.  Have you seen this problem before?  Is there a way to recover some of the bad data?

Thank you!

Etienne Rollin


AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484