[Aavso-photometry] odd observations of U CRT comp stars

[Michael Koppelman]

Did you have a V filter on? If not, that can cause what you see. If  
you did have a V filter, it could be:

1. A large color term in your CCD;
2. A bad sequence;
3. ?

M.


On May 22, 2007, at 10:01 AM, Yenal Ogmen wrote:

> Last night I observed U Crt. I took 5 images, each one
> is a stack of 10 frames of 10 seconds. When I tried to
> do photometry I see that there is something wrong.
> Brightness of the comparison stars 127 130 135 and 138
> of the chart d are different than what I see on my
> images. Fluxes of these stars show that 127 is fainter
> than 130 and 130 is fainter than 135. What am I doing wrong?