Stuck

nice2bme · Joined: 11 Apr 2006 Posts: 3

Hi,

I'm using IRAF to calibrate images taken on Nov 12, 2005. These images were taken using a 24" Telescope and for the scope we have to have an action called as 'peer-flip'.

Pre-flip the data I have is highly tilted from top left to bottom right, theres are 22 % tilt. After removing the Normalized Flat, and the bias from the object images, I am surprisingly enough worsening the effect. The tilt is increasing to 33%.

Post - flip the tilt is overcompensated. I have no clue why this is happening, and was wondering whether anyone knew what could possibly be done to remove the tilt. The Normalized Flat doesnt show this tilt, though the bias does, but theres an order of magnitude difference in the tilt...

Also I was wondering whether imstat can be used to get the value at a point?

I can provide more details if necessary.

fitz · Posted: Tue Apr 11, 2006 4:30 am Post subject:

Please post more about how you're trying to do the corrections, i.e. is it just CCDPROC (what are the params?) or are you doing something like calling imarith/imexpr directly?

> Also I was wondering whether imstat can be used to get the value at a point?

You could use image sections, e.g.

cl> imstat dev$pix[128,256]

will operate only on pixel (128,256). The statistics of one point are kinda silly, note you can use LISTPIXEL on the same section if all you want is the pixel value.
Trying to use this trick in a script to operate on entire images is also kinda silly, don't bother.

-Mike