This is a temporary page set up to display sample flat field images.

These flats were taken on 17-Oct-06 using the following equipment:

• ST-10XME and CFW-10.
• William Optics Zenithstar 105mm with a 0.8 FR/FF, effective focal ratio ~ f/5.6.
• A homebuilt lightbox with flashlight bulbs and a variable power source.

All flats were made using a sigma mean of 12 x 6 second integrations, binned 1x1 at -20C.  The lightbox was adjusted to make the pixel counts approximately 30,000-35,000 for each flat image.

Note that very similar flat field images have been obtained using T-shirt flats and also in a configuration without the FR/FF.

The problem is that there are unusual gradients apparent in the flats.  Strangely, these gradients do not seem to be the same in regular "light" images, so when I calibrate images using the unusual flats, I often wind up with a gradient artifact in the image that was not there before calibrating.

Clear SBIG (Custom Scientific): Looks "O.K."?  Maybe some odd brightness along edges...

Red SBIG (Custom Scientific): Looks "O.K."?

Green SBIG (Custom Scientific): Note odd brightness in lower left.

Blue SBIG (Custom Scientific):  Note odd brightness in lower right.  Dust motes are still there but the image is dominated by the bright spot.

H-Alpha Schuler:  Back to the left.

OIII Schuler:  Whole left side is wierd.

SII Schuler:  "T" pattern in the middle.