Quote:
Originally Posted by Octane
Peter,
Can you explain what advantage the sky flats had over the dome flats? I'm assuming by dome flats you mean projecting a light source onto the roof of your observatory dome and imaging that?
Would you suggest a pauper with a DSLR (like myself) to use sky flats over artificially created ones?
Regards,
Humayun
|
There is nothing wrong with DSLR's. They are a great tool for wide field work.
Dome flats/T-shirt flats/sky flats are variations on the theme of providing a perfectly blank field that can be used to calibrate the camera's images.
Sky flats are easy. They have to be taken just before dawn or after sunset, adjusting the exposure to give about 30% well saturation of the sensor. (you want a high S/N but don't want ABG to kick in). Take several frames near the zenith, moving the scope around between each frame to minimize any sky gradient. Median combining them will remove any random signal.
The problem you will have with a DSLR is sky flats will not be monochrome. (Easily fixed in Photoshop!), but if done correctly you will have a nice map of the optical vignetting of your telescope (or lens) and any dust doughnuts.
Hope that helps.