Flats Under Construction

  Using flats, dark images and bias images enables one to correct an astronomical image for a variety of defects in the optical system used for imaging. I'm not going to go into the theories of why this is possible. There are several good handbooks and white papers that elaborate on the theory in great detail. In addition, several application programs provide practical and automated processes to build the "master flats" used for removing image defects. Instead I'm going to explain how I optimized the sequence of taking flats.

  I've done a lot of research and experimentation to determine the optimum arrangement of filters and exposures for my imaging equipment. I've preferred to use the dusk sky as a source for flats. The trick is to sequence taking the sky flats through the various filters and binnings in such a way as to ensure that every exposure can be taken to produce a flat image with a nominal average ADU of about 30,000 (for my camera), and to minimize the wait time between those exposures where the sky is still too bright.

  Because I use ACP for my data collection, I can plan a run for flats either as part of a more extended observing plan with other targets, or as a separate observing run just for the purpose of getting flat, dark and bias images.

  More to come...