- A useful website that allows calculating the amount of field rotation given the amount of your polar alignment error.
- Of particular interest to me are the excellent astronomy forums. It also has occasional reviews and articles.
- Harry's PixInsight Videos are an excellent place to begin learning how to process images using PixInsight. They are how I (and many others) got started.
- Hickson objects are compact groupings of galaxies. This website has some excellent information on them. See especially the downloadable Observing Guide.
- A set of resources including but not limited to some tutorials for PixInsight.
- Various formulae of interest to imagers. I find myself using the image scale calculator fairly frequently.
- Good illustrations at bottom showing if your flattener is too close or too far from your sensor.