8. Source detection

The first step in doing photometry is deciding which objects you want photometry on. There are a few approaches to take:

• Find sources in your image and perform photometry on every source you can detect in the image.

• Perform photometry on objects from a catalog (either one you have created or from some other source); this presumes there is WCS information in the images so that catalog RA/Dec can be translated to pixel position on the image.

• Stack your images, detect the sources in that much deeper stacked image, treat those sources as your catalog and use that catlog to perform photometry.

The next series of notebooks will describe how to do source detection.

Note

The notebooks in this part of the guide draw heavily from the excellent photutils documentation