Source Detect Pipeline

This describes the pipeline that transforms images into x,y lists. It feeds into the BlindPipeline and/or the TweakPipeline.

what we do

We run simplexy via fits2xy.

Simplexy ought to be described in a LaTeX file in the codebase. Hogg is ticketed with that.

how we test it

Here is a random assemblage of possibly non-trivial images for simplexy to properly handle:

what we would do in an ideal world

  1. Obtain or determine a cosmic-ray mask, or more generally, a bad-pixel mask, either by user input or by runing la_cosmic or equivalent.
  2. If the later steps require it, interpolate over bad pixels.
  3. Obtain or determine an approximate inverse variance image, either by user input or by cheap statistics, modified by the bad-pixel mask.
  4. Obtain or determine an approximate seeing or resolution or point-source response for the image.
  5. Detect peaks by some sensible algorithm / code (using, possibly, the point-source response as some kind of filter), producing a brightness-ranked list of x,y positions, down to some plausible "plate limit".
  6. Group extremely nearby peaks by friends-of-friends (using, possibly, the point-source response size as the linking length) and keep in the list of image sources only the brightest peak in each group.
  7. Save these image sources in some well-defined format in some well-defined directory structure with some well-defined file name in the astrometry.net archive.