PI WBPP Astrometric Solutions & Image Registration Reference Image Selection

PixInsight’s Weighted Batch Pre Processing (WBPP) script is a very solid process that allows the user to manage all the pre processing processes for their data in a single place.  This includes calibrating, debayering them if needed, registering / aligning, doing local normalization and integrating the data into master light frames.  I learned about a particular issue which could prevent a user obtaining an astrometric solution and / or being able to register images.

When you’re setting up the WBPP script to process the light frames if you want to have the light frames get an astrometric solution (A) and/or have them registered/aligned (B) you need to make sure these items are checked.  Within either of these selections, you have the ability to set the specific parameters for registration (1) or for image solution (2).   

When you select them, each section has choices to automatically or manually select a reference image from the data.  

If you choose the automatic mode, things may work just fine but I’m not so sure.  If it fails, you won’t necessarily know specifically why it failed or what reference image was used.

My recommendation would be to change the Mode to manual and then select the reference image yourself.  You should already have an idea what a good reference image is from the data if you Blinked the data to review it prior to starting the preprocessing.  For reference, the Star Alignment process which is the separate process for registration / alignment does not have an auto function; you must specifically identify the reference image to be used for alignment.  In this way you would have more control over what reference frame is used and have more certainty that things will proceed according to plan.