PixInsight provides some very good tools, such as SpectroPhotometric Color Calibration and MultiScale Gradient Correction which require filter transmission curves. While you can usually find a close match in the built in PixInsight Filter Definitions, if you want to be as exact as possible, you will want to create a custom filter definition.
As usual for PixInsight, this is quite an involved process. Jason Cook has an excellent video on how to do this, as well as a database of filter definitions he created. You should follow the steps in his video. The only small hole in this process is filters that aren’t covered in that database. Often the filter manufacturers will only provide a jpg image of their filter performance curve. What I have created, via AI, is a Python script which will digitize that curve in the format needed to import into PixInsight. Please consider this release 0.1, it has not been extensively tested on a variety of images, only the Askar ColourMagic curves I needed. Please feel free to copy and extend or provide feedback.
The script reads in a picture file called “filter.jpg” and will return a jpg of the digitized curve for easy confirmation, as well as the csv file needed for PixInsight import. The csv file will need to be edited for the proper filter name. You will also need to install the cv2, numpy, matplotlib, and scipy libraries.
Download the python script here.
Sweetman Astrophotography 