Why do I need bias ...
Clear all

Why do I need bias to make master flats?  


Brown Dwarf Customer
Joined: 3 months ago
Posts: 9
January 19, 2021 12:02  


I got a new telescope, so I made a bunch of flats.  Now I want to use APP to make a set of master flats for later use.  However, it complains that I need to add bias or dark flats to make these master frames.  Why?  I thought a master flat was that you just stack all the flats (for one filter and gain setting) together.  I understand why you need bias and other types when actual processing images, but why during the making of the master frames?  BTW, I do have a master darks and bias library ready to use when processing real images.

Universe Admin
Joined: 4 years ago
Posts: 3058
January 19, 2021 13:00  

So APP needs a bias signal to substract that signal from the flats. This is important for the algorithm to know what the actual backgound in the image is and to scale the rest properly.