Why do I need bias ...
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2022-05-29: APP 2.0.0-beta2 has been released !

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Why do I need bias to make master flats?

Brown Dwarf Customer
Joined: 2 years ago
Posts: 9
Topic starter  


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.

Quasar Admin
Joined: 5 years ago
Posts: 4830

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.