SharpCap Forums

I've been using SC for both EAA and photometry, applying darks and flats on the fly as images are collected. A couple of 100,000ft questions:

1. How flat should my image be after Flat file correction? I know my processed image file is not perfectly flat. It's certainly greatly improved, but with hard stretching, I can still see the effects of vignetting.
2. What do you consider the keys to optimal Flat file generation?

CS Gary

Hi Gary,

An excellent question. With regards to Photometry, your equipment's Transformation Coefficients are affected by flatness and will therefore determine the error in your photometric measurements. To improve accuracy I recommend keeping your comparison stars within an arbitrary radius from the center of the frame. Keep stars within that radius when determining coefficients and also later when performing photometry.

In this Guide from the AAVSO:
https://www.aavso.org/sites/default/fil ... yGuide.pdf

Chapter 6 talks about transforming your data, however I highly recommend their online course "CCD Photometry 2". Usually, one takes "CCD Photometry 1" first, but depending on your experience they may let you skip it.

EDIT: The AAVSO ordinarily holds these classes in late winter when M67 in Cancer is coming round.

Brian