DRatledge wrote:I have been shooting twilight flats for 20 years and they all have stars on the images. But sigma clipping gets rid of them as long as the scope is moved a bit between each flat
Taking on-board Dave's comments, I've been able to make a much smoother synthetic flat
from the same data by running
NOFFSET2 on the original sequence of images (all of different star-fields, with different exposures) and then using
Add a Sequence with
Sigma clipping (coefficient =1, 3 iterations) and then
NGAIN 5000 to normalise the result.
This gave a rather better output (from star-filled images) than
IRIS's automatic
Make a Flat-field process.
And I've passed on the tips about maintaining the focus setting and using meridian-flip to the BRT team.