Quote:
Originally Posted by TrevorW
Refer attached file(s)
don't show up on any of the flats I used (although the flats used were not taken on the same night) or when the individual frames are stretched
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Then the dust motes probably have built up since.
Quote:
however when applying curves to the rgb stacked frame they do
also when no flats applied same thing appears
the flats were taken two weeks ago and used in my previous image of M46 and this effect doesn't show up in that image
 is it the flats or reflection issues or something else
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Dust motes. Large rings are likely on the mirror. Smaller, more defined spots would be on the ccd chamber window or ccd chip. Cant be the flats if you didnt use them ?? *confused
Get a flat from the same night next time, to compare?
Do you have an outdoor patio light? When your done, point the scope towards it; put a white shirt over, or opaque paper for an even illumination and take some flats at a exp time where you can see these nasties.