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(@bobw55)
White Dwarf Customer
Joined: 10 months ago
Posts: 14
April 8, 2020 06:40  

I only get these craters when I apply my calibration frames (F,D,B)  I have re-shot the calibration frames and checked them and do not see the craters in my calibration frames or light subs.

RAW M51

 

Did I click a setting I should not have?


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1740
April 8, 2020 12:59  

Hi Bob,

Wow, that's a first for me. 😉 Could you post a screenshot of your masterflat, masterdark and one of the single subs?


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(@bobw55)
White Dwarf Customer
Joined: 10 months ago
Posts: 14
April 9, 2020 03:16  

Still looking at things.   Found 4 not so good lights out of 145.

Going to reprocess it with out any calibration frames.  And then with Darks only, and Flats only. 

Thinking I may need to clean my image train.   I keep everything together all the time, even though I shot the Flats right after imaging.  I use a home made light box, May have to take out one of the LED strips.  I'm shooting really quickly to get my ADU value in the 25000 - 28000 range.

Will let you know


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1740
April 10, 2020 14:28  

I'm wondering if it's the flats, if they don't match you may get weird artefacts, though I didn't see this yet.


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(@bobw55)
White Dwarf Customer
Joined: 10 months ago
Posts: 14
April 10, 2020 14:43  

After spending 3 hours going through each light sub, you can see the artifacts in those.   I suspect 2 issues.

1)  Dirty image train, even though I keep it all assembled and never move things around.

2) Although my Flats were taken using a light box, I think it provides too much illumination, so my flats get taken at a way too fast speed to get the desired ADU value.

I have taken the light box apart and added 2 additional sheets of paper to help diffuse the light some more.  If that does not help increase the exposure time, I'll remove a few of the LEDs form it.

Will have to fire up my airbrush compressor and take everything apart and blow out the dust.  and start all over.  A shame,  Almost 2 hours of subs down the drain.   Lesson learned.........


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(@bobw55)
White Dwarf Customer
Joined: 10 months ago
Posts: 14
April 12, 2020 02:21  

Spent the entire day digging into this.....

Ended up being a BIG dust bunny right on the front of the camera glass.  

Took my Air Brush and gave the entire optics train a good air dusting.    Will not know 100% for sure till I can image again, but the flats look much cleaner.   Adding the extra diffuser I am able to take flats at a slightly slower exposure time and still get my ADU 25000 - 28000.


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(@mestutters)
Red Giant Customer
Joined: 3 years ago
Posts: 94
April 12, 2020 10:59  

Hi Bob,

I'm struck by the circularity of the artifacts in your image.  

I am wondering if instead of dust bunnies you actually had a few spots of light rain at some point during your imaging session.  These would impact the frames taken at that time but later evaporate so would be missed in the flats.

Just a thought

Regards

Mike


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(@bobw55)
White Dwarf Customer
Joined: 10 months ago
Posts: 14
April 12, 2020 16:35  

Mike that was also a thought.

When I went to retake the flats, I could vary the exposure time enough to where you could clearly see the same artifacts in the same location.   After cleaning the optical train, they are no longer visible.

I actually thought maybe I had an image of the moon in my light stack at first.   But 2 different targets with same issue.  Just waiting on clear sky's to try again


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