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Flats issue  

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(@regpratt)
Main Sequence Star Customer
Joined: 6 months ago
Posts: 25
October 25, 2020 16:15  
So I've taken flats the same way for 6 months have never had an issue until this week. For some reason When I apply my flats its like they invert and the resulting image shows a white donut on the image. I have no idea how to correct this. It only happens when I take flats with Hyperstar which I do by placing a white tshirt on top of the dew shield and an LED light panel turned down. I've tried flats at 15k, 20k, 25k, and 30k and stack in Astro Pixel Processor. These settings have always worked and continue to work with my other telescopes but with hyperstar I goes south. Any help would be greatly appreciated!
 
Master flat
Screenshot 2020 10 24 170106

 

Only darks and bias

Screenshot 2020 10 24 165628

 

darks bias flats

Screenshot 2020 10 24 165650

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(@vincent-mod)
Universe Admin
Joined: 3 years ago
Posts: 2670
October 28, 2020 11:54  

My guess would be that, since it only happens when using the hyperstar, something is not going right while taking the flats. There must be some difference between the time you take the lights and the flats, apparently the vignetting is stronger when taking a flat frame. Very tricky to pinpoint what it is exactly without hardware access.


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(@regpratt)
Main Sequence Star Customer
Joined: 6 months ago
Posts: 25
October 28, 2020 13:33  

I've taken my flats the same way since I got the HS and it has only become an issue recently. I can't imaging why it's all of a sudden not working 


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(@vincent-mod)
Universe Admin
Joined: 3 years ago
Posts: 2670
October 28, 2020 13:51  

Strange, no difference at all in the way you take the flats either? Did you use different bias frames or a different APP version (not that that would be the cause, bu just probing where there are differences 🙂 ).


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(@astrogee)
Neutron Star Customer
Joined: 2 years ago
Posts: 116
October 28, 2020 20:33  

Try doing your flats by imaging clear sky - before your imaging session. I'm not sure about hyper star but I saw once that putting a t-shirt at the end of the dew shield yielded bad results. I put the t-shirt right at the front of the telescope but the last time I did my flats I used the clear sky approach . Also, image train changes may result in bad images because of thinks like stray light. Did you change any image train components?


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