ASI1600 Weird pattern on Oiii flat

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nexusjeep
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ASI1600 Weird pattern on Oiii flat

Post by nexusjeep » Sat Feb 09, 2019 10:22 pm

Hi,
I have an ASI1600MM Pro and have noticed a weird pattern on the Oiii flat I have rotated the camera independent of anything else and the pattern does not move. So my assumption is that it is either on the inside of the cover class as I have cleaned the outside or it is on the cell cover glass, it only appears to show on the Oiii flat.

I have included one image for the Oiii below as well as the one from the Ha for comparison these are massively stretched to get them to show up and in reality the pattern calibrates out when processing the image I was just wondering if anyone else had seen the same thing.

Cheers
Nick
Attachments
Oii Flat.jpg
Single Oiii Flat
Oii Flat.jpg (59.93 KiB) Viewed 488 times
Ha Flat.jpg
Single Ha Flat
Ha Flat.jpg (66.16 KiB) Viewed 488 times

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oopfan
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Re: ASI1600 Weird pattern on Oiii flat

Post by oopfan » Sat Feb 09, 2019 11:46 pm

Do you have the OIII filter loaded in a filter wheel that remains stationary when you rotate the camera? If the filter is screwed into the camera nose then it is mostly likely the filter.

You might want to send these snapshots to Sam at ZWO. It could be that condensation has formed on the inside of the sensor window. More likely it is something on the outside. Use a bright light and high power magnifying glass. What are you using to clean the window and your filters?

Brian

PS: Oh OK, I see your telescope photos now. You've got a ZWO filter wheel. Never mind.

nexusjeep
Posts: 88
Joined: Thu Oct 18, 2018 3:01 pm

Re: ASI1600 Weird pattern on Oiii flat

Post by nexusjeep » Sun Feb 10, 2019 9:37 am

Hi Brian,
I will try emailing Sam as I don't think it is condensation as I can image fine and it only appears to show on the Oiii flat it has probably always been there it was only the fact that I decided to actually study a flat that I noticed it which was probably a mistake as ignorance was bliss. I have cleaned the outside of the window with Zeiss lens cleaning solution and lens micro fibre so assume it has to be internal and as you spotted the filter is in a ZWO wheel so it has to be something in/on the camera.

Also as I say it calibrates out fine on the actual images so is not technically an issue I was just bemused to the actual cause, as I say I will drop Sam an email to see what he thinks and post his response once I get it in case anyone else sees the same thing.

Cheers
Nick

nexusjeep
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Joined: Thu Oct 18, 2018 3:01 pm

Re: ASI1600 Weird pattern on Oiii flat

Post by nexusjeep » Mon Feb 18, 2019 10:31 pm

Well had a reply back from ZWO and apparently the pattern is nothing to worry about it is not condensation and they said to just accept that it is there as it will calibrate out with the flats. My main concern was that something was degrading but they have confirmed that this is not the case so panic over will just enjoy using the camera.

It was my own fault for stretching the Oiii flat if I had just left it as getting a good histogram spike rather than actually examining the flat stretched I would never have known and could have continued in blissful ignorance. :D

Cheers
Nick

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oopfan
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Re: ASI1600 Weird pattern on Oiii flat

Post by oopfan » Mon Feb 18, 2019 10:41 pm

Well that's good news! Did you stretch the Ha flat the same as the OIII flat? Now, after what you said I can sort of see the same pattern in both of them.

May I ask how many flats do you typically take?

Thanks,
Brian

nexusjeep
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Joined: Thu Oct 18, 2018 3:01 pm

Re: ASI1600 Weird pattern on Oiii flat

Post by nexusjeep » Tue Feb 19, 2019 10:15 am

Hi Brian
I take 70 flats and 70 dark flats / flat darks they were stretched the same I have also looked at an Sii flat and it is more visible in that one it looks like Ha just visible if you stand on one leg and squint, Sii more visible and Oiii very visible. However after flat calibration it is gone so it is not actually affecting the image after processing. As in the earlier post I was more concerned that it may be something degrading but after the email from ZWO I know that is not the case, I assume it may just be some form of stain in the coating to the backside of the window or even the cell cover / cell.

Cheers
Nick

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