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Reflection Artifacts in the ASI6200

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#26 sn2006gy

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Posted 12 September 2020 - 02:33 PM

Even on his no window examples, i still see filter halos.. which are oddly square in his reference images.



#27 rockstarbill

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Posted 12 September 2020 - 02:40 PM

Even on his no window examples, i still see filter halos.. which are oddly square in his reference images.

Relfective issues in the sensor area (slide 10). You dont see any filter halos in those images because none of those images used filters at all. Note 3 x 90 second unfiltered... 



#28 rockstarbill

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Posted 12 September 2020 - 02:44 PM

Oh yes I was referring to the ring pattern, sorry for not clarifying.

The ring pattern may be unavoidable. I am curious if the 583 you tested showed the same ring pattern using a refractor instead of the RC.



#29 sn2006gy

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Posted 12 September 2020 - 02:52 PM

Relfective issues in the sensor area (slide 10). You dont see any filter halos in those images because none of those images used filters at all. Note 3 x 90 second unfiltered... 

I still see square halos on every star... obviously the ones with the bad window i see a circle in it... i wonder if he's running square filters? if you look at every image around stars with spikes, the star glow is square regardless of the other artifacts. I can't unsee it now.


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#30 rockstarbill

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Posted 12 September 2020 - 02:53 PM

I still see square halos on every star... obviously the ones with the bad window i see a circle in it... i wonder if he's running square filters? if you look at every image around stars with spikes, the star glow is square regardless of the other artifacts. I can't unsee it now.

There are no filters in use in that write-up. The rectangle pattern is identified in the write-up and is fully explained.


Edited by rockstarbill, 12 September 2020 - 03:58 PM.


#31 andysea

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Posted 12 September 2020 - 03:37 PM

I have some 900s NB on Gamma Cass and the TOA130. I will look for them.

Are you sure that the no cover glass halo in the link you posted is rectangular? It looks like a square to me.

It is unclear to me how Richard explains it. Can you elaborate?



#32 rockstarbill

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Posted 12 September 2020 - 03:50 PM

The "No Window" sample is rectagular in shape. The longer edges are dimmer but if you look close you can see them.

 

He explains why that occurs on slide 9, Camera Interior and on slide 10, Sensor Area. The summary on slide 11 is good as well. 



#33 andysea

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Posted 12 September 2020 - 03:52 PM

He says that there are rectangular shiny surfaces. I don't see any explanation of where they are reflecting to.



#34 rockstarbill

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Posted 12 September 2020 - 03:55 PM

He says that there are rectangular shiny surfaces. I don't see any explanation of where they are reflecting to.

They are reflecting onto the sensor. 



#35 andysea

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Posted 12 September 2020 - 04:04 PM

To reflect back onto the sensor they must reflect to another surface first. What surface is the light bouncing off of? I must be missing that part in the slide.



#36 rebelxts

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Posted 12 September 2020 - 04:46 PM

I get the same donuts when there is a very bright star in the FOV with QHY16200 and 8” EdgeHD SCT. When I use a 140mm refractor, the donuts are not visible to my eyes. This reflection issue seems widespread.

#37 andysea

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Posted 12 September 2020 - 05:57 PM

Here is a crop of a 1200s sb of Gamma Cas QSI 583, TOA130 Astrodon 3nm Ha filter.

Attached Thumbnails

  • ha.jpg
  • ha_crop.jpg


#38 andysea

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Posted 12 September 2020 - 05:58 PM

This is the same crop of an Oiii 1200s sub with the Astrodon 3nm. This was post meridian flip, I aligned the frames and cropped. I think this is why the halo is oriented differently. Side note, looking this old data reminded me of how good the TOA was.

Attached Thumbnails

  • oiii.jpg

Edited by andysea, 12 September 2020 - 05:59 PM.


#39 ChrisWhite

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Posted 12 September 2020 - 06:06 PM

I think gamma cas is a pretty extreme example. I tried inaging with adons on my newt reduced to f2.8 and the halo was huge. Throw away data.

Bill, how do things look with less dominant stars? Like stars in m45 or propus where they are very bright but not gamma cas bright?

#40 rockstarbill

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Posted 12 September 2020 - 06:19 PM

This is the same crop of an Oiii 1200s sub with the Astrodon 3nm. This was post meridian flip, I aligned the frames and cropped. I think this is why the halo is oriented differently. Side note, looking this old data reminded me of how good the TOA was.

This is the same issue I saw on the 8300 and sent the camera back and had the window replaced. The problem went away after that.

 

I think gamma cas is a pretty extreme example. I tried inaging with adons on my newt reduced to f2.8 and the halo was huge. Throw away data.

Bill, how do things look with less dominant stars? Like stars in m45 or propus where they are very bright but not gamma cas bright?

Lots of attention on the GammaCyg image, but the others I shared have far less bright stars in them and show off-centered halo effects as well. There really are two things I see in the data when I review it. One, is the circular pattern from the center. This mostly occurs on very bright stars. This I was less concerned about and have seen in the past as well. Two, is the halo-like reflection effects on narrowband images that dont have hyper-bright stars in them. This conerns me, this is not something I have seen other than when the window on my 8300 had poor AR coating on it and needed to be replaced to resolve it. 

 

As a bonus concern, the grid-like donut pattern on GammaCyg was disturbing.


Edited by rockstarbill, 12 September 2020 - 06:20 PM.


#41 andysea

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Posted 12 September 2020 - 06:31 PM

The ring pattern may be unavoidable. I am curious if the 583 you tested showed the same ring pattern using a refractor instead of the RC.

I posted Gamma Cas because you asked to see data from a refractor. 


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#42 rockstarbill

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Posted 12 September 2020 - 07:10 PM

I have my calibration files shooting now, then I can stack up some of this data and see what the results look like.



#43 ChrisWhite

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Posted 12 September 2020 - 07:13 PM

This is the same issue I saw on the 8300 and sent the camera back and had the window replaced. The problem went away after that.

 

Lots of attention on the GammaCyg image, but the others I shared have far less bright stars in them and show off-centered halo effects as well. There really are two things I see in the data when I review it. One, is the circular pattern from the center. This mostly occurs on very bright stars. This I was less concerned about and have seen in the past as well. Two, is the halo-like reflection effects on narrowband images that dont have hyper-bright stars in them. This conerns me, this is not something I have seen other than when the window on my 8300 had poor AR coating on it and needed to be replaced to resolve it. 

 

As a bonus concern, the grid-like donut pattern on GammaCyg was disturbing.

What I'm seeing in your pacman data isnt terrible, but interesting.  Viewing the data at 1:1 isn't that revealing, you really need to get close to see the dramatic effect with the concentric rings.  This pattern isnt terrible in a single sub, although might look far worse in an integration especially after you mix channels. 

 

The GIANT donuts all across your Gamma Cyg image is very troubling.  That is simply terrible....


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#44 rockstarbill

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Posted 12 September 2020 - 07:25 PM

To reflect back onto the sensor they must reflect to another surface first. What surface is the light bouncing off of? I must be missing that part in the slide.

The cover slip to the sensor. 



#45 FredOS

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Posted 12 September 2020 - 08:34 PM

The Ha data is clearly problematic. I do wonder why it is not showing (or less ? ) on the AP130 GTX (looking at my own data, I couldn’t find anything similar). The Oiii data is a little less obvious, does it show with other filters - I'm assuming it is not related to collimation ?
The CMOS window appears to have an issue - has ZWO provided any views on this ?



#46 rockstarbill

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Posted 12 September 2020 - 08:47 PM

The Ha data is clearly problematic. I do wonder why it is not showing (or less ? ) on the AP130 GTX (looking at my own data, I couldn’t find anything similar). The Oiii data is a little less obvious, does it show with other filters - I'm assuming it is not related to collimation ?
The CMOS window appears to have an issue - has ZWO provided any views on this ?

No, this is not related to collimation. The AG is well collimated. I did go down that path to confirm once I saw the problem. 

 

Sam messaged me here, he did reply to me and the mail was buried in junk. I just found it. 

 

 

 

as sensor is IR sensetive and the relection of IR range will be large
this would be hard to coat with the whole range 400-1000 nm
the light pass better than 98.5% during 400-700nm

Edited by rockstarbill, 12 September 2020 - 09:07 PM.


#47 rockstarbill

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Posted 12 September 2020 - 11:49 PM

Here are two stacks of the OIII data, one was done with Drizzle and one without.

 

https://1drv.ms/u/s!...2tBTCQ?e=u9P4Cb

 

The offset halo effect I can still see, and see much better than before. The donut grid is not present. 



#48 GeneralT001

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Posted 13 September 2020 - 12:04 AM

Here are two stacks of the OIII data, one was done with Drizzle and one without.

 

https://1drv.ms/u/s!...2tBTCQ?e=u9P4Cb

 

The offset halo effect I can still see, and see much better than before. The donut grid is not present. 

Were these fully calibrated with bias/darks/flats?

 

Data looks great btw smile.gif


Edited by GeneralT001, 13 September 2020 - 12:04 AM.


#49 rockstarbill

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Posted 13 September 2020 - 12:08 AM

Were these fully calibrated with bias/darks/flats?

 

Data looks great btw smile.gif

Fully calibrated. The darks and bias were taken tonight, the flats were taken immediately after the lights. I only used that one night for the test to eliminate possible shifting of dust motes and other things that could have possibly skewed the results. 

 

The halo is still there, and apparently I am the only one that can see it. 

 

Thanks on the data, the iDK is an excellent scope. There is some fringe star issues going on but that is because I can't tilt the Gerd CTU anymore on one side that needs more correction. The tilt in this camera is absurdly bad.



#50 GeneralT001

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Posted 13 September 2020 - 12:14 AM

The halo is still definitely there, but its the type of thing that if you hadn't mentioned it would never had noticed. Those donuts pre-processing on the other hand.......... Its too bad about the ZWO 6200MM, hopefully they will correct this - you cannot be the only one with this issue. Great FOV!!




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