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ASI1294MC Pro artifact?

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#1 mprowland

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Posted 26 September 2020 - 12:04 AM

M45.jpg I have these 2 circles that appear at the top of every image.  I'm using a Stellarvue 102 with 2 different flatteners.  I get these same two circles regardless of flattener and camera orientation.  I feel like I'm missing something extremely obvious.  The camera sensor looks clean as can be.  I would think if it were an obstruction of some sort, I wouldn't be able to see a star within the circle.  I'm baffled...  Thanks for any input...


Edited by mprowland, 26 September 2020 - 06:38 AM.


#2 Tapio

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Posted 26 September 2020 - 01:07 AM

Do you take flats?
That will take care of dust mote problem.

#3 mprowland

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Posted 26 September 2020 - 01:16 AM

I used flats, I still have the issue after the stack. I also just bought the camera so I don't have much experience with it.

#4 Tapio

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Posted 26 September 2020 - 01:50 AM

Can you show the problem - ie images.



#5 mprowland

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Posted 26 September 2020 - 06:40 AM

Can you show the problem - i

Picture has been added.  I guess it's hard to ask for help when you can't see what the actual problem is!!



#6 Tapio

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Posted 26 September 2020 - 07:26 AM

Thanks for the image.
It looks like (stil) dust donut, or some condensation (maybe it dried out after you looked).

Here's a calculator where you can see where the problem may lie:

https://www.ccdware....urces/dust.html



#7 magnusl

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Posted 26 September 2020 - 08:19 AM

Hi!

 

I have the same camera model. Looks like dust on the sensor to me, or rather on the protecting glass in front of it. Edges of the circles are quite sharp. You should be able to see it with a magnifier, and probably remove it, blowing some air (with a blower made for this, not compressed air!!).

 

Magnus


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#8 jdupton

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Posted 26 September 2020 - 09:39 AM

mprowland,

 

   As others have indicated, the two spots are the shadows of tiny dust particles. The dust is located approximately 2mm from the silicon surface of the sensor. That puts them on the sensor cover glass inside the camera. Their size will be too small to see with the naked eye. (The distance from the dust to the sensor's surface can be found by using a Dust Donut Distance calculator.)

 

   There is no need to try to remove them. Doing so can just as easily add more or move these around. The use of Flat Frames should remove their effects completely. If you used Flats for the image posted, then there is another problem lurking -- your flats are not properly calibrating the frames as they should. It would seem that your Master Flat frame is under-correcting by some amount.

 

   It is best that you dig into the failure of the Flat Frames to correct for the dust. Can you post a short list of the steps you performed to get to the image you posted? That will help us point you to the reason for the poor flat calibration issue.

 

 

John


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#9 StarBurger

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Posted 26 September 2020 - 10:16 AM

Unfortunately dust motes come and go.IMG_0001.jpg IMG_0001_1.jpg During a take of M 33 this happened, 9x 120 sec frames in.

 

 

During the remaining 47 frames the black hole scooted around but remained resolutely in front of M 33.Final flats just did not cut it in post proc. Left with just the initial clean 9 with no clean flats. Lousy result....



#10 Dean J.

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Posted 26 September 2020 - 10:47 AM

mprowland,

 

   As others have indicated, the two spots are the shadows of tiny dust particles. The dust is located approximately 2mm from the silicon surface of the sensor. That puts them on the sensor cover glass inside the camera. Their size will be too small to see with the naked eye. (The distance from the dust to the sensor's surface can be found by using a Dust Donut Distance calculator.)

 

   There is no need to try to remove them. Doing so can just as easily add more or move these around. The use of Flat Frames should remove their effects completely. If you used Flats for the image posted, then there is another problem lurking -- your flats are not properly calibrating the frames as they should. It would seem that your Master Flat frame is under-correcting by some amount.

 

   It is best that you dig into the failure of the Flat Frames to correct for the dust. Can you post a short list of the steps you performed to get to the image you posted? That will help us point you to the reason for the poor flat calibration issue.

 

 

John

+1 to everything above.

 

I introduced a dust spot to the detector cover glass the last time I changed my desiccant tabs on my ASI1600.

 

It disappears with flat fielding.



#11 mprowland

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Posted 26 September 2020 - 01:10 PM

Thank you to everyone who responded.  The learning curve is less steep when others are willing to chime in and help out, I truly appreciate it.  I did use flats but I obviously did not do them correctly.  I assume I need to see the circles in the flat in order for them to be cancelled out?  I'll research and figure out how to take them correctly with this particular camera.  I'm just glad that my "new to me" camera is not permanently flawed.  Thanks again to everyone, I would have given up with the hobby a long time ago if it weren't for you! 




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