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Bright area in the center of the image on an ASI294MC Pro

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Thanks for all of the feedback. Is does appear that the issue is with my physical setup rather than the camera itself or software configuration so I'm thinking the topic has run it's course here.
I will try and work through the suggested tests.

In the interim I''m going to give the F12 a try and see how that all goes. Gave me a good excuse to build up another focuser control. I'm trying an ESP8266 version of a myFocuserPro2 (which I did before finding the existing doco so I may have some adjustments to make).
3 years 7 months ago #58633

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Same here
its the Altair version, just got it and playing around with it.
300s exp, dont know about the gain.
65/420 Apochromat

Did you have any luck figuring it out yet?
3 years 7 months ago #58751
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Other than finding that I'm not getting the issue with my reflectors I have not.
The original issue was occurring while using a Skywatcher ED100. I've since tested with a GSO 153mm F4 newt (with Coma corrector) and other than bad coma (I need to revisit the whole spacing question to resolve that) and a Skywatcher F12 150mm Makautov Cassegrain which is looking really promising.
I'm concentrating on trying to get that all working at the moment so I can take advantage of some nice weather and deal with the tests later.

I am still quite confused as to why I don't see the amp glow up near the top right corner in actual images as well. It's really obvious in darks but no sign of it in any of the lights I've taken. That has me wondering what deep sky stacker does to that part of the image when it's working with darks which have a glow in that spot.

It seems like I'm either getting some reflection from light leakage in the ED100 or the tube is too narrow for the sensor (although I've not seen any documentation to support that suspicion).
I did also get an odd search light type pattern on M4 which at the time I'd put down to the tube picking up light from somewhere else but thinking about it that showed up in every M4 image I took which seems unlikely if that was an artifact of some stray light.. .
3 years 7 months ago #58754
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You generally do not see amp glow in your light the same reason you do not see background noise. The amps glow obvious on darks because to see them, the autostretch feature have had to stretch the images rigorously. When you take a light exposure, the amp glow easily got overwhelmed with signal from the sky background and you wont see it when stretching. (But it's still there)
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3 years 7 months ago #58760

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Minhlead, thanks for explaining that.
3 years 7 months ago #58765

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if you are not getting it with reflectors, then I figure it must be infrared glow.
cant be the sensor size with me, because i am not getting the glow with my DSLR, which has a slightly bigger sensor, but which also has infrared blocking.

The amp glow is totally different, and as Minhlead pointed out, only visible in my darks.
3 years 7 months ago #58768

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This is a typical dark heavily stretched from this model camera.
Also bright areas in center can be result of flatteners and correctors causing unbalanced light values collected correct term eludes me atm.
solution is to do dark flats in your calibrations
Last edit: 3 years 7 months ago by Clive Garner.
3 years 7 months ago #58769
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I didn't get it with a Canon 550D on the ED100 (stock camera). I've not worked out the relative sensor sizes.
3 years 7 months ago #58770

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Guess the sentence was somehow chopped..... So you do not see any of those central blobs with the other telescopes?

Are you talking abour raw images? If you process them in DSS (I assume) the dark is subtracted, and with it the amp glow. If it is raw: the amp glow is a relatively weak signal that you can only see clearly when there is no other signal in the data (i.e., a dark frame), or if you do (strong) non-linear stretching of a raw light frame.
The telescope tube itself cannot be too narrow, as it usually has the diameter of the aperture. Critical parts would be the focusser or any filters. But those would cause a gradual darkening towards the rim (vignetting), and not a brightening of the center like you see it.
Also, if you do/did the daylight test with closed telescope cover, and didn't see light there, it is not a light leak but (diffuse) reflection through the main lens.
My guess: This for sure is from close-by Antares, supporting the scenario that what you see is diffuse reflection on some part in your optical train like focuser, dew cap, extension tube. That you get it circular in the initial image would suggest that it comes from all directions, i.e., you have quite high light pollution?
3 years 7 months ago #58771

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No visible central blobs using the other telescopes.

I do have moderately high light pollution (I'm just outside Brisbane) but not extreme. It all seems pretty strange that I didn't get any of the with the Canon 550D (other than the prior mention of the possibility of it being IR).
I don't currently have any filters in the setup although am pondering adding some filtering to dry and reduce the sky glow. An area I need to do some more reading on.
3 years 7 months ago #58776

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Hmm, that was a color camera, yes? Have you checked whether the blob is different in the 3 color channels? If IR, it would be mostly/strongest in the red.
If you don't see it with other OTAs it excludes (IMO) everything (camera, filters?) used in both cases, probably leaving mostly focuser and dew cap as reflecting surfaces.
You could try taking images with retracted and extended dew cap of the refractor and see if it changes the blob.
3 years 7 months ago #58925

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You can also try adding a Lum filter in front of the sensor to stop IR/UV from getting in.
3 years 7 months ago #58933

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