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Hi Everyone, I have not long ago started this hobby and my current scope is a Skywatcher Espirit 100ED and using the ASI2600 MC Pro OSC camera. A Few months back I purchased the camera and ever since I got it I am seeing bright white circle in the middle of my subs. The longer the exposure the brighter the bright circle is. Example:  Has anyone had this issue ? Is this normal? This also occured with my C8 Edge HD which has lead me to believe there's something wrong with my camera. I have tried using the optolong l-pro filter and even without it I still get the bright white circle in my subs. Any assistance with this will be very much appreciated. Thank you. PS: Apologies if I'm posting this in the wrong section. |
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I'm no expert, but a few more details may help here: Did you check the sensor if there's fogging or frost? Do you use calibration frames? Specially flats. Also, providing a full resolution file may help others in diagnosing your problem Hope that helps! |
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Hi, just remember your camera has a dew heater make sure it's turned. Also get a dew heater for your telescope that way you'll know its not dew. Also make sure your telescope is aclimetized (ie uncover it at least a hour before usage). I suffered the same problem for while. Also make sure there is no dust on the lense of the telescope and none on sensor of the camera, this will balloon anything on these areas, and will drive you crazy. If all is done then make sure all your subs are calibrated with darks, bias, flats. This will correct any issues. Welcome to world of the open skies, |
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| Can you please present flatfield frame? This will tell us more about conditions of your optics.. |
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Thank you all for providing assistance with this. I can confirm the dew heater was on and no fogging/frost build up. The link below has the fits lights frame: https://1drv.ms/u/s!AgFClZHt1sdHanUnL2-mub5aJgM?e=zL8JjN My concern is before the flats, darks and bias frames are applied meaning just the light frames only, should there be a bright circle appearing ? |
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this is too centered and too uniform to be dew. This looks like a reflection, I've seen it before. Do you see it happening wherever you're pointing in the sky? is there any lights near you that might create the reflection? Do you have an oag in the way? I would normally say that this is your EHD reducer, but if it is happening on the esprit, then it might be something else. is your spacing correct? if so, what else is common between the two setups aside from the camera? (oag, spacers, etc...) |
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| If it shows in your flats then it is just the way your imaging train works and you should be able to remove it entirely. I doubt it has anything to do with your camera. Cameras don't do that (well, normally at least). |
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Michel Makhlouta: Thank you for your response. I'm using a guide scope (evoguide 50) with my Espirit. As far as spacing goes: Espirit FF -->16.5MM + --> 21MM ZWO Filter Drawer + --> ASI2600MC Pro 17.5MM = 55MM This happens on any target/anywhere in the night sky. Plus I got the Espirit less than 2 weeks ago. There aren't any bright lights in the backyard or any lights interfering from the neighbours. The odd part is this happened with the EHD8 as well which I no longer have. So I am sure it's not the scope. This happened with the .7x reducer and also the hyperstar and even that gave me a much bigger and wider circle right in the center. |
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| @ikkhatri can you try replacing the ZWO filter drawer with the 21mm extension that came with your camera? |
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Michel Makhlouta: Yes, will do. Just the weather is quite bad here in Sydney. However on the next clear night I will give it a go and post the outcome here. Thank you. |
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Michel Makhlouta: you can try taking flats with it and see if the lighter circle appears, you might have to reducer exposure time and do some wizardry with stretching or it might be straightforward. If it does, it will be easier to troubleshoot indoors, first by removing the filter drawer things from your imaging train. |
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Ikkhatri, For the Esprit 100ED, the user's manual calls for a back focus distance of 63mm. That's measured from the bottom of the field flattener male threads on the camera side to the sensor of the 2600. Try increasing your distance another 8mm and see what happens. As for your C8, check your manual for the correct back focus distance. I have a C11 EHD and it's BF is 146mm. I just ordered a 2600MM-Pro and this issue concerns me. Hope it gets resolved. Another thing I thought of: try taking some darks with just the camera and it's dust cover on. If the circle still appears, than you may have a bad sensor. If the image is completely black, then you may have a light leak somewhere in your imaging train causing a reflection. CS Pat Graham |
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Because of the centered spot and the fact that the image darkens in concentric areas as you go out, I think that this is vignetting caused by spacer problems. The other suggestions that you re-check that you have the correct spacing between telescope and sensor look like the correct ones to me. Stargazer66207 |
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The stars are elongated radially in all four corners so I also would suggest the spacing is not right. That said the issue looks very odd. I have an ASI2600MM and a 2600MC and neither have shown anything quite as distinct as that. I would try shooting flats first to see what the flats show up and if it corrects the issue? If you are in Sydney, I would make a guess you likely bought the camera through Bintel (Or Testar perhaps?) It would be worth having a chat to them if flats and spacing don't help. |
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Hi Yes. I have had that exact same effect when the temperature of the imagers cooling system was 5-10degrees too low while the dew heater is on. I turned up the temp 10 degrees and it disappeared. That's a quick fix to try at least. I just read that the ASI2600 has a dew heater on its protective window, is it working? |
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Hi All, If I havent already, I would like to say Thank you for assisting with this. So from my experience and after trying what *Michael Wothington* suggested, I gave it a go by setting the temp down to -5 on the ASI2600MC Pro and the round bright circle no longer appears. Apparently it was due to condensation. (Dew heater was on and is working). Weather has been quite sad lately but I managed to get about 10 x 900 second exposures of the Rosette Nebula, and I was very happy with the results. (Only 2.5 hours of light frames!) from Bortle 8. For my Espirit 100ED *BLUE* also mentioned elongated stars on the edges. So I have also corrected that. (Thank you) This is how I have my backspacing setup: Espirit FF -->16.5MMSpacer (included with the camera) + --> 21MM ZWO Filter Drawer + --> ASI2600MC Pro 17.5MM + --> The Skywatcher Spacer (included with the scope) on the FF which is 8mm = This totals to 63mm of back focus. (Thanks Jim waters - CN) Hopefully someone starting out with AP like me having trouble with backfocus, hope this helps. So long story short, imaging at - 5 degrees = no problems. But -10 and lower temperatures (as per my tests), the bright circle appears. |
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To much humidity inside the camera? The ASI2600 has four dry tablets inside. You can take them out, put them 2 mins into the microwave and put them (quickly) back into the camera while they are still warm. It is very easy to open the camera, you do not void warranty and you do not misalign anything, if you are careful. |
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I've had the same camera for 2 months now and imaged with it every clear night, with no problem. It's my understanding the newer 2600's don't use the 4 tabs this camera has heater elements built in it, to prevent dewing. It must have a 12v source for the heaters to work. I am extremely happy with my camera, and gotten extremely good results. Good Luck, Steve Argereow |
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Steve Argereow: Thanks Steve. I am using the ASIAIR Plus with my setup, and I purchased a separate power supply (ZWO DC12V5A) for it as well since it doesnt come with it. And the ASI2600MC Pro is being powered by the ASIAIR. May I please ask if you attempt to image at cooler temps such as -20 for example, you dont see that round bright circle ? |
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I had a similar problem only once when cooling down to -20 and forgetting to switch on the dew heater. The dew heater heats the external window and prevents dew on the outside and inside only on that window. If the interior of the camera has catched a lot of humidity, the tabs become saturated and have no effect anymore. In that case, it condenses on the sensor, either as dew or as frost. I have opened my 2600 recently, it is 14 months old ... for other reasons ... the extremely nasty silicon oil spilling on the sensor required sensor cleaning. I refreshed the tabs as descripbed and I can cool down to -20 wihout any problem ... and I have lots of dew in general here. I do not know how humidity could have entered your camera. Has it been opened at some time? |
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Christoph Nieswand: Christoph Nieswand: Hi Christoph, Thanks for your kind response. The camera has never been opened. It was purchased in July, 2021. And since day 1 I had this issue. |
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I have the same issue with my new ASI 2600MCpro bought in Jan 2022. I use it with a Celestron C11, Hyperstar f/2 and Lightpollution-Filter IDAS LPS-D3. I´m not sure if the gradient phänomenon comes from an internal reflection of the LP-filter, the Hyperstar or if this problem maybe comes from the known "ASI 2600 Oil-leak problem"? Could it be, that the oil settle down on the heated camerawindow, when the sensor and the other area of the camera has cooled down? (Here you can see a strong hinstogrammstretch of the gradient phänomenon; sensor temp.= -5°C)  |
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| I had the same problem with 115/800 Apo, solved with another flattener. |
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| Likely an issue with the filter. Try without any. Oil leaks I'd rule out. |
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I had a similar pattern due to reflections in my imaging train. In my case I used a LP filter in front of my lens and the border of the metal ring around the filter reflected some stray light into my images. Exchanging the filter helped. Conclusion: There are light pollution filters which keep the light pollution out of your lens and there are light pollution filters which pollute your lens with light. It's just a matter of how the company interprets the term "light pollution filter" ... Good luck and clear skies Wolfgang |
