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Hassaan Zaheer: Below i have attached a single sub where i assume i can see the entire mirror shadow which is not visible in the final stacked image ruling out the movement/slop of mirror  |
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| I don't think is really well collimated and I also think you have massive light leaks. |
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andrea tasselli: andrea tasselli: HI andrea yes you are right my collimation was a bit off. As for light leaks i have covered every single space that can be covered and tested with dark frames and the issue with light leak has been resolved. Can poor collimation contribute to this? |
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| If it is really really bad, yes it could. But it is in the rather extreme scenarios case. |
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andrea tasselli: Thanks ill give it a shot. nothing for a week as i have clouds the entire week. Till then ill work on my collimation. |
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Hassaan Zaheer:andrea tasselli: I think that sometimes these kinds of reflections aren't necessarily caused by light leaks intruding from areas where people normally address (primary mirror cell, focuser drawtube, focuser flange) when trying to tackle light leaks on a newtonian, but are instead caused by a lack of baffles/flocking. I suspect that, at certain tube orientations, light pollution can intrude directly into the focuser if the inside isn't baffled. |
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Just to add 2 cent… I try to take calibration files, flats etc. at night in ROR, With aluminium tin foil covering primary ( sw130pds ) or any other suspected light leaks. Seems to work out better for me. With histogram mean target set @ 30% min 4 seconds for flats. This is probably not relevant to your issue ! |
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HI EVERYONE tonight ill be performing a star collimation test in field I have achieved very good collimation using the methods mentioned. Just wanted to know im using a CC so what would the defocused stars in the corner look like? will they also be complete donuts? |
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Probably not, there will be some clipping the further away from the optical axis. N.B.: If you collimating on a star is best NOT to use the CC. At least visually. |
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andrea tasselli: i just did a test. And i think i have nailed it. The collimation thru camera was nearly perfect. Did not check thru the EP yet but its looking much much much better. THANKS ANDREA FOR ALL YOUR HELP |
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  here are some test shots looks much better than before i think
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| Looks better but the real test is when you approach focus in that you should see smaller and smaller donuts as it gets closer and closer. And obviously how well corrected is at best focus. Just shoot the NCP so you don't have to track at all. 50-60 frames @ 5s should be enough if the sky is clear. |
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 I captured 8 min of the meehive cluster. The initial problem seems to have been resolved. i could capture only 8 minutes of data because of clouds. I can still see two circular patterns in the image. But for now i am happy with the progress.
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 Here is a bit more stretched image to see the artifact more clearly.
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Hi all, Thought I would chip in with my own experiences with reflections, halo's and all that. Not a professional on the issues by all means, just someone who had the same troubles and watched a lot of Youtube and read a lot of forums to get it figured out. In my time using my little Skywatcher 130pds, my images have been plagued with ugly halos and reflections. Some images its more prevalent than others. For example, my Tarantula Nebula image in 2021, there is a large ugly halo not too dissimilar to what Hassaan is getting in his image (Did my best to hide it but you can see it best in the bottom right corner): https://astrob.in/jccd4s/0/ Throughout my time doing Astrophotography in 2021, this large halo was in a lot of my images. Another example being my image of the Helix Nebula in 2021, this was the DSS stack (With calibration frames):  A "work around" I found in 2021 was stacking my images using WBPP in Pixinsight. For some reason Deepsky Stacker would produce these halo's whereas WBPP they wouldn't be visible at all. This might be worth a try if you want a quick "fix". More recently I have taken a 2.5 year break from Astrophotography, now that I'm back into it I thought that I would resolve the issues properly. About a month ago I made these changes to my scope: - Flocked the entire tube - Covered the back of the Primary Mirror (With a black reuseable supermarket bag, It's slightly see through and probably doesnt block all light but is significantly better) - Used electrical tape around the focuser and in any areas where there are potential light leaks - Painted the bottom of the focuser tube (Using Musou/Black 3.0) - Levelled the Focuser with the secondary mirror (Purchased an OCAL Collimator which showed me how far off my focuser really has been from being level with the secondary all these years) - Gotten much better Collimation using the OCAL (Was previously using a Laser, which I now realize was not nearly as effective as I previously thought) Not to say all these modifications contributed to the fix but after making these changes to my scope it has essentially fixed the halo and reflection issues. You can see this well in my flat frames before/after doing these modifications:  Top-Left (Taken 2021), Bottom-Left (Taken 2021) and Bottom-Right (Taken 2024) were my flat frames prior to modifying my scope. In each of these you can see a harsh circle shape in the center of the frame. This circle is actually present in my Light frames though due to other factors, that circle moves throughout the night while imaging. This means the Flat frames cant correct for that movement in the light's. Top-Right (Taken 2024) is after making those modifications. The flat is now a smooth gradient with no defined circle shape to be seen. The halo's now no longer show up in my stack in both DSS and WBPP. I've recently purchased an 8" Quattro which I'm now waiting on, will be going through this whole process with that scope once I receive it. Might sound a bit crazy but im looking forward to it, I found the whole modifying process and troubleshooting quite fun  Hope this helps someone in some way! Again, just my experience so not to say it's the same cause/issue for everyone. Hayden C.S |
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Hi Hayden thanks for your input. I have come to the conclusion that this a tough scope and will require alot of work. But im looking forward to it. I have decided to modify the scope as you have mentioned and as soon as i get some free time ill get to flocking and other stuff. I will try the WBPP technique though. thanks for the reply. |
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  images taken Right after one another. first shot the m51 and then took flats. Then moved to m81 in which the mount performed a flip. did not take flats after m81. So i thinks its safe to assume that the problem is with the secondary mirror sagging a bit when large slewing occurs. m81 is a bit cropped. |
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Hassaan Zaheer: so i think i should invest in secondary veins Anyone care to comment? |
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| Or the primary has shifted considerably. Truth to be told the main drawback of these scopes is the poor design of both primary and secondary cell. |
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andrea tasselli: i removed the primary and did thighten it up a bit. it does spin around with some force applied but as for some sort of huge movement i doubt it. i did test with a laser collimator. When i point it at the center donut and slew it does move away from the center. I tightened the secondary veins a bit and it did help but not alot. so i think the issue is with the secindary |
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Hassaan Zaheer: Fair enough. Your best bet is to replace the entire spider assembly, not just the vanes. TS makes a pretty good replacement spider assembly, should you look for one. |
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andrea tasselli:Hassaan Zaheer: https://www.aliexpress.com/item/1005006713885101.html?spm=a2g0o.home.0.0.650c76db5Ds6bL&mp=1 What about this? This looks solid too |
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This video may be useful for your problem solving https://youtu.be/OvQF14IEthI?si=b7sK0aUAt2ue7nIC |
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| @Dave B i saw the video just now but it did not offer any perticular solution. |
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 Here i have made a gif with the last image of the m51 and the first image of the m81. The frames are perfectly aligned as can be seen by the dust donuts. Huge movement in the ring. |
