ONIKKINEN

In surveys there are a lot of galaxies in this field of view, and some visible in your image too. So it might turn out an interesting image if you dump (too many) hours into it and make it a kind of deep field snapshot. Probably not worth the time though with the weather how it is.

The golden dovetail attached to the scope is upside down at the moment, flip it over. The fatter side goes towards the mount and this is what the 2 thumbscrews bite into when attaching. * or is it? Actually its hard to say from the image

i recalibrate every time, might be worth considering to do the same. Only takes a few minutes and since the scope is still cooling down at this point it doesnt actually bite into my imaging time. You could open up the mount during the upcoming summer when nights are short so you lose only a little or no imaging time at all when the mount is in pieces. Its not too difficult to do either with a guide if you take pictures of how everything looks before tearing down. New SKF bearings and proper PTFE lube cant hurt and if yours has a lot of mileage already the old bearings could be busted so might give you a boost in performance. Actually would be surprised if everything looks good after 10 years of use.

There is a slight problem here, how can you be sure that the cheshire is the correct tool out of the 2 you have used? It could be decentered in the focuser too but in a different way. You can check the focuser orthogonality by eyeballing it or spirit leveling it, but i doubt the issue is there, this sounds more like an inconsistent tool being used possibly because the tool itself is decentered or the way you connect the tool to the focuser is not repeatable accurately. If you haven't collimated the laser yet, do it at this point (they dont come well aligned from the factory). The best way to decide what tool to use is real world results, collimate using one and check corner aberrations in an image. The one that landed you on the better stars is the more correct one, but still the unreliability issue should be investigated and solved. And little issues like these are very common in even not so cheap reflectors, just part of the charm. Yes, newtonians are open on both ends and have focuser leakage, which is unavoidable because the focuser has to have a gap between the drawtube and the OTA or it would not be able to move. There is no way you can completely plug all the gaps and still have good ventilation of the tube (very important if you want to get sharp images due to thermal issues with a front open tube that is closed at the back). You need to take the camera off the scope, plug it completely and take darks in a dark room so that not a single photon of light gets to enter the camera. I recommend placing the camera in the fridge, that way its closer to outdoor temperatures already and will have no ambient light to leak into the sensor and so darks are true darks. Still worth it to keep in mind the light leak issues when shooting, if you're under a full Moon or under light pollution you need to plug the back of the scope somehow to prevent light leaks and weird gradients in the image. I recommend something made of a dark fabric rather than a solid cover so that air can still pass through.

That thread is painful to read, i made it to page 10 before i had to tab out from all the nonsense. I recommend that you do not take anything out of it. You definitely should not be applying any daylight color transformation nonsense in astrophotography, especially not in the preprocessing phase to the raw subs! There is no actual issue with colour calibration done with Siril. You can do whatever you want with the raw data that Siril will stack for you, whereas some kind of daylight colour transformation done on the raw subs will permanently and irreversibly damage it making subsequent processes such as photometric color calibration impossible, because the data is no longer linear. Of course the PCC tool in Siril is not perfect and it can only work if the data fed to it is of sufficient quality. If you feed it a decent integration it will churn out a very nicely balanced colour image in the end, but one you will need to saturate yourself. Your colours will look "boring" after a photometric color calibration in Siril because they are boring if the image is represented as completely real with no addition of saturation anywhere. You can (and probably should) saturate it afterwards, probably selectively with Photoshop using masks so that you dont saturate the background where just noise exists. I thought this quite from the Siril dev in that thread was the wisest thing in there:

Judging from the graphs: You shot at 8e- read noise compared to the usual 2e-. 4x the read noise means you need to expose 4^2=16x longer to swamp the read noise the same way as with the higher gain that has 2e- read noise. Did you expose for 16x longer? Doubt it, so it looks more noisy because it just is more noisy.

Whatever clearing method of the eventual debris is developed, it better be earth based or at most upper atmosphere based so that we dont add more debris up there. I like the idea of lasers. Maybe mount one on a hypersonic aircraft flying in the very upper atmosphere and vaporize the bigger pieces? Or, launch the junk-zapper into a medium earth orbit where it is safe from debris and shoot downwards towards the limb of the earth so that the beam doesn't actually make it to the surface.

Decay due to drag is painfully slow above a certain altitude, maybe 500km+ (of course depends on the density of the object, light debris will fall faster). Will take decades at least, and for objects at 1000km+ it would take so long that the people of today might as well call it permanent. But i think the whole Kessler syndrome thing is over-exaggerated, it wont stop our modern way of life with satellites and internet, it will just make it more costly to send new satellites out as in order for them to be at a safe altitude they need to be launched much higher, like where GPS satellites are today. That high there wont be a significant threat of space junk anymore and the satellites would survive as they do now. The extra cost might come from the fact that if its really bad at near earth orbits there might be a high chance of impact during launch so a lost vehicle every now and then but eventually one launch will succeed and then the satellite will work for several decades afterwards. Human spaceflight would end, but we dont really need it at all in my opinion.

Very nice, although cant help but notice that your stars on the left side of the image are teal/green?

The focus shift you will experience in any given night will be something like 0.1-0.2mm at worst (for an aluminium tube, less of an issue with anything else) so you can ignore focus position with flats as long as you dont go ahead and have the focuser be at some completely out of focus position. The flat panel in front of the scope is like a kilometer off focus so the tiny little movement at the back of the focuser is of no concern to the flats. I focus manually so cant tell what the right way to set up in software is, but i keep an eye on HFR readings during the first couple of hours of imaging. During that time i typically re-focus maybe 3 or 4 times as the scope is still cooling down from being stored indoors but after that focus typically stays more or less put and i dont need to babysit it anymore. If the night gets much colder, lets say by at least 5c, i might need to refocus well after the scope has cooled down. HFR numbers will tell you that, maybe set up a refocus call in whatever software you use when HFR has drifted by a certain amount? I know NINA can do this at least.

Regarding the barlow and bin thing reintroducing pixelation, you are exactly right. But actually its much worse now since the subs have much lower SNR before the bin happens, so binning back to the no-barlow resolution has only negatives. For fainter and smaller objects there is unfortunately no fast-lane to overtake the issues. Just need more time or a bigger scope, or both if the object is so faint. Binning improves SNR so you get a better image faster, but of course the image is now smaller. The most difficult thing to do in all of astrophotography (including EEVA i suppose) is to get a highly detailed and large dimensioned image of a faint distant target!

Not sure what to say if you dont want to believe me, but this is not correct at all regarding binning. Sum binning and average binning results in the exact same SNR improvement and you are not getting anything more out of sum binning here, you are just getting a brighter image with no extra benefit in it the same way as if you just multiplied all pixels values by 4x (with 2x2 bin). I am guessing autostretch does not stretch the image further if you average bin because there is no point (low SNR). Actually this mention of a barlow sheds some light to the issue. You are using a very small pixel camera, very short exposures and now a barlow lens that turns the scope into a very slow one, no wonder you have hot pixels - there is hardly any other signal going on at F/12 with 4s exposures! Here is what i suggest, not strictly a direct fix to your hot pixel dilemma but will help your EEVA adventures immensely: Drop the barlow, only use it for lunar and planetary. You are really killing the efficiency of your system here with using that and there is no way for me to get this point across too urgently! I am 99% sure you get no extra actual detail with the barlow and its just pure oversampling - which results in a pure loss of SNR with no extra gain whatsoever but it gets you the closer view you wanted. Here is an easier method that does not sacrifice SNR and maybe you dont need to bin (as much, probably still want to): Set the capture area to be smaller around the object you are observing, its as simple as that really. Now the view is zoomed in, you are still at F/5 so the 4s exposures are given a much better chance at success and since you were oversampling with the barlow you actually have the exact same amount of detail in the image! No negatives this way.

I think you kind of missed the point with signal here. How bright the image appears is surely of no concern if it contains no extra information? After all if you were after signal only you would put the camera to the maximum gain it can go and get a very bright image. With average binning the same signal to noise ratio improvement happens than with sum binning, the image just doesn't get brighter, but you can extract more information out of it by applying a harder stretch - which sharpcap should do for you if you click the autostretch button in the histogram. Its possible you get nothing more out of it if the SNR gain is so little but this also applies to the brightened addition binned image. By the way binning with CMOS cameras does not allow you to get away with shorter exposures as read noise gets "read" from the individual pixels whether you bin or not. But of course whatever little positive SNR you have from a short exposure will be multiplied by the bin factor, so it is still very useful if you are oversampling and the extra resolution is of no value to the observations - just not something you can rely on to make very short exposures be much better.

I would be interested to learn just how exactly does the binning happen on camera with the software you use. If it does debayering first to reach 1x and then bins to the desired value there will have been interpolation done on the raw frame. Debayering algorithms have a habit of turning single hot pixels into larger hot pixels, because the debayering process is just a guess on what colours should go in the blank spaces between pixels so there are mistakes (normal imaging employs dithering, so not an issue) Superpixel debayering, if an option, bins x2 and has no interpolation issues. Not debayering and binning results in a mono image, because the data from OSC cameras is really mono. On light grasp of binned images, no difference in addition and averaging methods because its not the signal you are after but the signal to noise ratio.

Dew shield? Never had dew or frost on the secondary in almost exclusively +90% humidity and between -25 and +15 with a dew shield. Dew everywhere else sure but on the mirror, never. Seems counterintuitive to heat the inside of the tube since tube currents with rising thermals are one of the issues newtonians want to avoid if sharpness is at all important.

Simple, easy to use, and astrophotography processing does not go together. You will have to compromise a little bit here, but not compromising on the astrophotography processing part will get you a headstart in learning to process astrophotographs that are very different from "normal" photographs. Try Siril, a free astrophotography processing software: https://siril.org/ Its free and relatively simple to learn. Fights toe to toe with paid software in terms of what it can do and certainly for a beginner will be the least uphill-battle kind of deal because the most important tools in it make processing a breeze. At first i would suggest ignoring everything but 3 tools in it, the background extraction tool, the color calibration tool and the histogram transformation tool.

The method of taking the flats you mentioned sounds ok to me. Only thing to make sure is that there is no screen flicker with the laptop (probably not a problem) and if there is the exposure needs to be long enough to even the flicker out but you can just add more interlayers with t-shirts or printer paper or something like that in that case (if the screen flickers try to make the automatic exposure at least 1/2s, that should even everything out). The mechanical accuracy and stability of everything between the lens cell and the camera sensor are what make or break flats, and just looking at the scope i would assume the focuser to be the weak link here. If the focuser can wobble from one side of the sky to the next it also means the vignetting profile changes, so flats become impossible to match to lights. Its a problem even with good scopes sometimes, the focuser really needs to be much better than just ok to be reliable for astrophotography so this might not be something you can fix easily. Looks like it might have a tension adjuster? If it does, tension it so that you can only barely move the focuser in and out to make it more stable.

No flats could work better than badly working flats, try without the flats? Also you will need to crop the image to a size that is inside the ring this way but you may have needed to do that anyway because of the field curvature (also the image is slightly out of focus on the red channel and completely out of focus on the green/blue channel because of chromatic aberration but not much you could do about this)

2 main reasons for the ring. The first is that you are using a 1.25'' filter with an APS-C sized camera, so there is severe vignetting. You need bigger filters for APS-C sized chips to get less vignetting. The second, and what is the bigger issue here, is that your flats have not worked. Looks like dust donuts are still visible so flats are not working, and the ring artifact would be also gone had flats worked. How did you take the flats? Did you take them immediately after imaging, or better yet during imaging without first moving the camera or touching anything on the scope in any way. And also, how is the focuser on the scope, if it cant keep the camera sturdily in all orientations you will never have proper flats.

And a scruffy mount in general. If the axis are sticky, or the system is not balanced (such as because the axis are sticky), or there is excessive backlash or some other mechanical gremlin then settling will take a while. My AZ-EQ6 has some gremlins in it and so the dither spike always appears.

Do you have solar filtering over the aperture? Specifically something that is designed to work with the large aperture (for solar 190mm is gigantic).

If you set settle time to 0 you will have a trailed frame aftet every dither, so in this case every frame because it takes a while for guiding to lock on again. I would advice to increase settle time to at least 30s. I use 40s and settling still fails about 70% of the time. Increasing the settling tolerance somehow would probably fix it but have not found where to do that, or have bothered to try and find that really.

You are joking, right??

I bought this one, but from the German version of amazon: https://www.amazon.co.uk/AGPTEK-Brightness-Animation-Designing-Stencilling/dp/B0771J6JY4/ref=sr_1_12?keywords=agptek+a4+led+tracing+light+pad&qid=1675896144&sprefix=agptek+a4+trac%2Caps%2C92&sr=8-12 It doesn't look exactly like in the advert, and mine wasn't new even though they sell it as new, i am pretty sure many of the adverts you see in Amazon are actually the same product with a different label and you might not get the exact one shown in the images. You get what you pay for in a 20 pound plastic toy but for taking flats its perfectly adequate. The light is a little bit on the blue side, but that also does not matter too much.

A4 sized LED tracing panel? Very cheap and will cover the 165mm dew shield for sure.