ONIKKINEN

No need to split afaik, just split the iamge that the stacker spits out before processing anything on it and you get the most bang out of the binning process. (integer resample = Bin)

Thats a nice M51, but i think there is more to be taken out of the image if you do somethings a bit differently. Looks like BXT has only tackled the core/very high SNR regions and so there is a "disconnect" in the visible levels of detail in the sharp core and soft everywhere else on the galaxy. Try integer resampling at least x2, probably x3 and you will get a much sharper image. BXT will not sharpen the soft parts of the image because from its perspective the too high a resolution image has nothing to sharpen. That said, my limited understanding of BXT is that it prefers not quite properly sampled images to properly sampled ones, so you might want to be a little bit oversampled for BXT to do its thing best. But still at least 2x or 3x integer resample will work.

You need a proper dark library and a bad pixel map, PHD2 should guide you through that. On top of that you need to set the minimum HFD value to something larger than a hot pixel but smaller than an actual star. What that value is depends on a number of things but if you have it set to 1 pixel increase it right away. * and bin the camera to something reasonable. 1x with either camera is far too high a resolution.

Yep, that's the best plan. I keep a folder of calibrated subs for every work-in-progress type target i am shooting so eventually when they are ready for stacking much of the work has already been done.

If the scope was left assembled during this time the flats should work. I have no such option and take flats each time and they always work, it doesn't take too long to take the flats so its time well spent as far as im concerned. But with a newtonian you have other things to worry about than whether the camera was removed, namely the mirror which can and should be able to move (but not accidentally, and not that much), focuser which might sag and the tube itself which might deform under different orientations/temperatures. All issues that result in any of the parts between the primary mirror and the camera sensor moving even a tiny little bit between taking the lights and flats will result in weird gradients (such as this ring). Its all wild guessing at this point, but you have one way to see if the flats worked at all and if they only worked for some of the data. Check the calibrated frames and see if this artifact appears in all of the subs or just some of them. If some of the subs have this ring and some dont, it means you have some mechanical problems somewhere in the scope that lead to flats and lights not matching.

Did you take the flats at the end of the session? Rings like these come from flatframes not matching light frames because they were taken at different times/different camera orientations/different collimations (100 little things in newtononians = always take flats for each night). Not saying its definitely caused by flats, but sure looks like it since you mention they are not present in the light frames.

You should have mentioned that filter as the first thing of the post. See the spectrum: Blue and cyan is passed, deep green-yellow-orange is mostly blocked. So the colour palette will be skewed, as the input data was skewed. You might want to just tweak the levels manually to get the palette you are looking for.

What kind of curves and what does the image look like if you dont do the curves but just do a simple stretch after SPCC?

What did you do to make it so cyan? Have you tried colour calibrating with SPCC, it churns out a well balanced image every time. Unfortunately my PI trial ran out and my bank account balance disagrees on the importance of buying the software so cant run it through now, but i am sure SPCC would not make it so cyan. The problem there is that the colour palette becomes quite boring and you'll have to selectively boost the blues quite a bit in case you wanted a typical neutral looking core and blue outer regions with red Ha poking out here and there. In that case you dont want to apply saturation globally, you want to avoid adding much yellow/orange saturation or the core becomes deep fried but instead apply saturation to the bluer and redder (Ha) parts of the image. On a side note, the image is way too big at 8k pixels in the wider axis which is also why the file size is ridiculous. You can safely at least bin x2, probably more, and lose nothing of value. Also helps a lot with your noise (only noise seems to exist in single pixel level detail).

Nice to see off the beaten path targets, and great job with the IFN! I accidentally found IFN here in this exact same field of view when searching for a high declination target to shoot with a non-cooperative mount. Swore to finish that project but never did for some reason. I think i put up to around 10 hours on it in 2021, mostly from not so great skies though and back then for sure did not know how to deal with the data (still dont, but now i know the extent to how i dont 😉). How much time did this take with the RASA? Thinking of maybe continuing where i left off, would be a shame to let the gigabytes go to waste.

Not familiar enough with the 183 to say if its something that can do without dithering, but as mentioned above the newest very clean IMX571/533 cameras can work without dithering, provided that the polar alignment is competently done, darks are well matched (and maybe that there is no significant cone error). The Siril background tool dither option is there to dither the background samplers in case you end up with a posterized result with obvious harsh transitions between areas of different illumination. Cant recall if i have ever needed it, but safe to say it does not cure walking noise nor is it intended to do so. On the topic of the background tool, make sure you have cropped the incomplete edges, dont place too many samplers and that none of the samplers are on stars or nebulosity. Put the preview mode to Histogram and negative to get the best view on faint stuff. Dont trust the automatic sampler placement!

Saturated stars are not useful for FWHM measurements, and of course in did not use them so the exposure is perfectly valid. Round stars are easy to get and thats not the point of guiding at all, the point is a round and small star. Equal errors in both RA and DEC at the same time result in a round star, yours are so big there must have been a sizeable error or terrible seeing, possibly both.

Have no say in the mount matter, couldn't afford any of the mounts discussed in this thread 😬 but obviously want one one day. But on the fits file, are you sure its a good idea to not guide with the mount? Looks like you have somewhere in the range of 3-4'' (or even more, depending on software used to measure) FWHM stars, which is unexpected with a high spec instrument such as this and wouldn't believe for a seconds its optical quality related. Honestly this is what i get with an 8'' newtonian on an AZ-EQ6 on an average-a bit worse than average seeing night guided at 0.6-0.8'' RMS, so either you really do want to guide or the seeing was horrendous this night. My 2 cents anyway. Stars do look round but just too large to believe its doing a great job without guiding.

Walking noise is really difficult to get rid of if you let it build up to the point of it being a nuisance in an image. The best way to reduce it, you guessed it, not having it! If you keep getting more data and you "overwhelm" the earlier sessions with well dithered subs you will get rid of it. But software solutions are all a pain, your best bet is to try and selectively desaturate the walking noise with masks first before trying to denoise it. Often there is a single colour that is most visible in the walking noise pattern that once removed takes much of the problem out with it (like purples for many DSLRs, maybe greens for some OSC cameras). Of course easiest to do after star removal with Starnet/StarXterminator so that the stars are not in the way. Then once desaturated you can try to denoise the grain but honestly its not something that can be trusted to do the job and you will likely end up with an image that looks like a bit of a painting if and when the denoise goes too far.

Speechless! What an image.

There is a real sense of scale and distance here with the bright foreground star and its diffraction spikes covering more area than an entire galaxy made up of billions of stars just like it. Great image! Also have noticed the best seeing always occurring with high cloud and low transparency. If i recall the meteorological explanation it was something about stable skies being helpful for cloud formation, so good seeing always has clouds just around the corner. @gorannif your skies are as baltic (unpredictable) as mine these good seeing nights are often forecasted as fully or partly cloudy, even during that sort of clear spell so its difficult to prepare.

Oh i get it, my galaxy season target list will last me at least the next 3 years of galaxy season 😅. Too much out there this time of year and so little time!

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.