ONIKKINEN

Its not quite correct to say that a newtonian prevents aberrations, its just that a newtonian does not suffer from chromatic aberration. Newtonians with a parabolic primary mirror do however suffer from coma, which requires a coma corrector to get rid of and here its not so simple as just get any coma corrector and the coma is gone. There are different types of coma corrector and not all of them do a good job, basically you're looking at twice the price of the scope in some cases for a competent coma corrector alone and if you go for one of the really cheap ones you can expect to exchange coma to some other aberration like astigmatism and/or spherical aberration. Cheap newtonians can also have large amounts of spherical aberration in their primary mirrors, which will not be solvable with any corrector. You also need a 2'' focuser to use a coma corrector, which is something that is really not viable for very small newtonians. For astrophotography the 130PDS is a great first purchase.

Im out imaging at the moment so cant check the dark, but just so you know the offset has to be removed somehow from both the light frame and the flatframe or calibration cannot happen. You can also subtract offset in some stacking software instead of with an actual bias/darkflat image. If you did not do this then it is likely this was your issue.

Convert to Mono in the tools? Not sure if this deals with your bayer matrix being visible but worth a try.

Flat looks ok to me, the light frame looks underexposed, or at the very least not optimally exposed. If you have used the exposure optimization calculations in Sharpcap you should know that those are a bare minimum viable exposure, not the best possible one (at least in my opinion). But that i dont think has anything to do with the flat calibration issue. What do your darks and darkflats look like? Post them if you want to, there may have been light leaks or something else in them that affects the whole process. Although not quite sure how they would create the concentric rings but maybe it makes sense in context with the darks.

ASTAP is the king of platesolving, if you're using some other software to capture (like NINA) you can still let ASTAP handle the platesolving on its own. There is also a sky quality measurement tool in ASTAP where you can measure your sky brightness from the images you have taken and dont have to rely on some external measurement like lightpollution.map. You can also do image annotation with the most common deep sky objects in the M,NGC,IC,PGC,Common stars catalogues. There is a blink tool as well, something that is missing from other free stacking software (as far as im aware). I know the tool does stacking as well, but this i have not used myself so cant say how it performs. Handy tool, great price to performance ratio being free and all.

Thank you! Yes, used the usual kit in my signature: 8'' newtonian, RisingCam IMX571 OSC camera, TeleVue Paracorr, UV/IR filter. Natively the newt is around f/4.4 so with the 1.15x paracorr it is just about f/5.

Around 8 hours from decent darkness across 3 short nights, but troubled seeing: Annotated version: And a closeup of the 2 spirals: NGC 4725 and NGC 4747 are the 2 interacting galaxies in the image at a distance of slightly greater than 70 million light years. NGC 4712, the photogenic looking spiral galaxy is unrelated to the interactive pair at a distance greater than 220 million light years. Some of the PGC fuzzies are crossing well into the billion light year territory, and who knows how far away some of the dimmer un-annotated specks of pixels are in the image! Quite satisfied with the image for now, given that average FWHM of the stacked image is around 4'', which is really not good for such a small target. Initially looked like a waste of time but detail does emerge after pushing sharpening really hard so maybe good seeing is not required to attempt smaller targets after all. Of course will look out for this target and may add sharper data in the future if a suitable night arises. Comments, critique welcome of course! -Oskari

Amazing!

Reprocess: Turned BlurXT and NoiseXT to 11, i think this is all there is to take from the data (for now anyway). Higher resolution too on this one. Stars are still ugly and i cant figure out how to un-ugly them from this set of data with some tube current/dew/humidity issues. Should be an easy fix once i get to shooting another set of data of M51 one day which is bound to happen.

Pulling some really nice detail from the core here! Im amazed your setup handles the 300PDS so well, it just seems like way too much scope for the modest mount but clearly it has worked.

Likewise, nice to meet other astro people in this niche hobby of ours! The seeing really did us dirty that night so its not too bad an image considering that. Last night was clear too but it was more of the same which is seismograph guiding and 4-5'' fwhm stars so you missed nothing in case you were wondering if its worth the effort to travel for imaging. Pretty sure its the warm days that do this to the seeing as have not had it this bad for the whole season.

The fan stays at ambient for a while in use and peaks at +0.2c above ambient in about an hour. After turning the fan off the temperature shoots up to +1,5c above ambient so it does produce at least a little bit of heat. This is from the back of the fan by the way, so its possible the inside is warmer as it sits between the mirror and its cell. So a theory: The fan removes heat from inside the tube for a while, helping with tube currents like it should, but then when it warms up it starts to create them. At this point i turn the fan off because i notice the stars have started to worsen and it helps for a short time. During this time the now warm fan slowly transfers its heat to the primary mirror and the tube which then restarts the tube currents. Rinse and repeat for a few hours. Maybe makes sense? Still dont quite understand why it was an issue on this particular night though and its not like the fan got really hot or anything.

Secondary is undersized by a fair bit at 63mm so anything on it should affect everything in the image. Re:tube currents; i should mention that i was imaging towards south and quite low in the sky at 40-30 degrees. Later i switched to a zenith target (M51) and most of the fuzziness disappeared. Not all of it, but it appeares more uniform in the images and not skewed on one side like here. In that case if there were tube currents rising from the tube they would not rise from one side of the tube but just straight up. Strange that this has not happened before as i always run the fan for about an hour after setting up. Sometimes not so long, sometimes longer, but never had issues caused by it. Maybe the bearings are gone and there is some extra heating from friction? I think i should test if it heats up in continued use 🤔.

Thank you! Colour calibration in this case was just manual fiddling in Photoshop as automated tools didn't do the trick at least the way i wanted them to. Thank you, was surprised to see it come out so clean despite the short time and dawn creeping in. Skies before dawn were the darkest i have imaged in yet at SQM 21.3 so there is that.

45x 120s in decent seeing: Half of the data is from dawn with brightening skies so a very limited set of data in terms of SNR. Managed to pull something out of it anyway. The stars are a mess but a sharp mess as FWHM of the stacked image is somewhere between 2.3-2.8'' . Hope to get more data in good seeing one day to increase the integration time to something that requires fewer compromises, but as this is the last week of the season we are probably looking at galaxy season 2024 for that! Squeezing out every available minute this week for short images until the summer break...

Mini-PCs do exist and are very popular in place of an Asiair if someone wants to have non ZWO cameras. I guess the reason why other manufacturers have not jumped on the Asiair competitor opportunity is that the Asiair is actually well priced for what you get with it. ZWO can sell the Asiair at a good price because they make the money back tenfold by imprisoning the user to the ZWO product catalogue for good. Another reason might be that its difficult to make one product to fit all imagers (which the Asiair does not do by the way). DSO imagers might be happy with slow storage, slow RAM, slow CPU speeds and USB2 ports while planetary and lunar imagers will absolutely need faster everything and USB3 ports.

The last 2 nights i was imaging from a very humid location by a lake and so i am assuming close to 100% humidity, the temperature also dropped by about 8 degrees in 4 hours coming to a stop at -2 just before sunrise. The scope was wet (and later frosty) within an hour of setting up but this is not the first time this has happened, just this time i noticed that stars on one side of the image were horrible, while the opposite side was much better, but still not great. One of the problem images (calibrated and split green channel image) below. The top right corner is awful while the left side is not so awful. An animation of a top right corner star from all the frames that night: And then an animation of a left side star: Ignoring the few frames that are out of focus these 2 look very different. The flaring out does not seem to happen on the left side of the image. I had the fan on at first as i always do to cool down the scope, but turned it off once i noticed the hairy flare on the right side. Doing this alleviated the issue a bit and the flaring retreated a bit, but came back after a few frames. Then turned the fan on and it again retreated, rinse and repeat for the entire night. I looked down the scope with a bright light and noticed that the primary mirror was a little bit misty which is not unusual for a night this wet. Usually this just very slightly reduces the reflectance of the mirror and i may notice a slight drop in levels from the images i have taken. Not given it much thought before. I looked at the reflection of the secondary and i saw no obvious dew or frost there, and neither did i see any on the coma corrector/camera. What dew related problem would this be then? Only affects one side of the image, leading me to think its something related to tube currents. But how the fan being turned on and more oddly, off, helps here i have no idea. Maybe the mirror fan heats up in use and so heats the back of the mirror very slightly? Then once the fan has ran for a while that heat gets overrun by the cooling humid air running over the mirror. Or maybe this is frost on the sensor itself? Could be, because it does not affect the entire image and the way i have understood it any smear on either the primary or the secondary would affect the entire image. Thoughts?

You are probably right, firearms and hunting is much more popular in the US so makes sense that the market is focused there. Have only been following astronomy for 3 years now so have an incomplete picture of what the prices were long ago.

Im sure you can figure this one out quite easily? Lets just say there is more demand for night vision kit at the moment for some places in Europe.

Harmonic drive and other non "normal" GEM type mounts will probably become more popular, and hopefully more affordable in the not too distant future. Light pollution combating equipment can only get more advanced as more and more areas around the world get consumed by city lights. AI tools for image processing and maybe even image capturing will become more popular if and when more tools are released, especially if someone starts to compete with Russel Croman tools and release their own suite of products. Cameras will keep getting better and better until one day discussions about optimal exposure times are met with rolling eyes and comments about not bothering. For many scope/camera combinations we are already there with very low noise cameras and fast scopes becoming the norm rather than a lavish expense. For visual only folks i think the world of astronomy will not change all that dramatically. Scopes keep getting better and cheaper and more ways to fight light pollution will become available. Camera aided EEVA being one of them, and maybe an electronic eyepiece type night vision another.

43x 120s with a UV/IR filter + the usual stuff: 8'' newton, paracorr, Rising Cam IMX571 OSC. Surprised how much red appears from the background with just a UV/IR filter and an OSC camera. Expected nothing but got an image that i quite like for such a short integration. Last minute decision to switch from imaging Arp94 to this, because the former was low in the sky and producing really bad data with up to 5'' stars - basically just wanted to image anything else so that the trip was not a complete waste of time. This one was also low in the sky but to the opposite direction which was much better. I was imaging at a lake which was only partially thawed and i think the open water sections produce some kind of thermal current rising from them that ruins the image every time the scope points over one. That and dew on the secondary, which was a first. Unplugged the cooling fan on the primary and it went away in a while thankfully, but the Arp94 data probably wont see the light of day at least yet.

Surprisingly detailed given this much cropping of this pair what Stellarium says is only about 6 arcminutes across. Only 4 hours too! Sounds too good to pass, im going to try and blatantly copy this framing with my 1018mm fl newt 👍.

Actually not a bad price compared to the vanilla 2600MC (but expensive compared to non ZWO imx571...). SC2210 is the chip used in the 220MM, so should be workable for fast scopes in narrowband too.

Of course, hoping that the camera does have the 220MM or some of the other new lower noise cameras. If its the 120MM then probably not so great (also why i changed the guide cam)

For those doubting guiding capabilities with filters i will mention that i am guiding with the new 220MM in an OAG in an 8'' f/5 newtonian through an Antlia Triband RGB ultra filter, which while not very narrow is still a narrowband-ish filter. No trouble finding stars to guide on and typically i am running on multiple stars if not the full 12. Guide star SNR is in the range of 40-1000 from what i can gather from my guide logs so room to go narrower or shorter in exposures (4s with mine). 7nm and the like filters are probably a pain but i reckon something like the L-enhance would still be tolerable in a fast-ish scope.