ONIKKINEN

Typically they are quite weak with maybe a little bit of green. The massive flare back in February really did look like many images with vibrant green everywhere in the sky, but that one also had a rare red component which made the sky look like it was literally on fire. But that was more of an exception than a rule, naked eye red aurora is quite rare even at 60N where i live. The light show week ago apparently was similar, but i was in a cloudy spot then so couldn't tell.

Hmm, the differences really do seem suspiciously small. If i had to guess which one had 5x the data im not sure i would make the right call blind. Your flats are overcorrecting by the way and that could throw a spanner into the works with normalization of the subs which will ruin all hopes of getting the best possible image especially if conditions are different on both nights. Without working normalization adding more subs might not necessarily improve the stack. Maybe something to do with it? Also looks like you have some pretty heavy light pollution judging from the levels of the stacks. Was one of the nights just with better transparency? I have seen transparency affect an imaging locations bortle rating by more than 1 (from 4 to 3).

Difficult to measure objective things about noise when the data is stretched, but to my eyes the image with both nights is noticeably better. Not that i know how to make those measurements objectively anyway . Could be just a difference in level of stretch of course, but just a preliminary eyeball-only measurement makes me think the left image has a much better signal to noise ratio. The core parts of M51 are incredibly bright so i dont think there are obvious SNR improvements to be seen there. Look at the tidal tail parts for example, they are smoother with significantly less RGB noise. Also many of the Ha regions and bright blue clusters look tighter in the left image. By the way, when you say sticking the 2 stacks together do you mean actually just stacking the stacks instead of the data from the 2 nights? Stacking stacks will be less effective than integrating the subs to a new stack.

I will admit i have not paid any attention to trying to get a specific offset pattern with mine since i collimate via laser. I only check the secondary is roughly central when i have removed and reinstalled the secondary for some reason, but the top image looks more familiar to me.

This is what i would do, as a newtonian imager a "dont try to fix what is not broken" mentality is good. You mention that everything is perfect in terms of collimation and tilt so is this really important? You have a real chance here to make things worse with fiddling - just leave it be and enjoy a well collimated newtonian. But anyway, looks like you just need to center the secondary under the focuser like you already concluded at first. The only thing this achieves is that you have less vignetting. Simple to do but again i would not bother. A centered secondary is no requirement for collimation by the way. Its just good to have since vignetting is lost light.

If a concrete launch pad built here on Earth gets atomized by the engines i am left wondering how is the upper stage ever going to land and lift off from the Moon or Mars? Yeah ok fewer engines on the upper stage and not nearly as much thrust required to lift off compared to Earth, but still it all seems way too risky. The engines would excavate a massive crater on the way down and on the way up so twice the risk of some regolith rich exhaust.

I tried not to look at your, or other images for reference during processing so that i dont introduce some bias on what is noise and what is actual detail because it was not at all clear when looking at the initial data. I wonder if i would have just excluded the tidal tail if i were to process the image without knowing it was there in the first place, maybe i would have knowing now how faint it is. Negative from the green channel below where it is just about visible:

110 x 120s captured on the 23rd with rapidly waning darkness: Annotated: Never imaged M106 before so did not know what to expect, but looks like an interesting target. Plenty of background objects to scratch the deep field itch i have and a main galaxy itself which looks like will need a fair bit more time to do proper justice, and maybe some narrowband one day. This was likely the last image of the season, unless i have forgotten about some dataset completely which could happen. Naught but reprocessing to be done over the summer otherwise! -Oskari

5-ish hours: Annotated: Hoped to get more data on this but the season has now ended and headed for the 4 month long summer break, which feels weird since just 2 nights ago i was scraping frost off my telescope 🤪. @ollypenrice did mention that the tidal tail was faint but i had to see it for myself, it is REALLY faint. Too faint for my attempt in fact, even with careful masked stretches it has ruined the background with mottling. There was also a reflection from Algieba just off the screen in the red channel which took some brute-force gradient removing to get rid of which may have made the tidal tail recovery attempts more difficult. Comments, critique welcome of course -Oskari

Increase the rejection for stacking and add weighing of the subs? The tree-visible subs will be given lower weights and should contribute less for the final image and the strict rejection would reject the rest in theory. If there are more subs with the tree visible than without, then its a problem because they would not be outliers in that case and you might want to scrap the worst ones.

Hello and welcome to the lounge, As a newtonian imager myself i will go ahead and inject my own biases here and say that you should go with the Quattro 8 out of the options you have. Really it seems the ideal choice for what you want, large aperture to help with the small faint targets you want to use it for, but not too much focal length like with the RC8 where your focal length and small sensor leaves you with a very narrow field of view and small images (if binned to reasonable resolution). With a 1.0x coma corrector such as the TS GPU you are looking at 0.62''/px which will leave you with a good seeing target of 1.24''/px or a not so good seeing night target of 1.84''/px at bin2 and bin3 respectively. Bin1 will be impossible or at least nonsensical. If i were you i would budget the focuser in the package from the start, or at least look at different focusers and see how much they cost to prepare for that. As for a laser, you dont need to spend 200€ to get a decent one. Try this one for example: https://www.teleskop-express.de/shop/product_info.php/info/p83_TS-Optics-Newtonian-Laser-Collimator---1-25----precise-collimation-of-Newtonians.html Its a GSO laser sold everywhere under 10 different names, here with the TS branding. You can remove the 45 degree angled silver surface from the middle and add an aperture stop between it and the laser diode. I just drilled a 1mm hole in some thin cardboard and taped it to the inside of the 45 degree block. This will remove any astigmatism and other aberrations native in the lens (mine was rice shaped at a distance of a meter) and spread the diffraction pattern over a larger area. This allows you to collimate using the shadow of the primary mirror marker instead of the center laser spot itself which is a more accurate method as center target here is way too large (2mm i think). You may want to double check that the factory installed center marker really is at the exact center to an accuracy of much better than 1mm and if not, replace it. At f/4 you are looking at nothing other than perfect collimation to have acceptable sharpness, although your small sensor will make things easier. I am imaging with an APS-C sized sensor (at f/5) and perfect stars corner to corner is really not something i am reasonably expecting to happen most of the times (and it doesn't). On top of the laser it is important to think what else is between the laser and the primary mirror. Namely the 2'' to 1.25'' adapter, it has to be of good quality. If you have one, then no cost added, if you dont then maybe you will be looking for a price of up to 200€ after all. The focuser of course has to be perfect (and you have to collimate with the laser target at roughly the focal point of the system with the focuser in the same height as when imaging). It will be a challenge, but one you can learn to do.

Simple GIF made from 35x 5sec shots with a 550D and a kit lens at minimum zoom (is it 30mm maybe?). Pointed at the big dipper just by accident as i just laid the camera on my car roof and it just so happened to point there. These looked just like clouds to the naked eye. Well, maybe a little bit oddly dancing for clouds, but did not see any colour, not really even green. Would have been a proper light show without the clouds! Towards north was completely clouded and i dont think the southern sky had any activity, so i got lucky by having the zenith at least a little bit clear for a while. Set up all the kit for astrophotography but this was all that the clouds allowed this time 😐.

For almost all cases i have been satisfied with bayer splitting (effective bin2) my OSC stuff to an end resolution of 1.52""/px, but this spring season i managed to spend some time under decent seeing and its not the case now. I noticed that APP reports registration RMS as around 0.2px in both cases, so obviously the bin2 data has it twice as bad when the error is in pixels. So i concluded in my case that if the data is really good there are actual gains in stacking at a higher resolution. I guess registering frames can only be so accurate and fwhm values of less than 3px are affected quite a lot.

Tried to do a bit of pixelmath with your dark and the concentric rings seem to remain, although i think they are weaker. But on a stacked image they should still come out. Dark looks OK otherwise, not the source of the rings at least. Maybe a bit of light leak on one side but could just be a gradient on the sensor (its normal, these cameras are not 100.0% ampglow free). Something about the flats will probably be the cause. Do you take them right after imaging each night?

For a first go this one is excellent, well done! I actually took a very similar looking image a while ago with a scope 3 times the aperture as yours, so you have managed to capture a lot of good nebulosity here. For processing, it seems like you're on the right track here and i cant spot any obvious issues. Maybe there is a little bit of greenish hue mixed with the nebulosity, which you may or may not want to get rid of and could remove itself had you been able to do the photometric calibration (often doesnt, in that case -> SCNR green, try to not use it at the full 1.0 scale and give lower values a try first). By the way the new way to do a photometric colour calibration in PixInsight has been made more difficult to do because the user interface development team of PI want to make everyone suffer and now you have to solve the image before you can use the tool. The tool will always just throw an error of "no platesolve available" or something if you dont do it before hand. Go to script-> image analysis -> image solver and run that tool. Then the SpectroPhotometricColourCalibration tool should work.

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.