ONIKKINEN

Odd looking galaxy, reminds me of M110 with the dusty core. Nice picture and interesting to see the comparison to the older attempt.

Carbon fiber parts cost an arm and a leg so not that strange of a price. 0.5mm thickness is a little bit too risky imo even if its carbon fiber. Better than the stock one by a mile still i would imagine. The metal spider i linked comes in a 286mm variant, you could shorten the vanes yourself to make it fit. They are held to the center simply with 3 screws so you could remove them, shorten each by 35mm and refit them.

I just eyeballed it, will try with spirit levels next. I will orient the tube so that its perfectly level and adjust the focuser until the spirit level agrees that both the focuser drawtube and tube are even. I have a Baader diamond steeltrack which is adjustable in both pitch and yaw so it shouldnt be too difficult. By the way, try this spider if the replacement is also unworkable: https://www.teleskop-express.de/shop/product_info.php/info/p9317_TS-Optics-massive-Metal-Spider-for-8--Newtonian-Telescopes-D-223mm.html I installed that on my VX8 and it is a lot better. It only barely fits inside the tube so it kept the tube from collapsing, unlike the thin and flimsy spider originally. Pretty sure the VX8 and CT8 share the same spider so might be a decent fix for yours too.

Thank you very much! I have cropped a little bit off the edges where double diffraction spikes start to appear. Jury is still out on whether its backfocus, collimation, or tilt induced collimation relataed since it was the second time out with the scope after i swapped the aluminium tube to a carbon one, so the focuser could be a little skewed against the tube still. Sharpness in the middle was for around 2.2-2.5'' fwhm stars.

This article mentions the collision : https://earthsky.org/space/earths-night-sky-milky-way-andromeda-merge/ Whether its true or not is another thing as its based on the assumption that our galactic halo is similar in size to Andromedas halo. May not be the case, and difficult to tell our halo size from within it.

The RisingCam camera body is only 80mm in diameter, so shouldn't be any more extreme than your average F4 newtonian obstruction. T2 inline focuser and should work nicely, will need some DIY hardcore steel spider though.

Also could try to lower the Amount, 0.9 is the most i have needed. The problem with the invert-SCNR-invert workflow is that it removes actual magenta from the image which exists in galaxies (hydrogen regions). For this target not an issue, but worth keeping in mind that some images dont benefit from that.

Most beginners would do backflips from joy if they got this as one of the first attempts, so you are right i thought a couple steps too far ahead. Pretty sure i have seen this image before, if i recall correctly you had a wratten #8 and an aperture mask? And binning of course, to counter the loss in aperture. These dust spots and edge artifacts would actually be not that difficult to remove in Photoshop with some clone stamp tool, content aware fill, healing brush etc, especially if the image is turned starless with starnet++ first. Not sure if GIMP has similar tools but would imagine it does. Probably not something a complete beginner would know or figure out how to do but not that difficult either so perfect flats more of a luxury at that point (and if the sensor were bigger).

Since you mentioned M81 here i might mention that it was one of the first targets i tried with a 200mm newtonian on an EQM35 unguided. Didnt produce a great image but not because of the lack in guiding. This high in declination the sky moves so slowly that the beginner might forego guiding completely. The mosaicing thing could be trouble, i think you need to have more or less perfect flats to give yourself a chance of getting a seamless mosaic and the budget mak might not be up to that with its movable mirror and maybe not as sturdy a visual back as it should be (not sure about that but would imagine its not rock solid).

I think you have a terrific image here with a wealth of dusty stuff around this difficult target, but a number of things could be done to make the best out of it. First, an easy fix to the background that looks magenta: Invert the image and run SCNR green on it and invert again. Inverting an image turns magenta into green so SCNR green will work, inverting back restores the colours to where they should be. I think in this case you should not have done SCNR green since the result is too magenta (too much green lost). For what little i have tried SPCC on it doesn't nearly as often require an SCNR green afterwards compared to the older tools, so test that out too with the linear files. Second issue is with the sampling. Looks like you have drizzled the image x2? What you should have done is gone the other way, binned x2. That will provide a very good sampling rate for your kit, 2x higher SNR (4x compared to drizzled) but still produce a healthy 3000x2000px image with your camera. The higher SNR will also allow you to sharpen much further and control noise in noisy parts of the image. In short, sampling went the wrong way x2, try without drizzle and integer resample x2 after stacking. Other than these 2 points i think you have done a really good job with the processing, these dusty dark nebulae are very tricky to process. Your attached file was not linear so a limited amount of stuff can be done with it but i tried anyway, also i was able to sharpen the image more since i binned it x4 but doing it from the linear phase would yield much better results:

Now this is a challenge! Never even considered maksutovs but actually why not? Exposure times will be inconvenient but a beginner has 10 other things to worry about so they probably dont care.

Does this scope exist? Seems too good to be true. Long focus achromat maybe but the 2kg is suspect?

I think i would rather have coma that can be fixed later by saving money for a coma corrector than have an achromat that will always have CA. Fringe killer/wratten#8 will hide it, but there is no way to get rid of it fully without a compromise. We are also comparing a tiny 62mm aperture to 130mm aperture so i think the choice is quite clear. My vote for the ultimate budget DSO telescope setup would be an EQ5, with DIY onstep motors if necessary, and a 130PDS. If the imager chooses a dedicated astro cam instead of a second hand DSLR the sensor size will be quite small in budget models so coma will be less of a nuisance than with a large sensor. Second hand DSLRs are often the cheapest so probably not the case. Something that is easy to overlook when figuring out a budget build is that you really cant afford to buy cheap/what you dont want as in the long run the intermediate choices cost you money instead of saved it. You should budget the kit so that there are the least amount of compromises or things you have to completely replace in a few years or however long it takes for you to save money for it. If you buy the achromat but you want to replace it later because of the CA and the small aperture you are now in the negative budget wise for however much the scope cost. Maybe you can sell it and get 70% back, but that is still a loss and no guarantee you can get rid of it in a timely manner. So my advice is to look ahead for something you want rather than something you think you could get away with in a pinch. Of course it doesnt mean that you must save up for a Planewave CDK, but you get the idea - think 2 steps ahead when budgeting.

Big aperture (for the target), dark and exceptionally transparent skies, 1e- read noise makes the magic happen. Presentation resolution is also a forgiving 2'' per pixel so SNR of the stack is very good. But yeah, very surprised too that it turned out so clean so quickly.

55x60s per panel for a total of 1h50min with an 8'' newtonian: Took this before the M81-M82 image i also just posted, so i had a very productive night between the 24th and 25th. Almost makes up for the fact that the last 2 months were nonstop cloud. Mosaiced in APP which did a fantastic job requiring no fiddling with the seams. Linear processing in PI with SPCC, BlurXT, NoiseXT and a small resample downscale to fit my 1440p monitor better at 100% zoom. Partially stretched and then moved on to PS for the starless nonlinear stuff which included sharpening and denoising with various methods including NoiseXT of course and some local contrast adjustments. Very happy with it for such a short image that i previously didn't dare image because i was worried mosaicing is difficult for some reason.

Somewhere around 240x60s exposures from a bortle 4 area in good seeing and transparency: So far the sharpest data i have yet to capture, but unfortunately a bit affected by some optical gremlins if you look to the corners so room for improvement still. I dont think they detract from the 2 main subjects so not too worried about that. Stacked in APP, Linear processed in PI with SPCC, BlurXT, NoiseXT, some HDRT. Nonlinear fiddling with Photoshop including StarXT. I added the stars within M81 back to the starless layer from the stars-only where layer (StarXT likes to deposit stars resolved within galaxies to the stars only layer) which is why M81 looks a bit sparkly. Not sure if i have overdone it, its still a new workflow for me so might have another opinion tomorrow or a week from now. Background looks a bit funky because there is IFN pushing through at some points. Not enough to try and process them out as a part of the image but also enough that i dont want to try and bruteforce remove it. If i get 2 or 3 nights more under similar conditions it should be possible to tickle it out of the noise floor. I thought about not posting yet because i do want to see the IFN, but who knows how many months/years from now i get the opportunity to shoot under dark moonless conditions again so might as well post now, and the galaxies being so bright are at a point where i like them to be anyway.

I have to travel a bit to find a location with enough decent visibility to the south so these opportunities are few and far between regardless of weather. Binning is working overtime to hide the starshapes here, i doubt i could get a nice image at a bin level of any less than 6x. Maybe 5x if seeing was really good but rarely is.

Im having fun experimenting with mosaicing and extreme binning to circumvent the low altitude sharpness issues. At 100% zoom of the original capture resolution it appears as an aberration bingo with a hit on every line, but reduce size to 1/6th and they all go away like magic. An Orion 3x3 mosaic is in the works too but that one was cut short due to arrival of clouds, so couldn't finish even a single run of the sequence but it should also turn out pretty good even if it is a few degrees closer to the horizon.

10x60s in a 2x2 mosaic of the Horsehead and Flame nebulae with an 8'' newtonian, Rising Cam IMX571 OSC camera and an Antlia Triband RGB ultra filter. This target is not really shootable from my latitude of 60N, at least not if one would go for high resolution data. So i binned it x6 to make up for the short integration and the terrible stars you get with 20 degrees of elevation. Seeing was also bad not just towards the horizon but everywhere else, so this was more of a necessity than a pure choice i wanted to make. Processing in PI, Siril and Photoshop. The colour palette is whatever PixInsights SPCC tool made of it when i input the filter information of the Triband RGB (removed a little bit of green afterwards). Applied BlurXT but it has very little effect because the resolution is already quite crunched to 4.5'' per pixel. Did sharpen stars a little bit, and maybe the edge of the horse a bit. Also generous application of NoiseXT to cull the noise a bit. No starless processing for this, didnt see the point as BlurXT fixed stars well and i find there is no need for specific starless processing afterwards.

Any chance that car headlights could sweep the sky just above the scope? If there was a thin layer of fog that is not apparent naked eye it could look like this. I often setup at car parks or slightly off a road and these things happen.

First light of a newly installed Helmerichs carbon tube: Perfect conditions for heavy frost, was above 0 and raining in the afternoon and then plunged to -6 for the night with humidity licking the 100% mark all the way. Also perfect conditions for 3'' fwhm seeing, but beggars cant be choosers so the scope goes out. Its mildly interesting that anything with electronics in it, namely the 2 cameras and the mount, are free of frost while everything else is completely frozen. Almost looks like the clean cameras dont belong in the scene with how dry they are.

Hmm, i do think the 0.47'' version looks better in all of the above comparisons so far to the binned one. Neither are comparable to HST data, but we are not comparing it to HST data are we? At least we shouldn't be. The comparison was between @tomatos 6'' refractor and whether or not BXT worked better with the unbinned or not. The middle one from the bottom row looks sharpest here, agree. But these are not apples to apples comparisons in my opinion as they are different processes so different choices must have been made. Also comparing mono to colour, which hardly has a point since the point is to present a colour image. My eye gravitates towards the colour image here at first, the HST image second and your sharpened version third.

Just stirring the pot a bit and adding some options, if you were looking at a 2600MC or similar camera. (prices are what i could find shipped to UK addresses) Altair, 1400 pounds: https://www.altairastro.com/altair-hypercam-26c-aps-c-colour-tec-astronomy-camera-16bit-6451-p.asp QHY, 1600 pounds: https://www.modernastronomy.com/shop/cameras/cooled-ccd/qhy-cooled-ccd-cameras/qhy268c-photo/ ZWO, 2000 pounds: https://www.firstlightoptics.com/zwo-cameras/zwo-asi-2600mc-pro-usb-30-cooled-colour-camera.html And a wildcard, a RisingCam from AliExpress. This is often the cheapest one and currently at 1121 pounds without VAT so just a tiny little bit cheaper than the currently excellently priced Altair one: https://www.aliexpress.com/item/4001359313736.html?spm=a2g0o.productlist.0.0.6f047164JGhOx6&algo_pvid=88c7fc7f-59b2-4b58-9bdc-a75b08237944&algo_exp_id=88c7fc7f-59b2-4b58-9bdc-a75b08237944-0 Pick your poison, all of these have the same sensor and more or less the same technical specs. Some small changes in drivers and read noise and such but generally you can treat each of these as the same camera when it comes to data that comes out of them.

Fewer pixels so the filesize is smaller naturally. By the way ASI fitsview is not very useful for actual image analysis as it stretches the image with some arbitrary set value so you are not really seeing the raw data. Its better to view the image in something like Siril where you can make objective measurements on the pixel values/standard deviation/whatnot and try to make an educated guess on the sub. But ultimately i dont recommend viewing subs at all, just check their statistics when stacking (and maybe reject the worst ones) and only judge the final stack on quality.

How do you quantify the amount of noise in bin1 vs bin3? If its with a stretched file you should make sure that they have an equal stretch. You should also view both at 100%. Bin3 will have 3x signal to noise ratio or in other words be equal to a bin1 exposure of 9 times the length. It just doesnt make sense (cannot be true) that the bin3 image is noisier.