ONIKKINEN

Looking very nice, all of them. Especially the long 3 panel mosaic looks very dramatic and imposing with this light. Regarding RGB, the image must be well colourbalanced before attempting to pull out anything with saturation. Registax 6 auto RGB does a decent job most of the time, give it a try and see if it works out for these ones? Usually necessary to tweak a bit afterwards, but its much easier when there isnt a single overpowering hue masking the image.

Scopes wont really reach equilibrium if the temperature difference is that large, not without active cooling with fans taking place anyway. Even open tube ones like newtonians have a rough time adjusting to 40 degree changes and the optics will probably remain a bit warmer than ambient through the night. My cheaper version of this scope can take about an hour to adjust to the 20 degree difference there currently is, and at this point the lens has dewed up. So not actually sure if equilibrium is reached without some dew control.

Thanks! I am going to print that mosaic and put it on the wall, customer service from one of these printing places also said that its a little bit too dark so you are onto something with that. The room i process has no real sunlight glare issues so is quite dark. Should always proof the processed image with different lighting conditions before finishing, but this time i was too excited to post it. Playing around with a smaller image to print so that i dont waste their time and my money printing a giant wallpaper that goes to trash!

All looking pretty good. Option 2 with Bin2 takes the cake though. On the topic of binning with OSC cameras (assuming OSC camera used). Binning x2 with an OSC camera will not get you a 2x SNR improvement from the "normally" processed image that has been debayered using an algorithm that uses interpolation between pixels to figure out the gaps in the sensor. This is because the 1x image is in effect a resampled image from the true data the sensor captures, in this case roughly 3000x2000 pixels instead of double that. This is because an OSC sensor takes 4 images with this half resolution, 1 red, 1 blue, and 2 different green ones and figures out the gaps between these with interpolation to present the "1x" image at 6000x4000px. All the detail remains in the 3000x2000px image however, so it is just basically resampled upwards to 200%. You might think that why bin at all then, if the gains are smaller? Well, there are no downsides to binning an OSC image x2, so might as well. If you need the bigger resolution in the end you could upsample the image as the last part of processing and you will end up with a better image than the one that was processed at 1x from the beginning. TLDR: Bin2 is the "normal" image with an OSC camera, not binned is upscaled. Unless bayer drizzle was used instead of debayering, but this works mostly with planetary and lunar with thousands of frames each dithered well because of seeing.

For better options than the PDS or photon there is the TS ONTC 6" f/4: https://www.teleskop-express.de/shop/product_info.php/info/p12848_TS-Optics-150-mm-f-4-ONTC-Newtonian-Telescope-with-2--Focuser.html Since the tube is rigid and well put together you skirt around a major part of collimation troubles. Also the UNC 6"f/5: https://www.teleskop-express.de/shop/product_info.php/info/p13462_TS-Optics-6--f-5-UNC-Newtonian-Telescope-with-Carbon-Tube.html Both are pricier than the 150PDS, but the price is in the right places. Astrophotography with a newtonian is viewed as troublesome mostly because most of the cheap newtonians are specced for visual, so have lacking mechanical rigidity and only ok focusers.

Mosaicing would be plan b if the wider shots dont end up working from the coma perspective. I find it much easier to babysit a single big panel for a while longer though so that is preferable. Still banking on seeing being better which might not happen, so a bit of a gamble anyway.

Just received an email from Markus Ludes, who did say that down to 2x is the limit for still good coma correction for the APM 2.7x one. Pretty sure this is what i will end up going with. Ideally i would be imaging with the entire chip for lunar, but that might be a tall order. 2560x1440 capture size would be very nice though, conveniently my desktop resolution and wide enough for most interesting features on the Moon. Seems likely to work, only means a 50% increase of the coma free field compared to just the barlow effect.

You can combine any combination of exposures, provided that they are not completely out of the same league (like 10s and 600s) when stacking. Choose a stacking software that does normalization of the input subs, and weighting of the subs based on their measured noise levels. This way you will make the most of different length subs and be greeted with the best image in the end. If you do end up taking very different subs, like 10s subs and 600s subs, normalizing them will be difficult and i would say not worth the effort. In this case you would merge them in processing later. Could be used to create a nonsaturated star layer for example, if your 600s subs had saturated all the stars. You will need to calibrate each different dataset with their own calibration frames though, including (especially) flats. Ideally you will take flats at the end of every night and use those flats to calibrate that nights data. If you have a permanent setup, or if your camera remains attached to the scope after use, you may find that reusing the same flats works ok. If you are imaging with an imperfect scope like a newtonian or one of the more affordable doublet refractors with suspect focusers, you will need to take flats every time. At least you will want to.

Read through the thread, it wasn't super helpful to be honest. People talking about the thing with refractors and entirely for visual, so the question remains unanswered as far as im concerned. 1600px is acceptable for sure with Lunar closeup feature imaging, but the problem is that everything in the optics must be exactly aligned, or that 1600px area will not coincide with the center of the sensor. At f/4.4 its very easy to be half a millimeter or a millimeter off center, and that would ruin half or most of the frame. Have tried that and had that exact problem (without the paracorr). Im guessing this is why almost no-one is doing lunar/planetary with f/4-f/4.5 type newtonians. I have sent APM a message, if anyone knows the answer to using the barlow with lesser backfocus, its them. Or another scope at that point to be honest... Rather not go that route

Currently i am imaging with an f/4.4 newtonian, TS 2.5x APO barlow + paracorr and ZWO 678MC (2 micron pixels). This barlow is of good quality, but it cant easily be shortened to be of lower magnification due to some weird proprietary thread that only connects to the body it comes with. For Lunar, i want to have some coma correction because the usable field of view is abysmally small otherwise. For planetary, dont care since Jupiter will be just 200 or so pixels anyway. So maybe the coma corrected 2.7x APM one? That works out to f/11.8 which ia too much if i were to aim for critical sampling at pixelsize x 4-5. Could i use it with a shorter nosepiece and get a little bit of coma correction and a more appropriate barlow factor? Let me know if you have tried this. Or a 2" barlow that i put the paracorr in. Also dont know if that would work well. For 1.25" general use barlows there seem to be a dozen different options to choose from. Which ones are worth the money? Not really made of money at the moment so cant afford to buy the wrong one, any ideas appreciated!

You can platesolve without having a mount connected, yes. It will show you the coordinates you are at and you can then manually move the scope closer. Rinse and repeat until there.

I wonder if your mini-pc on its last legs dying caused the failed subs with banding? That issue is still a mystery and i would say unrelated to lightleaks and temperature issues so the main problem could still be ahead. I guess you will find that out with a new one.

Not noticed that between indoor use with the supplied AC power brick and my outdoor setup with a 12V DC power station. But on the topic of thermal stability, taking short exposures will overwhelm the cooler really fast. You dont really notice this when outside shooting generally longer subs only, but when taking flats or darkflats (or worst offender: bias) frames the cooler will often lag behind a little bit for a few minutes. What i found to be the best way to avoid accidentally taking warmer flats is to first take 30 flats (mine are very short, so no time wasted) and then let the camera heat up during that. It will usually go from -10 to -9 or -8 even. Then the camera will ramp up its cooler power over a couple of minutes and once at -10 again i will take the actual flats that i will be using for the nights data.

If they are properly calibrated, then its ok. But there is an issue with higher temperatures causing possible calibration issues. The 0.2 degree difference between your flats and darkflats temperatures is irrelevant at -10 where the thermal signal is very low, but actually a measurable difference at +25 so the flats may not actually be calibrated well at high temperatures.

Great images, all of them! This one region in particular is very troublesome to do RGB with i think. The blues get deepfried quite fast, you have this workflow nailed down perfectly it looks like!

Alright, a few issues with these. Getting closer for sure. Fits headers reveal that your flats and darkflats were taken with the cooler off, or at least not working. Darkflat was taken at 24.7c, flat at 24.9c. Both the dark and light frame were taken at -10 or at least close to that. On top of that it looks like you have lightleaks, quite significant ones, with both the darks and the flats. Screenshots below with the false colour rendering mode and a histogram stretch to reveal every little thing wrong with frames (really useful for things like this): Darkflat, left to right gradient. Not sure it could be anything but light leak: Dark, central bright spot. My guess is you took the darks with the camera on the scope? Both have much higher median ADU values than the camera should have with 768 offset (from fits header, default, keep this as is). So light leaks is my guess, or perhaps its also possible something is wrong with the camera but wouldnt claim that yet before these are fixed. The flats you probably cant take accurately anymore if you have removed the camera from the scope, but if not you could take them again but this time also at -10. The darkflats and darks you can however retake and make sure the cooler is actually powered on. For darks and darkflats you need to take the camera off the scope and plug completely from light somehow. Just a few photons creeping through will ruin them. The thermal current buildup of the camera is so low that even at 25c you will have probably less than one electron of thermal signal with your 4s flats (just guessing, but it will be still very low). My suggestion would be to retake the darkflat, and dark, both at complete darkness and at -10 and try if the flats work. Probably wont be perfect as there is the temperature difference. If that doesnt work, try retaking flats at -10.

Hmm, same offset, gain, temperature and still no working flats. Something doesn't add up. I was thinking if your dark flats have a lower offset than your darks for some reason you would get undercorrection. The overcorrection without darks is right, because offset is not removed in that case. And also, i dont have PI (yet) and so cant open .xisf files. Could you upload one of each file, darkflat, flat, dark, light in 16-bit .TIF or .FITS format? Not sure i can help if everything is correct but cant hurt to have a look?

Linear PNG screenshot from Siril: Screen stretch mode set to Histogram in Siril: For this particular example the readout pattern is clearly visible, because the flat frame is only 0.0039s in exposure and so basically a bias frame with a bit of light mixed in. Not a problem with real world flats. For statistics that you cant really measure from these, 400x400 pixel selection box in the corner has a median ADU of about 32k, while in the center it is 35k so yes the sensor does have inherent vignetting even if there is a flat panel just 17.5mm from the sensor.

Ill take some flats with mine without any optics in front of the camera to check for the vignetting thing. The top image is a bit concerning, my first bet would be some kind of power supply related issue that is causing the camera to malfunction, but it could very well also be some kind of fault with your camera. The actual image with vignetting you posted clearly shows that the flats have simply not done anything. Post a single raw flat frame (choose one randomly) and a single light frame* in .FITS format and maybe we could help a bit more. Just guessing without the actual data. Just checking to be sure, but you have at least 700 offset and use the same offset for all calibration frames and light frames? Probably do, but just making sure. *Calibrated flat frame, and calibrated light frame. Or one of each type of image.

Could be worth a try, but i am doubtful in this case since the image is already around the size it would need to be if all the available detail were resolved. Drizzling a properly sampled/oversampled image will just result in a bigger blurry image, but no more detail.

Reprocessing some of the softer closeups with everything but the red channel discarded. Looks a little bit better i think: Aristoteles, red only: Theophilus, red only: The southern regions with Metius and Fabricius, red only: I think i took some wrong turns with the first pass of processing these and the terrible green and blue channels threw me off.

Here is my try, with ASTAP, Siril and Photoshop: First Binned 2x2 in ASTAP, then resampled a bit further to 80% in Siril as the stars are still a little bit big but i think binning 3x3 might be a bit too much. Then background extraction, Photometric colour calibration, Little bit of Asinh stretch to preserve colour for the subsequent stretches, SCNR green, Partial histogram transformation stretch and export to Photoshop. In Photoshop created a starless layer with StarXterminator and subtracted that from the original to create a stars-only layer. Camera raw fringe tool for the stars-only layer to reduce chromatic aberration somewhat. Not sure what the best way to reduce CA in refractor images is since i dont image with one, but this one was simple and worked somewhat well for this purpose. Stretched the galaxy only layer further while leaving the stars as-is from the partial Siril stretches. Did some layer masked desaturation, denoise and sharpening to parts where applicable (denoise and desat for background, other way around for the galaxy). Recombined the stars with a simple screen function for the galaxy layer in front of the stars. Now that i am looking at the image i am thinking maybe i left it a little bit too green, but i always get "colourblind" when processing and often change my mind the next day. But for testing the data it will do for now.

What scope are you shooting with? If you pair a somewhat fast scope, like a newtonian, and a modern low read noise astro camera you can get away with very short subs under moderately light polluted skies. The more light pollution the shorter you can make the subs after shot noise from the sky overwhelms other sources of noise - called read noise swamping. I had moderate success with an f/4.2 newtonian and a camera with about 1e- of read noise, and at the time was only taking 30s subs because of mount issues. I also deliberately chose targets at higher declinations because the sky moves slower (relatively) the closer you you shoot to the celestial pole.

That is pretty crazy for a phone image. Technology is improving so fast right now!

Following with great interest, looking good so far and this will make a killer composite image in the end for sure. You can kiss this kind of project good bye under Finnish skies so best get it done in Saudi while you can😃.