ONIKKINEN

Predictive PEC has worked for my mount on all but one occasion where i bumped the mount and i think it may have affected the prediction algorithms somehow. In that case the predictive correction happened too early and actually caused a spike rather than fixed it (below you see the correction happens before the spike, so the correction actually caused it). This spike is about 4'' in magnitude and in all other cases this disappears so the prediction algorithm seems to do its job well for my AZ-EQ6 with a not so great RA worm.

Coupled with one of these: https://www.qhyccd.com/scientific-camera-qhy6060/ It could shoot any of the usual targets with plenty of room to spare. I would image one of the common galaxy targets to see how much more 0.7m aperture would show compared to normal sized scopes, so something like M51, M81, M101. The GSENSE6060 sensor cameras cost about as much as a house, but if i could afford a 0.7m scope and a place to mount it im sure its just another accessory at that point.

I suppose its possible something about the measurement is wrong, but i have used the same tool to measure my Rising Cam and my 678MC, which both more or less agreed with the reported graphs. Just find it odd that there is such a difference.

Purchased an ASI 220MM in hopes of solving an issue with dropped guide frames that is either the fault of my ASI 120MM or a USB connection gremlin somewhere, and naturally i chose the new camera first as a good excuse to buy new astro toys. (and also replaced all cables etc) Below my sensor analysis done with sharpcap pro: And then the graphs from ZWOs website: You will notice that these 2 are in disagreement as to the amount of read noise measured (amongst other things). I dont think it performs worse than advertised, its just different which is just as annoying if you were to take the ZWO reported values as is and set the gain to 106 expecting 1e- read noise while you should be aiming between 150 and 200 for that. Anyway thought it interesting as someone is bound to ask a question one day as to what gain you should use for guiding with one of these. Personally i think i will be using somewhere in the 119-200 range with mine. And why care, its just a guide camera? I have an awkward combination of kit where the only place to put a filter is on the coma corrector, so the guide camera in an OAG is also filtered which makes guide frames very noisy when shot through a narrowband filter. The old 120MM technically works but exposures are longer than i would like and still very noisy, so the low read noise is welcome in this application.

Oh no the horror of accidental galaxy imaging... Speaking of that, there is a cluster of fairly distant and reddish galaxies nicely to the right from the top of NGC4236 that are already making an appearance in your image. I forget what the distances were as it was a while ago i last dumped hours on this but it may have been up to a billion ly.

Looking good already! The outer parts are seriously faint, i have over 20 hours on it and honestly its still not very good looking. With an OSC and mostly under Moonlight though so not the best combination.

Im picking a note from my nitpick hat for this one, but... Stars being large/aberrated is a symptom rather than the actual issue. Whatever aberration caused the stars to be wonky will do the same for the subject nebula/galaxy but since those are typically not point sources the effect is just an additional blur or loss in perceivable sharpness. But still, agree with you for the most part. More ways to work around the issue than there are ways to worry about it. Another solution for @pipnina . You could mosaic images 2x2 or even 3x3 and bin aggressively. Nobody cares what shape the stars were or what sharpness issues there were if the end result is shown at 4"/pixel where it is sharp to look at anyway.

You have captured the brightest Ha regions already in ONLY 4 hours, so you are doing better than expected i would say. Even with astromodification the absolute QE of your 600D is still not that great in the deep reds. More time put into the image and more Ha will show up. Some kind of narrowband filter would make adding just the Ha faster, but not contribute to the RGB data anymore, so its a compromise.

The image looks a little bit out of focus, but it would still be extremely oversampled even if it was in focus. Can you explain how exactly binning would not help with that and what does hardware binning have to do with that?

Can you post a screenshot or a sample JPEG of what the images look like? Since you can move past focus it just sounds like the stars are unexpectedly large which may not be focus related. With those pixels you are probably looking at Binning x3 to be nicely sampled, or even x4 if your seeing conditions are bad. At x1 you have 0.5'' per pixel, which will be nicely sampled if you are on a mountaintop in a desert and you have a guide error of 0.0 and actually still probably not good enough for that.

The flat panel orientation or some slight gap here and there issue is completely irrelevant, there is so much light going through the right way, the mirrors, to the camera that any little off axis shine is buried in it and so has no effect. If it did, there would be another type of issue with the flats, namely overcorrection like in the example where you had stacked with only flats. In fact i use an A4 sized flat panel (20€ amazon tracing panel for kids 🤪) that doesn't cover the entire front of my 240mm diameter tube and there is a gap to the sky but since there is so much light everywhere it doesn't matter and flats calibration works every time (and yes the panel also illuminates the focuser tube which undoubtedly leaks but also no issue here). Your focuser is probably the weakest link and if you want some peace of mind and a better experience using the scope you might want to look into replacing it with something sturdier. Any considerable option will cost more than the 130PDS did when new so maybe a silly upgrade. Or the primary mirror moving too much in its cell, even during the night which its not supposed to do. I used to get flats issues like this, but have not in a long time. I cant point to a single fix that did it as i fixed a whole bunch of things in my VX8. Namely swapped the secondary spider for a sturdier one, changed the focuser to a Baader diamond steeltrack, reinforced the tube with some tube clamps (i dont think the 130PDS has issues with this, since its a short and stubby tube with decent tube rings), flocked everything, made sure the mirror sits well in its cell, blackened mirror edges for both primary and secondary, and finally splurged on a Helmerichs carbon tube but actually at that point all the issues were fixed so its not a suggestion for you at all. Also, i take flats every single time i touch the setup in any way so at least once per night. More than once if i change camera orientation or remove the camera for some reason. So if you take flats in every session and these issues continue, time to look into some upgrades. I would change the focuser first, the camera has to shift only maybe 20 pixels in relation to the primary mirror for these flats issues to arise, and a focuser that is only ok will not do the trick.

Agree with @geeklee and came to a similar conclusion that the background is fixable. But it looks like for these 2 stacks you posted there is some issue with flats calibration. Looks very familiar as a newtonian imager, and the cause is a wild guess at best but something mechanical rather than software/flats exposure or something like that. Something between the primary mirror and camera sensor shifts very slightly between taking flats and lights, causing a wonky background. But its not too bad, definitely brute-forceable. I tried with Siril, i very much prefer it for background removal to DBE, especially if the gradient is difficult. Below is a false colour rendering and super stretched version that shows the initial condition nicely: The gradient is not perfectly linear, and it does look like there is a "ring" around the galaxy. This looks like its somehow flats/light leak/internal reflection related (like from lack of blackening/flocking). But its not nearly as bad as it could be. Then the fixed version where i placed the samplers manually while carefully avoiding any stars in them. The cluster of stars and the big bright star should be treated as not background in this case, and so no samplers close to them. It still looks a bit spotty in this rendering mode, but this is just for visualization and in reality the image is very clean and its not something anyone will notice in a finished image. Same story for the other image, no need to screenshot those i think.

My mini-PC has worked throughout anywhere between +10c and -25c and 80>99% humidity without much in the way of issues. The waste heat generated by the PC is enough to keep it free of frost and dew when in operation, even at the 99% humidity mark.

Ill have a look later today when i get off work 👍

Pretty sure its some kind of gremlin from a gradient removal process, but thats just a guess without seeing the linear data. You could post a linear stacked file for others to have a look at the data and maybe something more than a guess would appear.

The coordinates that Stellarium reports the comet to be in are fairly accurate, within half a degree for sure at least on the 3 comets i have tried so far. You can manually slew to those coordinates and you will at least see it in the frame and can adjust manually from there.

Dont know how to fix this, i am doing the same as you which is just re-centering again after the meridian flip has passed. For some reason NINA does not follow the same tolerance of re-centering accuracy after a meridian flip as when normally re-centering. Have not bothered to look into it more because i am always by the scope when its operating so at the worst i lose 1 sub to it, but if anyone comes up with a solution later i would also like to know what it is. As for whether you should stack the missed subs, depends on what you use to stack. APP has the MBB (multi band blending) option that can blend the missed exposures with the normal ones. If you have a short integration you will still be noticing a difference in noise around where the bad subs are blended into the good ones, so might not be worth it in the end. Also, if you have anything but perfectly matching flats you will get some gradients that are difficult to remove or just add noise to the image so in that case too its best to just scrap the bad ones.

Absolutely incredible. What bin level is this, must be at least 5x? Aperture at resolution doing some serious lifting with how just about every corner of the image is filled with detail where normally one would expect to have background.

True, just noticed that i have hot pixels in calibrated 60s subs that were previously calibrated out. The darks i used were more than a year old, so maybe once a year its a decent idea to retake darks. Worth saying that i only noticed them because i was shooting a comet and not dithering. Dithering would have removed those completely.

I hear you, astrophotography is not so much a slippery slope but rather like being thrown off a cliff with how many things can and will go wrong but of course too much is too much, and a tipping point could end up as a throw-the-scope-in-the-bin point which isn't good either as the hobby is supposed to be at least a little bit fun. Personally i would have the scope at least inspected by a professional, and fixed if they do come up with a workable solution and a manageable quote for a price. If the lenses end up being lemons in the inspection then its a writeoff, but at least there would be closure. I wish you the best of luck with this situation, sounds like a tough call with money going one way or another whatever the choice.

On the topic of NINA, the sky atlas and framing tool in it is excellent. You can set limitations such as size, coordinates in the sky, elevation from the horizon between your chosen period of time, magnitude, type of target etc. Found many interesting imaging ideas browsing that tool that i doubt i would have run into otherwise.

Tried processing it, i think i went a little too far in some points and took some wrong turns with the stars somewhere along the line, but im not going back to that now that its done. I think i left the registration interpolation algorithm to some funny one that produces the weirdly aberrated stars with specs of different colours on the cores (dont zoom in too much). Also didn't care for the starless and star only layer so some of the stars (those behind the comet) are not that tastefully put in. I used Pixinsight, Siril and Photoshop. StarXterminator and NoiseXterminator also used, so not the cheapest possible combination of tools. They are all replaceable by free ones though, just means that colour calibration cant be done in the linear phase (I think Starnet++V2 doesn't do linear images? Not sure about that). First stacked a starstack with the comet position ignored (also rejected some as you have some bad subs here mixed with the good stuff, looks like clouds!) with aggressive clipping to remove as much of the comet as possible. Then comet aligned the already registered subs and stacked a comet only image with those, also with aggressive clipping to hide the inevitable walking noise from the smeared stars. Then ran the same crop and dynamic background extraction on both files and linear fit them afterwards. Then removed stars from the starstack with StarXterminator while the stack is still linear. Simple pixelmath "+" combination of the stars-only image from the starstack and the comet only image to create the stars + comet composite. I think this method of compositing has the least chance of causing sudden baldness due to stress, i have not had nearly as much luck with DSS or other dedicated comet+stars stacking methods that seem to simply not work or produce horrible messes of the stars (or a surprise grayscale image like above in a previous comment). Since the composited data is still linear, it can be processed however you like. In this case i ran SPCC to colour calibrate(no SCNR green, wonder if i should have since stars ended up green too) . Stretched in Siril with Asinh stretch and histogram transformation and exported to Photoshop. In Photoshop i ran StarXterminator again to fix the inevitable mess that came from the stars being streaked (and your ampglow). The streaks and ampglow go away easily with the lasso tool and content aware fill since there is no background nebulosity to worry about. NoiseXterminator too at some point to reduce noise. Looking at the image now many parts of it look a bit artificial and could be improved, but this will do for now. Pretty good data by the way, much easier to work than the mess i captured a couple nights ago!

The mount needs a little bit of backlash to move freely, no way to adjust it to be tight and not effect binding. For the RA axis its not an issue anyway since the gear should be constantly under load when tracking (so no backlash). That said, which type of grease did you use and how much? You can have too much, there should be just enough to lubricate moving parts but not more than that. For the type you want to use some kind of white PTFE type grease that doesnt get sticky in the cold. Most "regular" type greases are more or less useless in sub zero conditions unless advertised otherwise. By the way are you guiding? Unguided 90s sounds like a fantasy, 15s sounds much more reasonable.

For at least planetary stacking RAM is very important, if OP is looking to upgrade their setup it might be something to keep in mind. Siril i think is not so RAM dependent but mostly write speed limited in the HDD/SSD department.

You kind of have to just research which kind of target the one you're imaging is. Galaxies, galaxy clusters, open clusters, dusty dark nebulae and reflection nebulae (bright blue ones, like the Pleiades) benefit from no filter at all, other than UV/IR. These are broad spectrum targets so there is no specific filter you can use to block unwanted wavelengths since all the wavelengths are wanted. For emission nebulae H-alpha is the brightest typically, Oxygen III the second brightest and Sulfur II the least bright. Those are pretty much your options if you want to go narrowband. H-alpha is the most useful, the other 2 depend on the target. Its best to research a target before imaging so you dont go ahead and image 10 hours of OIII on a target that is almost entirely H-alpha.