ONIKKINEN

Looks like RCS thrusters firing for sure, the pulse in the beginning at least. The spiral one could be de-spinning a spin stabilized spacecraft or spinning one up for a burn, if its backlit by the sun it will be easily visible like this from Earth.

Ill give this a try later, never thought about how its actually done. I am assuming offset/dark subtraction and a 16-bit to native 12-bit conversion has to be done so that the measurements and results make sense and only real signal is measured?

There are also the IMX461 based medium format cameras, or the GSENSE4040 based ones, both around 50mm+ diagonal. Still costs about as much as a decent car, but nothing compared to the 700mm RC so almost a good deal at 10k£ (at least).

I could definitely set it to at least 200, did not check how high it could be set as the very highest gain settings make little sense for guiding. By the way there is another confusion here, the gain goes up to 600 even though the sharpcap measurements and ZWO diagrams end at 400. Go figure.

Really stretching the definition of the word game changer here. Was there an issue with WO focusers, i thought they were good quality already?

Something inside the scope obstructing the light path, like a shiny screw or similar? Could be pinched optics too. Weird diffraction spike threads appear every now and then and often there isn't a solution 😮 . I have an extra diffraction spike on my newtonian, but only sometimes, and only on some parts of the image much like yours. No clue what is the cause, i am guessing some kind of pinching but have not bothered to figure out. The diagonal noise is walking noise, which partly goes away with taking and applying matching darks and completely goes away if you dither every now and then.

It occurred to me that ZWOs own capture software ASIcap has an electron per ADU readout that i believe is read straight from the driver as its not doing any measurements. I find that minimum gain is reported as 4.96 e-/ADU, unity gain is at gain 139, 0.5e-/ADU at 199, 0.25e-/ADU at 259. So its looks like none of this agrees with any other method. ASIcap is closer to my measurements than the reported ones, but its still not close 🤔.

My VX8, from the opposite end of the price spectrum so maybe less of an issue, came with a non round tube (it was squared on the secondary end and triangular on the mirror end because of the attachments bolted to the side of the tube), a bent secondary spider, a secondary mirror that was physically impossible to collimate because a) collimation screws were too short, b) the spider was drilled to the incorrect position, c) the focuser was drilled to the wrong position, d) a bit of all. (secondary mirror could not be brought under the focuser = true collimation impossible) Just a glance down the focuser tube and an attempt to bring the secondary correctly under it would have revealed the action to be impossible so this begs the question, was it assembled by a moron that does not understand how the product was obviously flawed, or was it assembled by someone who knew it was flawed and did not care to do anything about it, or third option: did nobody actually look down the focuser of the telescope to check that they are shipping a working scope? You tell me which one of the options is the least worst... Anyway, not a company i will throw any money ever again even though the scope worked out ok in the end.

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.