ONIKKINEN

Link doesn't seem to work for me. My AZ-EQ6 is not a particularly good copy but it doesnt seem to be all that picky about cold weather - as in i see no change in performance after having just set up and after having allowed the mount to cool down to ambient which is on both sides of -10c this time of year. Maybe yours could use some servicing? The RA axis in mine was particularly tight when i got it, the locknut that holds the entire axis in place was put in way too tight, like an impact wrench tightness or something. Was really difficult to get out but once i did it started rotating much smoother. Still not butter smooth and balancing is a bit of guess work on the RA axis but much better.

Have you completely disassembled the mount yet? I mean completely taken apart and not just the worm and its carrier. Should give some better insight as to what is binding.

For sequences containing less than 2048 images the sequence can be created with just the use of symbolic links, so it takes no actual disk space when imported to Siril. After registration there will be actual written files on the disk though, and this is pretty much the minimum disk space requirement for Siril. So there is a little bit of a tip here to try and make the sequence be less than that if you want to save on disk space temporarily. For more than 2048 you will need to write all the files into a .FITS cube (single .FITS file with 3000 layers) for them to be stackable. APP and as far as i know every other software has to do something like this under the covers as Windows OS prevents you from having more than 2048 files open at the same time so they have to be written to a single temporary file one way or another. There is a trick to remove atmospheric dispersion, but it takes some effort. I also image with a colour camera, but i dont treat the data as colour data really at any point. I calibrate the data and then use the "seqsplit_cfa" command to split the OSC data into its raw 4 monochrome channels without debayering. This results in 1 red, 1 blue, and 2 separate green images per input sub and also effectively bins them x2. Then i stack them using a single reference frame for all the RGB channels, this aligns everything to one sub in the stacking phase so no colour channel separation due to atmospheric dispersion is possible (never seen lopsided RGB in a star this way). The second option is to extract RGB layers as mono images from the stacked colour image, register them against each other (green channel probably best for reference) and recomposite back to an RGB image. That works almost all the time too. The cfa split method does require some extra effort, but it gets the job done well in the end. Not sure how practical it would be for you since you have 3000 images to begin with, so you would have 12 000 after the split! You could also batch bin the files with ASTAP and stacking should be much easier. Or use superpixel debayering with APP which also halves the image size and so should make the subsequent processes run much faster. No easy cheats available for dealing with large stacks im afraid, its all a compromise of some kind which is why i have a 1tb SSD that i really treat as a 500gb SSD with the other 500gb reserved for stacking purposes.

Really nice with only 4s subs and a relatively short integration of those. Surprised to see so many background galaxies for sure. Try Siril? Siril, at least for my computer, appears to be about 5x faster (at least) compared to APP or PixInsight (or anything i have tried) with large stacks. Yesterday i stacked 80gb of files - around 3000 subs and it took maybe an hour including registration, normalization and weighted rejection stacking (files were already calibrated though).

I would try it in the finder foot at first. If you start seeing suspicious star shapes but guiding reports everything is ok you have flexure and need to think of something else. But chances are high that wont happen so start with the finder shoe. The problem might not be with the connection between the guidescope foot and the finder shoe, but the tube under the finder shoe which might buckle and bend under gravity in different orientations of the tube. Not sure if that's a problem with the 150PDS but with my thin aluminum tube VX8 it was. Balancing the tube is solved by rotating the tube in its rings so that the camera and guide scope both point towards the ground with the center of mass in the middle (so neither should point directly down).

Superb!

If the input gradient is linear, which it is if flats have worked well, and there are no obvious flaws in the setup the output gradient should be linear too. This is how i thought it went: The gradient could be a complete 180 in a third night and it would more or less cancel out and still be a linear gradient, but now to some other direction. Another reason why i dont think its a good idea to automate BE on a per-sub basis is that there isn't a complete picture of the signal available in the background of the image and so accurate placement of background samplers is impossible. True signal will be treated as background in that case and some will be lost and also since the background extraction has very noisy data to make the decisions on - surely the end result will be noisier (=less accurate) too. I tested this with a fairly challenging dataset below, where there is a little bit of IFN in the background to ruin the automatic removal process by making the samplers placed on the single sub guaranteed to be inaccurate. For images without IFN you can have any number of things that do the same thing such as fainter stars, faint Ha nebulosity in nebulous regions etc. Images shown in the Histogram preview mode and false colour rendering to show issues obviously. Without gradient removal: With per-sub gradient removal: To my eyes it looks like the gradient removal process has created the issues rather than solved them. Your mileage will most likely vary, but since the Siril tool is so simple to use and so effective, i really dont think its worth it to try and automate it pre-stacking. By the way i will mention that i kind of moved the goalposts in this argument to my favour by picking this particular image where i know automatic BE fails. Of course there might be many images where such issues do not arise.

Any particular reason for removing the background on a per-sub basis rather than from the final image? I know the Siril tutorial mentions that it can be done both ways but i think its better to let the gradients be until the images are stacked. The per-sub extraction should be used as the last resort if the tool is unable to deal with the gradients in the stacked image for some reason. From personal experience that only happens when flats dont match the lights in orientation/tilt and there is a severe local light pollution gradient such as a light that shines directly down the tube causing reflections and all sorts of issues. The new tool introduced in 1.10 and afterwards can deal with very cursed gradients and have not seen an image that was not fixable. I am not mathematically oriented so cant give you an equation that would prove why BE before stacking is worse but i would assume removing the gradient before stacking makes the subs more noisy (as noise stays, cant remove that with background extraction) and so a less efficient end result as the subs now have worse SNR pre stacking. Sure the gradient will evolve with the night but typically it wont do a full 180 and whatever direction is towards the ground in the image will always have the worst gradient so the gradient doesn't get to be all that complex if flats have worked out ok and the locale isn't completely ruined by some nearby lights.

The simplest is to use the script and peer into the "Process" folder that the script creates in your working folder and grab the calibrated files from there (assuming its the default scripts you have used here). You will find a bunch of files with the prefix "pp_lights" which are your calibrated lights, the files are also debayered in case you ran the OSC script for colour data. You can then just drop these into some other folder where you might keep work-in-progress type data for later use in case you want to keep adding data. Then just drag and drop all the different files from all the different sessions to the Conversion tab window, or you could use the "+" icon to add them there. Name the sequence and click convert, it will create a new sequence from all the data you fed it. I recommend setting the Symbolic links option on as this way Siril does not actually write any new files and the sequence is imported basically instantly, instead of writing several gigabytes of files first. If you have more than 2048 files it gets a bit more complicated because of OS limitations but im assuming not, so wont get into that now. The less simple - at first - way is to create your own script that does whatever you want it to, such as just calibrate the data. The laziest method is to find the script in the Siril installation folder and edit the premade scripts to just calibrate the data and stop there. The files are in .ssf format but WordPad will open and work with this format just fine, the edited file has to be saved as .ssf after the edits. Simply remove the parts i have crossed below and the script will now save non-debayered files and not register or stack them. If you want to have the files be debayered at this phase then dont remove that part. If you save the files as not debayered you also have the option to use the "seqsplit_cfa" command to split debayer the OSC images. This creates 4 mono images from each raw input sub: 1 red, 1 blue, and 2 separate green ones. The image size is also effectively binned x2 this way. * Edit Realized that i did not really answer the question of how to stack manually, but its fairly simple. After the sequence is created you need to register the files through the Registration tab. Use Global Star Alignment with Lanczos-4 and Interpolation clamping option enabled (make sure you have the newest version of Siril). For RGB data its probably best to have the channel set to green as thats where the best SNR is likely to be found. After registration completes Siril will then draw a plot of various statistics into the Plot tab where you can remove images with bad FWHM, low star number, bad roundess, etc. Handy tool really, at least give it a small look before stacking everything as you will learn how good the data actually was. For Stacking, you can mostly stick with the defaults, at least i think these are defaults: Average with rejection, Normalisation as Additive with scaling, winsorized sigma clipping with 3 for high and low range for the Pixel Rejection part. If you have a lot of dubious data of various quality skies then be sure to use some kind of weighting for the subs, such as #stars or noise or whatever. If you want to get a tiny little bit better pixel rejection with less actual faint signal removed then use the Generalized Extreme Studentized Deviate Test method. It consistently clips fewer pixels so presumably clips less faint stuff, but gets rid of all outliers. It takes much longer though, like several times longer.

Very pleasing image to look at as it has a bit of everything, plenty of stars, dark nebula, reflection nebula, emission nebula. Really nicely processed too, everything looks very nice.

Ill add to the discussion that the exposure times required to have read noise dealt with are likely quite long for the f/10 scope so the mount needs to behave probably for 5-10 minutes in normal operation. Vlaiv has made good points and suggestions, other than M31, M33, and some galaxy clusters such as the Virgo and Coma clusters you will fit every galaxy in a 2m fl scope and an APS-C chip. That leaves you with dozens of good targets and hundreds of difficult ones.

Does your Omegon 150 have a 1.25" focuser? If so it will be difficult to find a coma corrector (not sure one exists on the market) that is more or less required to have good sharpness in the images for wider fields of view such as with DSLRs. I would suggest not pouring too much money on this particular setup for astrophotography, but buying something that can get you started for a not so obscene amount of money while still sticking with the scope for now. Idea: get a simple tracking motor and a planetary type camera that works better with the small focuser. You can take nice images of the Moon, planets and some of the brightest DSOs that fit the field of view. If one day you upgrade to a different setup you can keep using the same camera as an autoguider or a lunar/planetary camera so you waste a little money as possible. Be warned though that astrophotography twists your idea of "expensive" into really deranged numbers if you get hooked. No upper limit in spending, but most dedicated imagers will end up spending several thousand €/$/£ really quickly...

Siril will stack your different pixel scales together just fine in "normal" operation, choose one reference frame from either setup and stack everything to that (doesn't matter which filter, just choose one with a lot of stars). No need to do pixel math for the resolution matching or something like that although you may want to do that for the RGB composition phase if you are adding Ha to R or something similar. Dont know where the limit for scale difference is but i have stacked 1.8'' and 1.5''/p frames together and it all integrated just fine.

Looks like another miss (mostly) for northern astronomers, its under the horizon or daytime at the closest pass. Late october might work ok if it stays intact after the periapsis pass and the brightness estimates are to be believed.

Go-to inaccuracy and difference in image orientation pre and post meridian flip come to mind as potential issues. The first is of no concern to any imager who uses plateolving, the initial go-to will be inaccurate anyway so nothing lost here (except maybe the 10 seconds spent on the first slew). The second, change in image orientation, increases in effect the higher you point in declination and could well be an issue if you are shooting a mosaic with tight tolerances or a target that generally just barely fits the FOV at some specific camera angle. I have had fairly significant cone error (and still have) and have seen up to 3 degrees of difference after a meridian flip when shooting M81. Not an issue for my FOV but could be for some kit. For targets at lower declinations its of no concern at all.

Darks care about exposure length, temperature, gain, and offset. The telescope or whether there even is one attached to the camera does not matter for darks so they will work in any camera orientation. Flats do require retaking each time you remove the camera or change the orientation.

Beautiful image all around, rich background, extensive tidal streams and of course the galaxy itself. On StarX removing background galaxies, you could add them back to the starless layer from the stars only layer. Takes a bit of manual work with the eraser to remove the objects not wanted in the star layer. Then just subtract that layer from the original star layer and you're left with a layer that contains only the background galaxies. Now you can do with them as you please or add them to the starless layer for some extra work. Easy to do in PS, just takes a while with a background as rich as this! Actually you could do it the other way round too, removing all the objects that are actual milky way stars and then do the layer shuffle. Might be easier in very rich background images.

Actually since you mentioned wildlife i remembered the most dangerous part of darksite visits here: the drive. Have seen deer on the road countless times and have had to brake suddenly a few times.

Never felt unsafe at dark sites so far. Mildly annoyed maybe if some youths on a mid 2000s BMW with a DIY bodykit start drifting and making donuts nearby and generally causing a scene (you know exactly the kind of guy im talking here im sure...) but never felt actually in danger. Most people dont approach even though they look curiously what im doing (Finnish thing) and those that do are always nice encounters. Your mileage may wary of course but personally am not worried.

The porkkalanniemi carpark marked in the Ursa observing locations map. There were 5 cars at one point all imaging/observing, its become more popular as of late but plenty of room anyway.

Never heard of this one, added to my ever growing list of things to image 👍. Interesting looking galaxy, all kinds of messed up and a lot of different types of signal to be captured in spiral arms, H2 regions etc. I think the aversion to small and faint targets is somewhat easily explained by the typical weather a typical imager posting here on SGL experiences which greatly demotivates most of them from dumping dozens of hours on a target that may or may not be worth it in the end.

Previously i have been very happy with my Ecoflow River 300 (discontinued model) and would have recommended one or one like it. But last night it failed on me after about 7 hours. I checked the power level at around 1am and it was around 40% which was plenty for the 2-3 hours i was planning to stay for longer. At around 02:30 it had shut off and claimed 0% charge + low temperature discharge warning so it must have drained a lot of power in the final moments. Reading online the longevity of the River 300 was a big issue and probably why it was discontinued. Also probably why mine failed last night at -15 when i have used it for a similar amount of time in -25. Newer models may be better, at least would hope so. Newer models of the river advertise down to -10 discharge temperature where as mine is -20. Maybe they just realized -20 is too much and it kills the battery and so just changed it. Its still been a good purchase but after 2 years of mostly sub zero use its starting to show cracks. Maybe i shouldnt complain actually given its been kind of tortured for so long.

Was also imaging last night and saw this show from a latitude of 60N. That naked eye red light was really something else, you have captured the sensation of seeing the sky on fire nicely here.

Just arrived back home from an imaging trip, not in the UK mind you, but we had the same Aurora but i would imagine a bit stronger as i am at 60N. These were by far the strongest i have ever seen, i could see these vibrant green curtains dance in real time across enormous swathes of the sky including at the zenith and south! Occasionally some pillars of green light appeared as if out of nowhere and disappeared, as if there was some kind of celestial bombardment of light. I now understand where all the mythology of getting smitten or struck by something from the sky comes from! We had naked eye very obviously red Aurora too, which is a first as well. Typically only seen that through a camera, but this time it was like the sky was on fire. Funnily enough it ended up ruining a bunch of subs i was taking, but this type of ruining of the images is acceptable i suppose. Aurora gradient, hah, take that light pollution gradients! Some crummy out of focus shots with a shaking hand and a phone (was actually rather difficult to image, as the direction of the lightshow was everywhere, and i was busy trying to pick the pieces of my jaw off the ground):

Had a look at the Moon with the 90mm sort of achromat Long Perng. Seeing not great but very nice views with a 2.5x barlow + XW7 giving a nice power of 178x which the scope wont go above in any seeing. Or so i thought, but trying with the new narrower Baader solar continuum filter im seeing a crazy increase in clarity, its like seeing was suddenly an arcsecond better and most of the high frequency fuzz is gone! This time i could definitely use more power, but alas i have run out of glass for that. Recommend others give it a try, it really improved the views a lot with mine.