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Btw, this is the first time I see this particular feature in M101: There is whole another arm that I haven't seen before: I think that it is real feature as it is present in the image linked above as well.

So what is the conclusion here? I think that data is good. I think it is even very good as this can be rendered from L400 without any noise reduction what so ever: There is enough signal to tease out very fine structure in central part of the galaxy. Only thing that I did was to bin data x3 as x2 is just still over sampling.

It is definitively clipping. I used dcraw to extract raw numerical values from the image and for star A I got this: Max value is clipping value for 16bit integer. You can still see Bayer matrix pattern in this raw data, but it is very likely that saturation is in green as it is the most sensitive of the three.

Brightest star might have been clipped / over saturated and that will produce inaccurate results. Here is surface plot of star profile of A: looks like core of the star has been saturated. What you can try is to skip the star A and work with the rest as it seems to be only one that is saturated like that (the brightest). Instead use B as reference and see what values you'll get for C, D, E and F that way (if they are more accurate). In general, you want to use shorter exposures to avoid saturating star cores and then stack some of those to get better SNR, possibly even defocus image a bit as that spreads the light into doughnuts instead of them having sharp peak.

Do you mind posting that raw file for inspection?

How was image taken and processed prior to measurement? All measured values seem higher than expected, except for F star - which could mean gamma correction. Was image taken by phone at the eyepiece or something like that?

If your target is at DEC 30, after meridian flip, your camera will point to DEC -30 (it mirrors), so you need to move it 60 degrees to bring it back to target.

Take a look at ImageJ It is very versatile tool. It was developed for scientific microscope image manipulation, and has a bunch of plugins for various tasks. For what you are intending to do - you won't need any of them, stock app is capable of opening fits and stacking them, but you might be able to find some sort of motion tracking plugin that will help with meteor detection. It's open source and runs on Java - hence it's cross platform.

Star trails are easy to produce with any software capable of doing "max" stacking (just using maximum pixel instead of average). Make sure you don't align frames - just leave them as they are to get trailing. As for meteor detection - quick google search gave me this link: https://www.imo.net/resources/software/ There are several pieces of software linked there that all work with meteors (in one form or another). I'm guessing that extended google search would result in even more resources worth checking.

Here is a silly idea. Why don't you get two sets of batteries? Get light weight ones. I'm guessing that won't be much more money than battery + solar panel combo. Keep one battery in observatory and the other in the house. One in the house will be recharged until next astronomy cycle When you have astronomy night - bring spare battery with you and when you are finished - just swap them around. Leave fully charged battery for next session and bring used up one with you for recharging?

I'm not aware that there is such option, but it would not be too hard to align the two scopes to same point so you would not need to worry about offset. You don't need plate solving to do that - just use your optical finder to point the main scope to a bright star, and center it in FOV of your Maksutov. Then remove optical finder and put back the guide scope and then adjust its pointing so that the same bright star is in the center of it's FOV.

I think that you'll be fine. Using "settings" circles on EQ mounts is rather limited in precision - because of small precision you get from reading the marks (best you can do on small gauges is something like 1-2 degrees of precision - and that is enough for plossl at x25 or so), but you should be fine if you have several degrees of FOV with short FL lens. Ideally - easiest way to do it is to "set" the settings circles onto a know target and work from there, but I'm guessing these are fixed and don't rotate freely, so yes, just "mentally" set them to known position and do value subtraction between two targets.

Actually - it is the combination of the two that should perform the best, but it might be an overkill for such application? I've seen 3d printed generators that are grab'n'go type - really interesting. https://hackaday.io/project/185070-3d-printed-portable-wind-turbine

It really depends on panel in question. Theoretically, without impact of atmosphere - at 3pm, which would be at 45 degrees, one would expect drop to ~71% of nominal power ( cos(45 degrees) ), but given that air mass is also increased - it is a bit less for "conventional" panels. However, recent panels have significant IR sensitivity and air mass does not have as high impact as one might think. here is a graph for one of days that shows nice curve outline (although there were some intermittent clouds all over the place). Peak intensity around 12 o'clock was at about 7500W while envelope curve at around 15h is at ~5700W. Now, that is a bit more then theoretical max of 71% - but that is because above is not output from single flat panel, but rather 3 groups of panels - one facing east, one facing west and one facing south (tried to optimize roof surface, since I don't have enough south facing roof for the lot), so I don't get clear peak at 12h - but somewhat smaller value (my array is nominally 10.6K but I'm yet to see peak output higher than about 8000W).

Best to calculate your actual power needs and go from there. Winter is behind us, so using solar panels is feasible, but if you plan on extending usage into next winter - do give this a serious thought. I have solar array on my house - 10.6KW of power and average daily power production in "peak" (or rather trough if we think in term of waves / yearly cycle of power output) winter months was less than 10KWh. By that analogy - you'd get 120Wh from 120W panel in winter time or about 10Ah per day (of course, this is average, there will be days with very low production). I expect summer to be better by factor of at least x6 if not x8. I'm now at x4 compared to December / January, or about 40KWh per day.

Price of this one (3d printer excluded) - is probably at least 5-10 less than brand name vixen dovetail clamp (with shipping included). This is just one piece of larger project that I'm hoping to put together - Alt-Az mount and 80mm refractor - all 3d printed (well, most parts, not all, whatever I can source easily - I'll use, like aluminum tubing for OTA and such). While all that is easily bought - there is some satisfaction in making it and also - if it can be made cheaper, I guess some people will benefit from that.

I started a build of one - but I'm mid way through it at the moment. Not sure when I'll put some effort into finishing it though. Need to redo 12V power supply. It's there to power fan (I planned to do hepa filter + activated charcoal to recirculate air inside of enclosure) and lighting and to provide additional power for BananaPI for Klipper. I'm not overly happy with wiring and switches (I managed to mess up wiring so only output for BananaPI is working at the moment). I'll split it into two units. Main unit that provides 12V for lot and then "breakout" box with indicator leds and switches for fan and led lighting.

Good to know, so definitely change of material is in order.

I thought about that - but what about sheet loosing magnetic properties on higher print (or rather bed) temperatures? ASA and ABS require up to 90C bed temperature.

Yep, it won't get used in anywhere near as cold weather as you might experience in winter time.

I'm yet to try "advanced" materials. I have a spool of ASA that I haven't opened yet and need to purchase other filaments to try out. Whole odor and VACs VOCs thing got me little worried. I can actually smell HP Pla and if room is left closed (I print in small office like room) - smell can really build up. Another thing that I'm concerned about is print surface. Currently I use glass bed (carborundum glass thing) and I've seen some accounts of PETG and ASA taking chunks of glass because they stick too well? Looking into getting some FR4 sheets to use as print bed for those materials (I have suppliers here that sell large sheets - like 1x2 meters, and need to give them a call to see if I can order piece of such board - at least maybe a half if they don't cut to smaller size).

Apart from few superglue blemishes - it looks rather professional. It feels really solid in hand. I'm not sure how much it could hold, but I have no reservation to put smaller scopes on it. I used couple of M5 screws and nuts and few M5 rivnuts, bunch of m5 washer, 2 springs (ones that hold my 3d printer bed - which I replaced with stronger ones) and two pieces of 6mm linear rods with 2 bushings for "sliding" action. It will go on 3d printed Alt Az mount. It was printed with HP PLA from Creality with 55% infill (each part in orientation that is best suited for the loads it will bear).

We don't. Once you have measured photon's position - it no longer has energy it had to begin with. Think of scattering event - say photon scattering of an electron. We know energy prior to scattering, we know where scattering took place - but we have no idea in which direction photon scattered and what frequency it has (until we do further measurements on electron).

My favorite make of bob is uncle

Same / similar. For SNR - actual filter used will participate in calculations (sky flux passed through filter and brightness of target) - so each one will have its own SNR. It really depends on how you combine them SHO palette is created so that H takes place of green color. Out of RGB colors - green is most responsible for luminance, or rather greatest part of luminance comes from green color. It is hard to explain, but here is something that can help to clarify this: This is sRGB to XYZ conversion matrix. These are still linear values and Y component of XYZ is effectively luminance (or linear luminance). If you look at XYZ to Lab conversion - you will see that L in lab is just a function of Y and not other two components (unlike a and b), so L is some nonlinear version of Y - but both represent luminance. In any case, from above matrix we can see that Y = ~0.213 * R + 0.715 * G + 0.07 * B Almost 70% of luminance is made up from G (in linear light and sRGB red green and blue). People kill off green in their SHO images for some reason - but assigning Ha to green makes perfect sense as most SHO images benefit from having Ha related to luminance and green will be large part of that. Only difference to RGB is that with narrowband Ha naturally has high SNR and other two components have lower SNR. But if you wish, you can do SHO image composing for color and then use Ha as luminance in similar way as above (Lab or XYZ composition).