vlaiv

You can always plate solve your images. Ideally - you want DEC to be vertical, RA to be horizontal and both "grow" "up and right". However, some targets might be better in some other orientation - so there is no "definitive" rule on that on. Your recent HH and Flame image is rotated roughly 220 degrees:

Consensus is that they are good at what they do

Some types of scopes fully invert image - like left/right and up/down, while other types invert just one one direction - like Newtonian. There is then issue of sensor orientation in firmware - how is it being read? From "left to right" or in reverse (this has to do with internal addressing). It is very hard to tell which corner of the image corresponds to which side of optical arrangement - without testing it. Covering one side of sensor is sensible way to go about it. You can use piece of foil and filter cell or just filter wheel / slider to put tin foil in.

I have no idea. We would need to ask scientists working on large telescopes if there is any particular reason for this. It might be that instruments fitted to large telescopes simply don't record visible light, or that for scientific work - IR data is equally good or even better at revealing what is of interest. Atmosphere is much more stable in IR part of the spectrum (refraction of light depends on wavelength and shorter wavelengths are bent more than longer - hence rainbow) and maybe its simply not worth spending time on visible part of spectrum. Nowadays 99% of scientific work in astronomy is done outside of visible spectrum

In planetary imaging we match effective pixel size (compared to our target) to what the aperture can resolve - by using barlow lens and opting for certain F/ratio (or focal length). It does not matter whether you have 2.9um or 3.75um pixel size if you end up with same "/px (or sampling rate) for each that is dependent on aperture size. In either case, provided you are correctly sampled - you will capture all there is to be captured. Yes, that is the "problem" with some cameras - but it's really not the problem with cameras, but the way we treat our data. Each camera has different QE in different parts of spectrum - but none "is correct". We take raw data from the camera - and we just assign it to R, G and B of our working color space - without really doing anything to properly adjust it / transform it. When we do that - we simply get wrong color. From every sensor (none is "better" with regard to this). Only difference is that one produces colors - that "we think are more correct" - or perhaps "that are more pleasing to our eye". With additional step of color calibration - they would all produce correct color information and they would all produce the same image (ish - there would still be some small differences - but barely noticeable to human eye, if at all - every measuring device has measurement precision, and within that precision should produce correct results).

How come? What do you mean by better range of colors?

Think of replacing one sensor with another? I'd say - don't bother. Specs are so very close and ASI462 will have advantage in some areas that you might like - pixel size is not important for planetary - you will dial in optimum F/ratio with barlow in both cases - peak QE is comparable (no solid data on that to be 100% certain, but going by common numbers, I say 224 has very small edge there, but again, no data), but 462 is much much better at IR photography - if you fancy that sort of thing, like methane band or just simply IR pass filters (>825nm) - comparable read noise, both have around 0.5e - slightly larger sensor is advantageous when doing lunar (or solar) - for full disk images - less panels per mosaic

@Marvin Jenkins Yes, that certainly looks like EQ2 mount. It does not have dove tail clamp but rather integrated dove tail that will just accept rings directly. It also has that very distinct declination gauge that sort of sticks out from DEC axis. Mount in original image - looks much more like this: https://www.aliexpress.com/item/1005002335961470.html (it is listed as EQ3 class mount)

That looks like something called EQ3-1 mount by TS in Germany. I'm not 100% convinced it is equivalent of SkyWatcher Eq3 mount, but I'm certain it's not EQ2 mount either. This is what EQ2 by SkyWatcher looks like: It is much slimmer and does not have dove tail connection at the top (no clamp for vixen type dovetail). EQ3 class mount has it. Here is image of EQ3-1 mount by TS:

Not sure about spikes. Yes, it will grow closer and it will do some sort of interference, but I have no idea what sort of pattern one would get. We can run some simulations to find out, or - it can be tested in the field - whatever is easiest Yes, it is interesting topic - especially if you consider that similar (or even the same) approach is used in speckle interferometry. https://en.wikipedia.org/wiki/Speckle_imaging

Just to add - I'd never focus like that . Too imprecise in my view.

It will. Here is why: It will create double image when out of focus, but single image when in focus.

I would think of it as UHC that preserves star colors (to some extent).

This is very good source of info: https://www.telescope-optics.net/

Most astro photography gear comes with either T2 or M48 threaded connection (larger items do tend to use M54, M63 or M68 and there are a lot of custom threads as well for some reason). You can see technical details for each of them to see what sort of thread is available: 2" Filter thread is M48 thread. You need to work out distance needed between sensor and corrector and then plan your spacers, extension tubes, and adapters accordingly. This one for example needs 55mm (but this value is often "start" value that you adjust based on your optics as these FF/FRs work with different scopes and each will have slightly different distance) between T2 thread and sensor. Now you look up dedicated astro camera to work out rest of the spacing - for example: In this case you would need ~48.5mm of distance with T2-T2 adapter (or rather just T2 extension tube - you can chain several of them, and there are even ones that are adjustable - which is very handy in situations like these). https://www.teleskop-express.de/shop/product_info.php/info/p3732_Baader-VariLock-46---locakble-variable-T2-extension-29-46-mm--T2-part--25V-.html No idea, but as a general rule - clamped connections should be avoided for astrophotography. Threaded connections are much more secure and are much better at avoiding tilt. One reason that grooves / undercuts are not popular might be precisely because of tilt issues. Apply compression ring to undercut/groove and you can see how it can easily go out of whack.

That is effectively just compensating for mount performance. Over such large field, tilt component of seeing is random and averages to 0, so what is left is just due to mount. It is beneficial for long exposure/as guiding aid, but, as you pointed out - it would not improve planetary detail (nor stabilize scintillation for that matter).

Well, no. First - it is much easier to quantify distortion if there is single point of light - like a star (artificial or real). As soon as you have extended object - all points of it act as individual stars and distortions start to overlap so it is hard to say what the distortion is - even if it is uniform. Other issue is that distortion ceases to be uniform over such large area so there is really no single distortion covering jupiter - there is bunch of different distortions, and whichever you pick to use - other parts of jupiter won't be corrected (as it is different distortion).

It has nothing to do with brightness - it has to do with how atmosphere and light behave. Here is simplified diagram: Single point in the sky is effectively at infinity as far as we are concerned, so incoming light from that point that hits our telescope is effectively "parallel". For this reason - any point in the sky will actually have "a pillar" of light that is as wide as telescope aperture, but all these pillars will be at slightly different angle. For example - Jupiter is about 45 arc seconds in diameter - that means that one side of it is "at an angle" of 45 arc seconds to the other side (or these pillars are at that angle). Because atmosphere is causing turbulence - any two pillars that are at an angle will first pass thru same piece of atmosphere (bottom part of image) and then slowly diverge as they go up in atmosphere. At some point they will pass thru completely separate pieces of atmosphere. For small angle - pillars will pass thru same piece of atmosphere for the most part - for large angle - they will quickly diverge and become separate. As soon as you have two different parts of atmosphere act on light beams - they will be distorted differently. Adaptive optics can correct for either one or the other - but can't do both. In reality - there is infinite number of such pillars (for every point in the sky) and only group of them that are really close together - and pass thru same piece of atmosphere, can be corrected at the same time. This is isoplanatic angle that was mentioned before - maximum angle that can separate two pillars that will have mostly the same distortion. It is very small - few arc seconds, while Jupiter is x20 larger than that in diameter - so only very small segment can be corrected (in visible light) at any given moment. Rest of the image will be blurry. Due to nature of light - small telescopes can't even resolve image that is so small - 2" in diameter (or if you will they can cover it up with 10 or so pixels - and no more resolution than that).

Hi and welcome to SGL. Very nice amateur equipment is now more affordable then ever (although there has been now general price rise, so everything is a bit more expensive than few years ago). With just a bit of investment you can have equipment that will show you a lot. Planets and the moon, and wonders of the deep sky - galaxies, open and globular clusters and various nebulae in the sky. In order to give you best advice on what to get, it would be good if you could provide more info on your condition and needs/wants. For example: how light polluted is your back yard? Will you travel to darker spots so need something portable? What is your physical condition / fitness level. Could you manage larger instrument, or would something weighing 20Kg be too much to carry? Storage requirements? Transport requirements (do you have a car or maybe use a bike). All those things will help give good recommendation.

No, not too long, in fact - you can bump that up to double that and you'd still be fine.

I'd say it is collimation of the scope. Sensor tilt would present as different in different corners - while center would be good (or could be focused to good sharp stars). Maybe imaging bright defocused star (in/out focus) in center of the field would be more telling?

@Louis D orders things from TS and I believe everything is OK with regards to shipping and import fees. I even believe that you have something like $800 limit below which you don't pay any import fees and sometimes it is even cheaper to order from abroad, but I'm not 100% certain on that one (and it might be state dependent).

I think that any of these will work (listed in ascending price order, and possibly ascending quality - but not 100% sure on that. Last one is top level reducer and will be of higher quality than the rest): https://www.teleskop-express.de/shop/product_info.php/info/p5239_TS-Optics-REFRACTOR-0-8x-Reducer-Corrector-for-80-mm-f-7-ED--and-APO.html https://www.teleskop-express.de/shop/product_info.php/info/p5965_TS-Optics-REFRACTOR-0-79x-2--ED-Reducer-Corrector-fuer-APO-und-ED.html https://www.teleskop-express.de/shop/product_info.php/info/p12939_TS-Optics-REFRACTOR-0-8x-Corrector-for-TS-80-mm-f-6-CF-and-Photoline-80mm-Triplet-Apo.html https://www.teleskop-express.de/shop/product_info.php/info/p11122_Riccardi-0-75x-APO-Reducer-and-Flattener-with-M63x1-Thread.html

Stacking process. I believe that if data were to be stacked using Siril with say Lanczos interpolation for sub alignment - pattern would go away, but I'd be happier if someone actually confirmed that by doing it.

Just gave it a quick glance, and while approach is very valid in its roots, it simply falls short to deliver accurate color. Here is the problem: As soon as someone starts introducing white reference into color calibration - it is sure sign that something is not right. I'll expand to make this a bit more understandable. There is no white light - or rather there is no spectra that can be identified as white. White is product of our perception (very much the same as any other color) - but more importantly, we see some light as white only given certain viewing conditions. To give temperature analogy that I used above - white is "warm". Will 20C temperature feel warm to you to the touch? Well - that depends. If you are in freezing arctic conditions and you touch something that is 20C - it will feel warm to the touch. Similarly - we sometimes say: "White point" is D50 or D65 or some other illuminant. That just means that given conditions that you are likely to view the image in - to your brain D65 (or D50) will look white. Under some other conditions - it might look bluish or maybe even reddish (or rather yellowish). Whiteness also depends on intensity. Shine some light that you see as white and then put same source but of much higher intensity. First source will suddenly become gray rather than white. Color calibration is step (or rather should be) - independent of our perception. All observers must agree on measured value - regardless of what their sensation of phenomena is. It should also be performed in absolute color space (one that does not know maximum value - they can be arbitrarily high). Another problem is that R/G and B/G ratios are simplified version of color calibration matrix - "diagonal" matrix. Using full matrix would give better results (more accurate).