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Almost this one I say almost because I have high expectations for system described that way, and no, it won't be all sunshine and roses - but it's pretty close There are few issues that you might want to deal with: 1. make sure you have good and working flats. Some people experience issues with ASI294mc and flats, mostly when using duo band filters - so try without such filters first. 2. 130PDS will require some work - in form of mirror clip mask and focuser protruding into light path. You don't need to deal with this if you are not bothered by strange diffraction effects on bright stars that look like this: Left is stock 130pds - right is fixed with mirror clip mask, in fact - read about it here: 3. Choose good coma corrector for 130pds and try to avoid tilt - or at least be prepared to deal with it in order to get best field definition.

Both very fine choices and deciding factor should be based on planetary/lunar vs wide field priority. Mak can also be used on DSO. Most people say that they feel boxed in with Mak102, as if it only provides very narrow field of view, but I don't think that is necessarily true. It has only 100mm longer FL than most often recommended beginner (and in reality lifetime) scope - 200p dob. Former has 1300mm while later has 1200mm - not much of a difference, so FOV is almost the same with same eyepieces. I don't hear many dob owners complaining that they feel boxed in even when not using 2" eyepieces (I know I was certainly happy with 200p dob and 32mm plossl). Only thing that Mak won't do well is of course wide field views, but it will do lunar and planetary very well with decently priced eyepieces (~10mm plossl/ortho is still usable as far as eye relief and will provide one with x130 on Mak).

Good read on these gold line EPs; https://telescopicwatch.com/goldline-eyepieces/

I've got that eyepiece, and it is excellent eyepiece, but I don't think it will provide that feel that you are looking for: It is really tight fit. Most of the time - FOV is not quite as big as stated by manufacturers, so you will probably struggle to fit whole moon in FOV. Otherwise, if you accept that it's not going to give you whole disk at high mag - then yes, that is excellent choice - very sharp eyepiece and easy on the eye. These are known as gold line or red line eyepieces (Orion expanse clones), not good in fast scopes. Some people say they are good in slower scopes F/8 and above (9mm being the best reportedly), while other don't recommend them. There has been some reports of kidney beaning/blackouts with these.

That will work if you get well corrected eyepiece. Not much use of large FOV on lunar if outer 10% is soft and blurry. Quick calc for that sort of thing goes: you need 6.4mm or lower FL eyepiece to get x100 or higher. you also need at least 60 degrees (or higher) to fit whole lunar disk in FOV as moon is half a degree so at x100 it will be 50 degrees. You want at least few degrees on each side for nice framing. Eyepieces of those specs won't be cheap though. 5mm Starguider will fall short on showing full lunar disk as it gives x128 magnification - which makes moon 64 degrees and EP can only render 60 degrees. Affordable "wider" lines are these: https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html https://www.firstlightoptics.com/bst-starguider-eyepieces.html https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-6mm-125-ler-eyepiece.html I just checked all combinations - and none gives that whole lunar disk with a bit room to spare (in cheap category). Closest feel to this gives 7mm SkyWatcher planetary (58 degrees AFOV): But that is only x91 magnification

I probably would not push such scope past x100-120. Quick calculation of CA index gives 2.53, so that is quite colorful. More magnification - more CA will be an issue, so it's best to keep it up to about x120. In all likelihood with 80mm aperture and with young eyes, those sort of magnifications will be just right. How about this eyepiece: https://www.svbony.com/sv135-1-25inch-zoom-eyepiece-/ I've read good things about it - and it should cover wide range of magnifications

Not really seeing it in that frame if it is there at all. Here - look at this: That is 4 corners of green component - not seeing anything special.

I don't think so. Correction at edges looks good. There is tiny bit of elongation in bottom right corner, but that is unrelated. Any issue with distance to FF/FR would show there first as serious star issues.

Ok, I might be wrong, it just seems to me that final stack has that feature. It is present in your processing as well, but not as prominent because you did not perform sharpening in the same way I did:

Maybe focus drift? How long was the session and was there significant temperature drop?

From the data I got slight impression that your focusing was not really spot on, so first thing to do would be to sort that out. (I ran sharpening in Gimp on data as is and got some doughnuts): Once you get focusing spot on - I don't think you'll need smaller pixels. This size should be enough. I ended up binning data x2 for my processing. I also ran FWHM tool in AstroImageJ and stars in green image range from 2.6px to 4px. Ideally you'd want in properly sampled image this to be 1.6px-2px, so you are over sampled here almost by factor of 2 (hence bin x2). When you sort out focusing - you should get sharper stars. I've found that 3.8um pixel size works well with 380mm of FL natively, so 4.63 should be good match for 430mm. I've used no denoising when processing this image, and if I needed to, Gimp does excellent job on that. No need to purchase separate software for denoising (in my view). Starnet++ v2 also works very well and is free - again, in my view - no need to spend money on software for star removal when there is good version available for free.

ImageJ / Gimp / Starnet++ v2

I guess only people with PI can participate since you posted xisf instead of fits?

Following this ... I also thought about something like this, but decided to go for other designs like cycloidal drive or split gear planetary for my prototype.

Honestly, I have no idea. I used to have AZ3 mount, and it was not very good. It had limited range of altitude motion (almost no chance to observe near zenith) and slow motion controls worked in very small range (needed to readjust them after a while). I no longer have it. Otherwise it was not very unstable mount. This AZ pronto seems to be similar class of the mount. Maybe capable of a bit less weight but slow motions are now fixed and work thru the whole range. I think that it will still have issues near zenith with long tubes as there is a chance of scope hitting mount legs unless you use some sort of extension tube (there are extension tubes to be purchased separately). Take a look at this review: http://www.waloszek.de/astro_sw_az_pronto_e.php for more detail on the mount in real use.

Optics is likely to be the same (and probably from the same factory), but where things get different is accessories. With this scope you get erect image diagonal - which means your scope will be easily used for day time observation (like spotter scope) - but diagonal itself is still 90 degrees. 45 degrees erect image diagonal is much more useful for spotter role. Problem with such diagonals is that they are low quality. Both optically and mechanically. Regular mirror diagonal had about 30mm mirror (clear aperture of 1.25" is about 28mm), but these erect image diagonal actually use roof prism and usually have only about 24mm or even less of clear aperture. Roof prism will give you vertical spike on bright stars in night time observation and in general image is probably going to be less sharp than with regular mirror diagonal. Next thing that is different is telescope tube itself - you get that plastic dew shield (I really don't like that). Mount is EQ1 class mount (at least I think), so not very good. Details like mount and included accessories can make difference in price - just check out this scope: https://www.firstlightoptics.com/scopetech-telescopes/starbase-80-refractor-and-mount-package.html Very similar in specs to scopes that you were looking - 80mm F/10 achromat refractor - but it is x2-3 more expensive.

Couple of things. First, that scope was in "do it all" category, which means, it needs to do wider fields of view as well as higher power. With 32mm Plossl - it will actually provide you with very decent wide field view, here is comparison on some of the targets to 90/900: 90/660 is red circle - so it will show you more context in wide field of view. Second thing - it is shorter tube. Shorter tube is easier to mount and will produce less vibrations. I think (but can't be sure) that AZ-Pronto that is bundled with 90/660 is better / more stable mount than Eq2 that is usually bundled with 90/900. Add to that shorter scope - you get overall better performance as far as mount and vibrations go. Third thing is related to chromatic aberration. Sure, 90/900 will have less of it, but it will still be there. I have 4" F/10 achromat and sure enough - there is chromatic aberration present when one pushes above certain magnification. I also had 4" F/5 very short achromat at some point - and yes, it showed much more chromatic aberration, and it was useless on planets - unless you did a few tricks to it. Otherwise, it was very fine scope for what it was intended - lower power views. You can do some trick to lessen impact of chromatic aberration. For example - you can create aperture mask for your scope. If you create 70mm aperture mask for 90/660 - 70/660 will probably have less color than 90/900. There is something called color index - that will tell you how much chromatic aberration you can expect from your scope (although it is not 100% set in stone as CA will depend on glass type used, type of achromat and how well lens is figured) and you can compare two scopes for chromatic aberration using that. It is calculate by dividing F/ratio of the telescope by aperture size in inches. Use following graph as guideline of performance of achromatic scopes: On that chart 90/900 is F/10 scope so it gets color index of 2.82 - it still has quite a bit of CA. 70/660 will be F/9.42 scope, and aperture is 2.75. If we divide those two we get CA index of 3.42 so it will perform better. Only drawback of smaller aperture is a bit less resolution / max power, but it is sometimes worth the trade as CA also lowers contrast / resolution and reduces what you can see. In any case - you can make different aperture mask - 80mm perhaps, or tune it to your liking. Same holds true for 90/900 - you can reduce CA by using aperture mask on it (it will even be more effective), but my point is - CA can be controlled in several ways (using filters, aperture mask and so on), so it should not be determining factor at your budget level. If you want - you can certainly get color free views at 90mm of aperture by using something like 90 or 100 mm maksutov, but you sacrifice field of view more. I was not aware that Celestron has 90/660 version? Did you mean 90/900 is 100 pounds cheaper, let me check that. I've found 90/1000 by Celestron at TS for 300 euro (without tax and shipping), while 90/900 by Skywatcher is 256 euro (on EQ2 mount). These are all very basic scopes and I might sound a bit like people on your local forum, but do look up price of a decent 2" focuser - you will find that most are as expensive as these basic scopes. This simply means that you can't expect much in terms of quality of mechanics. Optics won't let you down for the most part - they will show you plenty, but mounts won't be as stable as they can be, focusers won't be as smooth as they can be, eyepieces and diagonal won't be as good as they can be. For example - Celestron that I mentioned above - has rubber/plastic type of dew shield. Some of these scopes have plastic focusers. This is all done to save on price and allow for decent optics.

Hi and welcome to SGL. Collapsible heritage can extend and retract secondary mirror cage / assembly but it can't do anything to its focal point / focus plane. It is feature of primary mirror and is fixed (unless you bend primary out of shape / re-figure it by grinding). In order to understand maximum angle at which scope can project image - you need to consider several things. First is - field of view of scope is usually very small - just few degrees. Fact that you have open tube design is a plus for transportation storage, but minus for viewing. Many people use shroud to shield the scope internals from stray light. Now onto the field of view. First thing that determines field of view is focal length. Here is little diagram to help you understand what is going on: This is image of reflector system and ray hitting center of the mirror. We can just look at one ray - don't need to look at all rays as they all focus at same point. With this ray it is easy to see that distance in focal plane from center of the field is function of incoming angle and focal length. Now, other things come into play. With newtonian, you need to consider size of secondary mirror. If angle is big enough - reflected ray will simply miss secondary and go out at the front of the scope. Size of secondary also limits the field that can be viewed. In the end - there is size of eyepiece / focuser tube. Eyepieces have certain size and only those points on focal plane that fit inside eyepiece will be shown. This is called field stop - and when you view thru the eyepiece - it is black edge of the view. That is physical ring in eyepiece that sits in focal plane and blocks any light that does not fall into opening. This is how field is formed in nutshell. Size of tube has nothing to do with it. Back on your question about beginner scope. If you want to view deep sky objects - which means frequent visits to dark site (you'll need a car and you'll probably need to go at least 50Km away from your city) - then get 130p Heritage. Here is a good resource for you to check how far away you need to drive: https://www.lightpollutionmap.info/#zoom=7.14&lat=42.6889&lon=24.4784&layers=B0FFFFFFFTFFFFFFFFFFF You really need to get to at least green zone to fully enjoy deep sky objects, but darker the better and see if you can get to a higher altitude as well. If you want telescope that will do it all - then get this one: https://www.firstlightoptics.com/evostar/sky-watcher-evostar-90-660-az-pronto.html That scope will give you wide enough field and still be able to show to moon and planets. It is no fuss refractor which you seem to prefer. Only drawback is chromatic aberration and that az mount. Any mount that you get with a scope with your budget is not going to be very good. Most will have issues with stability, but there are few tricks that you can use to get them to perform better. In the end, if you plan to do most observing form your town and you want to look at planets and the moon most often - then get this scope: https://www.firstlightoptics.com/maksutov/sky-watcher-skymax-102s-az-pronto.html That is excellent little scope for planets and the moon - which does not mean you can't observe DSOs with it (I managed to detect NGC7331 with my Mak102 in dark site). It is like 4" F/13 refractor with no chromatic aberration. Lastly, don't be hung up on idea that refractors give sharper image than reflectors. In the budget you have, that is simply not true.

I very much doubt it, at least not for lucky type imaging - it has 20+ (going up to 50) e of read noise! I really can't see any good astronomy use for this camera, and certainly not at that price. For someone wanting to do a bit of NIR imaging - there are other models, far cheaper that will let you image up to 1um. Wavelengths between 1um and 2um are quite a bit blocked by atmosphere (not completely but there are a few dips). Spectroscopy comes to mind - but there are very few pixels available for high resolution work (can be done - but small part of spectrum can be resolved at any given time).

At that price, I think I'll pass

I did a little search on google to really see about this dynamic range - and, sure enough, wiki article gives completely different definition of dynamic range - much more in line with what I would expect: and specific to photography: source: https://en.wikipedia.org/wiki/Dynamic_range No mention of read noise as it is really not important in this context (and neither is regular dynamic range in context of stacking as stacking two images - adds one bit of DR, stacking 4 images adds 2 bits and so on - one can have arbitrary dynamic range given enough time - which we already know, more time we spend imaging -better image we get ).

Very simple really. Say you have 12bit ADC and you have 20K FWC and maybe 2e of read noise. DR is simply log_base_2 (20000 / 2) = log_base_2 (10000) = ~13.2877 It has nothing to do with ADU at that point. Conversion to and from ADU is by using e/ADU value (gain). In this particular case, say that e/ADU is ~5. You want to measure dynamic range on your sub. You take your sub that has values in range of 0-4096 and you convert it back to electrons by multiplying with e/ADU value so you end up with 0-~20000 values You measure max signal in electrons, you measure standard deviation of bias sub (after bias signal is removed) - and you get max electron count and value of read noise - you divide the two and take log base 2 and you get DR What ADC is giving you is just "resolution" to write down measured number. In above case - where e/ADU is 5 - you get to write down "to every fifth electron", meaning that electron values 0-4 will be represented by value 0 in 12bit numbers, 5-9 will be 1ADU, electron values 10-14 will be 2ADU and so on. When you have value of say 47ADU - you don't really know how much electrons you captured, except that it was somewhere between 47*5 and 47*5+4 or 235 and 239 electrons for that pixel. That is quantization error and that is bad thing, but if you have some read noise - it gets hidden away (noise shaping), but it has no effect on DR as it is defined. Why then DR falls as we increase gain? Again very simple thing really Say that we have gain set to 0.5e/ADU You again take a sub, your sub will have 0-4095 values and when you multiply every pixel with 0.5 to get electrons - you will get only 0-2047 values out of it for electrons. Any signal above 2047e will saturate pixel at that gain - it will be too bright to accurately record. You then do the same as above - 2047/read_noise and take log base 2 You are bound to have lower DR just by virtue of lowering max signal that you can record. You can maintain same level of DR only if read noise is reduced proportionally - but it never is.

Not sure about that. You can't escape HDR techniques in astrophotography as difference in brightness can be quite substantial - even for targets that we don't usually consider high contrast. Take any of the brighter galaxies. Core is likely to be ~mag16 while outer reaches / spiral arms are known to go below mag26. That is 10 magnitudes of difference or more, between bright and faint parts or x10000 brightness difference. If we have SNR5 for faint parts (which means signal being about 25-30 electrons or more depending on LP) - that will make bright parts be 300000e. No regular amateur astronomy camera can record 300000e. In the end, we need to compress those x10000 of difference in only 8bits of intensity levels that regular images show, so we indeed must use HDR techniques. Stacking is first, non linear stretch is second ... DR is well defined and it is log base 2 of ratio between highest signal and noise level. If you double max ADU - you will increase ratio by factor of x2 and log base 2 will increase by 1. However - that does not mean that 12bit camera can have only up to 12bit dynamic range - it can have more than that. Remember, it is signal level divided by read noise, regardless of bit count used to represent data. 12 bits can only hold 0-4095 values, but that does not mean all 12bit cameras are limited to capturing only 4096e worth of signal. Many have much larger FWC - like 20K or similar. If you look at DR graph for ASI224 for example: Al those circled data points are above 12 stops of dynamic range although camera has 12bit ADC. This is because it has 19.2K FWC (and that is more than 14 bits for max signal). You really don't need 16bit camera to avoid posterization. That is myth. All cameras in question capture more intensity levels than we are used to see on our screens (8bit), and we never see posterization if we create smooth gradient. In fact, computer screen that I'm using right now has 6bit panel and I haven't seen posterization (6bit per channel for total of 18bits per color).

If you are coming at this from EEVA perspective then answer is simple - use very high gain setting. With short exposures you don't really care about FWC - you won't be able to saturate pixels with interesting signal (non star) in few seconds of each exposure and high gain equals low read noise. Since you'll be using short exposures, you really want to minimize read noise. Only difference there is as far as SNR is concerned between one long exposure and stack of shorter exposures of equal total length is in read noise. With long exposures we minimize this impact with other noise sources - like LP noise or thermal noise or shot noise, but with short exposures - you don't have that and it is beneficial to minimize read noise. That is the same thing planetary imagers do when utilizing lucky imaging technique with very short exposures - choose setting with the least amount of read noise (one of the reasons why ASI224 is so popular - look at read noise figures).

I remember seeing image like that. Wouldn't mind to try viewing like that, but in all likelihood - I'd end up in ditch waiting in darkness for tiger to roll along the street