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That is just an image I found online that shows aperture mask use, but telescope is Bresser AR102s Comet Seeker. Scope is no longer produced, but here is link with specs: https://www.bhphotovideo.com/c/product/1124708-REG/bresser_br_ar102s_00_rich_field_ar_102mm_for.html (btw Bresser still has F/4.5 fast 4" achromat but it looks different and uses some kind of ED glass - although CA is still very strong)

Just a bit more time consuming - depending on how much precision you want. You can roughly polar align and then you can track in one axis (slow motion track) - for limited amount of time before you need to issue correction in DEC axis as well Depends how accurate you want your polar align to be. You can get by with simple compass and roughly leveled tripod. This means that you'll be able to track objects in one axis with again - small corrections in DEC axis from time to time. Every time. Every time you move the mount, you'll need to do rough (or precise) polar alignment You can just slew around with EQ as well - motion of the mount is somewhat unintuitive until you get the hang of it. Afterwards - it becomes natural (like tying shoe laces or riding a bike). Yes - very limited astrophotography - yes, no problem. You'll be limited in max exposure length for example - that will be determined by your polar alignment and mount precision. If you add some sort of guiding - you'll be able to do a bit longer exposures. For AP though - you'll need as precise polar alignment as you can get. There are techniques for doing that even if Polaris can't be seen (drift align for example).

Hi, What eyepieces do you already have? I'm guessing stock 10mm and 25mm MA eyepieces? With that scope - it is really hard to get in close to view the planets. You won't be able to get very high magnification, and even if you do - planets simply won't be as sharp as in other scopes. Not all is lost. If you have barlow lens (I'm guessing x2 barlow lens), then try using that and 10mm eyepiece - and put cap on scope - but remove central section. Your front cover probably looks something like this: It means that this central section can be removed. Remove it and place cover on the scope. This will create aperture mask. It will let less light in scope - and is there fore very bad for general observing of faint things, but it will sharpen up view on high magnifications. You want to achieve this effect: (people make aperture masks out of various bits) If you find that you like barlow + 10mm and above scope cover on planets, then you can get dedicated eyepiece in that focal length that you'll be using without barlow that will provide you with same view (or a bit better than that 10mm + barlow): https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-5mm-ed-eyepiece.html That is very nice 5mm eyepiece that won't break the bank. Use it again with aperture mask to get sharp views.

Usually no, but it can impact HFD readings because background brightness value can change and therefore "floor" from which star is measured can be raised. High clouds sometimes create halos around bright stars because they scatter light somewhat, but I'm not seeing that in your image. Two brightest stars have "regular" amount of scatter for small aperture refractor.

If you have faster newtonian - that is easy to check. Take wide field (lower power) planetary eyepiece and observe planet at the center of the FOV and somewhere near the edge. Granted, some of aberrations will be due to eyepiece and not scope itself, but if you have well corrected eyepiece - you'll see blurring caused by miscollimation. Another way to visualize is to do simulation. Check out this page for different effects (like central obstruction, spherical aberration and seeing): http://www.damianpeach.com/simulation.htm Coma will produce similar blurring effect on the image.

This is very very good image. Only thing that I would personally see as improvement - scaling it to 50% of original size. This is rather personal preference. Most people don't view image at 100% zoom level. If you zoom to 100% in your image, then stars look just tiny bit out of focus (might not be focus issue - it could be down to seeing or guiding performance or something else entirely), more like "balls" or "circles" rather than points: and background is just a tad more grainy. But if you "limit" max zoom level to 50% (by down sizing image to 50% of current size) - all of that changes: Now stars look point like and background is smoother (not entirely smooth - that is bad, but rather "right amount of grain"). Detail in dust lanes also remains sharp: Fact that I'm nitpicking means that everything else is just spot on !

It is fairly easy to see, but you need to be careful of what is it that you are seeing. First of all - you need to go very high power until you can see the star as being disk rather than just point. You need to start resolving Airy disk and airy pattern (often 200-300 power or more for larger apertures). Second - all sorts of things can look like collimation issue. Thermals, seeing, you name it. Put star in dead center of the FOV, and it should look like this at high power: Left is good collimation - right is poor one. That is under perfect conditions. In reality, in very good seeing, it will look like this: And it will be slowly changing, maybe like this: (Taken from here: http://www.damianpeach.com/pickering.htm) If you move star of axis - towards the field stop of eyepiece - it should start slowly to look like right star in top most image - with that thicker ring always pointing towards near field stop (so first image / right star should show what star would look like when moved toward right field stop edge in the eyepiece). Telescopes can hold collimation very well. I haven't collimated my dob mounted 8" newtonian in maybe 2-3 years. I sometimes check collimation to make sure it is good and that is it. Make sure your scope is thermally stable and had plenty of time to cool and pick star that is high in the sky as stars towards horizon tend to be affected by seeing more. If you have manual mount - pick Polaris (or any star with high DEC as it will drift more slowly over FOV) as it is stationary and you won't need to nudge the scope.

You are partially right - but that relates to true color images. With NB images - if we did that - we would have ended up with almost monochromatic image. Ha usually has much much stronger signal than OIII and SII in particular. NB images are often processed so that each channel is treated separately and then they are combined in the end. Even for true color images - you need to be careful as non linear stretch causes issues with RGB ratios. This is the main reason why people often end up using saturation in the end - because non linear stretch of colors de-saturates them. Say that you do power stretch (simple curves stretch is in fact power stretch - or middle slider in levels, in gimp you can set exponent in box). Say you stretch by power or 0.5 (that is square root) That is how curves usually look like (in 0 - 1) range. Imagine now you have RGB as being 0.5 : 0.25 : 0.25, so ratio of R to G is x2 (0.5 : 0.25) After stretch, you'll have ~0.70711 : 0.5, 0.5 (each value is raised to power of 0.5 or square root is taken) Now R to G is no longer x2 - it is ~1.4142. Colors "came closer together", or contrast between color components reduced - and that is essentially de saturation. What you can do for NB images is to maintain linearity of each component - but scale them so that they are close in values. Instead of using non linear stretch - you can linearly stretch each before combining them, but then again - you need to do this visually so that colors are nicely "balanced". Alternative is to do regular stretch before combining them.

Ah, yes - more like one would expect. We mapped Ha to yellow and image is predominantly yellow because Ha is the strongest. Although I'm not sure I like this version though. I like the brightness of it, but I prefer the color tone of last one - one that is normalized. Actual color tone of the image will depend on stretch of each channel. That is important part. Stretching each wavelength a bit differently will change overall tone of the image. I'm not sure even what is the best approach - when to do non linear stretch - before or after color combination.

This will slightly alter things. If you want to divide - divide all three with the same number, but you don't really need to divide - you can "clip" - that is standard operation in color space conversion. In above equations - we have that red is equal to Ha + SII and that would mean it can easily be larger than 1 in value (or 100% or 255 - which ever range you use) - but all values larger than 1 are clipped to 1. To be absolutely precise about it we should really include gamma operations as well as standard sRGB values are gamma encoded (sRGB gamma) - so we need to undo gamma for calculation of above values and redo gamma when we are done composing the image - but that could be seen as "advanced" stuff so I did not want to bring it (that early) into discussion

Stars are elongated - there is some trailing. I think that trailing is either poor polar alignment or periodic error - not optical issue. If we exclude trailing - I think stars will be OK and that optics is fine.

A bit too much green in there - more than I would expect from selected primaries, but that is probably due to increased saturation. What is your processing workflow and what does image look like without boosting saturation?

I think it is Ukraine based company, so yes, probably aimed at Euro market (at least for now).

You don't really need Edge HD series for planetary imaging. Regular Celestron SCTs can produce as good if not better planetary images. Most telescope designs are quite sharp on axis and for planets - you'll be using only central portion of field of view. Even for lunar imaging - if you want full disk - you'll do mosaics. If you have the funds - I'd seriously consider getting C9.25 for planetary imaging instead. Maybe even C11. C11 will be right there on weight limit of the mount - but for planetary imaging - you can push the mount up to the limit - unlike for deep sky AP where you want great precision and you want to put less than 2/3 of max weight on the mount. Here is example of C11 being mounted on AZEQ5:

You can record it via PHD2. Start by calibrating guide scope like you normally would - close to meridian and on equator (DEC 0). Then turn off guide corrections and start guide session. Make sure you have logging enabled in PHD2. In EQmod at some point press timestamp button (this is used for synchronization). You need to record about 1-1.5h of data (several worm cycles). You don't need to image during this time and best time to do it is when the moon is full and it's clear outside. You probably won't image at this time so you can put aside couple of hours to do this. After you finished your run of data gathering - stop guiding and close PHD2. Now run PecPrep software (part of EQMod - http://eq-mod.sourceforge.net/pecprep/). Load phd2 guide log into it and start your analysis and preparation of PEC file. Alternative to all of this is to simply use EQMod and record PEC file while you image something. You again need to be guiding - but this time don't disable guide corrections - just have regular imaging session with guiding for example. At some point hit "record" PE button in EQMod and after again - several worm cycles (about hour to hour and a half) - just start using that PEC. EQMod will automatically do same thing you would manually do in PecPrep. If you want to go PecPrep route - check youtube for tutorial on how to do it (there are several videos covering basic procedure). Check out this document as well: http://eq-mod.sourceforge.net/docs/eqmod_vs-pec.pdf It should give you brief overview of EQmod pec and how you can record it while imaging.

Since you no longer have any plans to get EQ6 - something had to be done

https://www.firstlightoptics.com/equatorial-astronomy-mounts/asterion-ecliptica-light-tracking-platform-for-dobsonian-telescopes.html

Exquisite image.

Yes, but that is because Starnet is not part of PI - it is stand alone open source software. You can read more about it here (github repository for it): https://github.com/nekitmm/starnet

I don't think it is possible. With very bright stars - there is often "halo" or "skirt" associated. These look too much like background nebulosity and I don't think that software "knows" how to remove them. You could possibly try to teach it, although I'm not completely sure I can explain how to go about it. StarNet++ uses neural network in its core - meaning you can teach it how to remove stars. In order to do it - you need to train it - this means that you need to give it bunch of image pairs - one with stars and one without stars. See the problem - if we had starless version to begin with - we would not need StarNet++ . Kidding aside - you would need to know how to synthesize halo/skirt feature on bright stars. I think easiest way to train StarNet++ is to take high resolution images with very tight stars (like Hubble images) and run median filter on them for star removal and run blur on them to get fatter stars as one is expected to get with amateur equipment. Another approach would be to generate some sort of fractal type nebulosity images and then add in random star fields on top of that.

Not that I'm aware of. Its general purpose scientific image processing software - primarily made for microscope imaging rather than astronomical. I found it useful because it allows for many operations to performed on images (a lot of math stuff) and it also allows for scripting and has many plugins available (look up Fiji as well - it is the same thing / distribution of ImageJ but preloaded with plugins so you don't need to get them separately).

It is. YouTube channel is recent development. He's been reviewing scopes for much longer time.

I don't know resource that will do such long span, but you might want to look at this website: https://www.scopereviews.com/list.html Look under refractors. It contains reviews that are 20+ years old, and I guess that some of those scopes were in the market longer than that. In any case, Ed often talks about scopes from even earlier days in his reviews so it is worth reading them if you want to get the sense of what was common during any particular period of time and how much it costed. As far as optics goes - many things have been developed long since and just few things changed refractor landscape in past few decades: 1. Availability and drop in price of exotic glasses as well as high quality coatings 2. Computer aided design and more sophisticated testing 3. Cheaper manufacturing due to mass production and utilization of machines

I would say that best way to do it would be to create starless and stars only image. You need software that does math operations on image for that - I recommend ImageJ as free option. Take linear, color calibrated image out of Siril and open it in Gimp. Do levels - but only move right slider to the left - this will make image brighter but will still keep it linear. Don't over do it as stars will start to bloat if you over do it. This will be your "base image". You don't need to see nebulosity at this stage. We only do this because StarNet++ (last time I checked) can only work with 16bit data and we want it to give us starless version while still linear. Save base image from Gimp and apply StarNet++ on it to get starless version. Once you have Starless version - subtract it from base image to get "stars only" image . This is best done in software that can do image pixel math, but you can also try to do it in Gimp by loading base image and starless image as layer on top of it. Turn layer mode to subtract and hopefully that will do the trick as well to produce "stars only" image. Now you have two images - starless and stars only, which you then process separately. Starless you can stretch more aggressively and denoise / sharpen, whatever you like, and stars only image - well, you might as well keep it as is or give it very slight stretch to show fainter stars as well. Maybe apply round of sharpening on it to reduce star size. It is important that you leave background black in Stars only image - as there is no background there. Once you have two versions that you like - put stars back on top of starless version as layer (mode addition or which ever gives you best results). Btw, less is more - don't over process your images. Out of the two - I like version with normal stars more as one with reduced stars looks too over processed.

Why use EQ mount at all? You can have it on dob mount, or put it on SkyTee2? Newtonian scopes are much easier to use on alt-az type mount due to position of eyepiece. If you want tracking, for planetary or double star work - look into EQ platform and dob mount combination.