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I've read this warning many times - it is often written on TS website along Ha solar gear - like this: At some point I thought that Daystar quarks and their high return rate had something to do with this. Solar telescopes are shipped with good packaging - meaning a lot of styrofoam and such which is insulator. Quark eyepieces are shipped in regular small boxes and probably not well insulated. If shipment is in winter time or cargo is carried on an airplane - high altitude / low temperature, and I doubt that cargo bay is heated - this could lead to item being on lower temperature for some time. So yes, that is a hazard that needs to be addressed. Don't know how it relates to blocking filter - it is often quoted for Fabry Perot filters - which use oil, so air spaced ones should be fine?

Not sure if there is proper answer to that question. If you want to get realistic colors from your sensor, simple scaling is not the best way to do it - it is approximation. In fact, even more "sophisticated" methods are still approximation to some degree. For better results you want to use color conversion matrix rather than simple scaling. Simple color scaling is a kind of color conversion matrix - but only diagonal one. In any case, to determine suitable scaling - you can use a single star in your subs. Find a star of certain stellar type that will be your "white point". Probably best stellar class for this is F2 (non of the stars is pure white, some recommend using G type, although those are yellow stars, and some will use A class - that is bluish star). Take image of that star and compare intensity of each color - and that way you will get scaling factors (one that you should use to get star colors to be 1, 1, 1).

I think it is best compared with eyepieces - you can get very good eyepiece with three of four lens elements. But if you want large AFOV, good eye relief and correction to the edge - you need to go with 6 or 7 or maybe even larger count of lens in a design. Often wondered why there are no triplets made out of "regular" glass types as opposed to ED types and more exotic types. It all comes down to specs of the scope you want to build - what size of aperture you are going for and what F/ratio you want to achieve (probably even how flat field you want to get). One could probably design very good triplet at something like F/12 from regular glass types - but what would be the point? You can almost get very good color correction with achromatic doublet at that F/ratio (small aperture) and certainly with ED glass - although up until recently there were no slow ED scopes (there is now F/11 ED 4"). Combining more exotic glass types in triplet let's you optimize for particular scope design - fast with large aperture and relatively flat?

I think we have established a standard for scatter control here

I do get that some people prefer such scopes and might find this interesting, but not really my cup of tea. For AP applications - I can list few alternatives that will be cheaper than this and probably as effective (if not more so) - like already mentioned hyperbolic newtonian, or something like nice 6" Mak-Newt if one does not fancy diffraction spikes. For visual, I think people would rather choose something at F/7-F/8 if choosing doublets?

I was playing around with simulation of seeing effects and have very viable model in reproducing seeing effect - apart from one thing - creating seeing wavefront disturbance. Here is quick breakdown of technique used: I created "aperture" and random seeing disturbance: Aperture is wavefront intensity with 1 being in aperture circle and 0 elsewhere. Next I took very small image (24x24) and created Gaussian noise on that and then enlarged it to 512x512 image - this gives rather nice looking wavefront error (although probably away from accurately representing seeing wavefront): This image should be interpreted as phase of wavefront. Next step would be to compose two images - real and imaginary by combining phase and magnitude (which is simply sin(phase)*aperture and con(phase)*aperture): Here it is side by side: And of course, last step would be to find FFT of this complex wavefront representation and look at power spectrum of it: This image has been gamma corrected to better visually represent star as it would look when observed. It gives rather "credible" looking seeing distorted star. Depending on "granulation" of wave front and intensity of phase shift (first is controlled by size of base gaussian noise image and how much it is enlarged / it's relative size compared to aperture, and second is controlled by sigma of gaussian noise - it is phase shift at anyone point in radians) we can get different seeing levels like this: (fine fluctuations in wavefront - like when using large telescope) Or very decent seeing - second ring defined but broken in few places. However, I'm sure that above generated seeing wavefront is not accurate representation of seeing wavefront. It probably has different power spectrum than average seeing that we encounter. Does anyone know or have an idea how "accurate" seeing wavefront can be obtained (in terms of phase). Further more, how would one go about it's time dependence. I was thinking along the terms of multiple layers moving in different directions where one can define some sort of cell and combining those in some way. Much like if I were to make multiple images with gaussian noise and then slowly shift them and morph them and somehow combine them? I know that ultimate solution would be to do something silly like running simulation of Navier Stokes equations for 20km of atmosphere or similar - but let's go with next best thing, shall we?

Barlows can vignette depending on their design and size of sensor. In order to avoid vignetting it's best to use barlow that is meant for photographic applications - like Baader VIP barlow. It is designed to illuminate full frame sensor according to specs. Of course, depending on how much vignetting there is one can either crop or use flats to correct small amount of vignetting.

Very nice indeed. I have couple of suggestions for you if you are up to it. - Try doing a bit of frequency restoration on your image - using wavelets transform like it's done in planetary imaging. This will make rather noisy image but rate of expansion should be easier to see. - Maybe do calculation vs measurement on your image? We have approximate distance to the object and measured expansion rate of 1500m/s - it's rather easy to calculate what sort of angular size difference there would be in 20 years. You can then compare that with measurements from these two images - measure difference in pixels and convert to arc seconds from sampling rate of your system.

When choosing planetary camera there are couple of things that are important: - good QE. This is of course important for every application, better quantum efficiency means better SNR in same exposure time. This can be compensated in deep sky AP by using longer integration time (shooting for 5h instead of 4h for example), but not in planetary - where system is dynamic and you have limited window for data gathering (planets rotate and if you shoot too much you will have rotation blur - there is a way around that by "derotating" videos, but still, there is time limit on how much data you can gather). - fast readout time. This is essential. In planetary AP one uses very short exposure times - couple of milliseconds. This is related to coherence time for given seeing, but in general it is below 10ms most of the time (only very good seeing provides coherence time larger than about 10ms). This means that number of captured frames will be limited by readout speed rather than exposure length (for 30ms exposure you can only do about 33fps, but with 5ms exposure you can do 200fps, and if camera supports only up to 150fps you will be loosing about 1/4 of the frames because it can't download them fast enough). - read noise. This is also essential for planetary AP. Difference between one large exposure and stack of small exposures that have same total integration time as large exposure differs only in read noise. Read noise is only kind of noise that does not grow with time and is tied to single frame readout. When you gather tens of thousands of frames per recording - each one will have read noise associated. This is why you want your read noise to be the least possible. Above cameras have these characteristics, but they are not only possible options. ASI290 is also rather good and available as mono version. ASI178 is also decent camera. I'm listing only ZWO cameras because I know their model names, but you don't have to choose their cameras - other vendors also provide models of cameras with these sensors. Mind you, good planetary images can be recorded even with "entry level" planetary/guide cameras like ASI120. Good seeing will make more difference than camera model, but if you have the budget - go for best that you can afford.

I think that easiest solution for planetary imaging that will give you best images and will cost the least - is simply getting dedicated planetary camera. ASI224 / ASI385 would be a very good choice (if not the best). You will need such planetary camera regardless of the scope you are planing to use. Next thing would be to learn about planetary imaging. It is completely different thing than both daytime photography and also deep sky long exposure photography. It consists of recording a video rather than image (in fact very fast sequence of short exposures - as much as you can get) - most of the time up to few minutes in length with very short exposures and lots of frames - something like 200fps and above is ideal. You will of course need a laptop with USB3 connection and preferably SSD disk to be able to record that video in time. After that there is processing stage - where you calibrate, stack and sharpen and color balance your image. All software tools for this are available, and they are free - it is just a matter of learning the process.

In principle you can use barlow to extend focal length of your scope and capture "enlarged" target, but that really depends on ability of your setup to resolve enlarged target. If your setup (and sky conditions) don't allow for that additional detail - you will essentially end up with the same image as you would get if you just simply shot without barlow and enlarged result by factor of x2 (resampled image to enlarge target). Type of processing is also going to play a part here. In your particular case, I would say that with 130PDS mounted on HEQ5, if your guiding is good - meaning around 0.7" or less and your skies are decent - like 1.5" FWHM seeing, you should be able to sample at 1.5"/px. 1000D has 5.7um pixel size, which means that without barlow you would be sampling at 1.8"/px if you had mono sensor, but since you have color sensor, you are sampling at twice that - 3.6"/px. You can comfortably use x2 barlow / telecentric lens. You don't need to use coma corrector in this case (you will probably need to crop outer edges a bit since there might still be some coma in corners) and it is better not to use one - you will get better stars without one if you use barlow. Also - you will need to image for longer than usual because of reduced sampling rate.

I don't think it particularly matters, but can't be sure. Probably depends on method of PA alignment used. Method exists that does not require precise alignment of scope to RA axis - it only examines field rotation in a given scope - after all its about where scope is pointing along the rotation of RA axis and what is expected if RA axis is properly aligned to NCP. On the other hand, different polar alignment routine requires alignment of optics with RA axis - same as with PoleMaster and such - these observe single field around Polaris and how it rotates when the RA rotates.

Next to issues with amp glow (which is not really amp glow in CMOS) there is often issue with bias levels. I think it has something to do with the way cmos cameras work / fast readout. There appears to be two different modes of readout that one can't control - at least that is what I've read (might not be related to this issue after all) - short one, less then 1s where timing is kept in sensor itself and long one - where application controls exposure length. In any case, bias levels can be different in these two regimes (or in general - bias level can depend on exposure length). Not all cameras show this behavior, but I had such issue with my ASI1600 - bias sub had larger mean ADU then 10s dark sub - and that of course should not be the case. Another thing that can happen, but I doubt it happens with serious CMOS cameras, I only had it with guider cams and small sensor - automatic bias offset. Sensor does internal offset calibration on power up. That means that bias is not stable across bias power cycles and that you need to always take bias / darks at the same time (or rather after) lights / flats. No reusing of subs for later. Because of all of those issues - one should not scale darks with CMOS unless they determine that they can do it properly with their sensor data (best way would of course be to take two sets of darks and one set of bias and try dark/dark calibration and examine result for any DC offset and patterns - it should be pure noise with 0 mean ADU). One way to do dark scaling is to use two sets of darks of different exposure and not dark and bias. For example 2 min dark and 1 min dark can be used to get: bias as 2 * 1_min - 2_min and dark current only as 2_min - 1_min. After that it is easy to do scaling.

I just love amount of handles it has at the front - for one to brace themselves when having a first look On topic bino vs mono, as stated - there is no perceived brightness increase, but there is a benefit to it. In the same way as observing a target for longer makes us see more so does binoviewing. Eye/brain system does not work like camera sensor - there is no single exposure - it is continuous feed and brain does all sorts of wonderful things to this. It has noise filter - you never seem to see the photon shot noise although there should be shot noise visible at levels of light eye is able to see (just a hand full of photons can be detected, I believe threshold is something like 6-7). Our brain sort of forms "residual image" - it remembers what it saw just a bit ago, and image sort of stacks in our brain - this is why prolonged observing helps see more - once we see one detail and "know what to expect" at that place - it's easier to see it. Binoviewing does similar thing - our brain can use noise filtering more effectively - if it comes from one eye only, maybe it's noise, but if both eyes detect it - it's probably signal. Btw, I managed to see shot noise once, for anyone interested - here is how it happened. I was sitting in relatively lit up room (daylight no artificial light) - but there were some shades on windows so it was not overly bright. It was bright sunny day outside, so plenty of light there. I held Ha filter at some distance away from my eye (not very close but not at arms length either, about 20-30cm away) and looked thru it - I was looking at bright outside - thru the open terrace door. Image thru the filter was distinctly deep red but it behaved as an old TV when not tuned to any particular channel - just that white noise. In this case it was "red/black" type of noise over the image changing rapidly (really much like TV noise). I think that it happened because of lack of light coming from that direction while surrounding light levels were high enough to "turn off" brain denoise.

Just a small update. I'm now at 95% confidence level that I'll go with Mak 102. This is due to number of reasons: - It turns out that I'll probably need to spend a bit more money on rig than I previously thought. Initial idea was to purchase AzGti + scope package, but it seems that scopes coming in this package don't have collimation screws unlike regular OTA versions - at least Mak 102. This can be seen on images of this scope, but it's also confirmed by Skywatcher rep over on CN in one thread. I would not want to get myself in situation where I can't collimate my scope and need to send it back. There is also concern about quality of scope if it's not the same as regular skymax OTA. I also figured that I want a bit more accessories with the scope - ES 82 6.7mm and quality 1.25" diagonal. - Many people report that tripod coming with this package is rather poor in stability (probably to be expected from entry level scope/package), so purchasing only AzGti head and adapter to Eq5 class steel tripod seems like better option. I have spare tripod for this use (moved my HEQ5 on berlebach planet) - I've came across image of back side of Mak 102 that is good enough to do rough measurement of rear baffle tube diameter. According to this rough measurement - it is about 23 mm in diameter. That would mean that there is some vignetting on 32mm plossl (field stop of 26-27mm), but it should not be more than 50% or so at the edges. It also means that Mak102 can provide larger TFOV in comparison to Mak127 (not by much, but still a bit larger). This is Orion version, but I guess SW one can't be far off (if not exactly the same). - I don't think that stray light will be a problem with these maks even on very close focus according to these images: This is image of Mak127 - it looks like light is reaching about halfway down the baffle tube, so I think placing focus plane roughly 40mm away from end of baffle tube should not be impacted with stray light.

What sort of large dob do you have? Aperture rules in planetary imaging (if decent optical quality). In planetary AP, mount is not as important as in regular AP (where that importance can't be overstated - it really needs to be the best you can afford). Cheapest way into very good planetary imaging would be adding tracking to already existing dob if it is large and of decent optical quality. If it is goto dob - you are pretty much set, if not - have a look at suitable equatorial platform. That combination won't be as "plug&play" as goto mount - there will be learning curve to get scope onto target especially with small chip - maybe flip mirror could help there or similar - but that combination will get the job done and you will get good results - just use good planetary camera and appropriate barlow / telecentric lens. Depending on your budget, next option for planetary - both viewing and imaging would be largest compact scope you can afford and mount on AZEQ6 - something like C9.25 or maybe even 10" Classical Cassegrain. For DSO imaging to start with you want something that is in range of 500-700mm focal length and there are quite a range of options there. - for rather painless imaging - refractor + suitable field flattener/ reducer will do the trick - cheap option would be newtonian + coma corrector (130PDS / 150PDS class scope). You can go with 8" F/4 scope as well - but as you go faster, collimation and tube stiffness and rigidity and quality of focuser become increasingly important so you really step outside cheap range there - Maksutov newtonians are worth a look a well in this category

Very different requirements so it is very hard to package that all together. Depends how serious are you regarding each of requirements. If you are looking at a bit more serious planetary work, 8" scope is start in aperture. Problem with that is that it won't provide wide enough field for larger nebulae (most galaxies and planetaries will be fine at that focal length). On the other hand if planets are something to try out but you have no greater expectations - you can limit your self to 5-6 inch scope. In first case, there are really only few choices: 1. EdgeHD 8" 2. Classical Cassegrain - again 8" - like this one: https://www.teleskop-express.de/shop/product_info.php/info/p10753_TS-Optics-8--f-12-Cassegrain-telescope-203-2436-mm-OTA.html 3. 8" F/6 Newtonian (maybe even F/5, but that one will have larger secondary if optimized for photo work and collimation will be more demanding for planets, also higher power barlow / telecentric is required to reach critical sampling) 4. 8" RC scope (mind you, while better option for DSO photography - it's not the best for planetary work and might not suit visual as much as other scopes - large central obstruction). While you can go with larger scope - I would not recommend that unless you are rather serious with planetary work and are ready to completely neglect wider field DSO work. In second case - there are much more options. 1. Decent maksutov newtonian (intes micro), or even their photo maksutov cassegrain: https://www.teleskop-express.de/shop/product_info.php/info/p3316_Intes-Mikro-Alter-M606---Photo-Maksutov-Cassegrain-152-912mm.html There are other options, like SW 190 (Mak-Newt) and Explore scientific Comet Hunter 150mm Mak Newt 2. Decent apo triplet in 130mm class 3. F/5 newtonian of course - something like 150PDS You should consider cameras that you plan to use for each role and preferred targets when making a choice between scopes.

This is very useful info, thanks for that. "Problem" is that I would not use small sensor at prime focus (too high sampling rate, too small TFOV), but rather in a sort of afocal arrangement. Eyepiece + lens would be used between scope and camera. This acts as sort of focal reducer, depending on focal lengths of eyepiece and lens (you can actually choose reduction factor). For example, ASI178 has ~8.9mm diagonal. With 32mm plossl and 12mm lens - it would behave as ~23.7mm diagonal sensor - and vignetting there would certainly show (even field stop of EP would show depending on AFOV of eyepiece and angle of the lens). Fact that there is slight vignetting on 28.4mm diagonal sensor suggests that fully illuminated field has smaller diameter, but that scope can illuminate up to 28mm of field. I would certainly both use and recommend flats in this role. 32mm plossl (most likely to be used as projection EP) has 27mm field stop if I'm not mistaken.

Test is fairly simple, and here is diagram "of my concerns": These sort of scopes are made to be used with diagonal mirror, although they have extensive range of focus, I suppose that optimal focus is somewhere around 100mm or so behind the end of the scope (end of that receptacle with T2 thread - I would otherwise call it end of focuser, but focuser here is internal ). In the configuration I plan to use it for EEVA, eyepiece will be quite a bit forward - it will be inserted in back tube directly (without diagonal). This is primarily because of weight / stiffness / balance issues - closer to tube - better (there will be EP projection adapter, small lens and camera hanging of the eyepiece). My concern is that if focal plane is put too close to OTA, there could be light leak - light going directly past the secondary and down the main mirror central hole and onto the sensor. This would reduce contrast quite a bit, as most people doing that sort of thing probably live in LP areas (it's not a good thing even in dark skies). Testing for this is quite easy - just point the scope at sky (of course be careful about the Sun) and place your eye at the end of back tube (you can't push your eyeball inside obviously , but place it fairly close - where eyepiece shoulder would be) and move it to the side so that secondary is not centered but to the side (bottom part of the image). If you see sky at the edge - bad, if not, and you only see secondary - good I have couple of scopes that I could use to test this sort of eyepiece projection thing, but my idea was to do it on the scope that is not usually recommended for EEVA because it is too slow, and scope that could fit above role - being beginner scope that can pretty much do it all - visual and "taking some images" (in appropriate configuration). Of course it is also excuse to get another scope - one that I would use in sort of grab&go / lunar scope role. I planned to use Evostar 102 F/10 (not ED) in that role, but it does not quite fit it the way I expected - too large/heavy and a bit shaky on AZ-4 mount, so Evostar 102 will be for other things (solar work with herschel wedge and solar Ha with combo quark one day, maybe a bit of imaging - again trying to see if I can make usable imaging scope out of it with some tweaks - for those people that can't afford APO scopes for that). For above reasons - I'm leaning towards Mak102 - it's lighter, it's more affordable to people and probably better suited for AzGti mount. One of more important things would be - what sort of TFOV each of those provide - I want one with larger TFOV. Normally, one with shorter FL will provide larger TFOV, but in this case, I'm not sure. Both scopes, according to reports online, have smaller back hole than is needed to fully illuminate 1.25" eyepiece. Given that and the fact that this exit hole might be smaller on Mak102, and that F/ratio of Mak102 is a bit slower - I can't really tell which scope would provide larger TFOV - One of the reasons I'm interested in illuminated field of both scopes.

Don't worry about not checking straight away, I'm in no hurry with this. If you manage to find the time and it's not too much trouble for you - just take a look at daylight - as long as you can't see sky past the secondary - that should be ok. Odd reflection on baffle tube is ok - that is what it is there for.

At one point I did actually consider Bresser maks, but given pro/con lists above you can see that it is not quite suitable for my needs. - It's slightly heavier than Mak 127 (which is already where I don't feel comfortable on mount quoted at 5kg carry capacity) - It has very long focal length - something I would not fancy for visual as well as for primary use - EEVA (small TFOV capability) I did look at 102 version from Bresser - but there is also issue of getting one. FLO and TS don't stock 102mm OTAs, and Bresser does not ship to my country for some reason. If I were looking for scope that is primary visual and meant for Moon and planets - I would probably go with classical Cassegrain from TS (either 6" or 8"). Scope I'm after now has different primary role.

I would like to know following if anyone can provide the info: - how "sturdy" is the mount? It's rated at 5kg, but I'm guessing that is a bit optimistic. What's mechanical finish like? - Would counterweight shaft + cw help in AZ mode for a bit heavier scope - like 3 - 3.5 kg OTA + accessories? - I like it is full goto mount, but I will probably not use it as such in visual - can it work without extensive star alignment? Can I just set it level and point it roughly north and tell it: "there you go, you are all set now, I just need fairly decent tracking from you and not precise gotos"? - I have hand controller from HEQ5 syntrek (not synscan) - once I do initial thing via phone app, would I be able to use that just to adjust target position and pan around at low speed - like "cruising" terminator on the Moon or such? - Have you tried it in EQ mode, and if so - what sort of wedge would be recommended for it? I've seen couple of models and they differ in price quite a bit - can I get by with cheap one or should I invest more there. I'll use it in EQ mode very sparsely and only to do some EEVA. - Is there ASCOM software for this mount that present itself like proper mount via Wifi? What sort of connection would I need if I choose not to use wifi and go wired? Any help with above much appreciated.

Yes - if it does what it "says" it does - checks mean ADU level in linear stage (prior to any stretch). One issue that I have with attached master flat is that it is still 16bit format? That is "no-no" in my book - it should be 32bit float. 16bits is simply not enough to preserve all precision needed. Don't know why that is, but all calibration masters (and intermediary masters like - master flat dark) should be in 32bit precision. That way you won't add any noise due to bit precision (and that will happen pretty quickly with 16 bit format if you go above 16 calibration subs - and most people use and should use more than that). As for flat master itself - don't know, it looks rather "normal". It might be a bit noisier than I'm used to, but looks fine otherwise? Here is comparison between your master flat and my master flat (my is 32bit 256 subs stacked with 256 flat darks - at unity gain): Yours (1:1 zoom and crop somewhere near center): Mine (same zoom and roughly somewhere near center): Mine looks less noisy / smoother, but it shows certain pattern that is present on my ASI1600 - it is much better seen when one zooms in more: It is sort of checker board pattern of pixel sensitivities - nothing to worry about as differences between pixels are at max about 2%, and it calibrates lights fine. This is manufacturing "artifact" - but you need a lot of exposures to "expose" that variation - otherwise it stays within noise. By the way - if you shoot your flats at high gain - use a bit more than 32 subs for them - it will reduce noise, or preferably shoot at normal / unity gain.

Christmas presents time ... Nothing like "surprising" oneself with another piece of astro kit, right? Thread title pretty much says it all, need some swaying one way or another, but as mentioned - there is a twist to this story. It will be AZGti mounted scope and its primary use is as testing rig (or rather purchasing excuse? ). I'm strongly motivated to write EEVA software and feel that one of these might be perfect platform to test it out. In part this decision is driven by the fact that many people look for affordable scope that will do it all - do some planetary viewing, some planetary imaging, some DSO viewing, some "DSO imaging" - or as they frequently put it - "Would like to record what they saw in an image". Many will tell that such a slow scope is not suited for EEVA purpose, but I intend to trial it specific "configuration" - Eyepiece + suitable lens + small sensor CMOS camera (can be used for both planetary and EEVA). I concluded that it is possible good combination for doing this and would need to try it out. Secondary role of the scope will be of course some quick viewing, probably mostly Moon gazing and sometimes quick peek at DSOs (those that are within reach in my LP for the time being). Sort of grab&go setup that does not require extensive preparation/setup time and is suitable for "off the balcony" use. I'll list my so far pros/cons list and some technical question people might be able to answer (owners and former owners of said scopes). 102 pros: - I really like compact format and light weight of this scope - Slightly slower - which means easier on the EPs and probably less optical issues for Mak (Gregory type). Smaller secondary? Does this impact baffling / any stray light issues? - Potentially choice for more people looking for above mentioned type of scope due to slightly smaller cost (not issue for me, but could be issue for some) - Focal length of 1300mm - I think I would feel less "boxed in" because it is very close to FL of scope I regularly use to observe - 200/1200 dob - Latest version has "groove" at front of the scope (probably to fit cover) - which can be used to fit dew/stray light shield as well? 102 cons: - I have slight feeling that mechanically this version is not the same as 127 - design more for the "masses" and aimed at being affordable. At some point 127 was marketed as "Black Diamond" if I'm not mistaken along with 150 and 180 versions - which gave impression that these three were higher class instruments (not only by aperture and price) than 90 and 102 which were sort of beginner scopes? - For visual it will have lower resolution and light grasp vs 127 127 pros: - Obviously aperture, both in terms of planetary performance but also for DSO / EEVA - Possibly mechanically better instrument? - Possibly better optically? 127 cons: (should I even write those or we can just "invert" pros for 102? ) - bulkier / heavier - mind you I plan to use it on AZGti - with eyepiece, ep projection adapter, cooled ASI camera (178mmc) and small lens - I have sense it will all build up towards 4kg+ rather quickly. But there is also issue of size - I just love how 102 looks as small (but capable) instrument. - cool down issues? - I feel that 1500mm FL will be a bit too much for grab&go / general purpose scope That would be about it I think - maybe I'll remember something later as well. I'm also interested in couple of technical characteristics of said scopes, so I would be grateful to owners if they can provide such data. - for both scopes, do you know what is fully illuminated circle on both (would need that to calculate usable TFOV for EEVA, and proper combination of Eyepiece / lens). I always assumed that both scopes would illuminate 1.25" field (so up to about 28-30mm) but I'm not quite sure - this might not be full illumination and there could be some vignetting. I've read somewhere that back openings are quite smaller than this? - I'm not interested in working aperture of scopes - I know that it's a bit less than one would believe from scope designation (102mm and 127mm), but it does not really matter - I accept that as design limitation (need for larger secondary and some baffling inside), but would like to know if there is stray light in the field at "close" focus position - or rather when one sights down the tube on EP side - can you see past / to the side of central obstruction and if so - at what distance to T2 thread (end of scope in literal sense). If you check this - move eye to edge rather than keep it on axis to check for gap - Of course, in context of what is written above - any difference that you feel could sway me one way or another. Thanks

Nice image, although I'm not fan of artificial diffraction spikes