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There might be a chance that you have a faulty mirror. That sort of softness that is visible in the image is indicative of spherical aberration. Spherical aberration with newtonian can either be due to simple coma corrector used - like 2 element sky watcher x0.95 one, or due to poor parabola on the mirror. This will only show as softness when viewing at high power - like planetary and lunar views and of course - like stars being little balls in high resolution images. Alternative to that would be that seeing was really poor on particular night and that created bloated stars. If you want to check if your scope has spherical aberration (you say you did not use coma corrector) - take out of focus image of bright star - on both side of focus. Try to defocus it only slightly so that you still get rings visible, and do both sides of focus with roughly equal level of defocus. Here is guide of what you should be looking at: When you defocus star pattern slightly and have perfect mirror - you should get first row in above table. Note level of defocus - one that still shows a bit of rings. Your star will have "hole" in the middle when you start defocusing as you have central obstruction. In any case - perfect parabola will show same pattern regardless if you are in / out of focus. If you get two different images for same level of defocus - one where edge is fuzzy and center is darker and other where edge is better defined and center is brighter - you have some level of spherical aberration present in the system. Since you have camera - you can also post images here for analysis.

I just discovered something quite interesting. It turns out that good field illumination on 80mm F/7.5 and shorter is quite hard to achieve. I was in process of designing focuser for a telescope that I'm 3d printing (or rather assembling out of off the shelf components and 3d printed parts), and I wondered what sort of draw tube width I can go with. I have constraints on tube width due to mechanical properties of the focuser (how it all fits together), so I decided to check out what sort of field illumination I could get and if I'm able to go with 2" at all or should I stick with 1.25" backend. In any case, FreeCad / Sketcher is very nice tool to quickly calculate needed quantities. For example, if we want to use 2" drawtube or 51mm ID, and want to achieve only 38mm illuminated circle (max field stop for 2" eyepieces is around 46-47mm) - we need to limit our drawtube length to only about 100mm - anything longer will reduce illuminated field. Maximum distance between focal plane and clear opening of drawtube is 204.5mm (blue value) in above diagram. Out of those 204mm - about 104mm goes on 2" diagonal (depends on diagonal model, but most are just a bit higher than 100mm in optical length). Similar thing happens if I want to use 1.25" backend and want to have it as much illuminated as possible - say 25mm illumination, but want to use drawtube that is less than 2" - maybe 41mm ID one. We now have 174.5mm of distance - and about 75mm of those will go toward 1.25" diagonal (unless prism is used and I would not at that speed, but in any case, savings won't be that much). Still leaves only 100mm long draw tube - and that limits focus travel / adjustment range. What sort of illuminated field would you expect from such scope - like 80mm F/7.5 achromat?

Check out this thread to see how people are using their:

Hi and welcome to SGL. If you want to shoot planets and the moon, and do it properly - literally any mount will do - even that AZ3. Trick is to use very short exposures. You need to use short exposures for planets as they are bright, and that will stop any trailing as a bonus. Only drawback is that you'll have to adjust telescope pointing every few seconds to track the object. In order to avoid this - people use simple tracking mounts. This will also help with second thing that you have planned - that is to take long exposure images with camera and lens (if I understood you correctly). There are two solutions that come to mind. 1. EQ3 with RA motor: https://www.firstlightoptics.com/equatorial-astronomy-mounts/skywatcher-eq3-2-deluxe.html mount itself is not driven, and you need to attach at least RA motor to it, for it to be able to track the sky. There are ready made solutions, but you can also DIY one. https://www.firstlightoptics.com/sky-watcher-mount-accessories/single-axis-dc-motor-drive-for-eq3-2.html Or you can upgrade to dual motor drive if you want to add tracking. 2. AzGTI in EQ mode. AzGTI is nice little alt azimuth mount that can be converted to equatorial mode by adding a wedge and counterweight bar (and flashing official firmware that supports both modes of operation) - many people have converted theirs and use them for imaging. https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/sky-watcher-az-gti-wifi-alt-az-mount-tripod.html

I'm still confused as what the issue is? Effective aperture stop in diagram is located behind first lens group. First lens group is 70mm in diameter - but it's being stopped by aperture stop, and in order to see how much it's being stopped down - we need to know the power or focal length of first lens group. Since we don't know that - we can't calculate effective aperture and thus can't calculate F/ratio. We can do things in reverse. We can say - ok, we accept that effective F/ratio of system is F/4.5. At 289mm of focal length (effective) - that will be 64.222mm of effective aperture. Now we need a bit of math to calculate focal length of first group: From above diagram we can write equation: 32.11:(70+X) = 26.15:X or 32.11 * X = 26.15 * X + 1830.5 5.96 * X = 1830.5 X = 307.13mm Focal length of first group is ~377mm - or it is F/5.3 achromatic pair. We can now also work out focal length of second element (that acts as reducer) from this and spacing on the diagram .... However - this is only true if we assume that F/4.5 is correct and that effective aperture is indeed 64.222mm Alternatively - we can go in reverse - but to do that we need focal length of first lens pair.

I've decided on the course of action. Since I'll be needing same parts for both 3d printed version and manual to motorized conversion (namely stepper and driver, permanent magnet + hall effect sensor, micro controller) - I'll go ahead and make 3d printed version just to see if it could be done. At some point in the future I'll switch components over to motorized manual filter wheel.

Not sure why is that. Let me see if I can utilize my computer-fu to make it open.

There you go. This ought to be enough

Things get brighter (perceptually) when you get dark adapted. Maybe change of lighting helped to get better dark adaptation (leds are usually directional rather than omni directional).

Well that seems to be somewhat difficult to quantify in my case as there are several things at play. As far as my self personally - it seems to be the case of "being smart enough to not have to pay that much" kind of thing. It's not so much about saving money - as have been pointed out, in grand scheme of AP things - it is not grand saving after all. Then there is component of making things affordable to people that can't afford it. I really enjoy occasional video where people craft telescopes out of PVC pipes. Is it crude? Sure, but on some level - it gets the job done and will spark interest to someone that might not be fortunate enough to afford even cheap beginner scope. I like to think that way - but then harsh reality hits me - in order to make some of these things - one needs 3d printer, and while they have been really affordable lately (at least entry level models) - one who can't afford beginner scope - will not be able to afford 3d printer either. However, I've seen outreach programs where people with printers team up to make toys for children, so why not do the same for astro items - once we have good working designs. Third part is probably due to circumstances. I live in a country that has median net income of about 500euro - yep, half of working population earns less than 500e per month. I guess I've been exposed to this "saver" culture because of it. But of course I put value on it - it's my "let's design and make something" enjoyment time In the end, I might give that approach a go. I'm still thinking of 3d printing one - just for fun and to see if it could actually be used. I'll probably need to seriously beef it up to make it rigid so it won't be slim, but it might work.

This is actually part of the problem Knowing what goes into motorized filter wheel - I simply can't see how on earth it could cost that much, even with labor and shipping and all of that. Yes, there is matter of scale - and mass produced items cost less and maybe they don't have marked for high enough volume - but I think I can get 3d printed version for at least x10 less money if not more.

That happens to me on a daily basis How do you think I got the idea to 3d print filter wheel in the first place? This is actually very true - but it is also cause of concern. I might be able to to do something about it though. At the moment - I'm seeing T2 thread on camera side being printed in such way as to mating surface being printed as last layer (top of the print). That is causing a bit of concern as it is rather rough surface. I've played around with wet sanding paper and PLA and one can get incredibly flat and smooth finish - but I worry if I introduce tilt by sanding that part down. Need to figure out how to keep sanding paper perpendicular to optical axis while smoothing that face.

So far I've gathered that tilt is probably the biggest concern? That and any internal reflections. Yes, PLA tends to be very shiny - even black. I wonder if painting it with mat paint would improve things? Light leak is easily tested - I just need to print cover for the camera and take some darks with it on to see if they match regular darks. How to go about tilt? Critical focus zone is something like 60 microns for one of my scopes I intend to use this on. That is fairly small. I've seen "universal tilt jig" being discussed here on SGL - must look it up, maybe it will give me some ideas of what is involved and how to test for it.

Yep, that happened to me several times, although, to be honest, they were not designed properly (not enough walls, poor infill - small cross section). I guess forces involved when tensioning stuff can be quite high.

Software side of things should not be a problem - it is fairly simple protocol - move to position xy and that is it. Not sure what level of accuracy is going to be required here? I've printed several types of threads down to 0.6mm pitch and they worked fine. As far as I can tell 28 x 0.6 is going to be finest that will be printed and I've already done that. There are some clip in 1.25" filter thingies that I've printed for an acquaintance. I'm thinking PLA as choice of material, or rather PLA+ (not sure how we should call it) - I'm currently using Creality HP ultra PLA that is produced by BASF. From what I've gathered BASF produces some very fine PLA (I've seen one review where mechanical properties were superior to other choices of PLA). PLA has the most rigidity / least flex. Given that it will be night time use - I don't see how exposure to sun or UV might be a problem. I'll pack the scope after the session. Moisture absorption might be a problem and I'll have to look into that. I have similar feeling. It is down to surface area, and that can be somewhat controlled. We can do quick back of the napkin calculation. PLA has ultimate tensile strength of about 20MPa in Z direction (up to 60-70 in non layer direction). If we select thickness of our T2 thread to be 2mm then that is (21^2 - 19^2) * pi millimeters squared or about 250mm2. 20MPa * 250mm2 = 5000N (did I get this right?) It seems that we would need ~500Kg of load to break it. Even if I have poor layer adhesion and ultimate tensile strength is much less (like x10 less) - I'd be happy with that.

I'm thinking of printing the whole thing. Well - except for motor and controller obviously Not conversion of manual to motorized, but rather whole assembly - which is not much when you think about it - it is casing, wheel, maybe one bearing to make it move smoothly and stepper motor with controller. Maybe some sensor to find home position and that is it. Are there any obvious drawbacks? Temperature change issues with plastic? Threads being able to carry the thing (will 3d printed T2 be strong enough to hold camera + filter wheel itself)? Gear precision / repeatability issues? IR leak thru plastic? Light leak thru 3d printed structure (how well will it seal interior from light)? Any thoughts?

That will very much depend on your budget. If money is not an issue and you want future proof thing - then this one: https://www.firstlightoptics.com/zwo-cameras/zwo-asi-2600mc-pro-usb-30-cooled-colour-camera.html It has same sensor size as would regular DSLR / mirrorless (in fact even larger than some of them) - and it has great characteristics. All other options are really some sort of trade-off. This one is often recommended (and I don't object to that): https://www.firstlightoptics.com/zwo-cameras/zwo-asi-533mc-pro-usb-30-cooled-colour-camera.html but it is a small sensor. It will work good on short focal length scope, but if you want to sample properly with it - you will get images that are say 1500x1500px in size, which is on a bit smaller side by today's standards (when most people use 1920x1080 as base display resolution - so everything is in full hd or higher). You can save some money by getting that camera without cooling - but that will require you to pay special attention to calibration. Luckily - there is no amp glow, so it won't be that problematic - but you will still need to either scale darks or just use bias + dark offset removal. Similarly - there is this model: https://www.firstlightoptics.com/zwo-cameras/zwo-asi-183mc-pro-usb-3-cooled-colour-camera.html It has enough pixels, so yes - you can get cooled version. It will require proper calibration as it has some amp glow. I would not recommend that in non cooled version if you want good calibration as amp glow is PITA for that. ASI294 has some issues with flat calibration, so you have to be careful about that. Then there is this one: https://www.altairastro.com/altair-hypercam-269c-colour-camera---tec-cooled-1097-p.asp Looking at the specs - it could be "the entry level" camera, but I haven't seen much in terms of feedback and if it really performs as good as it ought to by the specs. Bottom line - you need to think in terms of money and level of convenience / inconvenience.

Yes, ASI120 is perfectly fine for guide camera. What model exactly, that will depend on your other aspirations. If you want it solely for guiding and want just a bit better guide performance - use mono. If you want it to double as your planetary camera - use color and get USB3.0 version. If you want cheapest option possible and don't care about planetary - use color USB2.0 version (it should be cheapest). As far as main imaging camera - that will largely depend on your budget and level of complexity. Simplest option would be to go for mirrorless type camera (DSLR but in mirrorless version at is lighter). Next up the ladder would be modified DSLR. Next step would be OSC / Color dedicated astronomy camera. Then cooled OSC camera and finally mono cooled dedicated camera + filters. Again - its all down to level of complexity you want and how much money you want to spend. For guiding mono will have small edge over color, but in principle - you won't see the difference in real use. All of my guide cameras (had several) were color and I never had issues. On paper - mono is just a bit more sensitive and it gives just a bit more precision, but in reality with small pixels and sensitive sensors - it won't make any significant difference. For main imaging camera - see above, it adds much in terms of complexity and cost, and you should probably start with color camera for sake of simplicity. I'd say - get second hand DSLR body and use that first until you learn stuff, but DSLR tends to be heavier - so I recommend you look into mirrorless instead - if you can find one second hand - then great, but they are relatively new and I'm not sure how often do they pop up second hand.

Ok, so what is your question here actually. Do you want to know about guide setup - camera + guide scope? If so, then please provide some additional detail 1) Budget and if cheap option is important 2) DIY skills in case you want to go real cheap 3) do you intent to use that guide setup only on AzGti or do you plan to expand in future 4) do you intend to use that camera for additional things like planetary / lunar imaging (I'm gathering that you meant SW 127 + AzGti as your current combo when you said "only used my 127 azi gti for visual "). Do you want to decide on main camera as well to be paired with 72ED (80ED will be to heavy for AzGTI) or smaller scope?

That script is probably doing something like measuring max signal value in the image (limited by clipping) against background noise (limited by determining what is background in the image). Totally useless. SNR value of 5 is probably minimum for detection threshold (not in dBs - just straight ratio). It is also worth noting that there is no single SNR value per image. Every pixel in the image contains its own specific SNR value. When we talk about SNR - like "target SNR" - then we make several assumptions. One is that we have uniform signal. This can be true for small patch of target - like tidal tail of galaxy or outer halo or maybe IFN or something similar. There is very easy way to produce SNR map of the image to be able to check what sort of SNR one has across the image. Here is how to do it. It is best to avoid complex stacking methods (although same can work with complex methods - but math is somewhat more complex) - and use simple average. Two different stacks are needed to produce SNR map. First is - regular average of the data, and second is standard deviation stack (stddev computed for each pixel instead of average). To produce SNR map - one can then divide the two and multiply result with square root of stacked subs (each pixel value multiplied with constant). One more thing - average stack needs to have background removed prior to dividing with stddev stack to remove unwanted signal. Such map can then be used as follows - select some part of the image - like outer part of galaxy and do average on that selection - this will give you average SNR achieved. It is meaningful only if signal does not change much in selection. Also - don't try to measure SNR on background without any signal (well you can and you'll get expected result) - as that area has SNR of zero - as there is no signal there (result of measurement should be very small number close to 0). Best way to "assert" what sort of SNR should one aim for would be to produce different types of SNR in same artificial image - like some text on black background polluted with different levels of noise. When image can be processed in such way that text is readable - you have good SNR.

Oh, I completely misread your post @Beardy30 Above is written for Svbony 105 - camera, not Svbony 165 - guide scope. As far as guide scope goes - again, get what is most accessible. Anything 30mm will do the trick. I'm using this one: https://www.firstlightoptics.com/guide-scopes/astro-essentials-30mm-f4-mini-guide-scope.html I'm sure that Svbony 165 will also perform great on mount like AzGTI - above part related to performance still applies - you don't need larger guide scope for that mount in EQ mode.

AzGTI is not really demanding on guide side of things as it can't perform like larger mounts. You will be limited by mount performance rather than guide system, therefore - any camera + guide scope will do the trick. Get what is most sensible to you - if you can get any sort of small guide camera second hand - go with that. If Svbony 165 Svbony 105 is something that you can easily get - go with that. Do bear in mind that Svbony 105 is just repackaged web camera. It's main drawback is that it can't output raw video / raw data. This will severely limit its use in other scenarios. Most people use guide camera as lunar / planetary camera as well. Svbony 105 is really not that good in such role. Similarly - if you move to more serious mount - you'll want better guide camera. Problem with cameras that use compression is - well just that, compression artifacts. Stars won't be nice and round, but will rather have artifacts associated with compression (think blocky Jpeg appearance - but not so severe). This can result in improper star position calculation. Again - that won't be much of an issue with AzGTI - since it can't perform very precisely itself - but it could be bottle neck for something like Heq5/EQ6 in the future. I personally have 30mm guide scope with ASI185mc (could be called an overkill, but that camera is what I have for guiding for more serious setups, so I use it for this as well) on my AzGti for guiding.

Yep. You could try calculating reflection distance using one of online calculators - by measuring diameter of reflections and using F/ratio of the system. Maybe repositioning filter by small amount will be enough to upset interference pattern that lead to reflections? It really depends on how bright source is. 5s of magnitude 0 star is equal to 500s of exposure of magnitude 5 star (x100 intensity for 5 magnitudes of difference).

Micro lens on pixels combined with some other reflecting element that is a bit further away - like a filter. It will be only visible on very very bright source with very long exposure times.

@Ouroboros Ok, I finally think I understand I think that I finally understand what has been bugging you. With RSA encryption - you don't encrypt message in blocks like with symmetric ciphers - you encrypt message as a whole. It would be easy to break the message if one would for example encrypt every byte on its own. That would give us 256 combination as each byte would always map to same number and we could then use statistical means to figure out which output number corresponds to which plain text byte - but that is not how RSA works - it encrypts whole message, and if message is short - is being padded to be of appropriate length - to create large enough whole number to be encrypted.