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Main difference between the two is slow motion controls. With AZ5 you can also toggle between two mount head angles - which can be handy for different OTA diameters.

If you plan on doing both planetary and DSO imaging than you better look at getting two scopes. 80mm or smaller refractor will quickly run out of steam for planetary. Maybe look into 6" F/8 newtonian as planetary imaging scope until you get SCT to replace it? That is probably the cheapest 6" planetary imaging scope that you can purchase and also - probably one of the best.

I really don't know. I tried my SA200 few times on 8" Dob just to see how it works. I was able to easily see spectra of brighter stars (not sure how bright - but fairly bright like brighter than mag5-6). Like you, I'm holding back to do spectroscopy with camera (hopefully soon), but will certainly have another go visually because I really like this challenge. I do know few things that will make a difference if you decide to give it a try. - focal length of eyepiece will magnify spectrum as well - higher magnification of spectrum - less bright it will be - distance from eyepiece will affect dispersion - larger distance (like with 1.25" extension) more dispersion. This is a bit like magnification but there is a difference. Increased dispersion will magnify only spectrum while it will keep star image the same. If you have poor seeing, you might want to use higher disperesion with longer FL eyepiece. In good seeing - it is best to magnify by eyepiece rather than change dispersion. Maybe using zoom EP would be good idea - that would let you trade off detail and brightness (spectrum when magnified looses brightness as light spreads around). - try both with and without dark adaptation. Eye has different sensitivity over spectrum in these two different "modes". Dark adaptation will make you more sensitive to light but you'll loose a bit of sharpness - which will make lines harder to see. - Don't focus on star - focus on spectrum. Due dispersion star and spectrum don't come to focus at the same point. Dual speed focuser surely helps to focus on particular part of spectrum (spectrum can't focus all at once either as it is "tilted", and depending on level of dispersion - you might notice different focus across spectrum or not).

When doing planetary imaging - don't use focal reducer. Which ZWO camera do you have? For 2.4µm pixel size, don't use barlow - go with native F/10, that is good F/ratio for that pixel size. With 3.75µm pixel size - get x1.5 barlow lens to get to F/15 (use barlow element that screws into nose piece of camera and then use some sort of distancing ring to get x1.5 magnification - you can test that during the day by examining images of distant object, with barlow you want size of object to be x1.5 versus no barlow - closer to sensor less magnification, further away from sensor more magnification). In any case, once you get to critical F/ratio for your pixel size - then set exposure time to about 5-6 milliseconds and boost gain as much as you can. Don't worry about histogram or image looking dark - that is ok and nothing wrong with that for planetary imaging. Point is to minimize read noise (high gain) and to freeze the seeing (short exposure length). Stacking will make everything all right and your image will have proper brightness once you process it.

At 0.78"/px you are guaranteed to be oversampling. 1.55"/px is much more realistic sampling rate. You can easily test what sort of sampling rate is good for a given image if you examine single frame and star FWHM in arc seconds. Measure average FWHM of average frame (or you can do it on final stack as well) and divide that value with 1.6. That is sampling rate you want to aim towards.

It would certainly be interesting challenge. I have one addition. It is not cheap when purchased, but can be made relatively cheaply that will enhance this type of challenge. Ready made solution is called StarAnalyzer. It is filter like device that can be screwed in the eyepiece and will show you the spectrum of stars while you observe. It is transmission grating and it will disperse light from the star into a line spectrum. One can examine spectrum and try to identify prominent lines in it to go along with spectral type. SA is a bit expensive, but there is alternative DIY type of solution that only involves access to laser printer and transparent plastic sheets used for overhead projectors. Transmission grating can also be printed and used in front of objective lens (at telescope aperture). One just needs to print as fine grating as printer will allow (say at 600dpi - lines that are 2-3 dots wide and separated the same). View with Star analyzer

I forgot that bit. Best F/ratio for ASI224 is around F/15 for planetary. That means that you need barlow around x3. Most barlows can reach that magnification because magnification varies with barlow to sensor distance. Specifically, you might want to look at this barlow lens if it will fit the budget (it's a bit pricy): https://www.teleskop-express.de/shop/product_info.php/info/p5662_APM-Comacorrected-1-25--ED-Barlow-Element-2-7x---photo---visual.html That is coma correcting barlow that is natively close to x3. It is also very good barlow element.

Depends on software you are zooming in with. If your software does not have this option - you can always change software. I also avoid zooming in past 100% because I know that there won't be any detail to be seen. In any case, my point was - under sampling does not cause blocky stars - software interpolation does. If you have two pieces of software and one shows blocky stars and other does not - will you conclude that data contain blocky stars or that one software makes them look blocky while other one does not?

Very nice setup. Here are a few pointers: - you have listed ASI224 and separate guide camera. This leads me to think that you are planing on imaging DSOs with ASI224? This will give you extremely small FOV. Here, look at M42, Orion's nebula: You'll be able to capture only central part of it. I would suggest that instead above you get the following: Keep ASI224 as dual role camera. It is good planetary camera and can be used as guide camera. Don't worry about color vs mono thing for guiding - color cameras guide equally well and you'll have no issues with color camera and your guide scope. Get DSLR or mirrorless type camera for imaging (even second hand one). Look what APS-C sized chip gives you on that scope: Much nicer field of view. Probably not. There is focuser to compensate 30-40mm of optical path with its range of motion. With newtonians it is better for focuser to be somewhat more racked out. When it is racked in - it can block a bit of light and create diffraction artifacts in image. Left star with diffraction artifacts, right normal looking star No need to combine the two if you are using barlow for say planetary. If you are using scope for planetary - keep planet in center of the FOV. Coma is not present there and you won't need coma corrector. If you are doing Lunar imaging - you can then calculate how much of sensor you can use with coma free field. There is formula to calculate how much of the central field is coma free depending on F/ratio of the scope. You then set ROI on your camera if necessary (on ASI224 it probably won't even be necessary as sensor is very small). In any case - don't combine CC and Barlow. If you really need to - there are hybrid options, coma correctors with amplification effect or barlow that has coma correction included Yes, if camera has only AR coated window. It is more useful when working with refractors as those don't focus IR properly. With mirrored systems it only ensures that you can get accurate color (you have to calibrate color to get accurate color) Guide scope. You can easily focus by hand but guiding by hand is pain Best camera would be something with larger sensor - like DSLR or mirrorless (for DSO, for planetary ASI224 is the best and it is also good for guiding).

I was right then to think it has to do with zooming in? In that case - stars don't look blocky because they are under sampled - they look blocky because of interpolation method used when zooming beyond 100%.

Here is an example with Canon IS STM 55-200 and Canon 750d, again one hour from Bortle 8 skies: Crop around North American nebula and Deneb. This lens is very sharp, but problem that I found with this combination is sensitivity. Lens is F/4.5 and with one hour of exposure I could not get enough data to get the color to show properly - that is why it is mostly desaturated in background signal as color noise is just too much.

I still don't get it. How can you tell a star is blocky if it for example covers only one pixel? @david_taurus83 Which ones? Above image was resampled RC image that has diffraction spikes on some stars - which could give impression of blockiness but that sort of thing won't happen on refractor After all, we might be talking about different thing? When people say they see blocky stars - I imagine this happens: but that happens when someone tries to zoom in past 100% and uses nearest neighbor interpolation algorithm. This is by the way that 5"/px image zoomed in to say 300% or so. Look what happens when I choose different interpolation algorithm: Stars don't look blocky anymore (they do have small ringing as interpolation artifact here) That is the sort blockiness that I think people are talking about, but maybe it is something entirely different?

I have Samyang 85mm F/1.4 and it is really good (actually cine version T1.5 without click stops for aperture). It does need to be stopped to F/2.8 in order to avoid chromatic blur. Wide open it shows quite a bit CA. Here is crop from ASI178mmc and that lens on M31: Bright stars do show blue and red halos. It is fast however, from Bortle 8 with just an hour of imaging it can capture quite a bit of M31 (this is mono version of above image stretched to show all that has been captured):

ST80 can produce some nice images. It is not ideal scope for imaging due to it being fast achromat lens, but it can produce nice images. Good lens will be better option for astrophotography, but it really depends if you want to have second grab n go scope for visual as well for astrophotography. With a few tricks, you can make very nice images with ST80, for example - this image was created with ST102 - bigger brother of ST80 that has even more chromatic aberration: This is achieved by stopping down the scope as you would the lens. Lens can't be used wide open as they will produce chromatic aberration as well. Depending on type of the lens, you'll probably need to use it at F/4 to F/5.6. ST80 is F/5 scope and in order to get CA free images - you probably need to stop it down to F/8 or so? Now the question is - how "close in" do you want to get to your targets? Do you want general wide field that is achievable with lens or you want to get closer in? Add to that part of using ST80 as visual scope - but also the fact that you need adapters and fact that ST80 focuser is really not the best piece of kit. Alternative is certainly to save up a bit and go for ED doublet in 60-70mm range that will fit on AzGTI.

Why is everyone constantly saying this? I'm yet to see blocky and pixelated star. Here, this is 5"/px: Are any of these stars blocky and pixelated?

Have a look at this video: https://www.youtube.com/watch?v=Ylb7xnc_03U It shows whole process of disassembling ST80 refractor telescope and blackening lens edges to improve contrast. Interesting parts are re seating the lens back in lens cell - tapping to get it to seat properly. This part is at around minute 5-6. Like Ed pointed out above - you can just slightly loosen retaining ring - and then tighten it as instructed in video - each time gently tapping / shaking scope to seat lens properly - and just slightly touch up on retaining ring without forcing it.

What scope are you using. If it is triangle shape - it could be pinched optics. Try slight defocus on a bright star and see what the pattern looks like. If it is still triangular, it could be pinched optics.

What do your views look like? Maybe one of these images: These show "progressive" improvement in seeing conditions. Only good and very good seeing will show definitive disk with either broken or full rings around it. If your view resembles - first three images, then I'm afraid, it is the seeing. Check out some of the guides for optimizing planetary views (cool down, choice of location, time of the night, target near zenith, etc ...) - same things apply here

Problem with oversampling is down to read noise. With F/30 and 3.75µm pixel size one really over samples by factor of x2. That spreads the light more and effect of read noise becomes more important. If you bin to get to actual resolution - you put 4 pixels together and that makes final sample have 4 "dozes" of read noise. Only difference between one long exposure and bunch of short exposures is in read noise and since in planetary imaging we keep exposure very short to freeze the seeing (at about 5-6 milliseconds) - stack is very sensitive to level of read noise. That is why ASI224 is good camera in the first place - it has lowest read noise of the bunch.

If you want to take images of planets than only feasible approach is to use so called Lucky planetary imaging. It consists of shooting a bunch of very short exposures (practically a video) and then selecting sharpest / the least distorted subs and stacking them. With some further processing like sharpening one can obtain decent results. ASI224 is one of the best cameras for this.

Any barlow that has removable barlow element will work as x1.5 barlow if you get correct distance (closer to sensor - smaller magnification - further away from sensor - larger magnification). If you want the best barlow out there - look at Baader VIP barlow. If not - then even something like this: https://www.firstlightoptics.com/barlows/baader-classic-q-225x-barlow.html will do. GSO made x2 barlow that had removable 1.25" element with filter thread - you can use one of those as well.

EQ conversion of AZGti is rather simple - just few steps to it really: 1. Get wedge - you can get one that is specifically made for this mount or you can use simple ball head if you have one 2. Get counter weight / counter weight shaft - again, there are ready made ones - or you can DIY one 3. Flash appropriate firmware - that might sound daunting - but it is really just downloading software and running it when mount is connected to network, not much to it really. With £100 you really won't get much in terms of refractor. Maybe something like second hand ST80 or maybe Mercury 705. Both of them are achromats and will have plenty of chromatic aberration, but will produce images. Starting with second hand lens might be better idea. Something in 100-150mm range F/4 or so could be very nice combination.

Are you referring to 6200? Well - it is in your comparison table and EdgeHD has about 42mm of corrected and illuminated circle - so it would be waste not to use full frame sensor on it. You can get smaller camera, but I think you'll be happier with both shorter FL scope and smaller camera as combination. If you want very decent starting setup - why not go for 150PDS coupled with decent coma corrector and 4/3 size camera like ASI294? These are all relatively cheap items that fit nicely together. Yellow is 150PDS + 294 camera - more FOV - fits more targets better - no need to worry about binning - just use super pixel mode for debayering and you'll be spot on.

What will your budget be? That will really determine what you'll be able to put together.

Camera that you have - ASI224 is one of the best planetary cameras out there. Planetary imaging is very different to regular imaging as it consists of taking video with very short exposure - like 5-6ms exposures at high gain and then processing that video in special way. ASI224 has 3.75µm and that means that you want around F/15. You'll need x1.5 barlow with your scope (as it is F/10) for best resolution. There is actual equation that gives you optimum F/ratio for given pixel size as far as planetary imaging goes. For long exposure imaging, well, yes, since you are using long FL instrument - you'll probably need to bin your pixels. To answer original question, with 9.25 EdgeHD scope, if money was not issue, I would choose ASI6200 mono with filters. I would not use reducer with this combination.