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That makes perfect sense and it would solve a lot of things, but unfortunately, most EQ mounts can't move that far "up". Take for example EQ5, which is sort of ideal mount for such a thing - wedge on it has a stop so it can be moved further. People have solved that with filing various bits so that they can move past each other. Here is an example: https://www.iceinspace.com.au/forum/showthread.php?t=130920 Apart from DIY it like in above example - there are goto mounts capable of this AZEQ5 and AZEQ6 - but they are powered (might not suit everyone) and are expensive. For example, AZEQ6 is £1,689 versus EQ6-R which is £1,449, so you pay additional £240 for this ability to convert - which should really come for "free" as it is feature of EQ mount if you set it as if you would on north pole. Software to switch between az and eq also comes for free - look at AzGTI - free firmware update let's you use it in both EQ and AZ mode (just need to provide a wedge for it).

That really depends on scope in question and sky conditions. In general - I don't think that 1"/px is feasible resolution for most people. 8"+ of aperture, premium mount and those few nights a year when seeing is great - then yes, 1"/px could be pulled off. I'd say that for most people - it would be somewhere in the middle - 1.5-1.8"/px. If you use small scope - like 4" or less - just go for 2"/px without worrying too much about it. Resolution of image to some degree depends on scope aperture as well (it sort of goes into the mix). If you want to know what sort of resolution your setup makes - just take some of your images - stacked data in linear stage before processing and look at FWHM of stars in that image. Divide value with 1.6 - that is resolution you should be aiming for. If you get that your FWHM is closer to 1.6" - then go for 1"/px, but if it is 3" or more - then 2"/px makes more sense.

Probably on same level as other DSLRs so it's best modded for that I think. Yes, that is quite cheap - and if modded - it's going to be very nice all around DSO camera, right?

Seen those, and not sure how to "classify" them yet. ASI178mc - £8.21 per mm2 ASI485mc - £5.59 per mm2 ASI183mc - £4.46 per mm2 ASI294mc - £2.69 per mm2 All of those can do planetary as well as DSO imaging, and size of camera contributes to speed of system. Just for DSO imaging - Canon M200 is hard to beat, about the same price as ASI482/485 - £398 at B&H - it costs £1.19 per mm2

Yes, it helps with spherochromatism as well. ST80 is one option, but there is even cheaper and lighter version: https://www.firstlightoptics.com/startravel/skywatcher-mercury-705.html Only problem is focuser. Putting something like DSLR on that thing (or ST80 / ST102) is asking for trouble . I used very light planetary type camera (drawback - small sensor). Maybe mirrorless would be a good match? Those are a bit lighter than DSLR-s.

It is a tradeoff. If you oversample image - there is nothing going to happen in terms of it looking bad or anything. When you view it in "fit to screen" - it will look as properly sampled image because software will scale it down so it fits inside your window. Problem with oversampled image comes when you look at it at 100% - as far as visual part goes. Look at the image you linked to at 100% zoom: This is just a crop of it. Stars look large - but that is not the main issue - in above crop that large "blob" star near center - is actually two stars that are not resolved. Look at that image sampled at 2"/px (which is much closer to actual resolution), when viewed at 100%: Ok, now sampling rate matches level of detail. If you want to see what image of star field looks like when properly sampled at 0.658"/px - then I scaled right image to match resolution and that is closer to actual pixel scale. Stars are simply tighter and detail is there that matches resolution. Yes, left image does not go as deep - but it simply does not have detail of right image. (it has also been deconvolved in order to try to recover some resolution - which caused SNR loss). In the end - when you oversample you loose SNR in comparison to properly sampling. That is the main problem. In order to get noise free image that goes deep - you need to spend much more time imaging than if you properly sampled.

It is mainly due to stopped down aperture and filter used. I did a test back then to see what combination would work with ST102. I ended up making 80mm, 66mm aperture masks (I think). In the end I chose 66mm based on that test: Columns are just different level of stretch of the same star image, while rows are Mask and then Mask + Wratten #8 filter, so full aperture, full aperture + filter, 80mm, 80mm + filter, 66mm and in the end 50mm - scope cover small opening (which is about 2" in diameter). I figured that 66mm + filter is virtually free of false color. In the end, I made another image to see if I can go deeper - this time only 2x2 mosaic (I might have even used flats this time around):

You can bin any data in software. It won't have benefit of hardware binning - if your gear is capable of it, but it will bin just fine in software. If you purchased gear with intent of hardware binning and it does not work - well then gear is defective and you can return it, can't you? (unless you bought it second hand).

Yes, it is a bit of a pain to process mosaics, but as far as I know AstroPixelProcessor is capable of doing that almost automatically (although it is not free of course)? As alternative - ImageJ / Fiji (distribution loaded with plugins) has everything you need to bin / stitch / process your mosaic images. Here is an image I did like that (ImageJ) with small sensor (ASI185) and achromatic refractor (ST102): Only thing missing to make this proper image is flats - but as it turns out - that is rather fortunate as it let us see the panels involved. This was done at F/7.5 with Wratten #8 filter to tame chromatic blur (and under heavy LP - so it did not go deep). This FOV is equivalent of about 166mm (500/3) with that sensor. You are quite right that novice imagers will have tough time with everything involved, let alone doing mosaics, but I'm not seeing you as novice imager, but rather someone who likes to experiment (and this is nice project - do comparison: lens vs scope + mosaic). In any case - binning of any CMOS data in software is a breeze (as long as your software supports that - it's nothing more than press of a button).

It's a bit like saying that we can't just assume that stacking works. Both things work - mathematically they are quite similar things. It is implementations of each that can be better or worse. Even hardware binning can fail if sensor manufacturing process failed - or you simply got defective units. Software binning can also "fail" - if it's not implemented properly. Binning can also "fail" if one uses it improperly. If we say take single sub and "stack" it with another 8 exact copies of itself - we might conclude that stacking simply does not work. Problem is that we did not get statistically independent samples - but rather copy of one sub and of course it won't work properly. Similarly, binning can also "fail" - If one bins debayered single sub - it won't produce expected results as debayering already contained interpolation and added pixels are not statistically independent. Similarly, binning stack of debayered subs is not the same as binning mono sensor data or binning stack of differently debayered subs (for example if one uses super pixel mode to debayer instead of interpolation). If all these things are taken care of - then binning works as expected every time.

Only on smaller sensors. CCD47 reduces FL by 0.67 - but also shrinks usable field. If RC8 can utilize about 27-28mm - that also gets multiplied with 0.67 - so it ends up being about 19mm. Most people don't use CCD47 / CCDT67 at prescribed x0.67 - but rather x0.72 - x0.75 as that is much better match for 4/3 sensor size like ASI1600, ASI294 or KAF8300 (28mm x 0.72 = 20.16mm). I'd rather go with Riccardi x0.75 FF/FR as that both reduces FL and corrects field curvature. I think that way up to APS-C becomes usable when reduced (that would be equivalent of almost 38mm not reduced - that sort of field is affected by field curvature quite a bit).

If your 200mm lens can go unguided - I don't see why your 432mm refractor can't be used unguided as well? Just because something has 432mm of FL - you don't need to use it as 432mm of FL. You can use it as 144mm FL for example. Lens have advantage that they are simpler to use (that is actually questionable - not sure how simple focusing is for example, or mounting of the lens and getting spacing right - maybe on DSLR, but not on astro camera), but have disadvantage of having optics that is not diffraction limited. Scope has "disadvantage" of being "long focal length" - but in reality, that is not disadvantage - it is simply use case scenario. What prevents you from taking your 432mm FL scope and making 3x3 panel mosaic with each mosaic pane being binned x3. Result will be almost the same as using 144mm FL lens (differences will be that telescope image will be diffraction limited and that you'll get slightly smaller FOV due to overlap needed to stitch mosaic). Processing is a bit more involved, but result is the same resolution as using 144mm lens. If you can use 200mm lens unguided - why wouldn't it work for 144mm FL?

How do you guide? Many people attach guide scope on dovetail bar under the OTA and that way add weight to the front of the scope - like this: I personally use OAG so above is not an option for me, but this Baader CW saves the day: https://www.teleskop-express.de/shop/product_info.php/info/p752_Baader-Balance-Weight-1kg-with-Vixen-Level-Clamp.html Out of those you listed - first one is Losmandy rail so probably not suited for RC6" which probably has standard Vixen dovetail bar. Second one is dual saddle - so good choice if you happen to have another scope with Losmandy dovetail and you plan to use CW with either. No idea what the difference is between last two - but they seem like sensible option.

Yes there is benefit as with increased focal length often comes increased aperture. You are now using 200mm diameter 1600mm FL scope - and you are happy to bin x2 (while in reality you should be binning x3 most of the time and sometimes even x4). Say you get 300mm F/5.3 imaging newtonian. It will also have ~1600mm, so nothing will change in the way you capture and process your data (you'll still need to bin with certain bin factor due to small pixels) - but 300mm will collect more photons than 200mm. Take this to another extreme - take 16" F/8 RC and pair it with ASI6200 - which again has small pixels at 3.76µm (almost the same as ASI1600 -3.8µm). It will give you the same FOV - you'll need to bin differently (maybe x6 or x7), but it will be x4 as fast as your current setup (with longer FL). It will also be x4 as expensive . Don't think that small pixels are advantage - rather think that small pixels are nuisance for astro imaging and that larger pixels actually better suit telescopes. Luckily CMOS sensors have low read noise and it makes sense to bin them in software. Small pixel size has another advantage - that no one is using at the moment (as far as I know). They are closer to true point sampling and introduce less pixel blur if used properly (split bin instead of regular binning).

According to TS website - 150P F/5 has 47mm minor axis diameter - 31.33% CO, while 150PDS has 52mm or 34.66% Can't be sure of those figures as I don't have either of said scopes.

I'm surprised that it does not. Maybe to keep the price down, I see that F/4 version comes with dual speed focuser. Dual speed focuser is important on faster scopes - anything at or below F/5 is considered to be fast scope, as critical focus zone is rather shallow and it helps to get the best focus - even for visual if you have dual speed. I installed dual speed addition to my 8" F/6 dobsonian and it was worthy investment - especially on planets that require very precise focusing, although I use that scope purely for visual. Imaging also requires precise focusing, so if you plan on doing AP - I'd recommend that you get scope with better focuser (dual speed are usually a bit higher quality and can hold more weight as well). If you have limited budget - using single speed will not prevent you from either observing or imaging - you'll just need to be more careful when focusing to get the focus just right.

Not that it would not work - most people find it very awkward to use although some get used to it. As you move the scope around the sky on EQ mount - Eyepiece position changes - it can be on one side and in next instant facing down towards the ground and so on. Cure to this is to rotate tube every time you change position of the scope - loosen rings, rotate tube, tighten rings. There are specialist rings that let you rotate tube as well - but are expensive. Refractors or compact scopes don't have this problem as eyepiece is at the end of tube not on its side - all you need to do is rotate diagonal mirror and you are good to observe. Alt-az type mount - whether it is dobsonian or regular alt-az - just keeps eyepiece at same position. In order to see how Eyepiece / focuser / finder can end up in strange positions - find some Youtube videos explaining operation of Newtonian scope on EQ mount.

Hi and welcome to SGL. If you plan on doing astrophotography, then get 150PDS or any other scope that has 2" dual speed focuser and optimized secondary mirror. 150p has smaller secondary mirror - which is good for observing (planetary especially - but if you are into planets, then 150mm F/8 version is even better) - but that is not so good as far as field illumination goes - more vignetting in your images that needs to be corrected. Here is alternative: https://www.firstlightoptics.com/ts-telescopes/ts-photon-6-f5-advanced-newtonian-telescope-with-metal-tube.html Do factor in that you'll have to use very sturdy equatorial mount for astrophotography (at least EQ5 and preferably HEQ5) and coma corrector (you don't need one - but you'll want one). For visual use - maybe make simple dob type mount for the scope - or alternatively put it on azimuth mount like this one: https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/skywatcher-skytee-2-alt-azimuth-mount.html It can also be used on something like AZ4 - but I think that you'll have issue of OTA hitting the tripod near zenith on that mount as scope tube is a bit on thick side. (image taken from: http://www.waloszek.de/astro_sw_az4_e.php)

I think it that simplest way to do it is right before you start processing your data. Calibrate, stack and then before you start - simply bin data to whatever bin factor you prefer. It might not be optimal way to do it - but it is the simplest way to do it.

There is literally way to get it accurate / objective with LRGB+Ha - although no one is using it Very nice image. I think that colors are very good and I don't mind red at all - In fact, I'd say it's nice rendition of Ha blended with the rest. I do think that background could be nicer. It has some color gradients in it (hard to deal with probably due to passing high altitude clouds or whatever) and it is "too smooth" at some places - maybe a bit too much of denoising?

Depends how you bin, but it should be done in linear stage. If you split bin - then obviously before stacking and after calibration (this is advanced thing, so don't worry about it if you don't know how to split bin and/or don't have software to do it), otherwise - you can either do it after calibration and before stacking or right after stacking. Easiest way to do it is to do it right after stacking before you start any processing on the data as that way you bin only one image - resulting stack (instead of each individual sub). If you are going to resize image in the end any way - bin to that size before processing. That will let you pull out more in processing or deal with noise much easier.

Not sure what "optimized" stands for - is it CMOS optimized or F/2 optimized. In any case - either can be true and not a marketing trick. Interference are essentially reflection filters - meaning they reflect light that is not within designated pass band. With fast optics - such as F/2-F/3 - there is significant change of the wavelength as filter sees it (not actual wavelength) - because part of beam hits filter at an angle and relationship of thickness of reflective coatings to wavelength changes - easiest way to cross the road is straight ahead and if you cross it at an angle - it takes longer. Therefore - you can optimize filter for fast optics. On the other hand, CMOS technology differs from CCD in pixel shapes / micro lens and sensor cover window. Often interference filters create reflection halos with CMOS sensors, so it is again possible that there are optimized coatings that take this into account and reduce reflections created by filters. For actual filters you linked - well, have no idea. I do know that Baader had to deal with reflections in several of their filters and maybe they perfected technology and these are really optimized for CMOS.

Yes. As far as gain is concerned - maybe best thing to do is measure read noise at particular gain and select the best one - the lowest read noise. Read noise measurement is straight forward. Take number of bias subs, multiply them with e/ADU value (should be reported by ASCOM driver in fits header for particular gain setting) to convert to electron count, split them into two halves, stack each with sum stack and then subtract the two. Measure resulting image standard deviation and divide with square root of subs. I personally think that best gain values are of form: Unity gain + N * 61 for ASI cameras (because their gain is such that it uses 0.1db units and every 6.1db actual e/ADU doubles). For ASI224 unity gain is 135 and lowest read noise are 300+ so that would be 318 or 379 - but again, I'd measure several values and check to make sure. Exposure length is something that is quite individual and depends on scope size and location / conditions. 5-7ms is general figure that is good in most conditions for 8" ish of aperture. In good seeing / on good location - it will be a bit longer. It also depends on aperture size as it is related to time that takes for turbulent cell to move over the aperture of the scope. See https://en.wikipedia.org/wiki/Greenwood_frequency It is best if you experiment with these and judge yourself for your location and equipment. You want your subs to look a bit like this: (I could not find planet representation - but Moon will do). They can be distorted and individual patches / parts even a bit blurred - but you want "clean split" between frames - you don't want to see motion blur morphing between them as that would indicate that you did not freeze the seeing but rather it is causing motion blur on top of distortion.

I think that you can make your own image of horizon to be included in Stellarium. Just snap couple of actual images of your horizon and then follow this tutorial (for example - I'm sure there are other tutorials on how to do that as well): https://www.skyatnightmagazine.com/advice/diy/stellarium-how-to-create-a-customised-landscape/

Yes, that will be interesting to do with the setup I'm planning to use. I'll probably use F/13 4" maksutov for this and artificial star at close range. First grating spectrum will be significantly shorter (maybe as short as 100-200px). I'll try placing it on several locations and under several directions to see if there is significant difference in measured spectrum. I'll probably go with 0.5mm front aperture printed grating (with 600dpi that is 25.4 / 600 = 0.0423333mm or 11.8 points per line - I can print with 10-11 points per line) . That is 2000 lines per meter and angle will be sin(theta) = theta = 300nm / 0.0005m = 0.0006 radians = 123.76" At 0.6"/px that is about 200px