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It's real indeed What is lacking is my understanding of Martian surface features

I agree, after fiddling around with meridian and that map, I got the same results. Problem is that image does not show it. Maybe too large alignment points and stacking artifacts?

Image is ok I would say - needs to be better centered and possibly captured with shorter exposures and few other technical things adjusted, but otherwise ok:

I'm still having trouble connecting the dots. Here is map of Martian surface: I've marked what I believe to be corresponding regions on your image. If I'm right, then Olympus Mons is not on your image, but just of the left side.

Ok, I see the confusion. Btw, how did you manage to image the Mars in the future?

Not quite good - you should collimate your scope for sure. I think that even your secondary is not properly aligned - and that is rather easy to do.

I took some effort to find what Mars should look at that time, but I think I've go it (a bit different tilt angle in Stellarium for some reason):

I'm not sure if I could do any better than you with this one. I just resampled it to 0.24"/px (I just love properly sampled images it seems ) and did a bit of color balance tweak - after all, everyone loves red mars, right? Just a pinch of wavelets here and there Like I said - not sure if this made an improvement.

Not sure if you need to during imaging session - just image with all three filters. Once you've stacked your data - Ha is the one with the strongest signal (almost all targets out there have significantly stronger Ha then other lines as Hydrogen is the most abundant element and easily excited).

Yes, it certainly won't have much impact on Jupiter image if you place the planet on optical axis - it is only about 45" wide - so 22.5" to each side? Even on fast scope there will be no difference. There might be some difference for lunar shots with larger sensor? My reasoning is that regular CCs need exact spacing, but are flexible in terms of F/ratio of scope. I guess that this barlow works pretty much the same - you can use it both on F/5 and on F/8 scope and it won't change much but it should be at about x2.7 for best CC performance. I'm just asking this because suitable magnification depends on wanted sampling rate and with any barlow one can dial that in by changing distance, but this particular barlow might have side effects in CC performance if there is large change in magnification (distance). Although you mentioned that you sampled at 0.14"/px I did a quick check to make sure image was not resized afterwards - measured diameter of ~312px which for 45" diameter gives about ~0.144"/px - so I figured that image was not scaled. Then I just took ratio of 0.14 and 0.24 being 0.58333 and then I scaled it to 58% using IrfanView and Lanczos resampling. Image is in 8bit format - so not really suitable for wavelet sharpening and I was surprised that it actually worked. I usually start with first slider and use higher as needed. This time I boosted by very small amount even fifth one. Not overly scientific about it - I just went by what looks the best. I did reset sliders a few times because I in first few rounds I just asses how much I can push things and then I go for finding balance.

@CraigT82 I have another question, I hope you don't mind. It is about processing - do you use wavelet sharpening? In fact, I hope you don't mind me having a bit of tweak of the image you posted? Data is exceptional and if one takes care to present it at optimum sampling rate for this gear (0.24"/pp) and does a bit of tweaking with sharpening, this is the result: I personally like it like that - it might be smaller in size but it is much sharper / more detailed, what do you think?

Very nice. Out of interest, did you go for 0.14"/pp on purpose or is it just consequence of gear used (APM barlow and ASI224 combined with your scope). Another question - did you measure distance from barlow element to sensor to be precise about x2.7 magnification? I have the same barlow, but only as an element and I use it with extensions - but never actually measured to get exact magnification. I wonder how much CC properties of this barlow change with change in distance to sensor?

No that I know of. Ha and SII are so close that there will be no definite difference in color - both will look deep red and have strange bluish/greenish interference reflections. Do you have separate Ha or SII filter - something old that you can use? Putting two filters one on top of another will either pass the light or block the light - two of the same should pass the light while two different ones will block the light - so I was thinking visual inspection - place for example 2" Ha filter in front of opening of filter wheel and look by naked eye - if you see something - you have Ha filter selected, if not - it is any other (except broad band filters). Maybe open filter wheel and check markings if they are mounted filters?

I'm not sure if 55mm is exact thing with coma correctors and in particular with Skywatcher CC and Skywatcher scope - they could be a good match and 55mm exact distance. I just mentioned that Field Flatteners have this issue where you have to dial in exact spacing - and yes - it is done like that - trial and error. You repeat procedure until you get best stars in your corners. This is why variable extensions come in handy - no need for bunch of different spacers. If you want to save some imaging time - then you do it during the day or cloudy night by using artificial star (ball bearing that is smooth and shiny really far away with torch pointed at it can be budget friendly artificial star). In any case, it would be worth checking if spacing is exact - either someone could contribute who used coma corrector or a quick search online. I think that you should make sure your focuser is in good shape - regardless of how you proceed with rotator. It should have lock screw and you should make sure that it stays in place once you lock it. There should be no tilt or play in focuser as well. Rotators are not quite resistance free, so I'm not sure it will solve the problem of focuser slipping. I have rotators for my systems (threaded connection) - one large in focuser and one separate M68. They both require some force and are not quite smooth although I don't have much weight hanging at the back - ASI1600 cool and filter drawer (which is light weight, much lighter than filter wheel).

Just had another idea to save some space / change distances: https://www.aliexpress.com/item/1970984046.html?spm=a2g0o.detail.1000014.1.5911718bxAenmh&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.14976.165864.0&scm_id=1007.14976.165864.0&scm-url=1007.14976.165864.0&pvid=02f83b59-6244-42de-9763-8e13e3be81ce&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.14976.165864.0,pvid:02f83b59-6244-42de-9763-8e13e3be81ce,tpp_buckets:668%230%23131923%235_668%23808%234093%2312_668%23888%233325%2314_4976%230%23165864%230_4976%232711%237538%23362_4976%233223%2310815%238_4976%233104%239653%234_4976%233141%239887%237_668%232846%238111%23492_668%232717%237566%23809_668%231000022185%231000069217%230_668%233422%2315392%23292

I'm by no means expert on this, but here are my thoughts on the subject and hopefully it will help in one way or another. Why do you need camera rotator in the first place? Camera rotators are very useful if you have threaded connection to telescope - which means everything is screwed together and screwed in focuser. Once everything is screwed together - you cannot adjust camera angle any more by rotation in focuser - as any rotation will disassemble the whole thing. As is, with your setup, you already have suitable mechanism for rotation - loosen focuser screws, rotate whole camera / CC assembly in focuser, tighten focuser screws. Simple as that. Although camera and CC are screwed together - that assembly is inserted into focuser rather than screwed onto it. If you think that having numbers for orientation is helpful - just start plate solving - it will tell you exact orientation of camera in degrees so you can match it between sessions. You can also DIY some sort of dial do you know how much you are turning your camera (but you really don't need one - you'll quickly learn by feel how much to turn). Even if you don't plate solve there are ways to orient your camera the same between imaging sessions - align X/Y to RA/DEC - either by slewing in exposure or drifting in exposure. You start exposure on a bright star and either slew telescope at low speed, or stop telescope tracking. Star will make a trail. Rotate camera until that line is horizontal (or vertical - depends how you want to frame your shot). If you really want to add this part, then here are other tips that I can think of: - longer male thread is a problem, longer female thread is not a problem. You calculate from "shoulder" to "shoulder". In your case you had 5mm female and 6mm male - so yes, there is a "gap" of 1mm that you should add to calculation. Don't worry about light leak - no way it will leak in the light - I don't know about coma correctors (never used one), but field flatteners and reducers need to be "dialed" in for particular telescope in question. This usually means that prescribed distance is only a guideline - you actually need to try it out and adjust it for best results. For this, variable length extension tubes are very good solution, and so are shims. You can get either plastic or aluminum shims of 0.1 to 0.5mm and 1mm that you put on M42 or M48 threads (between parts to add some distance - opposite of above "gap") - You can actually make different order of elements. Problem that you have is that you need to keep both female-to-female 11mm for camera since both camera and CC have male thread so you need to switch order at some point, and you need to keep T2/M48 adapter since you need to switch thread size as well. But you have some room to do things differently. You can arrange it like this: Camera - rotator (in reverse, it should not matter) - 11mm - whatever you need here - T2/M48 adapter This gives you another option - you can combine 11mm and whatever you need to reach distance into single variable length extension female/female T2. This is for T2 version of rotator.

How do you do your binning? Bin x2 implies 4 pixels added together - not averaged. You can average them out but it is usually via software, and you are right if they are averaged - your math is correct with respect to expected stddev value. I assumed you binned in drivers not in software. No, you have to differentiate dark current noise and dark current. Dark current is build up of signal and is modeled as Poisson process. Therefore noise associated with dark current signal is square root of that signal. It is irrelevant if you observe single pixel as 1/4 of binned pixel or binned pixel as they behave the same in terms of noise - read noise of binned pixel will be combined noise of individual pixels and dark current noise will be combined dark current of individual pixels - you can calculate dark current of binned pixel the same - no need to divide with anything and if you want to divide - you'll divide with 4 rather than square root of that - as we are dealing with signal here - electron build up in 4 pixels combined is just sum of of individual electron buildups. In above example, if all you are measuring is dark current rate per second - you should get the same value (roughly) regardless if you measure it for 100s, 200s or 400s - and that is not the case with your example. I'm just pointing out that you should be careful of how you actually measure something to get the proper value. We mostly agree on how noise behaves and everything - except the fact that you for some reason want to relate LP noise levels to number of dark subs in master dark. I see no practical link between the two. LP noise level has practical link to read noise and exposure duration for two reasons - LP is dominant noise source with respect to read noise in most cases and read noise value is per exposure - it does not depend on exposure length while LP noise depends on exposure length - accumulates with time. You are suggesting that somehow number of darks in master dark can be related to LP noise levels. I'm just saying that there is no practical reason to do so, because: a) both depend on time in the same way and ratio of dark noise and LP noise in single sub remains constant regardless of the exposure length. b) stack of darks and related dark noise already has dominant noise source that will overpower it - single sub dark noise. No need to compare it with LP noise since single sub dark noise - that of light sub that we will calibrate - it will be much higher than master dark resulting noise. I have shown you that you'll increase single sub dark noise by less than 2% if you use only 25 dark subs in your master dark. This is true if you image in SQM 18 or SQM 22 skies. Same thing will happen with dark noise alone for every sub you calibrate. If same thing happens in SQM 18 and SQM 22 - why would we want to base number of darks in master dark on LP noise?

No it does not, but that is really not the point. Neither does perfect dither - or rather you can never dither to integer shift value. Those are two extreme cases that we use to asses what will happen. In reality something in between will happen and results will be in between - closer you get to either - closer the results will be to academic ones. Your reasoning is somewhat flawed here. By analyzing one light and one dark - you can't change contribution of dark current to the light frame. You can never do anything about their ratio. Both LP noise and dark current noise raise at the same rate as their sources depend on time in the same way. Dark current accumulates with time at a certain rate and LP levels accumulate at a certain rate. Take 60s long sub and take another that is 120s long - both LP level and dark current levels in second will be twice as high as in the first one and they will keep their ratio. If dark current noise is 10% of LP noise - it will be the same regardless of what is exposure length. Adding calibration frames can only make this number worse - it can't improve it. Next thing to understand is that for calculation of how many darks you need - you don't need LP levels at all. You already have "competing" noise - dark itself. Stack of 25 darks will have 5 times less noise than single dark - and that is already plenty of reduction so that their sum will increase by less than 2% (look at above calculation). Again, how did you measure? If you have 2x2 binned pixel, since this is CMOS sensor - it will have double the read noise. Since you are adding 4 pixels it will also have twice the dark current. If X is for a single pixel then adding 4 pixels together will be sqrt(X^2 + X^2 + X^2 + X^2) = sqrt(4*X^2) = X*sqrt(4) = 2*X I would expect 2x2 binned from 0 seconds exposure if bias signal is removed to have about 3.4 as a result at unity gain (if we take 1.7e to be read noise per pixel). Let's forget the binning and just check if above values match properly. You say that you have read noise of 13 and you have total noise of 200s be 15 and total noise of 400s be 18. Let's calculate dark current per second for both cases and compare them, shall we? dark_current_200 = (15^2 - 13^2)/200 = 56/200 = 0.28ADU/s/px dark current_400 = (18^2 - 13^2)/400 = 155/400 = 0.3875ADU/s/px Dark current at 400s is higher by about 50% than that at 200s - that can't be right, can it? Here we did not do any comparison to other values - just checked your measurements one against another.

This is what I would do (I'm not saying that you should as well - it's just an option): If tight on funds, I would sell C6 and use that money to buy RC6 and some bits and bobs (as you'll probably have some cash to spare or put towards the camera). Get yourself this camera: https://www.firstlightoptics.com/zwo-cameras/zwo-asi-294mc-pro-usb-30-cooled-colour-camera.html Or alternatively, if you prefer CCD cameras, this one second hand (if available): QHY8L-C Depending on which camera of the two you purchase - workflow will be somewhat different. I would recommend Bayer drizzle or regular debayering for QHY8L and superpixel debayering for ASI294 to get you proper resolution. This option will leave you without visual scope as C6 is no doubt very good visual scope and RC6 can be used for visual but it has large central obstruction. C6 is also probably better planetary scope than RC6. Another thing to consider is collimation of RC6 - some people find it very difficult. I have RC8 and have collimated it without any trouble, so I'm sort of used to such scope, but some people get intimidated by it.

I don't think there is a great concern with that. If anything, it will be doing them a favor Where I think the value of this video lies is that it informs general public that doing astronomy and astrophotography in general is not an easy task and it is accomplishment of significant value to take an image of astronomical object - be that planet or galaxy or something else. Since prevailing thought these days is - it is all "Photoshopped" anyway - it is good to have a video that explains complexities of it in fun way.

No, small sensor is not a good idea. Want to use slow scope - slow as in large F/ratio - you need to use large sensor to make it work (at any sensible capture speed). How about doing it this way - name your goals and budget so we can work from there - we'll try to find best solution.

I'm not sure I'm following your reasoning. Every single light sub you take will have some dark current and hence dark current noise. Let that be X. Let's also leave other noise sources aside as we don't need them yet for what I'm about to point out here. Let's say that you take 25 of darks for your master dark. This means that master dark has X/5 of dark noise - as we stacked 25 of darks to get master dark. This also means that once you calibrate your light sub with such master dark - total dark noise will be sqrt(X^2+(X/5)^2) = sqrt(X^2 + X^2/25) = sqrt(26 * X^2 / 25) = X * sqrt(26) / sqrt(25) = ~1.0198. We increased our dark current noise by only 2% by using 25 of darks. This is regardless of any shot, lp or read noise. Want to reduce it to even more insignificant levels? Take more darks for your master dark. You can calculate how much you increase dark current noise with simple formula sqrt(N+1)/sqrt(N) where N is number of dark subs you take. Want to make real difference - dither. This is going to be a bit more tricky to explain, but it is really important. What I've written above works only if you dither. If you don't dither then we can't add master dark like that. Take for example perfect guiding - you don't need to register any of the light subs - they are perfectly aligned. Dark value that you are subtracting from each pixel will be exactly the same for every single light pixel across your light subs. You can pull that dark in front of sum and what you end up doing is polluting final stack with considerable amount of dark (and bias) noise. Let's say you have X of dark noise and you take 25 darks for your stack. You also take 100 light subs (just because it's easy to calculate). Perfect dither case, resulting stack will have 1.0198 * X / 10 = 0.10198. Why? Because we have seen that that 25 darks increases every light sub's dark noise by factor of 1.0198 and then we stack 100 of those and we reduce total amount of noise by x10. We can do that because of perfect dither and fact that it makes every calibration independent (because it is shifted with respect to every other). Now look what happens with perfectly aligned case: we will have ( (L1 - MD) + (L2 - MD) + (L3 - MD) + .... + (L100 - MD) ) / 100 (L1,2,3, .... being light subs and MD being master dark) Now we can rearrange that as (L1 + L2+ L3 + ..... L100) / 100 + (MD+MD+MD+....+MD)/100 We can do this because in every calibration MD aligns with every other MD and they are the same - no shifts so each pixel gets onto itself - same value, no randomness. Which is then stack_of_lums - 100 * MD / 100 = stack_of_lums - MD Now let's see what sort of noise we have now? sqrt( (X/10)^2 + (X/5)^2 ) = sqrt( (X^2 + 4*X^2) / 100 ) = X * sqrt(5)/10 = X * ~0.2236 That is twice as much noise from dark current than in perfectly dithered case!

Biggest thing with set point cooling camera is not really reduction in thermal noise but rather ability to do proper darks - always on the same temperature. This makes rest of calibration work properly.

I'm rather fond of ability to do proper calibration of subs and that requires set point cooling, so I would rank importance of gear as: 1. mount 2. cooled camera 3. telescope

This was actually quite entertaining. I suddenly have a craving for HP laptop with NVIDIA graphics card for some unknown reason. Subliminal messaging perhaps?