vlaiv

No except for time dedicated to flats. I take a lot of them - like 256 (divisible with 2 actually power of two - I had couple of beers - that is divisible by 2 ), and that takes about 10 or so minutes mostly because SGP takes a bit to download sub for some reason - although camera is capable of 10+ FPS on full ROI with 16 bit readout. Flats are like any other exposure - if you have dim source you need long exposure - if not - you can use short exposure. My flat box is good and does not produce flickering. I actually did have issue once - but it had to do with power connector - it was a bit loose and did not form proper connection to power source and I had flickering because of that, but once I solved the power connector issue - I don't have issues anymore. It could be down to calibration. If you use bias instead of flat darks - then this could be issue. It seems that some cameras, ASI1600 included (at least with old driver version) has two different regimes - up to 1s and above 1s. In first, timing is kept by camera itself, while in second, it is up to driver (computer) to do exposure timing. Bias/offset values differ between the two. For this reason, bias is not usable for long exposure as average ADU is higher than exposure of say 30s or 1 minute (which should not happen as darks have dark current signal which bias does not have). In any case - since bias is "Strange" - calibrating with bias can end up in over / under correction. Proper way to do it is to do dark flats - which is basically same flat exposure with scope covered instead of using flat panel.

I think it would be interesting to compile list of mounts that are in same price class as HEQ5 (or preferably cheaper) but offer some advantage over it. I'd say we need to put some limits on what a mount can do like: 1. carry 10Kg photographic payload 2. Easily image with 2"/px resolution (1" RMS guiding out of the box - or such performance without guiding) 3. Capable of short exposures unguided (HEQ5 has 10+ minute period with periodic error of about 30-35" P2P Ideally improvements would be: - reduction/elimination of backlash - ease of operation (USB connection) - longer unguided subs - lower RMS out of the box

Not sure if I'm an expert, but verdict is this: 1. Your focus is off. 2. Your collimation is off - but that might be focuser tilt as camera could be too heavy for 1.25" attachment with compression ring (it is better to just use T2 ring and screw camera onto the scope). 3. You are over sampled and you should really look into binning 4. There is definitively something causing flaring in bottom right corner - it is not only one star that is affected - but multiple stars there is faint flare next to one of the stars, and there is flare of the star that is outside of the FOV - but flare is inside: I'm really not sure what could be causing these. The one thing I can tell you - it is not because front corrector plate or secondary mirror. It needs to be inside optical path, near the focus plane of the telescope as it affects only one side of the image (not all stars). My guess is that you have internal reflections from that 1.25" nose piece. Hold it against light and see if internal side is shiny (or has some sort of grooves and is colored black - this second thing is good, rest is bad).

That can also be misleading. Give same kit to two different people and ask them to image the same target - odds are, you'll end up with two very different images. If you browse a bit imaging section - you can see examples where people work with same data and produce very different results.

I use milliseconds for my flats with ASI1600. They work just fine.

Actually, I think that EQ1/EQ2 CW shaft fits AZ-GTI perfectly.

I usually do it twice a year, there is summer and winter set of darks that I do at different temperature (I often can't cool camera down to -20°C in summer). Do it when you change settings - like driver update or offset/gain.

I've found that most of the time, questions like that can be categorized in two different classes: - ones that have enough budget to fit "regular" imaging setup - then discussion becomes whether to get Heq5 or go with Eq5 with just tracking, how much DIY versus maybe second hand gear and so on ... In this category, heq5 is, if budget allows - most hassle free and future proof recommendation. - ones that simply don't have sensible budget. Second class is far more "interesting" as it really requires thinking outside of the box. I have some very interesting solutions for the second case, however, all of them require more or less "non standard" fiddling with equipment. Solutions like Az-Gti in EQ mode are for example, recommendations like that. I've made such recommendation several times, but we always must be careful when doing so. We are expecting from someone new to all of this, confused enough by different recommendations and things they've read to: - get separate CW shaft that will fit the mount - get CWs for it - get separate wedge - sort out polar alignment somehow - Flash custom firmware to enable them to use EQ mode. - additionally complicate things if they want to guide with having to work with mobile phone and wifi connections (or get separate cable) and of course - knowing that you need to do all of that just to get your mount to work, versus just using "plug&play" versions of mounts (nothing is really p&p in this hobby - but some things are easier than others). Similarly - I rarely hear afocal method being explained and recommended to beginners. Everyone has smart phone these days - and if smart phone has CameraAPI2 (android) or whatever equivalent for Apple devices is - one can use that. There are few simple calculations to be performed - matching exit / entrance pupils, selecting proper eyepiece and adapter, finding exit pupil and so on. My point is - although all of these methods are available - they are not something to be recommended to a novice without explaining what is involved - and that might just put them off the idea.

You did not include regular darks in your calibration. This is important if you want proper flat calibration. This way - you are "flattening" - both light signal as well as dark signal that is not removed since dark calibration was not performed. However - dark signal should not be flattened - as it is not subject to optical train and does not vignette or have dust on it (it is not related to light entering the telescope).

That is rather nice solution. To be honest, at this point, when I think of custom boxes for electronics and other things - I instantly think 3d printing for some reason. I guess this is because I've been thinking a lot about it lately

@wuthton Out of interest, "I'm new to all of this and I want to do some visual, but mostly I'd like to get nice images of galaxies, globular clusters, planetary nebulae and some planets. I have some background in daytime photography and I've seen nice image of DSOs people make on the net and also images in magazines. Like with all newcomers, idea of having multiple scopes is really not even remote possibility at this stage. I have budget that is almost enough but I could stretch it a bit if need be" What would you recommend to me and why?

I can't really agree with this, since I've given advice more than once, and more than once I recommended different things depending on what person wanted to achieve. I often mention barn door tracker in DIY variety to people with very thin budgets. I also recommend Eq5 + simple tracking motor for those a bit more ambitious that are on tight budget. I also believe that decent star tracker can be 3d printed for a fraction of the cost of commercial units. I even recently started a thread on choice of reduction mechanism (Strain-wave vs Cycloidal vs Split Ring Compound Epicyclic gear).

Yes you are probably right. I think correct and more often used statement is: "Heq5 is entry point to serious AP". (bold and italics is instead of quotation marks - so I don't double quote) Want to image a galaxy with some sort of detail? Well, you can't use resolutions of 5-6"/px or higher - you need to start using at least 3-4"/px to image detail in galaxies (even large ones like M31 and M33). That again depends on how serious you are. If you are even remotely serious about AP - then I would recommend that you start any rig build with mount and then add other bits based on your mount selection.

You need to learn how to pixel peep None of these stars are ok really. They all show some sort of deformation. Central stars look the most ok, and they look like they have some issues with seeing or poor guiding or something - until you see corners and start identifying aberrations and then you see that those aberrations are present in center stars as well but to lesser degree. Astigmatism and field curvature. There is possibly some tilt as well. I can't really say if any of it is due to damage.

Depends how many boards do you need to make. I recently saw quite affordable milling machine that can route PCBs quite accurately.

What is your minor axis size? I'm guessing about 50-60? https://www.teleskop-express.de/shop/product_info.php/info/p1669_TS-Optics-Newtonian-Secondary-Mirror-elliptical---D-50-mm-minor-axis.html

Oh nooo - but off axis, slow spherical mirror to the rescue! No central obstruction!

Good reflector?

In any case - thread on those is 1/4-20 UNC (1/4" photo thread).

It is also down to personal preference besides usual things like seeing and thermal stability. Not all of us have same visual acuity, some don't need as much magnification to be able to see all that scope is capable of. Usually quoted figure is x2 per mm of aperture as "max" magnification. This would mean about x250 for this scope. I've found that for my eyesight and preference (I like less mag but sharper looking image) it is closer to x1.2. Does not mean that scope can't be pushed higher - like that something is wrong with the image. I usually don't really need more magnification than that. This is why 11mm gives best views on my little mak. That scope is very sharp by the way so it's not down to optics as is often believed. 1300 / 11 = x118.2. Using 6.7mm really softens up the view for me and is not to my liking - that is why I want to try 8.8mm on the moon. With dob I also go for about x250 max

That really depends what sort of views you are after. I have 102mm Mak for lunar. Biggest issue that I have with that scope is size of exit pupil. I guess that is just because I'm used to faster scopes for general observing and the fact that I observed mostly from light polluted areas. With F/6 scope and 32mm eyepiece - sky will look bluish/grey at low magnifications / wide field in light polluted skies. For me it feels strange to use 32mm eyepiece and get very dark background - not something that I'm used to. Mind you - I don't really feel that boxed in as far as field of view goes. My main observing scope is F/6 8" dob - which has 1200mm of focal length - only 100mm shorter than my mak at 1300mm. It is just that when I use 32mm on 102 mak - it feels like using 8" dob with 3/4 of aperture covered with something - image is darker (again - it is due to what I'm used to). I usually use ES 82° eyepieces with my Mak. These give good sharp view (11mm, 6.7mm). I also have 16mm 68°. If you want a bit more expensive / better eyepieces / wider field of view - I'd say look into ES 62 and 68mm lines for longer focal lengths and ES82 for shorter focal lengths. Why did I mention exit pupil? Well - those more expensive eyepieces have wider field of view and that means shorter focal length for same field stop. ES68 24mm will show you the same amount of sky as say 30/32mm plossl (52° or 50° degrees AFOV) - but will do so with smaller exit pupil. You'll be around 2mm exit pupil with such eyepiece on F/12 scope. You might not mind that and you might find it nicer to have dark background - for me it feels sort of strange. In any case - most more expensive eyepieces will have wider field of view and hence smaller exit pupil than simple plossls and alike. If you are after best planetary performance with tracked scope then look at Vixen SLV line - these are very sharp eyepieces. Again - don't go below about 8mm. I have ES82 6.7mm and it gives too much magnification for my eyes even on lunar (which can take up quite a bit of mag). I'll probably get ES82 8.8mm for that scope at some point

Depends what you want guide scope to do. If it's solely for guiding - then get cheapest, easy to work with option (decent way to focus and good mounting support). You don't need larger aperture and you don't need ED optics for guiding. I'm very happy with this one: https://www.firstlightoptics.com/guide-scopes/astro-essentials-32mm-f4-mini-guide-scope.html

I don't think it is wise to spend money on barlow lens with that scope. Barlow lens is meant to allow one to attain higher magnification. That scope already has 1500mm of focal length and you don't really need shorter focal length eyepiece than say 7-8mm. Here is example list of what you could get for that scope that won't break the bank: - Lower power EP: 30mm Vixen NPL https://www.firstlightoptics.com/vixen-eyepieces/vixen-npl-eyepieces.html (don't go for 40mm. As much as it is tempting - it has same true FOV as 30mm but smaller apparent FOV and longer eye relief that can actually be a problem - holding exit pupil is not so comfortable with very long eye relief). - Medium power EP: https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-20mm-125-superview-eyepiece.html - Get this as well for high power viewing: https://www.svbony.com/SV135-1-25inch-Zoom-Eyepiece-/ Although it has 7-21mm range, you'll probably use it in say 7-14mm range because very small FOV in longer focal lengths.

That is image scale or pixel scale - arc seconds per pixel. Cut off frequency is something related to Nyquist sampling theorem and aperture and all of that. Here is formula for that: https://en.wikipedia.org/wiki/Spatial_cutoff_frequency If you apply Nyquist sampling theorem to that (need to sample at twice highest frequency component) and rearrange for F# (F/ratio) you get: F/ratio = pixel size * 2 / wavelength (where pixel size and wavelength are in same units) So for example - if you want to see what is optimum F/ratio for 540nm wavelength and 3.76µm pixel size then you calculate: F/ratio = 2 * 3.76µm / 0.54µm (as 540nm = 0.540µm) F/ratio = ~13.925925926 = F/13.9 similarly you get for Ha, but substitute 656nm as wavelength. When you want to calculate critical sampling frequency for full spectrum / RGB - it would be sensible to take 400nm, but blue part of spectrum is affected the worst by seeing and this leads to slight over sampling in other wavelengths. Peak of human luminance sensitivity is around 500nm - so that is where we perceive the most sharpness - for that reason, I advocate use of 500nm wavelength to calculate cut off for full spectrum / color images This gives handy formula: F/ratio = pixel_size * 2 / 0 .5 = 4 * pixel_size - easy to remember.

I did not say f/ratio will impact filter performance (although filter performance is affected by F/ratio - but that is another topic altogether), I said that optimum F/ratio will change based on filter used. There is optimum F/ratio for any given pixel size. This is because pixel size in combination with focal length defines sampling rate of the image (arc seconds per pixel), and aperture of telescope defines maximum detail that this telescope can resolve (larger telescopes are able to resolve more). There is no point in sampling more than telescope can resolve (this is called oversampling and is generally not a good thing for number of reasons) - and if you want to record all the detail available - you don't want to undersample as well - so there is this optimum sampling that will be just right for level of detail available. In long exposure this mostly depends on seeing and mount performance, but in planetary where we want to circumvent seeing effects by using lucky imaging - detail is solely defined by aperture size (and wavelength of light). There is simple formula for calculating optimum F/ratio where this happens, and for ASI2600 with 3.76µm pixel size - it is F/13.9 for solar continuum filter (~540nm) and F/11.4 for Ha filter (656nm). On a separate topic - filter performance is affected by F/ratio used if you use interference filters. These filters depend on thickness of different dielectric layers and these layers have different width depending on the angle light hits the filter. For this reason - there is shift in filter curve for different angles of incidence. With slow F/ratios - most of light hits at very steep angle and "sees" layer thickness close to designed. With fast F/ratios - portion of light hits at shallower angles and see layers much thicker. For this reason - you can see some NB filters "optimized" for - fast F/ratios - like down to F/2 or similar (where this effect was taken into account).