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Ah, yes, I was going to mention that - but you obviously know the benefits. This just shows that there is no magic involved - fast ED doublet is not going to be well corrected for AP, even with aggressive filtering.

Did you use UV/IR cut filter? ASI485MC has only AR coated window, so it needs UV/IR cut filter. This can also be reason for bloated stars.

Seeing should not play a part here. Optimum sampling for lucky imaging is based solely on aperture size. We ignore seeing influence because we hope to get lucky few subs that are almost unaffected by it. In fact, seeing effects don't disturb cut off point. They just lower MTF curve and produce result that needs to be sharpened more - but cutoff point remains the same and is only product of aperture size.

339.8px and 0.1407"/px seems about right. That gives diameter of Jupiter to be 339.8 * 0.1407 = 47.80986" which seems right. Stellarium is giving apparent diameter at the moment to be 47.27" and this image was probably taken some time ago. These two criteria have nothing to do with sampling rate. They give rule of the thumb for visual separation of two equally bright stars. Sampling rate is determined by maximum frequency of the image in frequency domain by applying Nyquist sampling theorem. There is cutoff frequency due to nature of light (waves and interference). This is "hard" cutoff frequency - meaning it is indeed maximum frequency that the optics of given aperture can produce. There are no higher frequencies. This limit is given by simple expression: https://en.wikipedia.org/wiki/Spatial_cutoff_frequency but actual math behind deriving that expression is a bit more complex (involves Fourier transform of aperture to get Airy disk function and then another Fourier transform of Airy disk function to derive low pass filter resulting from Airy pattern). Formula that I presented above directly derived from above formula on wiki page: and application of Nyquist sampling theorem (which states that you need to sample at twice max frequency - or that pixel needs to be half of shortest wavelength associated with max frequency). By the way - when we speak of frequency and wavelength in this context - it is not frequency and wavelength of light / photons - but rather Fourier transform of image represented by 2d function (so FT of that function). There is really simple way to check that. 0.1407"/px implies that your setup is at effective: 0.1407 = 2.9 * 206.3 / focal_length => focal_length = 2.9 * 206.3 / 0.1407 = ~4252mm C14 has 356mm of aperture so effective F/ratio is F/11.96 For 400nm wavelength you want to sample at x5 pixel size, so F/ratio should be 2.9 * 5 = F/14.5 If you go by that criteria, then you are slightly under sampled, but I don't think that you are, as I often say that it is better to use 500nm as baseline and instead use x4 pixel size (from above mentioned formula F/ratio = pixel_size * 2 / 0.5um = pixel_size *4), because of seeing effect on shortest wavelengths and fact that most sharpness (perceived) comes from green part of spectrum - which is 500-550nm. Going by that criteria 2.9 * 4 = F/11.6 - so you are spot on.

Quite simple procedure. Take your Jupiter image as recorded (no drizzle, no binning, no rescaling) - but it can be stacked and sharpened (and it really should be for measurement precision). Measure diameter of Jupiter disk on equator (there is actually quite bit of difference as I recently found out between measuring at equator and at an angle) and check current or rather at the date of recording, apparent angular diameter of Jupiter. Divide the two to get pixel scale - and from that and pixel size - derive actual focal length.

Not sure where this item can be found in UK. There are several versions of this scope, so one or another might be available locally. TS has its on version, although a bit pricier and without all accessories (so it's loose / loose situation): https://www.teleskop-express.de/shop/product_info.php/info/p14747_TS-Optics-62-mm-f-8-4-4-Element-Flatfield-Refractor-for-Observation-and-Photography.html

Well, if we are going to go rather small - then there is this interesting model: https://www.tecnosky.eu/index.php/quadrupletto-tecnosky-62-520mm.html It comes with a lot of accessories and is quite decent optically. That amici prism alone is £89 (branded as William Optics at FLO, but there are cheaper versions like 70 euro Lacerta version - all produced by Long Perng if I'm not mistaken). One would need to invest in decent astronomical diagonal mirror, but telescope itself can double as daytime spotter scope with amici prism. Here is review of said scope branded as Orion StarBlast: https://www.skyatnightmagazine.com/reviews/telescopes/orion-starblast-62mm-compact-travel-refractor/

It really helps if one understands underlying physics (at least on the basic level of actual formula used) and looks at the context. When discussing regular OSC planetary imaging, then I would say that using x3 pixel size is wrong advice - but it does not have to be, depending on what is being recommended. I'll explain. Actual formula goes like this: F/ratio = pixel_size * 2 / wavelength_of_light Where Wavelength of light and pixel size are in same units of length (micrometers for example). Using 400nm as shortest wavelength to be recorded - above turns into F/ratio = pixel_size * 2 / 0.4 = pixel_size * 5 So for general RGB / OSC planetary imaging correct F/ratio = 5 * pixel_size How can then x3 be right? Well, it depends on context. Maybe advice was given in context of lunar imaging with use of Ha narrowband filter? NB filters (and Ha in particular) are often used by Lunar imagers to tame the seeing. Then using the same formula - we can get different result: F/ratio = pixel_size * 2 / 0.656 This time we use 0.656um as wavelength because we use Ha filter that is centered at ~656nm. This reduces to F/ratio = pixel_size * 3.04878.... = pixel_size * 3 In context of mono + Ha for lunar - yes, F/ratio = pixel_size * 3 is good formula and good recommendation. I'll give you even weirder one. If you use ASI462 - and want to do IR imaging at 850nm, then following is correct: F/ratio = pixel_size * 2 / 0.85 = pixel_size * 2.35 How about that? With 2.9um pixels you actually need only F/6.8 if you want to shoot IR at 850nm and above. If you said someone that they need not go over F/7 for planetary imaging (example Jupiter at with IR pass filter) - they would say that you are nuts

Depends on few factors: 1. Do you need proper calibration of your data? Like for photometry or getting the accurate color? Then yes 2. Do you have amp glow that you want to remove? Then yes 3. Do you also perform flat calibration? Then yes Otherwise - you don't have to.

Pass that one for planets and the moon. In that price range, this one is better: https://www.firstlightoptics.com/evostar/sky-watcher-mercury-707-az-telescope.html It is a bit more expensive, but will offer sharper image and higher magnification.

I think we are talking about different things, but please do correct me if I'm wrong as I'm only applying common knowledge and don't have any specific details on processes involved. You are talking about color of trail and not the color of "head". In long exposure image - streak is formed by bright head - which is much brighter than the tail. Here is screen shot from your video: tail is indeed green as it consists out of ionized oxygen that is left in trail behind meteor itself - but we can clearly see that meteor itself is shining with yellow color - which would indicate temperature of about 5000K.

I'm sure you can do it in any image processing software. DPI is just value written along the image and changing it won't affect image in any way. You can print 100dpi image at 300dpi just by setting print resolution in print driver.

Another important aspect of meteor is that it has uneven brightness. As it enters atmosphere it is slowed down. This change of velocity will produce change in brightness. It can have relatively even brightness only if you captured part of its trajectory in FOV.

That can be calculated. We can take say 10Km as fight level - you can get alt/azimuth from time of recording, your location and target RA/DEC We also have sensor size and lens FL - which will give us field of view And so on... If you suspect meteor (shooting star) - then color is important part of the puzzle as is multiple / single trails. Meteor can not go from multiple to single trail, while airplane can (change of angle we look it at as it moves across the sky / any banking to execute heading adjustment). Meteor can usually go from single streak to multiple as it falls apart from friction in atmosphere. Color is indicator of temperature. Red/Orange/Yellow/white/blue - that is ascending temperature color - or this diagram: Meteor usually heats up as it enters atmosphere. From multiple / single streak point of view - logical trajectory of meteor would be from right to left (single streak to multiple) From color point of view - logical trajectory of meteor would be from left to right (Red/orange towards white and bluish). These two contradict each other.

Brightness of the streak depends on relative speed of object (as well as its brightness). Airliner that is far away (high altitude) will slowly traverse the frame and it will leave brighter trail. Image that you linked second is typical on lower flying airplane that is on approach to airport or getting ready to land (or maybe just took off). I used to get such trails when I was shooting at about 60-70Km from airport. However, when airplane is much higher in the air - it is also much smaller and there is less distance between wing tips. Blinking will actually "join" to form wavy pattern rather than being separate dashes. In any case, if you don't think it is an airplane and want to investigate further - here are some pointers. Try calculating speed based on exposure length, direction of exposure and atmosphere thickness if you think it is space debris falling down. Then compare that with possible terminal velocity of such object. Look at this website for info on satellites or other things that orbit: https://www.heavens-above.com/

Looks more like passing airliner. Several light streaks are visible next to each other - which could be tail and wing fin lights. Also changing colors can indicate blinking lights.

I can explain this - but those numbers are anything but SNR. First things first. There is no single SNR number for the image. Every pixel has SNR as SNR is ratio of two quantities - signal and noise and both vary across the image, so no reason to think that there is single universal SNR across the image. Just think about background - it has no signal, right? So SNR is effectively zero there as S/N = 0 / N = 0, regardless of what the value of noise is. On the other hand - we know that target contains non zero value of SNR, and there you have it - we have shown that there are at least two SNR values per image rather than one (in reality - there is much more as not all parts of target are equally bright nor have equal amount of noise). How can we then estimate SNR as a single number? Well, one idea would be to somehow measure noise in part of the image - as part of SNR calculation - and only way to do it would be to estimate it by variation of pixel values. Here we come to actual reason. You say you drizzled your image. What parameters were you using? Actual drizzle algorithm has few parameters that you must set in order to control drizzle process. I've also seen drizzle algorithm being improperly implemented as well. Drizzle works only with under sampled data - otherwise - all you might get (if wrong parameters are used or improper implementation is used) is pixel to pixel correlation or smoothing of the data due to loss or resolution. When you enlarge data - you are performing certain interpolation on the data (actual drizzle algorithm tries to avoid this with careful selection of parameters). Depending on interpolation algorithm used - there will be certain level of smoothing of the data (which reduces noise). If you measure FWHM - you will find that it is larger on Drizzled then binned stack versus regular stack because of this smoothing. Point is - background noise was "reshapen" and data was smoothed - which then causes noise estimation to miss more then it would otherwise.

ST102 is lovely wide field scope, but if you want it to be all around performer, maybe consider something else. It performs rather poorly on planets and the Moon (the moon being probably most observed quick grab'n'go target). Any achromat refractor is going to have chromatic aberration - but there is a way to get around it with some models. You can use aperture stop and/or filters to reduce impact of CA. Problem is - longer achromats are better and this, but longer the scope - less grab'n'go it becomes. Both in mounting requirements and in transport length. That 90/660 that you already mentioned seems like nice middle ground between focal / ota length and ability to tame CA as well as ability to serve wider field views. Depending on your budget - you might actually like something like this: https://www.teleskop-express.de/shop/product_info.php/info/p7169_TS-Optics-ED-APO-80-mm-f-7-Refractor-with-2-5--R-P-focuser.html I believe it is the same as this scope: https://www.svbony.com/sv503-80ed-f7-doublet-telescope/ just different branding. See which one has the best price after shipping and any import fees. Also - check out this, which is probably again the same scope with different branding: https://www.altairastro.com/starwave-ascent-80ed-f7-refractor-telescope-geared-focuser-469-p.asp it might be best price when you consider shipping and import fees. By the way - if planets and the moon are not your priorities then, yes - ST102 all the way (or maybe ST80 if ST102 is too big / heavy for you).

Yes - but my idea was simpler, not so sophisticated and nicely executed I like the way you used 3d printed bevel gears and timing belt to make it ergonomically the same as regular focuser. Mine idea was much more like focuser on SCT/MCT type scope or maybe spotter scope. Only thing that I can't decipher from the image is what the belt is turning - how did you attach gt2 pulley to nut? Is pulley attached to threaded rod and whole rod is turning or is it just nut?

Depends on efficiency of panel Baseline is 1KW per square meter under ideal conditions - clear sky and sun at zenith shining perpendicularly on panel. Most panels now have about 20% of efficiency, so we would need 5 meters squared for 1KW of nominal power, or if we want 500W - that would be 2.5m2 in panel surface. Here are specs for 585W panel (maybe exact model I'm using - although I'm not sure which model is installed on my rooftop): Rated Power in Watts-Pmax(Wp): 585 Open Circuit Voltage-Voc(V): 41.10 Short Circuit Current-Isc(A): 18.11 Maximum Power Voltage-Vmpp(V): 34.22 Maximum Power Current-I mpp(A): 17.10 Module Efficiency (%): 20.7 Solar cells: Monocrystalline Cell configuration: 120 cells (6 10+6• 10) Moduie dimensions: 2172 x 1303 x 35 mm Weight:35kg We have surface right - as above is about 2.2 x 1.3 meters (2.86m2 for 585W) - but more important bit is that it weighs in at 35Kg.

If you run your heater for say 10h each night, your power consumption is 0.3KWh (10h * 30W) I'm running full scale solar array for my house now (10KW), just got connected and running for 10 days, and my average at the moment is 1/4th of nominal power per hour (I produce about 25KWh in about 10h of daylight, so 2.5KWh per hour on average and that is 1/4 of 10KW installed). It has been rather sunny last 10 days, so I estimate that in winter time, with more clouds - this will drop to about 1/10th of nominal power, per hour. Say that you have 6 hours of daylight in wintertime and you need to get 0.3KWh per day - that is about 50Wh each hour, and if that is 1/10th of nominal power - I'd say you'll need 500W of solar panels. That is quite large solar panel. I have 585W panels (18 of those) and they are massive. Depending how large is your battery and how often do you run heater (I guess it is not every night as sometimes you use obsy) - you might get away smaller solar panel. Another thing that I did not factor in is losses in conversion. I'm running 3 phase inverter which has peak efficiency at ~98% - so that is quite high. Not sure what would efficiency be for simple DC device (charge controller to charge your battery).

I purchased this one: https://www.teleskop-express.de/shop/product_info.php/info/p5769_TS-Optics-2-5--Rack-and-Pinion-Focuser---supports-up-to-6-kg---travel-95-mm.html It is direct replacement (M90) no adapters needed. It has rotation which is good for threaded applications as you don't need separate rotator. It also has M63 thread. At the time I purchased it - it was about 25% cheaper than now (prices are of course going crazy at the moment). I remember deciding between that and this one: https://www.teleskop-express.de/shop/product_info.php/info/p6421_TS-Optics-PHOTOLINE-2-5-inch-Deluxe-Rack-and-Pinion-Focuser-for-Astro-Imagers.html But I decided to go with first one as specs were almost the same (it can even handle more weight) - and price was smaller (as is at the moment).

For me, it was to replace focuser with better 2.5" R&P unit (that also has threaded connection instead of clamping one).

Forgot to add - it will move one thread pitch per revolution, so if one wants to have faster focuser - there is another option instead of standard metric threaded rods. That is trapezoidal / lead screw + corresponding nut. These usually have multiple starts and longer pitch. Standard 802 has pitch of 2mm and 4 starts - which means it moves 8mm per turn.

Here is an idea ... It is mostly for 3d printed focusers but I can't see why it could not be used as fine focus in any DIY focuser. All we need is a draw tube and focuser body, draw tube being suspended on bearings or Teflon pads so it can slide in and out. Focusing motion is performed by threaded rod and nut - or two pieces of threaded rod. Either nut or one piece of threaded rod is attached to draw tube and can't move / rotate. Other, longer piece of threaded rod is attached to focuser body via bearings and can rotate freely. It is either threaded thru the nut or in close contact with other piece of threaded rod. Rotating it causes draw tube to rack in / out. Maybe easiest way to explain it would be to imagine fastening the screw in something - as we turn the screw - it is driven inwards. Now just "fix" the screw and let the object move instead.