vlaiv

Indeed!

That topic is rather complicated. You don't need 3 elements, 2 is enough to get a "perfect" barlow. Barlow is really simple optical design so you can't go wrong much in design itself - but you can in manufacturing. Much more important than number of elements is how good the product is in use. That x2.5 GSO barlow is very good barlow and certainly very good value for the money. Much better than stock / plastic items that usually come with the scope. There certainly are better barlows out there like Baader VIP barlow that you can "tune" to required magnification by using extensions but it costs like x3-x4 more than GSO one and difference will be minimal. In fact - I'm more concerned with fact that you are using Bird-Jones type scope than anything else. Again similar thing with that - in itself Bird-Jones design is not a bad design - only problem is that it is often poorly executed design and advice that you'll find most often on such scope is to stay clear of them. Not saying that your particular model is poor - I've neither seen Meade model nor read review of it so far. It could be rather decent, but there is a chance that scope simply provides blurred image at higher magnifications (having cheap plastic stock barlow won't help either). Knowing this, I don't think you should go overboard with expensive barlows - as it might not result in improvements that you are after.

In theory, you should be fine with that scope with magnifications of about x120-x150 range. That should give you good sharp image even in average seeing conditions. With x2 barlow, you'll get x100 and x133 magnification. With x2.5 barlow you'll get x125 and x166 magnification. This really gives you idea of what barlow you want - one that is x2.5 (but in reality is closer to x2.2), is triplet lens and is sensibly priced - look no further than: https://www.365astronomy.com/GSO-2.5x-Achromatic-3-Element-Barlow-31.7mm-1.25.html Given that you already have 15mm and 20mm eyepieces, x2.5 GSO barlow should not be too hard to purchase locally?

That one is in very good agreement with above "relaxed" criteria - sampling point per arc minute for critical sampling. It gives around x113 for 100mm of aperture and that equates to 100 / 113 = ~0.9mm exit pupil. I believe that one can see detail with even less magnification, but we can say that this is "safe" lower bound of magnification, and indeed, it is no wonder that people report seeing all there is to see with very sharp image at 1mm exit pupil.

Meade Polaris 127mm seems to be Bird-Jones design and has focal length of 1000mm. Using barlow with this scope is going to bring in very high magnifications - more than atmosphere and scope can support. Things are going to be blurry. For the time being, just avoid using barlow lens until you get some experience of how different sky conditions impact quality of the image. Once you learn to distinguish between different conditions (good or bad atmosphere) - then you can start using barlow lens and you'll be able to tell if it is atmosphere that is causing the most damage to the view or is it barlow lens.

You are thinking about astrophotography in the wrong way. Let me explain just little bit about it and things will get clearer. With telescopes it is all about collecting light - larger telescope collects more light. Difference between astrophotography and visual come from "how long is light collected". Eye/brain collects light only for about 1/30 of a second. This is the reason why we can watch movies (movies = moving pictures = series of still images shown for about 1/30th of a second). Astrophotography on the other hand takes hours and hours worth of images. Single images in astrophotography are at least few minutes long, but they end up summed in computers (this is called stacking). Camera will gather x30 more light in one second than human eye at eyepiece and astrophotography gathers light for thousands times longer. This is why you can never see better detail and "deeper" at the scope - no matter how large it is than a photograph taken with even small telescope - if it was recorded for long time. Now that we know what happens - it is obvious that camera will show you more even if you use very small scope. You will never see something like this at your eyepiece: Yet, it was taken with very modest 80mm scope. If you want to do astrophotography - there are plenty of concepts that you need to learn and understand. Telescope size is not very important concept in grand scheme of things. You need to understand that most important part of your astrophotography gear is one that has nothing to do with light - the mount. Then you need to decide what sort of images you are going to take - wide field, high resolution, something in between. Will you concentrate on nebulae, or on galaxies or small planetaries or star clusters. Do you want to do all of those with the same scope? Best start in astrophotography is to get yourself a book that explains all of that. Often recommended one is "Making every photon count" by Steve Richards (member here on SGL). I have not read it personally, but have no doubt you'll learn from it what is needed to get you started on the right path. My dream AP setup is rather expensive one. At the moment that would be Mesu200 / 16" F/8 RC scope / ASI6200 mono camera. Your dream AP setup is likely to be something like: HEQ5 / Skywatcher 150PDS + suitable coma corrector / ASI294 pro (cooled) and nice little guide scope + ASI120 guide camera.

here is comparison image: I took this one when I was at the beginning, but somewhat different gear was involved. Conditions are different as well. Differences to your image would be: - Sampling rate. Small scopes simply can't resolve 1"/px. With 100mm scope you need to aim to about 1.7"/px at best - Maybe slightly larger sensor - above image was taken with ASI178 - Scope without chromatic aberration - TS80 photoline F/6 apo - Same mount, but I think I guided mine. This is 8h worth of data from bortle 7-8 skies (SQM around 18.5), but I used cooled camera. Processing is not the best and there is gradient evident due to LP.

You can use several different criteria and they all give very low magnifications. This is the latest one that you can actually test "in-house". First part of the equation is human vision and how well can we see. That is pretty much standardized and we say a person with 20/20 vision has good eyesight. https://en.wikipedia.org/wiki/Visual_acuity Is a good starting point, but here is important part: In order to resolve something, we need to be able to spot a gap that is wide 1 arc minute (it talks about 6/6 above - that is same as 20/20 which is American standard - also explained in the text). You have probably seen this (or similar chart) at some point in your life (eye exam): In order to see where the symbol is pointing you need to be able to see the gap - which is 1 arc minute wide for 20/20. Now that we know what constitutes a good vision, we need to match that to image that is formed in focal plane of the telescope. Let's use simple case - Rayleigh criterion: We say that two point sources are resolved if they look like top image. Condition being that two point sources are at Airy disk diameter away from each other. In order to see that with 20/20 vision, we need to map that to roughly three 1 arc minute segments. White / black / white pattern (star - gap - star). Two airy disk diameters need to be 3 arc minutes wide when magnified. For 100mm of aperture, Airy disk diameter is 2.57" wide. Two of them will be 5.14" and those need to be magnified to be equal to 3x1' = 3 x 60" = 180". Magnification is therefore 180" / 5.14" = ~ x35 This is very "strict" criteria, and I used much more relaxed criteria above - one that is comparable to images that I posted. That one relies on sampling resolution for imaging. Same math involved, but in this case, I did not use "star-gap-star" as basis for resolving - I used single pixel for resolving. With 100mm of aperture, critical sampling rate for green light at 510nm is 0.53"/px. So a single pixel is 0.53" wide and we want to be able to "see it" (with this sampling there will never be case of white pixel / dark pixel / white pixel because there will be need for multiple pixels per airy disk - about 5 or so). We want to magnify 0.53" to 60" (1 arc minute) and that is 60/0.53 = x113.2 What ever criteria you use - you actually get rather small magnifications that you need to be able to resolve things at lower bound. I gave you two examples - one very strict and one rather loose. You can check this in house - generate star pairs or image of planet for display on screen using one of these two criteria and then stand at certain distance to the screen. Distance you need to stand away from the computer screen can be calculated based on your display DPI in order for single pixel to be 1 arc minute (or in first case if you want to actually have double star / Rayleigh criterion - you'll need to do a bit of math - again optimum sampling / pixel resolution - distance, and of course properly generated and sampled image).

I don't think I would put such thing on my scope - that design is just begging to be mistaken for a handle (Eggs! Never use word lemon next to a fine scope!).

Couple of things come to mind: 1. Astrographs are usually fast systems - that will put some strain on eyepieces and "demand" expensive ones for good / to the edge correction. Otherwise, if you can live with only central part of the view being sharp - you can use regular ones as well 2. They will be slightly less performant than their visual counter parts if mirrors are used. This is due to central obstruction which both blocks some light and also robs you of some planetary contrast (but helps with finest frequencies - which are usually killed by seeing). It is not unusual for astrograph to have 40-50% central obstruction (by diameter). 3. They will be somewhat more difficult to collimate - faster optics requires greater precision of alignment. 4. Some astrographs are corrected with "distance to sensor" in mind. This means that you need to put eyepiece into exact position which varies with eyepiece - similarly to visual coma corrector that needs system to adjust for each eyepiece. It would be best to avoid astrographs with built in correctors that are distance sensitive - it is very hard to find variable eyepiece distance adapter that you can fit on such scope. If you use fast newtonian then you should consider visual coma corrector like one of these: https://www.firstlightoptics.com/coma-correctors/explore-scientific-hr-coma-corrector.html or https://www.firstlightoptics.com/coma-correctors/tv_paracorr_2.html both of which have system for adjusting eyepiece distance together with coma corrector - so it's all in one package that works good. Probably the main reason you would want to use such scope for visual is that you want it to double as imaging scope as well? You'll most likely need coma corrector in that case anyway (for imaging), so factor it in the price. Other reason could be that you want very wide field larger aperture scope. In that case, you'll want to enjoy pretty stars to the edge - so again, CC is recommended.

This is rather interesting as it is first time I'm seeing walking noise in action thanks to your animated gif! Couple of questions: 1. Is camera cooled and if so - was it cooled at the time? 2. Did you take calibration frames for it and are images above calibrated? 3. Do you guide? Interestingly enough - direction of noise walk is not either RA nor DEC but rather combination of the two - which is strange. Is there particular direction of the drift between first and last frame you took? Do they all move in same direction (small shift between exposures)? In fact, could you do a animated gif like one you did, but this time using all the frames in order they were recorded (for one channel - green or the one you choose)? There is big difference in background intensity in the gif - can you explain that? Is there a light source that goes on and off randomly or could it be high altitude clouds passing?

Don't get me wrong - I'm not implying that you should stop using magnification that suits you just because science says so. I'm just trying to figure out why people report things that they report. I have quite good understanding why would someone use higher magnification - it is easier to see things and eye/brain does not need to work as hard and not everyone has 20/20 vision. What I don't understand is - why people report that too much magnification "breaks down" the image. From telescope perspective - it projects the same image of focal plane and does not really care what sort of eyepiece is used to magnify the image, so there is no change in image itself with magnification (one that telescope produces) - hence it can't "fall apart". But it looks like there could be both real physical reasons (exit pupil size vs eye shape) and psychological reasons for image break down (brain can't tolerate certain level of blurriness and dim image).

Actually, I just realized there is one factor that can mess up image at higher magnifications - and it's not the scope nor the eyepiece. Scope produces same image at focal plane regardless of what eyepiece is used to magnify it. For this reason, it can't be scopes fault if we see magnified image as worse than it should be when magnified. Second suspect is eyepiece - and indeed, not all eyepieces are equally sharp, but I think that we can rule out this one as well - there are plenty observers that report on this that have expensive glass and very sharp eyepieces in short focal lengths. Third reason that I can think of is human eyeball. When we say someone has 20/20 vision (and we base our calculations of what can be seen on that) - that figure is obtained by measurement performed in such way that wave front hits quite a bit of eye lens. In normal daytime / artificial light of exam room - it should be something like 3-4mm, right? Bring that down to 1mm and many observers that suffer astigmatism in above conditions start observing without problems - at 1mm aperture - eye is not out of shape locally enough to cause issues associated with astigmatism. But smaller exit pupil than this - above 0.5mm could be suffering from another problem - local wavefront aberrations caused by physical defect being now larger relative to pupil size. Similarly to that how smaller apertures suffer less from seeing and dominant aberrations being tilt - here it would be somewhat different due to eye placement - with such small exit pupil - rays at different angles will hit eye lens in different spots and possibly experience different level of tilt - which compounds to produce blur at this level of scale? Not sure if above makes sense, but could be something to it? Exit pupil too small - not only image gets dimmer but also blurrier due to eye?

Yes, but science says that for 100mm of aperture x113.2 (or less - depending on what you are using as a criteria, this is "worst" case scenario - using twice resolving power of human eye) will show you all you need in order to see it all.

I have to ask - what defines usable magnification? On a both good and bad scope in good and poor seeing conditions - after certain threshold image just stays the same only magnified. Yes, it will get dimmer, but regarding the detail - it will remain more or less the same (at some point image will be too dim and some features will start disappearing - but I don't believe we are reaching that threshold in this case). At what point in this magnifying process do we say - ok, now image is no longer "usable"? Let's consider these: First one can be considered I don't know x100 with 8" scope when you are suitable distance from computer screen (depends on pixel size of your computer), and others are respectively x200, x300 and x400. Which one of these is no longer usable?

Do you mean web cam or dedicated planetary camera? Things to look for are different between the two. With regular web camera there are couple of things that you want: 1. Easy to modify so it can be used in prime focus - easy to remove front lens while making sure camera still works and making some sort of 1.25" nose piece or other kind of attachment to telescope 2. What sort of video modes camera supports - here I'm not talking about resolution (like 640x480 or 1920x1080) - I'm talking about video formats and bit rates. You want your video output to be in RAW format, but most regular web cameras don't offer this. They offer only compressed video formats - like mjpeg or mpeg4 or similar. That is a problem because these video formats compress data by altering it slightly which is bad for lucky planetary imaging type and stacking. 3. You want camera that is capable of higher frame rates. I used modded Logitech C270 camera With dedicated planetary camera things are different because most dedicated planetary cameras offer all of the above - out of the box. That sort of makes them in a special "league" with respect to everything else - a top tier. Here you need to take different things into account (some are the same): 1. Frame rate - same as above, but here you need to factor in USB2/3 - go for USB3 and make sure you have computer to support it - also USB 3.0 connection and SSD type drive. 2. Decide if you want to go for mono + filters or color type camera 3. Quantum efficiency of sensor - you want this to be as high as possible 4. Read noise of sensor - you want this to be as low as possible. Used QHY5LII-c. Now have ASI185 and ASI178 - both color. I have ASI1600 as well that can be used in planetary role (although not the best stats listed above - it is mono and that has its advantages in certain applications). If you want the best - go for ASI224. If that is small enough - go with ASI385.

This will do almost nothing. Gain is just conversion factor between number of captured photons / electrons and numerical value that you get when reading image off camera. There are somethings related to gain settings (like level of read noise and such) - but you are not there yet. Your focus seems pretty good to me. Slight problem with star sizes that you see is due to telescope used - fast achromatic refractor. This is certainly something to consider. If you are currently at 1"/px - you are way high in resolution for the telescope that you are using. ASI290 will be the same camera (except for raw performance - and that is important). If these are cameras without cooling (and I suspect they are) - just get second hand DSLR camera. It will be less expensive and will serve you better. You can keep the camera you have once you decide to guide. Yes, that will be good if you want to do better images. That will reduce chromatic aberration. If you want to keep current setup / camera - getting 130PDS as imaging scope will produce nicer looking image. Not sure if that is necessary. Even £1370 will get you gear that will provide you with exceptional results: https://www.firstlightoptics.com/reflectors/skywatcher-explorer-150p-ds-ota.html ~ £230 https://www.firstlightoptics.com/zwo-cameras/zwo-asi-294mc-pro-usb-30-cooled-colour-camera.html ~ £1010 https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html ~ £130

Not a tall. AS!3 has bad pixel map feature. What sort of mount are you using for tracking? For bad pixels - best solution is to have your mount track less than perfect - so that planet moves across the sensor. Software will then pick up which frames have dead pixels in certain position - and use other frames to make that particular pixel - thus completely removing dead pixels from your image. But like I mentioned, for this to work the best - planet should not always be in the same spot as that makes bad pixel in the same place in all the frames - you don't want that. From the video you posted - there is something really interesting - defocused image of Jupiter. It looks like just a quarter of aperture is used (defocused image will start to show image of aperture). Do you know if something was blocking the front of the scope or maybe optics is out of alignment?

Wear glasses? Try changing your observing eye first. Eyes usually don't have same level of astigmatism. My right eye is next to useless while my left one is very sharp. Naturally I use my left (dominant) eye for observations. Other option is no to wear them when doing high power observing. That will depend on exit pupil and how much astigmatism you have in your eye. Impact of astigmatism often depends on exit pupil because small exit pupil uses only small portion of your eye lens and small portion will be less distorted (relative to its size) than whole lens. Often people don't notice astigmatism effects below 1mm exit pupil. Binoculars have rather large exit pupils and you'll readily see any astigmatism you have.

I probably won't be of much of a help with feed back and comments but I wanted to say a few words. I did briefly watch your videos and I can sense the unease that you have in front of the camera. I want to encourage you to keep at it. It might not be something that you feel comfortable at the moment but I truly believe - the more you do it - more you'll feel comfortable and at home doing. I think that videos you are doing have value to astronomers and for this reason I believe it is important you persevere at it. I can only see you getting better with time and bringing more value to astro community.

Any particular reason for that? I only had one experience with QHY camera - guiding / planetary class and ASI counterpart was much better in terms of software support. I don't know about large sensor models, is there something that should sway potential buyer towards QHY?

Very very hard to make it on that budget. First thing that you want to solve is telescope tracking. In order to take photos of planets - your telescope needs to track. It does not need to track perfectly for planetary photography because exposures are rather short - but it needs to track planet long enough for you to take a lot of such exposures. First part would be to research for how much money can you get tracking system. There are really three options there: 1. Get second hand EQ mount exceptionally cheaply and restore it to working order (you won't be able to get very low price on proper working one) - aim for EQ2 / EQ3 type mount - anything more serious will be over budget. Then you'll need a bit of DIY to fashion a tacking system for that mount. You'll need a stepper motor, some electronics / reduction gears. You can even use plain DC motor - as you don't need precise tracking - just add simple speed control - like single potentiometer. 2. DIY mini dob platform - you don't need it to be very big nor heavy and you can save a lot on material because your scope is small and light weight - same as above you'll need motor and control. This is probably more serious project than number 1 3. DIY barn door tracker. For this one, I'm not even sure it will track properly at magnifications you want - so a bit of research there on their precision and can they keep planet in FOV for duration of recording. Now that you have tracking sorted, you need to think about camera. Probably cheapest way to go is to use second hand web camera that you will modify by removing front lens and exposing sensor. This is what I did for my first planetary camera. I used Logitech C270 and a piece of PVC pipe to make a nosepiece. Then you'll need to watch some tutorials on how to do lucky imaging - take a lot of exposures and use software like Autostakkert!3 to stack those exposures and then use software like Registax 6 to perform wavelet sharpening and your favorite software for a bit more processing (Gimp is fine and free). Otherwise, you'll need to increase your budget about x5 to get everything (Eq3 mount with tracking motor and ASI120 planetary camera). Hope this helps.

Iridium flare can be very slowly moving if it is moving towards you and it can appear almost stationary. From your description, it could probably be iridium flare. Once I looked at one for about 20 seconds or so and got really scared because it was looking as a meteor that was about to hit us - getting brighter and brighter - but obviously coming at us because it stayed at pretty much the same place - then it died out slowly. However, as I've just found out - Iridium flares are no more - last satellite deorbited in December last year. Might be some other satellite - check this website: https://www.heavens-above.com/?lat=53.2972&lng=5.0262&loc=Unnamed&alt=0&tz=CET

Which part? That it needs collimation? That is kind of obvious - look at the star shapes: Here is collimated RC scope (RC8): Stars are tight and round. Another telltale is that stars look different in different corners and they are not round even in center. If primary is not aligned properly but secondary is - then stars will be distorted in corners but not in center, a bit like this: Close to center: Corner :

You mean black spot? But Olympus Mons is still there I think: