vlaiv

I'd say that 4K monitor only makes sense as a larger screen at closer viewing distances. At normal working distances, 92ppi is right about there at the edge of human capability to resolve detail, so any addition of pixels is just waste of resources (as far as I see it).

Ok, so your image size is 4000x2264 px That is way too big image to be shown on 1920x1080 FullHD screen - and will always be resized to fit the screen. First thing you need to do - is select area around Jupiter and crop image so that only sensible size of pixels around Jupiter is contained in the image. Select crop tool: Make selection around Jupiter with it: Say around 800x600 px. Then press enter to perform actual crop. Next, to save it as jpg - choose Export as option in File menu: Now you can save it as jpeg. Given that it is now smaller than your computer screen - it will no longer be scaled down and it will look like this:

When you say this, what do you actually mean?

Does your scope track? If so - maybe lookup smart phone eyepiece attachment - or if you have access to 3d printer - I'm sure one can be printed. In any case - it will be much easier to take image that way then by holding smart phone over the eyepiece. That is as basic as it gets - but you will still be able to do what you expect.

Yep, that's the one. Only "drawback" might be 8ms refresh time. I personally never had any issues with game play on 8ms gray-to-gray monitors, but then again, I'm not much of a gamer (used to enjoy FPSs and flight/driving sims back in the day).

If you are visual only - go with 102mm scope. 115mm is triplet and is better corrected for color, but this is only visible in images (human eyes are mostly not sensitive enough at far ends of spectrum to notice this). Triplet is heavier, and cools down slower. These are things that are often important for visual observers. If you don't mind a bit more weight and a bit longer cool down time - and you think 15mm more aperture is worth it - then obviously the triplet. Between the two - I'd go for triplet - but then again, that is me with my priorities.

There are quite a few parameters that can impact result of stacking. Of the top of my head - alignment point size will change its relative size compared to features if you change pixel scale. Shooting at two different scales and not adjusting alignment point size can have effect on stacking result even if you have exactly the same level of detail in both recordings. In any case, not sure if there is any point discussing this further, you know what works best for you.

It seems that there misunderstanding on different image sizes. I'll try to explain several aspects of image size and how things (usually) work. First is physical / recorded image size. Second is viewing size. It is very often the case that viewing size is adjusted to suit display device and might not be actual recorded (or resampled) image size. Many people use APS-C sized sensor to create images and often end up with images that are 6000x4000 or similar in pixels. Very few display devices (if any) have that much pixels to be able to display image fully. If you look at that image on your FullHD computer screen or mobile phone of certain resolution - it will be resampled for viewing purposes - to fit the display area. Take for example another image - this one recorded at 3000x2000 - so x4 smaller then previous. This one is still larger than display device and will also be scaled down for viewing. If you view them on same computer screens side by side - they will look like they are of the same size - but in reality they are not. You are just viewing them scaled to say 15% and 30% of their size respectively. This happens automatically by software used to display things. If you want to appreciate all recorded information - always enlarge image to 100% scale. This will often make it larger than screen and you'll have to scroll and pan around to see every bit of it. Planetary images are almost always smaller than display device. In majority of cases - such images are not scaled up to fill the screen but are left as they are (at least on computer screens - not sure about mobile phones). With these images you don't need to go 100% unless they are automatically scaled up. In any case - when we talk about image size - we are most often talking about pixel count used to record the image and not file size, nor FOV / display size on the screen.

You can always adjust barlow magnification by changing sensor to barlow element distance. It is best to get barlow with detachable element - that way you can use variable extension to dial in needed magnification and F/ratio. Increasing distance between the two increases magnification and vice verse. If you know focal length of barlow element - you can calculate needed distance by using: magnification = 1 + distance / barlow_focal_length

In this particular case - it is the same as AS!3 uses special debayering algorithm - bayer drizzle that restores original resolution even from OSC sensor. So formula works for both mono and OSC.

One of bottom two images was made by enlarging scaled down to 80% version (top row). Can you tell which one? If not - then all the data is contained in 80% sized version - or x4 is enough and difference in your example is due to seeing and not due to sampling.

If I was in a market for a new monitor - I'd look at this one: DELL U2422H (I already have DELL UltraSharp model - but quite a bit older one). Might not be wallet friendly, though? Not sure what constitutes that in a monitor . It is 24" and that is big step from 22" that you now have. It also has very good color gamut.

Another way to achieve the same effect is to sample at F/10 and then simply enlarge finished image in software. This way you will get the same level of detail (you simply can't capture more than your telescope is able to resolve), but at the time of capture you won't spread light over more pixels than necessary thus reducing SNR and making it harder for stacking software to recognize sharp from soft frames, or in worse case - too dim image forces you to extend exposure to get bright image (sometimes it is hard to fight this urge although you should set exposure based on coherence time rather than on brightness) - and you start getting softer recordings because of atmosphere induced motion blur is affecting more and more subs.

It was taken with rather modest equipment. SkyWatcher 130/900 newtonian on EQ2 mount. Camera used was QHY5IILc (same sensor as ASI120c USB2.0) and crappy Celeron laptop Image was taken around opposition in spring 2015. Jupiter at that time was at altitude of about 60 degrees from my location (so pretty decent). I used simple GSO x2.0 barlow lens (one with removable barlow element). Trick is to use very short exposures - like 5ms, regardless of histogram (which is useful to detect clipping but not much else). Recording is often faint - but after stacking it can be processed to look good. Capture in raw format and use ROI so you can get good frame rate. Trick is to capture planet in moments of good seeing and seeing needs to be "frozen". I don't have recording of that Jupiter image, but here is Saturn with same equipment: Good frame (not debayered): Poor frame: Result after frame selection, stacking in (AS!2 at the time) and Registax 6 sharpening:

I would not trust sensor data either. ASI1600 is quoted at 3.8um pixel size and following specs (Panasonic data sheet): But if we divide height with number of pixels we get: 17.6472 / 4656 = ~3.7902 Similarly with width we get: 13.3228 / 3518 = ~3.787 We can't really tell what is exact pixel size. For this reason we can only compare two esprits for focal length - but not measure with precision until we establish actual pixel size somehow.

Maybe distance thing again. With reducers - changing distance changes reduction factor and focal length / focus position. Not sure if similar thing happens with pure flattener.

Good point. I was thinking of making a slot in 3d printed part for that plastic housing to sit in. Rollers won't make contact on the other side - but you are probably right, these are made to slide rather than to sit in single position. Maybe groove could be made for them to "float" back and forth as draw tube moves. They would only move half of draw tube travel. Will need to think about it. They are less than euro each, so I'll get few of them just for fun and to try out things.

I think that lens is lens - it has same focal length from front and from rear so it can't really provide you with different magnification depending on which side you choose to look at. Only difference is in correction - sharpness. Lens is usually best corrected for some distance - telescope optics is corrected for infinity, but most lenses are not, but are rather corrected for some sensible distance like - 5 meters or so. Macro lens are corrected for closer distance. If you think about it - eyepiece takes diverging light rays from very close focal plane and turn those into collimated beam - like this: Telescope focal plane to the left and exit pupil / our eye on the right. Camera lens works "in opposite" direction: here light goes from right to left - object at the distance to the right (at infinity - we get collimated rays) and then it converges in camera body towards the sensor (on the left). If you look at rays in both images - it stands to reason that we need to replace sensor with focal plane of telescope and object at infinity (or far away) - with our eye. We should be looking at the front of camera lens and turn back side (which sits in camera) towards the scope. In linked article - it is other way around, and that is why I asked if there is difference (maybe a bit of sharpness due to spherical correction or something).

Which way around did you try it? Article says that front of the lens should go inside focuser and that back of the lens should be eyepiece side, but I wondered what would happen if we reversed lens.

Only way that I can think of to test if there is difference in focal length between two Esprit 150 scopes is to compare plate solve data taken with same camera (or shoot target at same distance and measure some feature). There could be other reason for different focus position with respect to OTA - that is placement of cell and collimation. If there is push/pull mechanism in cell - one lens can be more pushed than pulled in collimation procedure which will change focus position with respect to ota but not focal length. Temperature can also play a part as tube changes length. If one OTA is carbon fiber and other is aluminum - there could be difference there. What I don't get is that you mention OAG and ASI120. If OAG / guide sensor / main camera setup is the same - just changed scope - then it should work regardless of any potential change in FL or change of FL position with respect to OTA as all is compensated with focuser.

If you examine UV/IR curves from others - you'll see that they are pretty much standard in how they look. ZWO: So, whatever manufacturer of actual filter - you'll get curve that looks like one of the above.

Not sure what you are after? If you want to know response curve for replacement UV/IR cut filter - then it is safe to say that it looks like this: Most astronomical UV/IR cut filters are like that (red line) - about 90-95% over 400-700 range. Pretty flat looking with steep edges.

Just an update. After about 15h of printing, I'm currently here: right is proof of concept worm wheel for azimuth adjustment of equatorial wedge - left is actual assembly being, well, assembled I seem to started suffering from moist filament, so need to sort out drying before I proceed (a lot of zits, blobs and increased stringing). Next is well - worm itself and rest of the housing including clutch for locking of azimuth motion. Here is design so far: I still haven't done rest of it - hopefully this week. Bill of material so far: x2 608, x1 6006, x1 51108 - those are standard bearings (very cheap). As far as I can see - I'll probably need x3 more 608 and couple of 6005 for wedge itself. Some M4 and M5 nuts and bolts and M5 threaded rod (about 10cm of it so far). I think that wedge will be usable on its own - for mounting SA or AZ-Gti. Not sure of carrying capacity though.

Depends. There is optimum sampling rate for given conditions - one that will capture all detail available (and let you sharpen your image further) - but will not over sample or use more pixels for the job than necessary. You can think of it as dividing line - below this line is under sampling - using "less than needed" pixels to record image and above this line is over sampling - using "more than needed" pixels to record the image. Nothing wrong with under sampling. In fact - you often need to under sample if you want to get wide field image as you simply don't have enough pixels to cover big patches of the sky. Over sampling is causing two problems. One is aesthetic in nature - and I guess often people simply don't bother with it. Other is problem with speed. If you use more pixels than needed - you spread light over more pixels, and in return each pixel gets less light - weaker signal, and SNR suffers. For example - if you sample at 1"/px instead of 1.5"/px (that might be optimal in given case) - you will need to image x2.25 longer to get same SNR. This number is ratio of surfaces of pixels - 1"/px is actually 1" x 1" = 1" squared per pixel. While 1.5"/px is actually 1.5" x 1.5" = 2.25" squared. That is x2.25 more sky surface per pixel. Aesthetic problem is related to when you zoom in to 100%. Over sampled image will simply show bloated stars and blurred object instead of pinpoint stars and nicely defined object. Some people are not bothered by this as they never look at image at 100%. I always look at image at 100% - otherwise, what is the point of capturing it with so many pixels if you are not going to look at it like that? Astronomy tools CCD suitability is flawed tool. I started thread at one point to discuss this and to maybe get it changed so it gives good values - but nothing came out of it. Sampling rate does not depend only on seeing - but in general on FWHM of stars in your image - which in turn depends on seeing, mount performance, aperture size and sharpness of the optics (meaning spot diagram of scope + any flattener combination). In any case - you'll be hard pressed to actually produce 1"/px image. Most setups can only achieve about 1.8 - 2"/px. Some can go down to 1.5"/px -and very few can go below 1.5"/px and only in good conditions.

Here are a few interesting ideas from past couple of days: - Making eyepiece from old camera lens with aid of 3d printer. Here is needed info on eyepiece design: https://www.skyatnightmagazine.com/advice/make-a-50mm-eyepiece/ I reckon that 1.25" nose piece - to - lens filter thread adapter can be easily 3d printed. So can eye guard that will go instead of back cover. - Making DIY telescope requires optical parts. I've stumbled upon interesting source of small diameter achromat lens (up to say 4"-5") that are more than affordable: https://www.aliexpress.com/item/4000843113053.html?spm=a2g0o.store_pc_groupList.8148356.29.13645edeQEzrMI&pdp_npi=2%40dis!EUR!€ 36%2C98!€ 33%2C28!€ 33%2C28!!!!%400b0a182b16611130503026215ecb8f!12000016656249049!sh For example - you can choose 80mm F600 lens (same as in this telescope: https://www.teleskop-express.de/shop/product_info.php/info/p7935_TS-Optics-80-600mm-Refractor-Teleskope---optical-tube-with-rings.html) at very reasonable price and free shipping (at least to my destination - much better than those crazy "deals" where you have to pay shipping 2 or 3 times more than the item itself). You get to choose if you want green or blue coating as well - 3d printed focuser. Well, there are plenty of examples floating around, but I've noticed that most use regular bearings that are a bit chunky in that role. Searching around for good bearings for that role came up with this: Look up FF 2010 or FF 3020 (difference is size - former are suitable for smaller 1.25" focusers, while later are more suited for 2" with longer draw tube).