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There is something called periodic error and that causes drift like elongation of the stars - while object stays relatively stationary. For example, in above image you can see two types of drift - right to left is DEC drift - due to poor polar alignment, but up/down drift is due to periodic error. On average stars stay at the same "height" although they jump up and down. On some subs stars get elongated because of that. Longer the sub - more elongation you will see. With 5 minute subs - odds are that every sub will show elongation since worm period is often order of 8-10 minutes and 5 minutes would be roughly half of period (so either up or down part ). Cures: PEC or guiding.

Well, need to take object that changes on fast enough scales and then take few images of it at different times and compare those. Actual imaged object is rather small - it is super nova remnant that went off recently - SN1987a, so the cloud is still small and visible by large space telescopes like Hubble. In theory, you could observe crab pulsar like that (last image). Many amateurs take images of crab nebula, M1 and that swirl although often imaged in X-rays (way beyond amateur equipment) - can be imaged in visible, at least I think so (I think I once saw image taken at ~500nm that show inner structure).

This one: https://www.firstlightoptics.com/reflectors/skywatcher-explorer-130m.html

You need to collimate your scope. Stars are rather poor looking. DSS can't make them out as they look more like small DSOs than pin point stars. One way of tricking the DSS or other software is to bin your data (in a certain way to keep color information) - so that star size reduces. For example - here is x6 reduced image (single sub): Now stars look more point like. BTW - you really need flats and darks, and using offset of 0 is not good idea.

Just to add - here are a few examples where we can see the change (and potential color change) within human lifetime:

Yes, way too long for people to be able to notice the effect, but you can do what people that are studying galaxy evolution do - there is enough stuff out there that you can find example of each evolutionary step. Want to know how star color changes as the star evolves over certain period of time - find similar sized stars in different stages of evolution and look at their color. Similarly you can do the same for galaxies. Interestingly enough, things that change the fastest - Super nova remnants and planetary nebulae - are most difficult to study like that as there are not enough similar samples to be seen close by (they are small so can't be seen over large distances).

Nice first image. Two technical points from me - too much noise reduction and clipped background. For noise reduction - look into masked noise reduction. This is simply done by creating two layers - one regular and one denoised on top of it. Then you make mask on denoised layer and use that same layer inverted for the mask (so that only dark areas of that layer are really used - that will denoise background and leave visible detail sharp).

How is your canon astromodified? If original IR/UV cut filter was replaced with one suitable for astronomy - then you already have UV/IR cut filter installed and you don't need another one.

I think it is the same one (except for color) - full diameter is around 125mm but inner opening is still around 70mm

I have to correct myself - there seems to be very cheap version of iris that can be adopted for achromat use. https://www.amazon.com/Aluminum-Template-Adjustable-Measurement-Measuring/dp/B08N6CH24H/ref=psdc_12896671_t1_B08QMKNH5N Only issue is that max aperture is ~70mm. Ideally we would like something like 50-100 range or maybe 50-120mm

That is going to be one killer full disk lunar scope

I always wanted iris style aperture mask - but no one is making them (at least not affordable to mortals ). Such mask could be "dialed in" on the fly depending on target. Maybe 3d printed version of DIY iris - like this one: https://www.instructables.com/How-to-make-a-12-leaves-Mechanical-Irirs/

Yes - same thing I wrote above. Camera pixels have certain bayer matrix over them - and that is fixed and can't change, however - once you read out image, actual bayer pattern in data will depend on "which way" you look at the image. For example - I wrote above comment in two lines. You will read that text left to right, top row first, downwards. That is how we read text, and that is how text makes sense. If you try to read the text - some other way - it will not make sense to you. Drivers read out "text" or pixels in certain way - but all you get is sequence of numbers. Was it read top to bottom, or bottom to top? That depends on software that is reading in pixels - it decides what is "correct" order. Nothing wrong with that - except for the fact that bayer matrix order reverses. Here we have RGGB bayer matrix - because we are reading it top/down, left to right. But if you start reading pixels as you would say function graph in mathematics - in "coordinate system" order: where Y grows in up direction so you'd read bottom / up and left/right - what would letters be then: GBRG (GB for first or bottom row, and RG for second / top row) Now you have to tell the software that uses "coordinate system" order that your bayer matrix is not really RGGB - but that it is GRBG and it will decode bayer matrix properly. That is important bit in the end - how software interprets pixels - like in "text" - going from top to bottom, or as in "coordinate system" - going form from bottom up.

It is better to make your own, it can be as simple as cardboard cutout or fancy like 3d printed part. If you make one - you'll control diameter of opening (say go for 80mm or 100mm) - and it is best if opening is in the center of the lens rather than to one side. Newtonian scopes often use off axis aperture mask due to central obstruction, but for refractors - it is better to go on axis.

Not necessarily. There is always a problem of "direction". Most people agree that pixels should be read from left to right - as that is the way we are used to read text (apart from some languages that are right to left or up / down oriented). However - there is problem of vertical direction. Is pixel 0 top left pixel of the sensor or bottom left pixel of the sensor? For mono images - it does not matter much - you read out image and if it's flipped - you just flip it back. Odds are - it will be flipped one way or another - because of scope (mirrors / lens thing). For OSC - it is a big deal - changing image orientation changes bayer matrix order (at least readout part - how scope flips the image is independent of that). Maybe developers of NINA work in one convention - like top/bottom while developers of ASCOM driver did it in other - bottom/up, so it's not really a glitch - more lack of uniform convention.

Did I get this right, you have Evostar 120 with you right now? Why don't you use that one to get the sense of 80mm F/12.5 scope? If you make 80mm aperture mask for that scope - you'll get 80mm with 1000mm FL - which gives F/12.5. Btw, that is effective way to get planetary scope out of larger achromat. You can try different size masks to see which one gives you best view as aperture too stopped down will impact level of detail, and not stopped enough will leave some CA. Depending on how sensitive you are - you can hit balance between the two for the best views. You can even combine aperture masks with filters (say Baader Contrast Booster).

Welcome to SGL

I think that is a good scope. Yes, it will have some chromatic aberration - but it can be tamed in various ways, if it really bothers you. Creating aperture mask is one of those ways. Useful for lunar and planetary viewing. Don't use it on deep sky objects as it restricts the light, but for bright objects like the Moon and planets - it is ok. For deep sky you don't need it because CA is not visible on those levels of light (except on very bright stars). For example - you can create aperture mask that turns this scope into 4" F/10 variant (btw - I have that scope, Skywatcher 102mm F/10 Evostar - which is "younger brother" of your scope). It gives very nice views of planets (still a bit chromatic aberration left). Next thing would be use of Wratten #8 filter or Baader contrast booster filter. First one gives yellow tint obviously, but removes purple fringing. Second keeps more natural tone and also improves contrast (but it is a bit more expensive). You can also mix the two - aperture mask and a filter, for best effect. Again - this is for planetary use. Mounting that scope is going to be somewhat of a challenge. Although specs say that it is ~5Kg - you would not want to put it on mounts that can handle for example 6-7kg like Skywatcher Az4 or Az5. This is because scope is long. It is about 1m long and has a lot of arm momentum. Best mount for it (in budget range) would be something like SkyTee2 (in az category) or Eq5 (in eq category). Btw, scopes are bigger than they appear on images (for some strange reason - it is very rare that scope is smaller in person that it appears - it is almost always the opposite - it is larger than it looks). For that reason, it is good idea to see some images of it together with a person holding it - so you can get the sense of the size. Let me see if I can find some online. Ok, this seems like nice video to give you idea of the size:

Not sure which option is correct setting for that camera - but you can try them out. Try GRBG first and GBRG second (if RGGB is default)

Wrong bayer matrix order selected when debayering.

So both are 4' long - one us 8" OD and wall thickness is 0.125" and other is 6" and wall thickness is 0.25" Since they have same length and I'm guessing they are same material - it comes down to one number - that is Area Moment of Inertia for pipe. One that has this number higher - will be less prone to bend under wind load. 8" pipe has: 23.979 6" pipe has: 18.69923 so 8" is better. We can then go on to calculate actual deflection angle for say 6m/s wind and TSA120 scope. I'd round area cross section of that scope to 0.15m2 Load will be 3.24N We have 4' long pipe that is 1.2192m, and above number for meters^4 instead of inches^4 for 8" pipe is 0.00001904107882336 For steel we'll take 210Gpa so 210,000,000,000Pa Then it's simple 3.24N * 1.2192^3 / ( 3 * 210,000,000,000 * 0.00001904107882336) = 5.87178130931712 / 11424647.294016 meters = ~0.514µm of movement at the top To calculate angle we use length and movement and do arctan to it - in the end we get ~0.087" of deflection. Less than 1/10th of arc second. Btw - that is completely inconsequential for planetary type imaging - it is only important for long exposure imaging if this angle is high enough.

We can easily calculate that if you give me exact pipe dimensions.

If you want to keep within your budget, then look at this option: https://www.firstlightoptics.com/evostar/sky-watcher-evostar-90-660-az-pronto.html and some upgrades to that scope in form of eyepieces and diagonal (maybe even focuser upgrade). Ideally, if going refractor route - you'd want something like 4" ED doublet, but I think that will be way over your budget (such scope can be later used for AP).

Ok, I see where confusion comes from. There is observing deck and pier will be anchored below it. Observing deck is at about 1 meter of the floor and has hole for pier. Pier is decoupled from the rest of the construction. I can easily get fins below observing deck and they won't get in the way when on observing deck. I can't however use legs at all because of that (or can below observing deck - but fins look like adding more rigidity).

Hi and welcome to SGL. Not sure if your budget will allow for scope that will both satisfy your need for observing at the moment and be usable for AP in the future. Maybe look into 130PDS on AZ4 mount (will need to purchase those two separately). Even that is over the budget. If we take FLO prices - 130 PDS is ~£220 and AZ4 is ~ £190 and that does not include eyepieces. combined total is about £400 or $740AUD. It would be best to concentrate on good visual scope at the moment and think about AP later. What size scope are you comfortable with to store and transport? You can always get something like this: https://www.firstlightoptics.com/dobsonians/sky-watcher-heritage-150p-flextube-dobsonian-telescope.html