Whirlwind

I barely captured it on my AllSky Camera. It was north and east but only just appeared just above the horizon (started no more than 10-15 degrees above the horizon and then went 'down' from there. I'm located just west of Leicester so somewhere in the north sea makes sense.

An external focuser is something you attach to the back of the telescope. The focusing mechanism on the SCT can be less precise and repeatable because of it's design (you are moving the main mirror). Because of mirror movement you can find that moving in/out doesn't bring the focus to the same position and hence isn't repeatable. An external focuser avoids this problem (something like this https://www.firstlightoptics.com/moonlite-focusers/moonlite-cs-dual-speed-sct-crayford-for-325-thread-fr-compatible.html) but there a lot of second hand market versions and you might want to see if there is one that can be adapted to both the 8" and 11"). You can also get motorised versions which helps get more precise focus and means you don't have to touch the telescope. Celestron have redesigned the focusers for the RASA versions that is meant to better but have yet to see whether they are going to bring it forward for the main line of Edges and SCTs in the future, that would probably remove the need in the future for external focusers. The old celestron F6.3 reducer was really designed for smaller CCDs going back to the 2000's and has a quoted imaging diameter of 24mm. Some of your options above are bigger than this so you will get distorted stars at the edges. ASA made a version with a wider field as well as Optec and Starizona I believe. The Skywatcher reducers are probably fine, but just check reviews for what their imaging circle is. This should be greater than the sensor diagonal otherwise you will get distorted stars at the edge. There are lots of reducer combinations out there for refractors you don't need to commit to the 'approved' ones - the only advantage is that they are usually threaded for the correct telescope so no adapters are needed. Just have a browse around and see what people are using successfully (e.g. on astrobin). As for the filter, it's not just the sensor size that is important but also how close the filter is to the CCD. Light approaches the CCD as a cone so the further away the filter is the larger it has to be. If you are placing your filter right next to the CMOS sensor you could probably get away with the 1.25" filter with these camera. However, I'd probably recommend using the 2" filter, you can then use that with any 2" eyepieces you have then (although not ideal to use a CCD version for visual).

None of these should be bad choices. For the image scale you can always bin using the software you using even with the 183. One advantage of the smaller pixels is the better scale for very short focal lengths if you had any lens's to hand. For the terminology the sensitivity is the proportion of photons that hit a pixel will be turned into a signal. The higher the better but isn't too much to get hung up on. The Full well depth is how much data a pixel can hold before it is full (so any further information is then lost) - called saturation. In effect it limits your exposure time but for CMOS you are usually exposing for short periods of time anyway. Bigger well depths when you are imaging objects where the brightness between the brightest parts and the faintest parts are substantial (e.g. the orion nebula). But there are way round this (you take sequences of shorter, mid and long exposures). Read Noise is how much data a pixel would capture even in a perfectly darkened room. It's noice that you can't get rid of and you need to expose long enough to overwhelm this signal. Hence longer exposures are usually better. For colour imaging, especially in light polluted areas, this is less of an issue (usually what you are observing overwhelms this quickly, for narrowband imaging it is much more important). The Celestron focal reducer will be terrible for the larger CCDs, you will get distorted stars. Also these are standard SCTs so this will apply even at their native focal length. However, they are fine for planetary imaging, but might want to consider and external focuser. I don't know much about the reducers for the refractor but would want to check they generate a flat field (so no distortions in the stars). Also it might be worth considering a light pollution filter. Not only will it help you control any residual colour aberration in the ED80 but would also help with London light pollution.

There is a QHY8 colour camera on UKAstrobuyandsell right now for £400. Might be worth a look if you want to consider moving to CCD and this has a similar CCD size to the DSLR.

Because you need some force to stop things moving, which is one of the fundamental laws of physics. Unless they literally crash into each other which, in space, is extremely rare then the object continues moving past the object until the gravity well pulls it back and hence you have an orbit.

The other benefit of longer telescopes is that you are usually getting a larger aperture. Therefore if you are binning to the same resolution as a smaller 80mm refractor then you get the benefit of the extra aperture overall (barring some noise differences from binning). Your field of view will be overall smaller though. For example a C8 edge with reducer or 200mm F4 reflector would give you a similar 1.1" resolution. Ideally you'd want the largest telescope with a short focal length but they are usually quite expensive... So it depends on how much you want to spend!

What defines Jupiter as a planet is that it is the primary gravitational body within that region (it doesn't have to be the only object that crosses that path). The Trojan / Greek asteroids are there because Jupiter is the dominant body (without it they would be scattered all over the place). The same goes for Neptune. Strictly speaking Pluto 'crosses' Neptune's orbit but when they come to be close together Neptune will hardly notice Pluto, whereas Pluto will definitely notice Neptune!

From a terminology perspective the answer to this is no. One aspect of the definition of a planet is that it is the primary gravitational body within its orbital path (summarised). As such you can't have two 'planets' on the same orbital path. Though potentially two dwarf planets. What you are describing really is one of the theories of planetary system formation in that many bodies are formed and they eventually merge to former a few larger bodies/planets (or get ejected from the system). If the question is that whether such a system could form and be stable for hundreds of millions of years then in principle if you have two perfectly circular orbits, a perfect star system, and they are exactly opposite each other in ther orbit then in principle the answer is yes, but the chance of such a system forming is so infinitesimally small that the answer really is no. Lagrangian points need two larger bodies though (e.g. Jupiter / Sun) so needs another body as well. So strictly speaking you can't have planets at lagrangian points as at best they would be dwarf planets (the other larger body would be the planet).

A budget would help. When you talk about buying a mount once, that's great but if you want the best mounts out there for imaging then you are looking in the region of £4k upwards at least. If you are looking at casual imaging once in a while (or solar system only) then you can get away with a lesser mount and then get a short focal length refractor for imaging. You might also want to consider portability if you aren't going to have a permanent set up. If you really want top range mounts (and portability that will image with a C11 edge) then you could look at something like (in no particular order):- Mach1 (used) or Mach2 (new) from Astrophysics M-uno from Avalon instruments GM1000HPS from 10 Micron MyT from Software Bisque Even a TTS Panther Mount if visual / solar system imaging are more your intent (these have potential limitations for deep sky) However there are other portable mounts that will get you reasonably close (Ioptron, Skywatcher, Vixen etc) but generally they sit a bit below those stated above according to the community (*caveat I have not tested every single of these mounts!)

The youtube comments that it is about to blow are all conjecture without any real basis or evidence. There is little historic data on pre-supernova sequences (and indeed could be different dependent on mass of the progenitor). Betelgeuse is already a known variable likely due to pulsations and large dark convection cell spots (like our own stellar spots but much larger). Alternatively it could have recently shed a lot of dusty material that is now in out line of sight (though I've read that the luminosity reduction is the same across all wavelengths and if it was dust then we'd expect wavelengths to be dimmed by different amounts). So it is probably just a case of multiple periodic cycles lining up - it's pulsated to a smaller size and there is a dark convective cell on the visible face to us. To put things into context if the luminosity change was *just* due to a size reduction then a 1 magnitude change would equate to a current radius about 65% of what it was in October (and assuming no temperature change).

It depends on what you are intending to use it for. For Deep sky it allows for a much greater field of view without optical distortions becoming apparent. Most SCT flatteners have more limited fields in this regards because of limitations of their design whereas the Edge's I believe are corrected for full frame (or close to) cameras which requires a lot more glass and hence expense. In addition there are mechanical differences between the two. There is likely also the impact of what the market will pay for an off the shelf design factor and in the UK I think there is a bit of one distributor syndrome that is coming into play. If you are a deepsky imager with a large CCD then the Edge wins. For visual, photometry, spectroscopy or solar system imaging the Edge only really has the mechanical benefits (e.g. mirror lock etc).

I would suggest asking local scrap merchants to see if anything comes there way. It is unlikely to be able to be sold and my suspicion is that it may have been picked up for the metal value by ad hoc thieves (and completely ignoring the value of the telescope itself).

It depends on what you are imaging and what you are imaging with. If you are using a colour camera and want a 'fast' refractor and/or wish to image broadband objects then you would want a triplet A fast doublet refractor would not bring enough of the wavelength range to focus at the same point and hence stars would bloat badly. On the other hand a slow refractor would have less of this issue as the best focus range is much larger and it is much better at focussing a longer range of wavelengths - you can offset the decrease f ratio by binning the camera. If you want to solely focus on narrowband objects then strictly speaking (and assuming all optics are made equally) then a doublet should be better. As you are working at narrowband then all of that narrow range would be focussed equally so bloat can be avoided. You would have to focus each time you changed narrowband range though (e.g. SII, HII, OIII etc). The doublet would then be better as it should cool down faster and be more temperature stable (less glass) and have less surfaces so should result in less scatter so stars should be smaller and light throughput should be higher. In principle it should also be easier to manage as it would be lighter as well. As for the size of stars that is probably a combination of optics, aperture, seeing and image processing. With no seeing (i.e. in space) then the size of a star is limited by the aperture (assuming no central obstruction) - in a perfect world a larger aperture would result in a smaller star. However, seeing, poor focus (perhaps from temperature changes) optical imperfections and so forth generally scatter enough light so they bloat to some extent. Many then use software tools to shrink down the stars. In the UK I would guess most stars are fatter then other images (from say Chile) because of seeing assuming both parties have equally understanding of imaging (e.g. can find the point of best focus).

The Baader website only shows the OIII ultra narrowband as out of stock at the moment. The long lead times in the UK are probably because they don't hold them in stock and order them in specifically.

As you can rotate the focuser compared to the optical tube you could do this and re-orientate the camera. If the pattern stays the same then it is likely something to do with the optical tube. If the pattern rotates then it is probably something to do with the focuser. However, it does look like pinched optics to me. These things happen and FLO is good at helping sort the issue.

I've heard that for RCs a truss design makes it easier to centre the secondary because you can look directly at it whereas for a solid tube design this isn't possible (except with Superman vision).

You don't really need a V filter for exoplanet work as most science is done in flux rather than magnitudes these days. Photometric filters are more important for binary eclipse work because the varying depths of the eclipses (or variation) can be an indication of the temperatures of the different components. For exoplanets you can just go with a luminosity filter as there is no emission from planet; the transit depth is the same regardless of the wavelength (except maybe far IR if it is a jovian sized object but then you'd need to be observing from Hawaii to get above most of the atmosphere. Depths of exoplanets are quite small so you want to maximise flux to increase the S/N. Having GPS corrected signal is highly important though if it is for true science work so the time can be converted to heliocentric julian date (HJD). With accurate times people look for transit time variations (TTVs); basically the start of the eclipse changes, which can indicate the presence of other planets in the system. There are plenty of WASP objects to start with though (and these were found using camera lenses).

OK so you probably wouldn't be able to get a focal length reduction without potentially running into focussing issues. However, your pixel scale should be fine at 650mm focal length with that camera without the need to bin (but you can if you want). One thing to note with the 1600 class cameras is that you get microlens artefacts because of how the CMOS is made (no AR coating apparently). You might want to check some images of bright stars where this is obvious so you can determine whether you are happy with this effect. An alternative would be the ASI183 which is a sony based camera and my understanding is that you don't get the same effect. Disadvantage is that it is a smaller chip (although you can mitigate that somewhat by using a camera lens for very widefield views) and the smaller pixel scale which introduces greater challenges (though they are slightly cheaper). Advantage of either of the CMOS is that they can have high frame rates so planetary imaging is possible with these too. It can also depend on what you want to image. If you prefer large nebulae (e.g. M42) then the large chip would help. If you prefer galaxies / planetary nebulae / planets then the larger chip isn't really necessary.

Are you intending to use the 250PX for imaging based on your profile or is there something else you intend to use?

"Chewed their ear off" might be a better way of putting it...🤣 , we did talk about the new 'scope briefly but didn't get chance to talk to anyone in detail about the specs; and I missed the chance to thank Ian for some assistance a month or so back. Hence was interested in the specs but couldn't quite recall the aperture (got the 2 and the 4 mixed up). I think it was mentioned that it was going to the Pixelastro site and you were going to use it as a tester for equipment but didn't realise the data would be made available? A large part of the design is in the mechanicals. A great set of lens can still be limited by this. It's good to hear that testers are involved - that would stand them above the other similar competitors. I do like the handle though - it makes moving telescopes that much easier.

Ah OK, so I had the size wrong in my mind. So this would be similar (same optics?) as the Orion EON ED-X2 telescopes or the Omegon versions (I think Primaluce also did a version). Naturally though it depends on the mechanicals. I wonder whether they are all optically tested as well given the FLO relationship. Should be a good replacement for the FLT98 that are no longer made? As for the rest, come on spill the beans! Not all of us got a chance to speak to everyone! I need to prepare the finances...

The mounts they were referring to were the RainbowAstro (e.g. RST135 mounts). Looked impressive in the amount of weight they can carry for the portability. The refractors appeared to a be new (or not something that I recognise but the name escapes me). There was a 102mm example of display. Didn't get chance to check out the specs in detail. It will be interesting to see where they are pitched against something like the Esprit's.

If you have MaximDL then potentially you have the software from the Curdridge Observatory that can run 2/3 set ups but you need to have a different computer for each system I believe:- http://astro.neutral.org/software/multiple-camera-sync-maxim.html

Had a good day. Was busier in the morning but by the afternoon had gotten a lot quieter. Yes the RVO hall was very quiet. I think they would have been better off sharing room with others to get a higher footfall. Liked to see some the scopes in person to give an idea of the size. Spent many hours talking to those at ICAstronomy and Pixelskies remote hosting booth. I can't thank David / Colin enough for happily letting me talk about everything and anything. Didn't quite get a chance to talk to others at the IKI / FLO displays but then they were always busy. I was hoping to pick up a red/spacecat as a portable 'take anywhere' scope from them so in some ways the credit card came back more relieved. Did pick up an ASI183MM Pro to match it with though (sorry but I do like to support multiple UK businesses so do spread expenditure around a bit!).

A bit late to the conversation but Prism is worth looking at too because it is all in one and there is no need to use multiple software packages. Used by professional observatories too