Cosmic Geoff

Indeed. I suggest you look up the recommendations for lifting heavy objects, and see how that fits with the weights of the above-mentioned objects and whether you will be lifting them from the ground or just from e.g. a bench to the tripod. Personally I take great care to avoid lifting my CPC800 (20KG) off the ground and endeavor to keep my back straight when lifting it. If I have to hold something up at arm's length, then 10 Kg (the weight of an 8" Newt) is plenty. I move the CPC800 OTA/fork assy around on a trolley. One can buy special trolleys that take a tripod and associated kit.

If a part is missing, the likelihood of finding a replacement is probably nil, unless you can acquire another scrap C6. Or have a part made, e,g by 3d printing.

These might be worth a significant amount of money, and inexpert attempts to dismantle or clean them is likely to reduce their value.

It occurs to me that Apple's new Vision Pro smart glasses (see PC Pro magazine, April 2024 issue 355) would do what you want. You'd just need to produce your own software, as before. They cost $3499 though. If you want to produce your own telescope-like device, you would need a LCD screen (120mm in diameter???) and an achromatic lens of about a quarter of the focal length of the ST120 objective (ie about 150mm) to project an image of the screen into the eyepiece plane. Or to simplify things, just have an eyepiece that focuses directly onto a smartphone screen. Note that a lot of eyepieces won't do this so you might have to make or modify one. Also there are commercially available digital setting circles which will give a readout of where in the sky the attached telescope is pointing - see Nexus DSC.

I think you should have a good look at what a 12" scope looks like when mounted on your preferred mount. I had a 8" f5 Newtonian on an EQ-5 and was not pleased to find that with the tripod legs fully extended the eyepiece was about 7 feet off the ground with the scope aimed near the zenith.

Don't back the film with plexiglass, glass or clear acrylic. This is not necessary, and unless the material is of optical quality, it will degrade the image. It won't do any harm to paint the opaque part of the cap, but I doubt this is necessary.

Not necessarily an inherent feature of SCT scopes. The manufacturing quality seems to have been variable in the past. I have found them sensitive to slight mis-collimation. Some people claim the EDGE HD models perform better visually. Also ED vs SCT is not a level comparison, as (unless you can afford an 11" ED or APO) the ED scopes will have a smaller aperture and hence less vulnerable to atmospheric churn. In theory, (asides from the effect of any central obstruction) you might get the same effect by stopping down the larger scope.

I don't see why you would need two from this list. Just buy one of them. I would need some convincing that the 120ED would be much of an advance on the 127mm Mak.

I would have thought that the GPS does not need to be set up. I have GPS built into one of my Celestron mounts and it just works if one turns the mount on, selects an alignment mode and waits a bit.

Cone error is an error pertaining to German equatorial mounts. If you are not using a German equatorial, this suggests you have a problem with the software. In any case I do not see what this has to do with the GPS dongle.

Your options for a Alt-Az GoTo fall into two groups, those barely adequate for your 4.1Kg scope (and don't forget the added weight of finder and eyepiece) and those like the Az-EQ5 with a much greater capacity and a much higher price tag. One of our astro club menbers had the ST120 on an Ioptron alt-az GoTo, IIRC.

The plug connection between cable and mount is a common source of trouble. Touching it can cause the connection to momentarily break, causing the GoTo setting to fail. You can fettle the split center pin or use a cable tie etc to stabilise the cable. There is no 'best battery' - any power source that supplies a clean 12 to 14 volts and adequate current will suffice.

A decent field of view for what? Potential deep-space imaging targets vary hugely in size, from the Orion ring (very large) to planetary nebulae (often very small). Any given rig will only cover a limited range of targets to advantage. A telescope like the one you cite will cover a range of targets but you may struggle with the very large, or the very small. With the Seestar S50, for instance, some nebulae fit nicely, but some are too big for it, and all but the nearest and brightest galaxies come out looking rather small. I would suggest that both your quoted mounts are totally inadequate for the intended purpose. I suggest you look at the EQ-5 Synscan as a minimum. A lot of imagers who presumably know what they are doing use an Eq-6. For long exposure runs you would want an equatorial mount to avoid field rotation.

The Powerseeker 127 does not have a good reputation, because of its 'Bird-Jones' optical design, which compromises optical performance in favour of compactness. If you can't source a cheap used tripod & mount for it, it might be better to cut your losses and buy something else. Astronomy is not a cheap hobby. 🙁

I can't say I have managed to capture the Encke division. It's extremely narrow (about 325 miles) compared with the overall size of the ring system. (The diameter of Saturn is about 74,000 miles, and the diameter of the ring system about 170,000 miles.) The Edge versions are allegedly finished to a higher standard.

Depends on how these scopes of yours are mounted. If the C11 is not permanently mounted on the EQ6, I foresee a certain reluctance to heave these heavy items outdoors, erect and align them for a session interrupted by cloud etc. If it is permanently available, I do not see any pressing need for yet another scope. Have you seen and handled a C11? You might conclude that mounting it up without assistance would be no fun. I have retained my C8 SE + Starsense as a lighter weight and quick to deploy alternative to my CPC800 which is much heavier and has to be assembled before use. BTW I imaged E & F in the Trapezium with the CPC800 so the C11 should do it too.

I have a slightly different take on this as I have a EQ-5 Synscan mount permanently set up on a pillar. The setting circles: Purely ornamental. Total waste of time. ignore them. Mechanical polar align: get Polaris near the middle of the field of view in the polarscope. Scope horizontal. (I can't get my head around the instructions for aiming more accurately). Check that the finder (a red dot) is pointing close to Polaris. Electronic alignment (or re-align): Start with the scope in the start (or park) position with scope above mount pointing to pole, and counterweight down, to North. Follow the handset instructions for 2-star align, it should slew to near the first alignment star, centre with red dot finder, then scope. Repeat for second star. When done, if you have recent software, you should get a prompt to fine tune the mechanical adjustment (probably not easy to follow). At end of session, command the mount to Park, and remove the power. At beginning of next session, command the mount to start from Park position. No more aligning! If perfectly set up, the GoTo performance of the mount should be quite good, but in practice I found the all-sky GoTo performance of mine to be awful, and I rely on Plate-Solve and resync in Sharpcap to find anything. You query what is a red-dot finder? It projects a red dot (or circle) against the night sky. If you don't have a finder (either red-dot or optical) you will find aligning the mount to be extremely difficult.

I have a 8-24 mm BST Starguider zoom eyepiece, which was very inexpensive. It looks the same as the Celestron zoom, and in fact a number of the more budget 8-24 zoom eyepiece brands look (or looked) the same, as though they all came off the same production line. The Starguider zoom is OK optically, but the action is so stiff that I can't zoom it in situ, but have to take it out of the holder and grip it firmly in both hands to adjust the zoom. You get what you pay for, I guess.

As a Seestar owner/user, I can point out that while having an altazimuth mount should cause field rotation to be apparent on longer exposures, one finds that on some exposures field exposure is indeed apparent, shown by wedge effects at the edges of the frame, but on other exposures the field rotation is not apparent. I don't know why, but I suspect that the Seestar software tries to disguise it for the smartphone images, and the degree of success may depend on sky transparency remaining the same throughout the exposure.

Celestron C9.25 XLT Reviewed: Highly Recommended! (telescopicwatch.com)

Of course it does. A dewshield should be standard equipment on a SCT. Refractors have dewshields.

I would also be nervous about buying a £1000 scope on ebay. The Stargazers Lounge or Astrobuysell would be safer. Or an established dealer in used astro gear.

Certainly not cheap if you buy new. But a used SCT would be half the price of a new one, and if you don't like it you can move it on without much loss. I have bought two used SCTs and (after collimation) I have no complaints about their optical performance.

My personal relevant experience was that visual observing of planets was a somewhat disappointing activity. I could reveal much more detail by imaging. For instance, with my 127mm Mak I'm not sure if I ever saw the Great Red Spot visually, but I managed to image the GRS easily. Re. SCT vs Newtonian, my C8 SE performed rather better on double stars than my 8" Newtonian (now sold). I also found that SCT performance was significantly affected by an almost un-noticeable error of collimation, only revealed by a side-by-side test with two 8" SCTs.

I think that any kind of scope could be used as a planetary scope, with the exception of short-focus achromatic refractors. Aperture is desirable, the more the better, the constraints being budget, portability, and the greater sensitivity of big scopes to poor seeing. If you want to image, the SCT scores on account of having a wide focal range, meaning you can attach a camera, diagonal, filter wheel, or flip mirror or some combination of these, without any danger of being unable to get focus. With a Newtonian you may find that you can't even attach a camera without having to modify the scope, and anything like a flip mirror will be a no-no. Then there is the question of the mount. A big scope, if you require GoTo, requires a heavy expensive mount and , and in large sizes, maybe even a permanent observatory. Here again the SCT scores in the larger sizes as it is shorter and lighter than an equivalent Newtonian and the mount requirement scales accordingly. If you are not going to image, a Dobsonian will offer a big cost saving over a SCT or German equatorial mounted Newtonian