Cosmic Geoff

A 10" reflector should give great views in Bortle 3 skies if working properly. You have two eyepieces. You have not mentioned the mount (I assume it has one?) or the finder scope - you need one and it has to be lined up with the main scope - best done in daylight. You don't need anything else to get going.

The 120 will have a larger image scale, which might or might not translate into slightly more resolution depending on its chromatic aberration, and the quality of seeing, especially nearer the horizon. For the typical EAA target, resolution won't be a priority. If high resolution is really a priority for you, you will need a much bigger aperture, an apochromatic, mirror or catadrioptic scope, and a better mount, in short a whole rabbit hole of expense.

The 120 will give a slightly larger image scale, but a narrower field of view, and be 70% heavier. More to the point, it will not show fainter objects in EAA mode than the 102, if the focal ratio is the same.

I was tempted to suggest the Startravel 102, which is what I use for EAA, but I thought you were intent on buying a much more expensive ED scope. I also use the ASI224MC with it.

What is your budget? What fast focal ratio small telescopes do you have already? What is your budget for a camera or do you have something already?

I see no reason why a 6" CC on an AVX would not work. The AVX should support the weight easily, and even if it is 'jumpy' (why?) the 'lucky imaging' method used for planetary imaging will tolerate a lot of movement. The balance point of the OTA will probably be near the back end but I don't see why this should be a problem either.

Your collimation looks "good enough for galaxies". I have only collimated visually. AFAIR you need to use a high powered eyepiece and put the star (e.g. Polaris) slightly out of focus and see if the diffraction rings look deformed. A very small tweak (e.g. 1/8 turn) on one of the 3 collimating screws on the secondary holder is enough to make a difference, if the collimation is slightly out. If the collimation is very far out, stars can look like a badminton shuttlecock, and a lot of trial and error, and re-aiming the scope may be needed to get it right.

You have to enter the focal length into the settings. Also get a sharp focus and make sure the exposure is long enough to get enough stars. If it won't solve, nudging the telescope to a different position may work. With a 102mm f5 refractor the platesolving should work very well.

I have an EQ-5 garden mounted on a Sky-watcher tri-pier (search for 'pillar mount'). It works well, and being able to start from Park is a huge gain in convenience over having to set up and align each time. No need for an expensive pier foundation or mount-pier adapter. I keep the telescope indoors. There is (or was) a variant of the Sky-watcher tri-pier that takes the EQ-6 mount. I saw the SW CQ350 Pro at the Practical Astronomy show. Looked like a big mount.

Strictly speaking the 6 SE is the telescope + mount. The telescope is a C6. I see no advantage in mounting the C6 on the AZ-GTI rather than the SE mount, which is the same as the 8 SE mount. (The C8 weights abut 6Kg).

Maybe your binoculars are out of collimation - a common problem with binoculars especially if dropped or knocked.

As stated above, the problem is in the power supply. As a safety measure, you could earth the mount, either by wiring it to a stake in damp ground or to the earth of the mains supply. I earthed my multi-satellite dish (powered via mains-powered boxes) to a water pipe, just to be safe when I was messing about with it on the flat roof. If earthing the mount causes a fuse to blow, congratulate yourself on a lucky escape.

very small chance of vibration? That remains to be seen - unless you have an update? I have found that even with paving slabs laid on soil, if one's foot presses on the same slab that a tripod leg is resting on, it causes a disturbance at the eyepiece. I would expect that If you have a telescope and a human at opposite ends of a raised wooden floor, the vibration transmission would be significant. Some DIY observatory builders go to the lengths of isolating a concrete pier foundation from a cast concrete floor slab. But if you are sticking to the plan you originally indicated, of observing remotely from inside the house, the flexing floor should not be a problem.

You can buy a ready-made full aperture filter for the 6 SE, for observing in white light. To observe flares you need a narrowband filter. If you want to use the 6 SE you will need a full aperture energy-reduction filter and a narrowband filter. It might be easier to just buy a solar scope made for the purpose (wallet warning ☹️).

Possibly. If you posted a clear picture of the leg attachment points on the one you have got, we could answer with more confidence. Some DIY might still be required. You could measure up yours and send the seller a question. That might help you decide if it's worth an investment of £35.45.

So the telescope is in fact a 4 and a half inch reflector with a focal length of 900 mm(?). That it was made in Japan is a plus. Options are to have somebody make up a set of three legs, or figure out how to attach it to a ready-made tripod. Both will require some DIY skills. Ideally you should find someone familiar with astro telescopes, who could assemble the telescope and check it over. In theory the scope could be mounted on a different mount using scope rings and a dovetail (q.v.) but I suspect this would be well outside your budget.

Be aware that the EQ-5 Synscan is a popular mount that works well (I have one) wheras some reviews from EQM35 owners are very negative.

A few photos would help us see exactly what you have and give us a clue as to how to mount it on a tripod. The telescope itself may be worth keeping - it might even be quite decent. If you got this for a fiver, the cost of a decent mount for it may come as a nasty shock. Don't buy a cheap and cheerful scope from Amazon - asides from further enriching a billionaire, it is unlikely to be better than what you've got. Tasco 60mm worth checking out? - Classic Telescopes - Cloudy Nights

I would suggest getting a planetary-type camera that will fit your focuser. You can buy alleged planetary cameras on ebay for a few pounds, and if the bug bites, you can upgrade it to a proper one from ZWO, etc. A RA drive for the mount would be very useful. A Barlow lens will be needed for planetary imaging with this scope, but you might have received one already with the kit. A good quality planetary camera will also work for deep-space imaging, and EEVA (q.v.) imaging, subject to the limitations of the small chip and small field of view, and the limitations of your mount. These suggestions could cost as much as the scope and mount did in the first place. You have been warned...

Dewing up occurs primarily because telescope parts radiate heat to the sky, which (when clear) is very cold. Moisture from damp air then condenses on the cold telescope parts. Hence one can suppose that pointing your telescope straight up and leaving it was a bad idea. In the limited time I owned a Newtonian I did not put a dew shield on it, and it never dewed up. My understanding is that a dew shield is not necessary except in extreme cases. There will be a support between the secondary mirror and the sky, which should prevent dewing except in extreme conditions.

Actually a Celestron C8 SCT weighs several Kg less than an 8" Newtonian. I have owned both.

What is your budget?

You should not expect one scope to do everything well. If you want to do " swinging the scope around at being amazed at what I find", find objects with GoTo, and do deep-space astrophotography, you may need up to three scope/mount setups. A 200PDS really needs a HEQ5 Pro Synscan, or an EQ-6 if you intend to image. It would really be easier to start imaging with a small refractor, which is what many deep-sky imagers use. £1000 will not get you far here - you probably need to spend more. I had a 203mm Newt on a manual EQ-5 at one time. I thought the combination was awful, and I had great difficulty in finding anything with it. I changed it for an 8" SCT with GoTo as soon as I could. Opinions may differ, of course.

Can't help much with the red- dot finder. There ought to be enough adjustment range. If there isn't, fiddle with the finder mount in daylight and see if you can shift it or pack under one end. Good news - you only need it once or twice a night, to set up the GoTo. Red-dot alignment needs to be exact enough to get your GoTo alignment stars in the field of the low-power eyepiece - after that it doesn't matter. I use FLO's 'Clear Outside', and the Met Office forecast - sometimes they actually agree. 🙂

I assume the single larger port is for guiding. Nearly all the found options will require some soldering etc for making up leads. If you are not used to connecting up electronic stuff, it would be safer to confine your attention to power sources that will plug into the small round port as-is. You need to confirm that the plug size and polarity match up to the original. Is a small mains-powered PSU an option?