Cosmic Geoff

The Nexstar 6/8 mount requires a Vixen (a.k.a 43mm) rail, same as that on the C5. It's now a universal pattern used for mounting almost all smaller scopes. If that is not what is attached to the side of your C8, you will have to source another bar. A guy in the same position of you, who de-forked his old C8, and posted about it on this forum, managed to source a bar kit that screwed straight on. An alternative is to buy a length of Vixen bar and use the other bar as a pattern to drill holes in it (hopefully the old bar is not too wide.) My own C8 is attached to its bar by 3 screws - one at front and two at back. If you end up going down a different route for the mount, larger scopes mount with a wider bar called the 'Losmandy' about 70mm wide, and some C8 OTAs are now offered with this bar as an option, which fits various of the heavier duty mounts.

A small point, but the Goto has a function for finding objects by RA and Dec (after alignment is done). The SE mount legs are telescopic, but you have probably already seen them under your C5.

I don't know. Maybe the weight of the older OTAs is on record somewhere. It's only fair to point out that the modern C8 is at the upper end of what the modern SE8 mount will support. (The same mount is used for the modern C6). But if you went for the Evolution (also used on C9.25) or a AVX or EQ-5 you should be OK.

Could be a good deal if you trust the seller. The implied value of a new SE mount and tripod is about twice that. Hard to price these mounts as they rarely come up. For regular items in good condition, over here we reckon around 66% of the new price as being a fair asking price for used astro items.

I had a bit of a battle to produce this image. First, the conditions were awful, with a ground mist and thin cloud moving around. The exposures were much longer than normal. Second, when I opened the video in Registax 6 it remained determinedly monochrome. (The Mars images taken a little later were fine.) After some fiddling with various programs the image below emerged. Far better than I expected, and I think I see the GRS just at the extreme left. Taken with CPC800 & ASI462MC + ADC, 5000 frame video, processed in Autostakkert & Registax.

The trick is to learn a small number of alignment stars that work for you, for that season. You just need two on any given night. The Celestron Nexstar system is actually easier to use than the rival Synscan system, which has a habit of ignoring stars you can see in the sky and offering others one has never heard of... Select "2 star auto align". Scroll through the list till you find your first star, picking one you a) know and b) is in a suitable position. It is immaterial where it is in the list (they are probably in alphabetical order.) Aim the telescope at the first star and do the stuff (see handbook). Select the second star, picking one that is some distance from the other, that a) you know what it is, and b) you can see it is in a suitable position. Its position on the list is immaterial. Press Enter and the scope will slew to the vicinity of the second star. Do the stuff (see handbook). Job done. Don't concern yourself with plate-solving unless your scope is already set up for imaging. For imagers, it is a handy method of fine-tuning aim at a desired object.

What are your expectations of what you will see, and how will you mount the OTA? The Startravel is a widefield achromat, and useful for looking at large star clusters and the like. It's quite well made, with metal rather than plastic parts. Its performance on planets (of prime interest to many beginners) is unimpressive. I actually use mine for imaging, not for looking through.

You may want to check this elsewhere, but this may be the same issue as with the Sky-watcher Synscan handsets, where the newer ones have a USB port, but if you want to use the USB port for firmware updates and such, you still need a serial chip driver loaded on your laptop or PC. If your Starsense software dates from 2016, yes, you really ought to update it, as IIRC this fixes various issues.

You mention you have a cheap Celestron eyepiece set. What is in it and why do you not use it? At f10 the C8 is quite tolerant of eyepieces, and a Celestron Omni Plossl eyepiece will work well. With a decent mount you can use higher powers with a C8 and a 8mm eyepiece will be quite usable in good seeing conditions. I would say don't buy a focal reducer. They are not cheap and are really intended for imaging. (I have found that the Celestron f6.3 focal reducer works great with the C8 for imaging certain objects, but you don't express any interest in imaging). Your first step should be to sort out the eyepiece question. You really want a set of various focal lengths (but you already have a set?) If you are looking to get an even wider field than the 32mm eyepiece gives, maybe you should just buy a widefield scope. The alternative, if you insist, is to buy a 2" visual back, 2" diagonal, and one or more low-power 2" eyepieces, and the cost of these items adds up. I have a further suggestion which you probably won't like. 🙂 Retire the original mount and buy the C8 the modern GoTo mount that it deserves. It would go on any mount such as the AVX or the EQ-5 Synscan, but the Celestron SE or Evolution mounts commonly bundled with a C8 nowadays occasionally come up for sale.

I'd agree that the experience of a direct view can be great, and the screen view limited. But what if you can't see anything at all through the eyepiece? There are plenty of objects I have seen only with camera assistance, e.g. M1, M33, the spiral arms of sundry galaxies, and various planetary nebulae.

It depends what your expectations are. The experiences are quite different. Visually, you can have whatever magnification and field of view you like, by swapping eyepieces, but with a camera system you are stuck with the field defined by the focal length of the objective and the size of the camera chip. If you want a wide field of view, comparative to that delivered by a 32mm eyepiece, you will need either a DSLR or an expensive astro camera. Inexpensive cameras and webcams tend to have small chips. Even the ASI224MC, which isn't sold at pocket money prices, gives a field of view comparable to a 5mm eyepiece. And if you have a basic type of mount, just how are you going to get the object you want to view into that small FOV? As noted in posts above, the camera system can give you a lot more detail, but it's not an instant view, being delayed by the exposure or stacking time, or the need to process the recording next day (in the case of planetary imaging). It will also be more work to set up the equipment and make it behave.

With a given telescope and camera, the width of the field is fixed unless you use a Barlow lens to zoom in, or crop the field digitally. With a 400mm fl scope and the SPC900NC (without its lens) the field ought to be moon-sized. The focal length will be too short, and the telescope too small, to get a good image of a planet, though you should be able to distinguish Saturn's rings. You should also read up on the process of 'lucky imaging' and taking & processing a video. I suggest you try imaging some star clusters, galaxies and nebulae and see what you get. For planets you really need a bigger scope with a longer focal length (££££), and a modern planetary camera (at minimum an ASI120MC-S, and preferably an ASI462MC) -£££ - would help.

I wanted to repeat the 'Pluto discovery' images I took a year or two back, now with the advantage of 'Platesolve & resync' in Sharpcap 4 and without failed attempts. It was not as straightforward as I hoped. The preferred mount proved not tall enough to get Pluto in field above a fence and nearby building, so I had to use the SLT mount on its wooden tripod. So I got some images and found on processing them that Pluto was out of field. Pluto is of course totally invisible visually with most amateur telescopes so I was aiming blind. "TheSkyLive" has a good finder chart but uses the J2000 co-ordinates. Eventually figured that I had to enter the Jnow RA & Dec (from Stellarium, etc) into the GoTo, and not use 'Pluto' (J2000 co-ordinates), as there is enough difference between the two to put Pluto out of field on a small-chip camera. As it eventually proved, using the Jnow position and a 1-star align on Altair (without the plate-solve & re-sync) was enough to get Pluto on the camera chip. Here is the last image taken, on 21 Aug 2022, at about 22:20 UT, with a 102mm f5 achro and ASI224MC camera, stacked exposure 10x20 secs. Image processed in GIMP, and Pluto located by plate-solving the saved image with Platesolve2 I have an earlier image where Pluto is just about detectable in a different position.

I have the basic Neximage 'Solar System Imager.' I have not tried using it with Windows 10 as I replaced it with an ASI120MC within weeks. On reading your post I plugged the Neximage into my Win10 imaging laptop and fired up Sharpcap4. I did not download any drivers for it. No complaints from the software and I got a camera window. The unfocused camera clearly responds to light so it ought to image. BTW the ASI120MC is a very adequate planetary camera but the ASI224MC is faster and more versatile and the ASI462 has smaller pixels and high infrared sensitivity. I have not tried using a DSLR on planets but you might find it a pain to use compared with a dedicated planetary camera. And check the pixel size...

There is no 'better'. Whether you go for a reflector or refractor is ultimately a matter of personal prejudice. There are are other factors, of course, which you can research online. Astronomy unfortunately can be an expensive hobby, but some scope designs can be better value for money than others, depending on what aspect of scope performance you actually want. What do you want to see, and how much money do you want to spend? I assume the Hubble Space telescope is out of your budget. 😀

I had another go at Pluto on the 21st, this time entering the Jnow co-ordinates into 'GoTo RA/Dec'. I had only used a 1-star align, but this got it in field (I could recognise the star pattern now), and the 'Platesolve & re-sync' from Sharpcap4 was only a minor adjustment. Platesolving the images next morning confirmed that I had 'found' the minor planet.

You just need to press ESC to get out of the setup menus. It's bad design, not a fault.

I have been scratching my head trying to figure out why I was having so much trouble trying to make a 'discovery' image of Pluto. I would use the SLT GoTo and plate-solve to find the area, and then on analysing the images find out that where it was pointing did not match the "TheSKyLive" finder chart at all. Only one image, with a radical offset to the west, got the planet (confirmed by plate-solving the processed image with Platesolver2.) I noticed that "TheSkyLive" is using J2000 co-ordinates. It occurred to me to check the Jnow co-ordinates for Pluto, which is easily done. Running the cursor across the "TheSkyLive" finder chart, one can see that it makes a BIG difference, and puts the minor planet much further west (in terms of the 30x20 minute of arc field of the camera chip). So why doesn't the platesolve sort it? Maybe because I am using an old Nexstar* handset (the Nexstar+ one failed). I suspect the old handset uses J2000, even if the up-to-date ones don't. If you are wondering why I am using the SLT mount and an old handset, it's because it's the only mount to hand that will lift the 102mm scope high enough to clear a fence and building.

That'll do (as they say in Yorkshire). Capture a .ser video In (IIRC) Raw8, and that will save you the bother of debayering it afterwards. It probably will not matter if the polar alignment is a bit off, if you are using a GoTO mount that has been star aligned. If you are not, expect some drift during a session. More detailed procedures should be findable online.

Some images taken with my CPC800 and ASI462MC on early morning of 12th Aug. Also used ADC. I also tried an x2 Barlow but this did not add anything to the detail captured on this occasion. Saturn (at opposition on 14 Aug) can now be found in late evening, but I preferred to set up around 2am to get all three planets. I am quite pleased with the Mars images which show some surface detail in visible and IR despite the small apparent size (8.7") I am getting better images with this scope after I tweaked the collimation. Saturn's rings look quite bright - I understand this is a near-opposition effect.

Plenty of advice on this forum. Choice of eyepieces is a regular topic. But if you got the original kit eyepieces with the outfit, the 9 or 10mm one is unlikely to be much good. If you are buying with a budget, Plossl eyepieces will be adequate with a scope of this type.

Is the Essex climate especially dew-prone? I use a dew-shield on my scope and leave the laptop next to the scope in the open. I rarely if ever have a problem. I don't need to write anything down while planetary imaging, as the laptop saves all necessary details. I actually use a wire mesh table (part of a re-purposed mini green house) to support the laptop and accessory box.

I suspect that in changing to the Bob's Knobs you have completely de-collimated the SCT. If all it needs now is collimation, this is a task that most users should be able to do themselves after reading up on how to do it. The only equipment you need is a clear night and a sightline to Polaris. You should find this considerably less tiresome than packing the scope up, paying a wad of money and waiting weeks. I managed to collimate both my SCTs.

Check the Internet. Large numbers of them have been sold, and used. In essence, the C8 SE is a fine outfit if you want a compact portable 8" scope, for visual use. If you intend to try imaging anything with it, you want to get one of the variants which have the same OTA on a more substantial mount (as Sth Bohemia suggests).

With the ST102 a 25mm 1.25" eyepiece gives x20 magnification. The exit pupil will be 5mm. I would question whether lower magnifications possible with a 2 dia eyepiece would deliver much benefit without making the exit pupil too large and wasting light.