Cosmic Geoff

I found that my binoviewer worked fine with the smooth-sided and short bodyed eyepieces supplied, once I got the knack of using it. I bought another 20mm Plossl eyepiece to make a pair to increase the magnification, unfortunately it was almost impossible to synchronise the images, possibly because one of the otherwise identical eyepieces had an undercut and the other did not.

If you want to look at "planets and easy to find objects" you can dispense with a GoTo. GoTo comes into its own for "hard to find objects" A manual alt-azimuth mount will be quicker and simpler to set up, but if you are determined to have a GoTo outfit, I recommend you get one with the Celestron Nexstar system, as it is easier to learn and use than the Sky-watcher Synscan system (I have used both.) I got a result with the Nexstar the first time I took it outdoors. And since you are not interested in astrophotography, you can avoid equatorial mounts, which are more troublesome to set up.

I suggest that you match your ambitions to your equipment and budget. Neither the achromats you mention nor your alt-az mount are suitable for "proper" deep space imaging. For the latter you need to spend a lot of money for an APO scope and a heavy imaging equatorial GoTo mount. However if you tailor your ambition to dabbling in some EVAA imaging, you can use a Startravel 102mm and the Nexstar alt-az mount. I have used a Startravel 102mm + a Nexstar SLT mount (albeit on a more rigid permanent tripod) + a ASI224MC camera to take many pleasing shots of galaxies, star clusters, planetary nebulae, comets etc. An exposure of a few seconds suffices. The images can be live-stacked with suitable software. If you search in the EVAA reports section, you may find some of my results.

Re. diagonals, I have read comparative surveys which indicate that even the cheap ones will be optically flat enough, and the expensive ones merely have better reflectivity, or longer lasting coatings, or better build quality (or all three). Since we are discussing a Startravel achromat, I would expect the view to the the same regardless of what star diagonal is fitted. Apparently prism diagonals are not recommended for short focus instruments below f6 or so (i.e. refractors) as they introduce distortion, but are fine for long focus refractors, Maksutovs and SCTs. And they have no coatings to deteriorate.

I have an OIII filter which makes planetary nebulae and the Orion nebula easier to see, if rather green. 🙂 I tried imaging a planetary nebula with it and it lengthend the exposure time a lot and the result - a monochromatic blob - was uninspiring. BTW the Startravel 102 is quite good for trying some basic imaging and electronically assisted observing - I have imaged all sorts of stuff with mine + an ASI224MC camera.

Using a moon filter is purely a matter of personal choice. I have never bothered with one. Light pollution filters are a more complex subject. The older design of light pollution filters were designed to counter yellow sodium street lighting, and are useless against white LEDs. There are filters that are claimed to have a slight benefit vs LEDs, but they cost as much as your scope did, if not more. Then there are narrowband filters designed for imaging nebulae, which work for that purpose even in the presence of light pollution. In short, don't bother with either. Plossls are inexpensive eyepieces and work fairly well in most scopes, but there are reasons why some observers prefer more exotic designs. Some people consider that using a coloured filter with scopes like the Startravel ST102 makes the chromatic aberration less evident.

What is the exposure time? And are you using the full pixels? Both may have an effect on the frame rate. For instance, if the exposure is 100ms, you can't get more than 10 frames/sec whatever you do. IIRC, there is some issue with the ASI120MC (older USB2 version) that gave trouble under some circumstances.

If it is the 102mm f5 Startravel, it is not the ideal scope for viewing planets, but if you replace the terrestrial 45 deg diagonal (if supplied) with a 90 deg star diagonal, fit the x2 Barlow that most likely came with it, and add a 10mm eyepiece (not the one that came with it but a better replacement) then you will be getting the best you can out of it.

It is hard to match the versatility of visual optics, with high and low power eyepieces, while using a fixed sensor. A large sensor with many pixels would be required, which would be expensive. An ASI224MC for example has a sensor of 1304x976 pixels each of 3.75 microns, and the chip is only a few mm across, giving it a field of view similar to a 5mm eyepiece. A DSLR has a physically bigger sensor, but won't match the resolving power of a high-power eyepiece. These cameras are capable of recording things that can't be seen in a visual view, but that does not mean they will do well at mimicing a visual view onscreen.

You can use a dedicated camera like the ZWO 120MC-S, but even then the live image is typically rather blurry and jitters about. A much better image is available if you take a video recording on a laptop, and post-process it (details are available online) but then you are on the slippery slope of imaging rather than visual observing. Live stacking in EVAA mode works well on some objects e.g. star clusters, in partcular brightening objects that look faint visually (again probably requires a laptop). If a live unedited view is required there is really no substitute for looking through the eyepiece.

There are hundreds of ex-business refurbished laptops on Ebay available from dealers, if you do not wish to buy new. You should be able to find one of a suitable spec, provided it is in business use and not just aspirational. I just bought one cheaply with astro in mind - it is several years old but has USB3 ports, 8GB of RAM, i5 processor and 256 GB SSD. You may not get a SSD much bigger than this even in a new laptop - some have 250GB. The ten year old laptop I was using has a 500 GB hard drive, but these are no longer a standard fitment. According to the manual, my new purchase has connections inside for a hard drive as well as the SSD, but I have no plans to try fitting one. Instead, I will just move the files off to a desktop more often. Adding a hard drive would increase the power drain and reduce the battery endurance out by the telescope.

Here is a comparison of the N8 and N8i which you may find helpful. https://www.cloudynights.com/articles/cat/user-reviews/telescopes/schmidt-cassegrains-scts/celestron-nexstar-8i-vs-nexstar-8-celestron’s-newest-8”-go-to-capable-sct-takes-on-its-older-sibling-r641 It appears that the N8i was more desirable. Neither had handsets that were upgradeable over the Internet. (Later versions of handset are upgradeable).

Have you looked into replacing the handset? This would solve your problem for far less cost than replacing the entire mount. This handset should work with your mount: https://nexstarsite.com/download/manuals/NexStarHandControlVersion4UsersGuide.pdf This is the latest handset: https://nexstarsite.com/download/manuals/NexStarHandControlVersion4UsersGuide.pdf It doesn't say that it works with your 8i, but it doesn't either say that it won't. And I have both types and they both work with my C8 SE. There is no need to replace the mount if you were happy with it for now - you just need to fix the handset. And did you try re-seating the handset cable as suggested? You didn't say...🙂 Your outfit looks fixable. Look on the bright side. 🙂 Many owners of vintage SCTs have had to bin the obsolete or broken mount and re-mount the OTA. And have you checked the price of a new C8 OTA?

I second Knightly2112's advice. My C8 SE acted up shortly after I bought it, until I gave the handset cable a firm push at the mount end. If it is really dead, check what nexstarsite.com has to say about the compatibility of the handsets and mounts. (I found that in practice my mount would work with three different models of handset). As for fitting the OTA on an AVX, that would be a good idea if you want to do deep space imaging (not easy), but if you want to stick with visual and planetary imaging, an alt-azimuth mount would be less bother. If you have to change the dovetail bar, that should not be a big deal.

An 8" with GoTo will pull a lot of objects out of the murk in those conditions. And if you visit the sticks you may be amazed at what the 8" GoTo will find out there that can't be seen in the city.

I bought a C8 SE because it had a GoTo mount. But each to their own...🙂 If you just want to look at Jupiter you can simplify things by using the Solar System Align with Jupiter as the target aligning object.

Assuming that one telescope can do everything is a fundamental error. Even on the visual side,one has to choose whether one wants a portable or semi-portable instrument, GoTo or manual, and on the imaging side, what kind of object you want to image. Hardware for imaging planets will be different from that for imaging deep space objects. And a setup that can image the whole of M31 or a large nebula won't do for imaging a small distant galaxy or a small planetary nebula. You should assume that unless you want to concentrate on one particular aspect of amateur astronomy, you will eventually be owning more than one telescope and camera.

I have one of these and it is best suited for two things: as a visual widefield scope for comet hunting, star clusters etc As an instrument for EVAA (electronically assisted astronomy) and basic dabbling with imaging. If you want "good quality images" you should look at getting an ED or APO refractor. It is not suited for anything to do with planets - it has too much chromatic aberration etc.

I remember it had a 4mm eyepiece and the vibration was annoying with that eyepiece in use (x175). If you pushed the C90 to its maximum usable magnification I imagine the result would be almost as bad.

This is the scope and mount in my signature pic. I am surprised that anyone would actually want one. The objective in mine was poor and the mount was rathewr wobbly.

Since you appear to have the latest handset, there should not be a problem. ( Generally speaking, you may or may not be able to skip the intermediate upgrades, and the latest version may not install on old hardware. ) Also note there is no "must" about firmware upgrades, unless you have an issue and the small print for the upgrade says that it will fix it. Most household appliances now contain firmware. When did you last upgrade any of them? 🙂

Check out the base of the mount and the flat-topped Skywatcher tripod available from FLO. I understand that one or two people have fitted the SLT mount head onto this tripod with a small amount of DIY.

The heaviest scope you cam put on a SLT mount is one like the 127Mak mentioned above, and that's for visual use. I have done EVAA imaging with a smaller scope on a SLT mount but I had to be careful not to touch it or move a muscle while it was operating. For a 150mm OTA of any description you really want a mount in the EQ3-2 class for visual or HEQ5 or EQ6 for serious imaging. Yes they cost a lot but that's just how it is. You do not need aperture for imaging, just expensive kit.

While the printed instructions could be better drafted, what they actually mean is : enter the required parameters, get the desired object somewhere in the eyepiece field, press ENTER, centre the object in the eyepiece field, press ALIGN. Note that a CPC800 has negligible backlash, apparently because of spring-loaded worms etc, but a SE mount has quite a lot. If the slew speed is accidentally set to a low rate, nothing will appear to be happening if you press the slew buttons. The slew speed should initially default to a high rate, and then change to a lower rate for the final aligning on ENTER being pressed. If you think Nexstar is hard to use, try getting a Skywatcher Synscan to work. 🙁 As mentioned above, there is a big change of focus between near terrestrial objects, and astro objects.

The 6SE and 8SE actually have the same mount, so the 8SE has a larger aperture, is more expensive, and is putting more load on a mount which is better suited to the smaller telescope. (The 8SE is clearly much more popular than the 6SE.) Note that these setups are intended for visual use only. Even the 8SE can be picked up as a complete assembly of OTA/mount/tripod and carried through a standard doorway. As for the focal reducer, these are intended for imaging, and if you think you need one, maybe you should have bought a wider field scope in the first place. 🙂 A visual alternative is to fit the lowest power/widest field eyepiece possible, maybe with a 2" visual back and diagonal. With a 25mm eyepiece, the C8 SE just gets the full moon in field. Note that if you are interested in the 6" Celestron SCT, it actually comes bundled with a wide range of mounts from the wobbly (SLT), the SE, through to the Evolution (better than the SE) and the AVX (for imagers) Some of the prices are now rather high, but if you are shopping for a second-hand SCT there are some bargains to be had. Mine cost about half the price of a new one, and just as good, and even better bargains are possible. One forum menber recently paid £650 for a 10" Meade LX200 that would have cost thousands of pounds when new.