Cosmic Geoff

Legislation and attitudes clearly differ in the UK vs. USA. Helicopters regularly fly over my location and I occassionally see a police helicopter hovering around. Personally I see no need to use these laser pointers on the night sky and any amateur astronomer who gets his/her collar felt by the police is not likely to get much sympathy from me.

As a concrete example, taking a 5000 frame shot of Jupiter with an ASI224MC camera and C8, Sharpcap and a USB2 port laptop results in a 350Mb file recorded in about 20 secs at around 250 frames/sec. That's for a 320x240 px reduced frame. Exposure per frame is about 2ms. Recording a full frame of 1304x976px takes proportionately longer.

You really need to invest in a new(er) laptop, as your old one is clearly inadequate. I recently bought a Dell Vostro 7th gen I5, 8GB memory, 250GB SSD (mainly brand loyalty as I already had an older Vostro). It is decidedly quick and has enough storage for several night's imaging, and it has three USB3 ports, which match the later ZWO cameras with their USB3 ports. Also wifi and Internet port. It cost about £130. No need to buy any hubs or SD cards. The SSD had enough space for a suite of astro programs as well as Win 10. Win 10 needs at least 4GB of RAM (8 Gb preferred).

I have several red dot finders and found them plagued with bad connections eg with the brightness control. One would not work from new till I packed the battery with a bit of foil. No battery problems as such.

If the 130/900 is any good, the 127mm Mak will not be an advance for double stars. That said, the 127Mak is a fine instrument that will work well on double stars, but you need good eyepieces, not the tat supplied as starter eyepieces. I would suggest you re-mount the Newtonian anyway so you are encouraged to use it more.

Your primary interest seems to be astrophotography. You should therefore buy and read the book "Making Every Photon Count", by Steve Richards, (available from forum sponsor FLO), as this will put you on the right track for deep space imaging and save us from repeating its contents here, and you will avoid expensive purchasing mistakes. As a general comment, deep space imaging is best done with a heavy GoTO mount and a small refractor telescope. At the entry level, a C8 is not suited for deep space imaging , but is very suitable for planetary imaging, with a planetary imaging astro video camera, on a modern mount. I would suggest you think in terms of all-new kit for the deep space imaging. The C8 could be de-forked and placed on a modern GoTo mount (e.g. the AVX) without too much trouble, giving you an instrument suited for visual use, and planetary imaging. The C5 SE would be a good (if somewhat expensive) starter outfit for your son, well suited for visual use, and some planetary imaging. Attaching your existing cameras to a small refractor (or the C8) should not be a problem - you just need to buy the right T-adaptors. A cautionary note here - I bought a Canon 300D for a trifling sum to look into using it on my telescopes, but found that none of the auto controls worked in the dark, I could not see to work the controls in the dark, and it did not have "Live View" so the only way to check images for exact focus was to transfer them to a PC, which was not a simple process, as the support software only ran on Windows XP. Too much trouble. Do your cameras have Live View and a large operating screen? Another approach to deep space imaging is to put a camera and telephoto lens on a small tracking mount, dispensing with a telescope and GoTo mount altogether.

My elderly Win7 desktop which I am typing this on has a TPM chip, which however needs enabling or something. PC Pro magazine has run a couple of articles on Windows 11. The impression I got was that it is nice but non-essential. Will it make your astronomy software run better? I don't think so. I don't like Windows 10 that much. The Windows Explorer has too many self-generated folders, and Windows 10 networking is awful and almost unusable, in contrast to Windows 7 networking which works every time. I'll leave it till I have to buy another (used) machine and it comes with Win 11 installed.

Thanks. I installed this driver, and "Celestron" now appears in the relevant Sharpcap setup menu. I await a clear night so I can proceed to the next stage of testing and debugging.

I hope this is the best section for asking this question. I have recently acquired a more recent and powerful laptop, mostly for astro use, and have been installing and commissioning various bits of software. Sharpcap 4, I discovered, includes platesolving and re-positioning. The platesolving (aided by an i5 processor) works great with ASPS, but I am struggling to connect Sharpcap to a Nexstar mount. The Sharpcap instructions do not include the words "Celestron" or "Nexstar" and mention the need to install the ASCOM platform. I have ASCOM installed, but regardless I cannot figure out how to make the connection work. I know that I do NOT need ASCOM to connect Stellarium or Nexstar Observer List to a Nexstar mount, but I do need it to connect Stellarium to a Skywatcher Synscan mount (I never installed ASCOM till I tried out my Synscan mount with the old laptop). I have the serial cable and USB/Serial cable I used to connect the mounts to the old laptop, and the USB/serial has the driver installed. I have not tried connecting the new laptop to the Synscan mount yet...

It's useually called the C8 SE. There will be some variants of solution: For my Nexstars I bought a fairly standard handset-to-serial cable which has a phone-like plug at one end and a 15 pin D socket at the other, and a standard USB-to-serial adapter. The two are plugged together in series. You also need a driver for the USB-to-serial adapter, and if it does not come with the adapter you can download it. The same should work with your Starsense. Alternatively, you can probably buy an integrated cable for the purpose, eg from Lynx. Ask FLO so sell you the appropriate cable. Once you have the cable(s), you still need the installation manager software from Celestron, and a further download of software that enables the Celestron installer to run. And then you can try the actual upgrade. Further guidance may be found on nexstarsite.com Yes, it does sound complicated, and it is, but in the case of a Starsense is probably worth doing as the upgrades clear various issues. Nornally I advise would-be firmware upgraders to leave well alone unless they have a clear and present reason for needing to update. 😳

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.