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NigeB

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About NigeB

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    Star Forming

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    http://www2.le.ac.uk/departments/physics/people/nigelbannister

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    Rutland, UK
  1. Well, it's definitely to be avoided of course, but accidents do happen, and there are two features which offer some protection. This is a friction drive mount and there are no clutches. Even when it's tracking, it's possible to move the telescope by hand without releasing anything if you really want to. So conversely, if there's a clash, the system will slip rather than crumple your camera, and that should save major issues. There are encoders on both the motor and the axis in RA and Dec; if the Sitech detects a mismatch between the motor vs axis encoder (I think it's around 10° difference), it stops tracking (there's a message which appears on the on-screen Sitech panel). I've had that happen a few times when I was pushing my luck with meridian flip adjustments, and absolutely no harm done to mount or camera. If the clash is during a slew, then of course, there's a fair amount of momentum in the telescope assembly, and even if the mount stops, the motion can't be halted instantly without something giving - but again the friction drive seems to me to be the one most likely to keep your hardware intact because of the ability to slip if required.
  2. Gorann - definitely worth doing, but I feel the pain! Note that I've tried mounting my TOA150 + C11 together on the Mesu, and it's fine; I found some of the currently available side-by-side mounting plates introduced a bit of flexibility and lengthened damping times noticeably, and there were some issues with cameras clashing with my pillar - the dual mounting plate pushes the OTAs out over the side, so you need to watch out. In the end I found a Casady tandem bar used which is a phenomenal lump makes for a stable setup. So in principle you don't need to have either/or, you can have both your Esprit 150 and C11 (and probably the ED80 as well) up and running together. Good luck!
  3. Thanks Gorann! I think my EdgeHD14 is a similar story - good price so an opportunistic buy, but ultimately I find it hard to convince myself to remove the frac from the mount. But I think it's definitely worth a try. Regarding the soft stars - I think Wim has captured the situation very well in his reply to you. Certainly my experience with side-by-side comparisons between the TOA150 and C11 co-aligned is that the performance of these two designs is much closer than often portrayed in some forums - once you take into account the very high plate scales of the SCT and try to match that with the refractor, things look a lot more equal between a good frac and a well collimated SCT. Not perfectly so - that central obstruction in the SCT does spread the power out around the central maximum more than in the case of a refractor - but as Wim has identified, it's only part of the story. Much is down to simple image scale. I don't regret for one moment the money I spent on the 'frac, but it shows just how good modern SCT's are; in terms of "bang for buck" they're really amazing - even if a little more maintenance intensive to get good results from. Regards Nigel
  4. Hi Wim, Many thanks! Yes, I think seeing is the key limiting factor. The 14" was an itch I had to scratch, and it doesn't disappoint, but previously I've noticed how similar deep sky images from the 'frac and my C11 are. Planetary imaging is a different matter and that may be a good reason for keeping the 14" on the mount, but I've not tried that yet (unlikely to either, unless the trees in the wood opposite suddenly fall down so I can see below about 30° altitude!) I think you probably made the right decision with the MN190 vs the Edge 8... The mechanical compromises with the Celestron do take the "edge" off slightly. Thank you very much for that processing advice - this is really helpful, and I'm going to try re-processing the image adding this technique - I'll re-post when done. Best Regards Nigel
  5. Evening All A few weeks ago I decided to take my TOA150 off the mount for a while to give the Celestron Edge 14 a proper try-out. The refractor is beautifully straightforward to use - it "just works", has a wide field which makes plate solving easy, and a reasonably trouble-free focuser. I anticipated some problems moving to a long focal length mirror-shift SCT. I've fitted the Edge with a Lakeside motor focuser - rather than going the Crayford route I've put it on the normal primary mirror focus knob. I expected this to throw up challenges due to mirror shift, but after some experimentation with SGP settings I found the right combination of focus direction and backlash compensation which generates good V-curves and little net image shift between the beginning and the end of the focus run. I can definitely recommend the solution which Peter at Lakeside has come up with for this fitting. I'm using the OTA at native F/11 (3910 mm focal length), with an Atik 460ex CCD and Lodestar guider via an OAG on a Mesu-200 mount. Plate solving was an issue to begin with - the 460ex imaging area is quite small, and the system is slow. I've found that adopting 4 x 4 binning and 15 sec exposures for plate solving captures, usually works, and I can now centre a target in the middle of the frame from any part of the sky in 2 or max 3 plate solve cycles. By far the biggest challenge with the entire thing so far has been finding and keeping guidestars - in the wide field of the refractor it's hardly ever a problem, but with the 14" it's a real challenge for some targets because the area of sky captured by the Lodestar is so small. Very often there aren't any usefully bright ones available in the 4-8 second guide exposure times I'm using in PHD2, and now and again I've hit problems in which the guide star is lost because it has moved out of the guide square in PHD2 after a focus run - although I seem to have managed to tune most of that out now (I really wish there was a setting in SGP to perform a re-centre after auto-focus - that would solve lots of problems). Guiding at f/11 has posed no problem at all - really flat PHD2 curves. The "Target" view in PHD2 has shown clustering of points within the 0.5" circle most of the time this week. Collimation is probably not brilliant, and I've found having to think about that business to be a bit of a pain compared to the trouble-free experience of the refractor - not that it's difficult, just that it's something you have to do. At the beginning I spent a night jumping around from object to object, marvelling at how targets that are tiny in the refractor field of view suddenly fill the frame. But eventually I settled on NGC 2683 as the target for a proper first attempt at imaging with this combination. Result shown below. Exposures: 26 x L, 10 x R, 9 x G, 9 x B subs - all 600 sec with 2 x 2 binning. It's clearly far from perfect - I've tried not to introduce too much noise in processing but there's definitely noise there with mottled background being a real issue - though that's my processing not the instrument. I also have a problem in L with a couple of dust bunnies that aren't flat fielding out properly - either the filter wheel is not returning to exactly the same position, or I've had a small shift in the orientation of the camera. Need to check collimation as well. I think it's promising although there's more work to be done on the image and on the setup. However, by coincidence I'm posting on the same evening as @wimvb who has posted an image of the same target taken with an MN190 and 460ex, and the level of detail in Wim's image compares very well indeed with mine, despite the difference in the aperture and plate scale of the combination used - make of that what you will. I have my own views on why, and ultimately it's the refractor which will be mounted for most of the time - but the 14" certainly offers a lot of different options for imaging and I think it's worth working to tame the challenges which the design introduces. Nigel
  6. NigeB

    NGC 2683 revisited

    Really nice image Wim! I also have an improvised counterweight arrangement - I declined to spend £100+ on a Geoptic lump and bought a weightlifting weight of the same mass for £10. I'm surprised to see quite thin snow on the ground - I thought you'd be up to the eyeballs in the stuff by now... By coincidence I logged on to post my own NGC 2683 image - coming shortly. Regards Nigel
  7. I'm selling my C11 OTA with some accessories - it sits between the other OTAs I have and isn't getting used. C11 XLT OTA with Fastar-Ready secondary. Used but in nice overall condition. The only point of note is a small indentation on one side of the tube, which I think happened when mounting up a couple of years ago. I've tried to show on the photos but it's really hard to see (no paint damage). Also included are the standard accessories: - 1.25" Celestron Diagonal - Celestron Finder scope - 40mm Celestron Plossl - The original Celestron CG5 (Vixen)-size dovetail Additional items included: - Celestron F6.3 flattener/reducer (Made In Japan version) - Celestron Losmandy-style dovetail - Celestron flexible dew shield (as shown on the photo, some of the Celestron lettering has come off). Price £1100. Inspection welcome. Sale by cash or bank transfer, buyer collection only.
  8. I think you should be OK with 5 m; all my cables are of that length and I don't have problems (I do make sure that my data cables and power cables don't run immediately next to each other - I've had banding in images caused by that, but once separated the problem disappeared). A powered hub at the other end shouldn't be necessary if you are plugging directly into the computer's built in USB port. If on the other hand you are having to use a hub at that side as well because of lack of free ports, then it's probably as well to have a powered one there as well. My solution was different - I bought a USB expansion card to give more ports in my desktop machine - like this: https://www.amazon.co.uk/CSL-express-controller-Interface-internal/dp/B00W4YFNAW/ref=sr_1_9?ie=UTF8&qid=1548547517&sr=8-9&keywords=pcie+usb+3.0+card Of course you may not have that option depending on what kind of computer you're using. Nigel
  9. Hi Spaced Out, That cable certainly gets a lot of positive reviews - though few of the users are likely to be putting the cable through the kind of conditions that connections have to put up with in our field... I've never had a USB cable fail in my office - but I've had a number of USB cables fail in my observatory. Note also the link you gave is for a 3 m length - I've had a quick look but not managed to find a 5 m version, though I may not have looked hard enough. The approach I usually take is to go a step or so higher than the cheapest cable I can find. Today I've just ordered this one, for exactly the same application as you: https://www.amazon.co.uk/LINDY-36744-Type-Cable-Anthra/dp/B07FWFVDNV/ref=sr_1_14?ie=UTF8&qid=1548529612&sr=8-14&keywords=lindy+usb+3+b It's a cable from a known source, and its performance is characterised and rated for 8K UltraHigh Def AV applications, which gives me a little more confidence that the quality of the materials and construction will be OK: https://www.lindycables.com/length-performance/ This is the Anthra line - the next version up (Cromo) is twice the price. What evidence do I have that the one you were looking at would fail, or that the Lindy version is better? None... But having experienced the frustration of a failed data cable mid way through a great night, my prejudice is to spend a little more to get something with known properties aimed at a demanding, though different, application. Even if you went for their Cromo version at around £25, it's small beer compared to the cost of everything else on your rig! Cheers Nigel
  10. Hi, Thanks for your interest; no, it's the Chinese version. I've updated the ad accordingly. Thanks Nigel
  11. Meade F/3.3 CCD focal reducer (China version). Little used, comes with top and bottom dust caps, in a Meade bolt case. Note that there are no T-adapters/extenders with this reducer - just what is shown in the photo. Price includes UK postage. £55.
  12. NOW SOLD. From the manufacturer's description: The Meade #128 3x Short-Focus Barlow 1.25" is a high-power compact Barlow - ideals for systems with limited focus travel. Triple the power of your eyepiece with this high-quality short telenegative Barlow. Works well with the Meade ETX range and numerous other popular instruments. Little used, comes in bolt case. Price includes UK postage. £20
  13. This is a used C11 package consisting of: - Celestron C11 with Starbright XLT optics and the Fastar-ready secondary - Celestron Advanced GT Go-To mount - Celestron NexStar hand controller - 3 x counterweights (only 2 shown in the photo) - 1.25" visual back, diagonal and 40mm E-lux Plossl eyepiece - 12V power lead (car cigar lighter style plug). - Manuals All in excellent working order. As the photo shows, the corrector plate has dust and dew marks, commensurate with long nights under the stars. The plate has not been cleaned (i.e. is untouched since new) and in my view is no where near the point where cleaning is required, so I've left alone. Oakham (LE15) area. £1250. NOW SOLD
  14. NigeB

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