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tonyowens_uk

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About tonyowens_uk

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    Hillwalking, cycling, engineering, travel, wine, politics, telescope-making, model-making, invention, history
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    Wicklow, Ireland

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  1. From what I've seen, Skywatcher (Nantong Schmidt Instrument Company) have enormous manufacturing operations of their own, for optics, tubes, machined parts, worm wheels, finishes, assembly, test and many other things. Obviously they dont make their own PCB's, castings, small lenses and so forth. No OEM does. Such things come from specialist suppliers. But they do have an excellent design engineering team, who are very much involved in the latest developments, and plenty of resources. So far as harmonic gears are concerned, as used in the compact mounts referred to on this thread, these al
  2. Hi Mike. Loved your account of the 12" Cass/RC build on your site BTW! The EQ8 is awkward as its neither fish nor fowl. The underlying mechanical precision and structural stiffness is superior enough to encourage seeing-limited imaging, but the omission of anti-backlash worm gear meshing and extensive use of thermally-reactive aluminium components (shafts, structure, worm wheels) frustrates being able to set a stable mesh clearance as ambient temperature changes. On top of that, many have run-out issues of the Dec worm wheel relative to the Dec worm, caused by tolerance stack effects.
  3. Andy that isnt a great approach. The badly designed clutches on EQ8's do affect backlash on Dec (as well as cause image shift) on opening and closing them. But the effect is not predictable or controllable or desirable. Overlaid on this, is a seasonal variation in backlash due to differential thermal expansion of the mount components and varying ambient temperature. The mount is tight or binding in winter, whiel backlash grows in summer. If you are an imager, my advice would be not to waste your time messing around with a half-assed response, and either make the adjustment yourself o
  4. There is a special interest group on Google for EQ8 mounts here: https://groups.io/g/SkywatcherEQ8/topics Backlash adjustment instruction and help are available. All worm gear drive mounts that dont have antibacklash gears have significant backlash (for an imager). Either adjust it yourself or get your dealer to do it. Its perfectly normal.
  5. If you have to tote a tripod for non-permanent use, and need this to be capable, I'd highly recommend a heavy-duty well-designed wooden tripod. Berlebach is a German firm that offers models stiff and well-damped enough to work well, yet the weight for moving it around (in the deployed state) is manageable. The engineering is painstaking. I use one of their Planet models with an EQ8 occasionally to carry up to 30Kg imaging payloads and the stability is most impressive. Tony
  6. Yes of course. The issue have less to do with the conical back than to do with the hassle factor of altering established polishing and testing setups to suit a large optic with a conical rear. You need to look out for a small highly capable firm used to jobbing precision optics and capable of making one that large. Know what profile of conical rear you need and have a proper enginering drawing ready before you make an approach, or you may look like a time-waster. If you dont have the FEA capability to design a hub-mounted blank with the right profile to give you deformations low enough to meet
  7. The EQ8-R is functionally identical to the older EQ8 Pro. The improvements (through-the-mount cabling, improved microstepping quality, better static balance, better clutch design) are useful but not groundbreaking. The more fundamental upgrade, antibacklash gearing, was not implemented. The -Rh variant with an RA encoder apparently does a good job of reducing RA worm periodic error. On the other hand, autoguiding, especially with an off-axis guider (where possible) on the original EQ8-Pro can match the -Rh's guiding quality, provided the OEM clutches are modified, antibacklash gear modif
  8. As a prominent Western prophet said "the truth will set you free". Objective eyepiece testing is far from straightforward and in any case is not the only criterion for value of an ocular. I had the chance to return the XW30 I had bought, following my own comparison (using my own preferred equipment). But though I intended to, I have not done so. 20 years ago I remember being blown away by the overall experience of using an XW10 compared with various commercially-available and privately developed high quality oculars - the ease of use, the lack of scatter, the ergonomics, even the smell. That
  9. Here is a summary of the testing I carried out on these two oculars a month and a half ago after I received the APM 30mm UFF which was briefly out of stock at APM: Test of Pentax XW30 v APM UFF30 Date: 25/05/20 Setup: Intes-Micro MN86 Deluxe, collimated, F5.9, flatfield EQ8, tracking Visual use with and without glasses My vision is within 1 diopter of normal, negligible astigmatism, reduced accommodation Seeing: 7/10, traces of high cloud occasionally, 12 C, not truly dark. Various sky targets Targets M27 Dumbbell nebu
  10. I have an APM 30mm UFF on backorder with APM. I plan to assess the Pentax XW30 v the APM UFF 30 when I get my hands on one. I'll do this with and without the field flattener fitted to the 80mm APO.
  11. Hi. I bought an 80 mm Skywatcher triplet scope a couple of years ago with portable imaging and occasional visual use in mind. Until recently it hasnt had much use. Debugging the imaging side of things is being attended to currently, but I had hoped to come up with a choice of quality eyepieces that allowed widefield sweeping of the Milky Way at one extreme, down to around 160x or so for lunar views while travelling. I have the Skywatcher fleld flattener by the way. So recently I replaced a Televue Panoptic 27 with a Pentax XW30, as I hadnt been happy with the edge of field performance of the P
  12. I'm sure Bog Snorkelling is an important formative experience for Irish undergraduates: As for Green Swamp server (GSS) its been around for a while. Unlike EQMOD its in active development. Initially the target mount was just EQ8/HDI 110 but it now includes other Nantong Schmidt EQ mounts. There are several controls which extract better performance from EQ8's when autoguiding than EQMOD does. One, is homing that is far more reliable. But the key ones for imagers are motor current doubling during tracking and autoguiding, (which doubles stepper motor torque in
  13. Hi Goran. Your point about the original EQ8 and the quality of guiding it provides is well made. I have modernised or refurbished a number of them and all provides around 0.5 arcsec RMS following error on each axis when they left. Neither revised nor original EQ8 offer antibacklash gearing. Also, the original EQ8 used a badly designed clutch that directly caused minute deformations of the mount that manifested as image shifts and (for Declination axis) binding and run-out. The Declination shaft bearings can make this problem worse, as can other constructional details. But all of this is s
  14. For those who have bought one of these but are not instrument design engineers, here are my thoughts. I happen to have designed and built very high resolution traction drives for special machines with similar accuracy requirements, though not for telescopes. In friction mounts the weaknesses are: 1. susceptibility to moisture and dust (affects the reduction ratio of the friction final drive 2. low output torque (this is limited by the maximum safe contact pressure at the friction final drive that does not result in indentation - I note the reference to ceramic material which is int
  15. FWIW I'll add my own experience of getting stuck in the firmware update loop with an AZGTi and how it was resolved. My unit was on firmware rev. 3.12 and never updated. After a rebuild I tried to flash it to the current non-EQ version, which is 3.20, using the Synscan Pro app on an iPhone, across the wifi link to the AZGTi. The flash failed part-way through, and foolishly I cycled the power as instructed by the MCU update app, and tried again. The AZGTi would now only broadcast the ID "ESP_xxxxxx" instead of the ID "Synscan_5227" I had previously seen from my unit. The LED was cycling through
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