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Horwig

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Horwig last won the day on October 16 2015

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About Horwig

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    Sub Dwarf

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  • Location
    Caernarfon, Gwynedd

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  1. If I could afford those I could also employ someone to do the imaging for me
  2. Now if I had limitless resources...
  3. Thanks Neil, love the idea of the blanket. At the moment everything is stripped out, I'm re working the DEC drive and have removed the OTA, will update the thread when everything is up and running again. as you can see I'm getting serious Huw
  4. Thanks Sara good to hear your input, a new one it would have to be, but I'm trying hard not to buy one, I'm not a believer in throwing money at a problem. I'm struggling to get my self built fork mount to behave itself, DEC guiding is abysmal but RA is quite good, I've had 0.5" RMS in RA guiding (and I'm sure it could be better with more work), whilst DEC just bounces all over the place. At the moment it's all stripped out once again for a major rework of the DEC axis. If this rework doesn't produce better results I might just give up on it. I've got two imaging scales on this scope, 1.28" or 0.44" so if I replace this mount any replacement is going to be pushed quite hard, the main constraint I have is physical, the dome was made to house a fork, so a GEM would need to be small so the OTA would still fit, the EQ8 I believe is only 190mm or so from the Polar axis to the OTA Huw
  5. Horwig

    Offsetting OTA in fork mount to balance

    Yes that was the hope, I've got a 2.5Kg counterweight at the moment, that should come down considerably. Thanks Huw
  6. I've recently put a heavier focuser on my fork mounted truss Newtonian, the focuser hangs down from the OTA so I'm considering offsetting the whole OTA upwards to counteract it so I can reduce the counterweight I need, ie, the centre of rotation would not be across the centre of the optical axis, what effect if any would this have on my go-tos and pointing? Huw
  7. Yes it does appear to be a pendulum effect, the OTA was miss-balanced by about 1/2 Kilo at the top end. I did also play with aggressiveness, took it from 100% down to 20% with not much joy.
  8. Thanks Dave and William, a long hard think is required. Your solution would certainly work Oddsocks, but I'm worried that the original design was flawed, It might be better to scrap and start again. I do particularly like the swung block you show Dave, wonder if sandwiching the pivot between two large diameter thrust bearings would help. Huw
  9. Thanks Gina, but loaded with nearly 34 Kg?
  10. Thanks both. The request for info on the EQ8 was a sign of desperation this morning, guiding tests did not go well, here are some results, some were even worse: The mount if fairly well polar aligned, so with DEC guiding disabled it would giving a nice slowly diverging line, but once guiding is re enabled it's either oscillating or diverging off the scale. Backlash on both axes is now controllable, and the reverse direction problem has indeed gone, but watching a dti on a rod from the end of the OTA as the scope is moved at guiding speed in dec still shows jerkiness of a cyclic nature, a steel rule attached to the worm axle also shows the same pattern jerkiness. This morning I removed the scope from the mount, and ran the same tests, everything was smooth and regular, so it's obviously load induced. Oddsocks, you spotted the flange bearing with only two screws, that was only to test fit the drive components, it runs with all four bolts. The spring on the worm block is valve spring from a Rover V8 engine, it's no wimp. Yes indeed, I think it's time to beef up the worm adjuster, but if that doesn't work, this mount will be facing an uncertain future, I'm getting tired of fighting it. On a different note, I'm using good old fashioned ST4 guiding, for some reason Ascom pulse has stopped working altogether on this system. Huw Edit: Sorry dave, my post took so long to write, yours came in whilst I was writing, yes, in theory that is a much better solution, that's how Mathis Instruments mount their worm blocks, what worries me about it is the possibility of play in the pivot causing motion in and out of the page (does that make sense)
  11. I've come to the point where I might have to spend on a new mount for my obsy, where does the EQ8 stand now for imaging? I know the initial release was patchy, with dec backlash problems, but has that been sorted in later mounts? I'd be loading it with about 33 kilos of scope/camera etc, and a focal length of 1450mm. Thanks for your thoughts. Huw
  12. I'm going to say this very quietly, I think it's sorted! Sprung worm carrier re-worked to bring everything into alignment, then two hours spent with toothpaste on the gear, don't know if it will do any good, but it won't harm it I hope, but what a mess. With the covers off I could hear the motor better, and it was occasionally making strange ticking sounds, and the backlash was variable, luckily I had a spare gearbox, so swapped them and the ticking went away, Direction reversal problem seems to have vanished, and the backlash in both axes is now about the same figure, which Sitech removes easily, waiting for dark so I can try some guiding tests. Thanks all for the suggestions, in the end it was a bit of everything. Huw
  13. Trouble is, it's at guiding speed (1/3 siderial) I see the problem. That picture was taken soon after the gear was assembled, I hope it's an artefact of the image. Thank you both for your input, at times like this it's nice to have someone looking over your shoulder. This evening I stripped everything out, washed the worm and wheel in petrol to remove grease, and re assembled everything dry without the covers, and guess what, the worm was not true to the wheel, and not by a little, lets put it this way, I didn't need a micrometer to see the problem, mk 1 eyeball was enough. Very embarrassed. Quite a bit or re jigging to be done, hope it's what causing the problem, it sounds about right. Huw
  14. The worm and wheel were bought new from Beacon Hill for this mount, I assume he does lap them, but true, that would cause what I'm seeing. Will clean and inspect them tomorrow. The drive belt is as tight as I can make it, I tried clamping a one meter rod to the end of the worm axle, think giant clock hand, that turned smoothly at guide speed. What strikes me is that the worm might not be accurately perpendicular to the wheel, more measuring to be done. Thanks for all the avenues for investigation. Huw
  15. More time playing with the mount. Yes, there is a slight reversal of motion in the RA, but it is tiny, a couple of microns on the edge of the fork, so nothing at all to worry about. The problem with the DEC appears to be linked to the meshing of the worm and wheel. The rotation of the worm axle seems regular and smooth, and there is no endfloat I can measure. Now I have replaced the spring adjuster with a solid one, I have been playing with mesh tightness. I can change the backlash and direction reversal, but not remove it. Also, compared to moving the RA at guide speed (1/3 siderial), the DEC is very 'jumpy' not regular at all. Time to strip and clean everything down and look at them on the bench I think. It might be the basic design of the worm block, it's hinged, and swung up to the wheel, but that's how the RA works as well. This is the culprit during its build, it was modified since these photos were taken, the hinge, (the horizontal block coming out from the fork tine, and fixed to the worm carrier by two black socket headed bolts) has been widened to the whole width of the worm carrier. The spring is out of sight under the assembly, running parallel to the hinge. Is this the best way of doing it with reasonable engineering skills? Huw
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