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    SGL 2017 SP

AlistairW

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About AlistairW

  • Rank
    Proto Star
  • Birthday 23/02/74

Profile Information

  • Gender
    Male
  • Interests
    Chromatic Free Base Accordion, Chess, Astronomy, Boxing.
  • Location
    Bath

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810 profile views
  1. I am after a 2" Howie Glatter laser collimator. Please drop be a PM if you have one. Thanks Alistair
  2. Wow - didn't know - RIP Howie Glatter
  3. Anyone know where I can buy one of these ? Howie Glatter Single-Beam 2-inch Laser (preferable in the UK) Thanks Alistair
  4. Just wondering about tilt again. Say there is some tilt at the point where the focuser assembly touches the OTA. But let say it can be countered by messing about with thumb screws on the FF/FR. So by having two opposing amounts of tilt, - then I am wondering if that actually really cancels the tilt. Kind if like having a tilt adjuster. Wondering if this messes up the light cone. Thanks Alistair
  5. Hello, I have read about using a ball bearing, a piece if black card and a light source to create an artificial star. Could someone explain what an artificial star is used for, and how this method works - I can't quite picture the configuration. Thanks Alistair
  6. Interesting read - lot more in this than I thought. I am guessing there should be a reasonable degree of uniformity though. So having the "X" and the "+" symbols together is no proof of tilt correction. Just wish there was a test I could do in the day time to look at any tilt in the system.
  7. Thanks everyone, got a few things to try, will let you know how I get on. (All this push fit and thumb screw stuff makes me realise that it not the best solution, - actual screw on adapters and SCA seem a better way to go)
  8. I was wondering if there was any merit in this approach I was trying this morning. Let us assume that my refractor objective is collimated correctly. I set up a Flat Panel and start to take flats (Lum filter @ 2 seconds). I then run this throught CCD inspector Flat Analyser. This I believe shows the pattern of brightness across the whole image. So given everything is "true" the image should be symmetrical. However there are two crosses on the screen, one that (I think) shows the true centre and the other where the image train is pointing. My idea is that these two crosses should be on top of one another. So this is what I did by tweaking the OTA, and now the illumination across the filed is near perfect. I know this is not a star test that CCD can do, but is it a good stab as suggesting the tilt is now "minimal" as the light illumination on the chip is even. (I probably have some technicalities wrong here, but I hope you get the idea). Thanks Alistair.
  9. Much appreciate you help Oddsocks
  10. One other thing I might try is Aluminium tape arond the FF/FR barrel. Then build the tape up to take up the slack. Screwfix sell it, and its 40 microns thick.
  11. WO twist lock I don't think will work for me as I have switched to a Moonlite.
  12. Whilst I have not tested this - what I have tried is to place a 2" diameter piston ring clip at the position of the first undercut of the WO FR/FR. Originally I was finding the 3 thumb screws were tightening on the undercut ridge, and introducing a lot of play. The piston ring, not only acts as a spacer, but now allows the FF/FR to butt up tight to the drawtube. But, I still have to lock it down hard with my Allen bolts. It certainly does not wiggle anymore - I do worry about the pinched optics from the FF/FR. Not tried this yet but guess I will be looking for tilt and triangular stars. Never easy this hobby !
  13. Thanks for the replies. I am wondering about the backfocus for the Hotech - is it 55mm for the WOGT81 in your experience Oddsocks ?
  14. I would put a post on the SGPro forum. The moderators are very good at getting back. If you have enabled logging then I expect they would be able to narrow the problem down very quickly. Alistair
  15. Hello, I am after some ideas for an issue I am seeing with my setup. My focuser drawtube is a standard 2" and I simply push the Flattener\Reducer in to the tube and tighten the compression ring with the aid of 3 radial thumb screws. My issue is that I cannot get the FF/FR square in on the focuser tube. As soon as I tighten one screw the FF/FR tilts. I do this very carefully by tightening one screw at a time but is still very hit and miss. With the maximum pressure I can physically exert on the thumbscrews, the assembly still wiggles. So I replaced the thumbscrews with Allen bolts, which meant I could get a lot more torque and tighten the FF/FR in the tube, but I expect there is still some more tilt due to the nature of tightening one screw at a time - (plus I am now worried I could pinch the optics, - though the casing is a very solid metal on the FF/FR). I had thought about the Hotech self centring FF, but I don't want to just throw money at the problem. I was wondering if it would make sense to make a thicker compression ring, so that the amount of play between ring and screw thread is less and therefore cannot add any more wiggle. I am beginning to think that compression rings and thumbscrew are a bit of a pain for imagining, where you need to be very accurate. Thanks Alistair