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runoffshed

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Everything posted by runoffshed

  1. Sorry, should have explained. Someone once came up with a solar projector (they called it the Solar Gun) which used a telescope to project an image onto a screen from behind - you view the image through the screen from the other side ...rear projection. The downside of this is that you are looking towards the sun to view the image so a development is to use a prism / secondary etc...to bend the image and view it at right angles to the sun. A flowerpot is the ideal thing to hold the back projection material and also, using half a flowerpot, to shield the screen. I'll try and attach a photo to make this clear. Many apologies if I've now gone off topic and hijacked the original thread. However, my idea for the 'bolt eye' finder is what I use on this projector. John
  2. Could perhaps also think of using a simple coach bolt with round eye bolted through the top end of the tube with a small "projection" screen a little further down. Find the sun in the main scope, then mark the centre of the eye shadow on the screen and it should be lined up for life then. I know it sounds simple but I use this for finding the sun with my 'flowerpot' solar projector and it works really well. Also, you line it up looking away from the sun. Just an idea. John
  3. Truly inspirational. Can't get over the quality of the secondary mounts....and in fact everything else! I am amazed the mechanicals have only cost about £500 so far. You've got to find that extra £4000! Good luck John Ps. Personally, I would like to see more use made of badly sawn plywood - like all my projects)
  4. Wonderful things these dual speeds but I was surprised just how heavy a 10-1 can be. My dual speed made by GSO required some serious re-balancing....it's also huge. John
  5. I favour Sky and Telescope and, after reading it for many years, the writers have become like old friends (excuse me while I wipe away a tear and watch an episode of The Waltons) but it's gone down hill in the last year or so with each edition seeming to get thinner and thinner ....and it's not just the reduction in advertising. Still love it but with so much info available on the web it's hard to justify. A year's subs will buy a pretty decent eyepiece! I'd still like their dvd 6 decade S & T archive though! John
  6. Is it the mount head or the tripod that is causing the jitters? If it's the tripod - and it's wood - it wouldn't be too difficult to brace it to reduce the shakes. Wood is actually a very good material for tripods and absorbs vibrations much better than metal .....I've got a dreadful old metal vixen tripod which takes about 5 seconds to 'settle down' so know about these things! However, get an old vixen polaris mount on a wooden tripod (they aren't that expensive if they don't have the drives ) and you've got a very stable mount. Overall though, I'ld go with the 6 or 8 inch dob idea. Good luck John
  7. Zomz = Zagorski optical-mechanical plant, the eye logo being used from the 60s onwards. The green tint/coating would suggest something around 1980 onwards, the typical Russian coating before then often being yellow. I think this factory now produce, amongst others, the current Kronos range. Focussing often a little slack but generally good optics and very good value for money ...especially for £1.00!
  8. I have used this stuff on binoculars and my Vixen 4". Like you I was a bit nervous about using anything like this but I have to say that I was very, very impressed. John
  9. Very useful, Dave. I hadn't come across this before. Many thanks John
  10. I really like the wooden tee idea and also the fixed feet locators but can I just mention that for a bit more accuracy you should find out from an OS map how much your local magnetic north varies from true north. If you know this you can take it into account when using the compass and offset your alignment from the compass reading. John
  11. Just seen the link ...what a remarkable piece of engineering!
  12. I don't think my house has been built as well as this .....however, at least it doesn't smell of cat urine! Fabulous job
  13. Fabulous shot. I bought an dslr a couple of months back and still haven't tried any astro stuff. Having seen this, though, I'll certainly give it a go. I think my old vixen polaris mount will be ok for this.
  14. Getting the optical paths close enough (the width of your eyes apart) but 'away from' the tubes so you can physically get your head in position would be very tricky ....transfer lenses, perhaps? Like to see someone have a go, though. John
  15. Hi Steve, welcome to the hobby. You could do a lot worse than buying the odd copy of Sky At Night magazine. Lots of good information regarding what to look out for in the night sky each month, and not too technical. John
  16. Tasco 60 mm for xmas circa 1970 ... the most exciting xmas present I have every had. Can still remember the huge thrill of looking at the Moon and Saturn through this - to me at the time - monster scope.
  17. I may be wrong but I think most people are being way too suspicious. I agree with the opinion already given that some people who haven't used ebay much - and only to buy - are just not very good at the listing side of it and don't necessarily see how their listing looks to others. If they are happy for potential buyers to have a look I don't see the problem.
  18. Should have added that the balance problem isn't really an issue when a platform is employed as the platform usually only allows for a run time of 1 hour or so therefore looking at 7.5 degrees or so either side of level. However, with your 'wedged up' dob, the c of g is immediately flung over the edge of the wedge/support and, with a tall box may even simply tip over. There is still then the problem of balance. I wonder what latitude it might work well at, though? 70 degrees + maybe? John
  19. Yes, that's correct. There is loads of stuff on the web about platform building and a very good chapter in the Springer books series "Telescope Making" should you decide to go down this route. Although it may be simple to 'wedge up' the dob you may encounter balance problems not met when it's level on the ground. The box of a dob isn't, and doesn't have to be, balanced. ie because of the front board section, the centre of gravity of the box isn't immediately under the altitude rings ....it will be more toward the front of the box. This doesn't matter when it sits flat on the ground but it will when it's tilted. You may have to employ a brake or additional weight to the back of the box. Very interested to know though, how you get on with this as it's such a simple design. Good luck with it John
  20. I think you have it correct, Badgerchap. In your diagram, if you continue your line to the celestial pole back through the base board of the dob to the ground you get your latitude angle - 52.26 The angle where the line passes through the baseboard is 90 and the angle of the baseboard to the ground (and your wedge angle) is 90 - 52.26 = 37.74. However, this may not be the same as the sector angle calculations for a platform as there are at least 2 main methods for obtaining these - supports at right angle to board and supports angled to board. It looks like your tilted dob design is basically the same as a fork mount and I think you have the angle of the board to the ground correct.
  21. Sorry, can't get it to 'take' at all. Very nice idea, though.
  22. Ah.....£3 to hear the guest speakers! I read it as charging the guest speakers. This is one of the many, many reasons I'll never win Mastermind ......I only ever use half my brain and the half I do use isn't that sharp. A very welcome event to the asto calender.
  23. According to the listing on UK Buy and Sell - Entrance £5.00 for visitors ...very reasonable indeed £3.00 for guest speakers at the event...bit cheeky! Still, I'm sure this will be a very popular event.
  24. Great job ... a concise guide and very useful. Many thanks and keep them coming.
  25. HI Mike, just a bit more on Jim Hysom. I have a 12" Newtonian which I purchased second hand in about 1993. It was made by a well known British manufacturer but the mirror turned out to have a very severe turned turn edge. I had heard of Jim Hysom as a very fine mirror maker who took a real pride in his optics, and at the time he was still working - as Hytel optics, I think - so I sent it off to him and he corrected the mirror using a sub-diameter tool for, what I thought, was a very reasonable cost. That's why I think, like Peter, that he would be very unlikely to let a mirror with a turned edge leave the factory .... if it has got a bad edge I suppose it may not be one of their mirrors. I don't know if Jim Hysom is still working but you could always try and track him down and get his opinion. Are there any markings on the mirror back? Good luck and keep us updated on progress please. John
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