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About Glasspusher

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    Proto Star

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  1. To clean the nut tool between grits I scrub with a stiff brush under running water if not satisfied with that I use a wire brush which usually does the job. With tiles or glass chunks water can ingress into the dental stone down the edges which can cause the pieces to become loose and draw in abrasives. You can see this more obviously at the edges of the tool where the tiles are exposed. Always try to set the tiles in from the edge so that they are surrounded by dental plaster and use the thickest tiles you can find, 4 mm is a little thin in my experience. John
  2. Over the years I have tried every type of grinding tool and a nut tool is difficult to beat. I use M16 steel nuts set in dental plaster. Cover the concave glass mirror with something like greaseproof paper, place a damn round the edge, place the nuts on the greaseproof paper and carefully mix up the plaster and pour into the mould. Allow to set and that is it. During use if the tool has dried out immerse in water for a few minutes before use. Worth thinking about! Good luck with your mirror! John
  3. Looking for M90 x1 extension tubes. Thanks for looking. John
  4. Hello, I have slumped my own blanks in a kiln but gave up due to the expense of running the kiln. To properly anneal a large blank takes many hours of controlled cooling which is expensive. You then have the problem of supporting the meniscus blank during grinding which is not straight forward. It is more economical to go the monolithic blank route which is well tried and tested. Hope this helps. John
  5. I could not agree more, well done Robin! John
  6. Many thanks for the replies. I have fiddled around with various versions of Stellarium and Stellariumscope, checking on the recommendations on the website of the latter, all to no avail. I decided to give cartes du ciel a go (thanks solarboy) and got it up and running immediately. Not used in anger yet but initial thoughts are that it is certainly an improvement on the Stellarium/Stellariumscope option. John
  7. Yes Julian, ran Stellarium scope and established a connection with eqmod, the handset opens on the screen. John
  8. Hello, Previously I have had no problems using Stellarium and eqmod with my EQ6. I decided to install a newer version of Stellarium and now I can't connect to the telescope using the telescope control plug in. Not at all sure what is happening. Could someone kindly remind me of the correct steps to take when using the telescope control plug in? Any help gratefully received, many thanks in anticipation. John
  9. Saganite, Thanks for your input, you can find more about the UKIRT here: https://sites.google.com/site/grubbparsons/home/grubb-parsons/telescopes-made-by-grubb-parsons/150-in-mirror-ukirt-hawaii-1976 UKIRT was a very successful telescope, unfortunately UK funding was terminated some years ago and the telescope was taken over by the University of Hawaii I believe. The telescope was closed down a while ago, together with two others on Mauna Kea, possibly in an attempt to appease the protesters objecting to the construction of the Thirty Meter Telescope. Mauna Kea is considered to be a sacred place by native Hawaiians. John
  10. The 29th August marks the anniversary of the passing of David Sinden former chief optician at Grubb Parsons, Newcastle. Although not large by today's standards David worked on many telescopes which at the time represented the cutting edge of telescope technology. These included the Anglo Australian Telescope (now renamed the Australian Astronomical Telescope), The Isaac Newton Telescope and the United Kingdom Infra-red Telescope (UKIRT). After leaving Grubb Parsons David went on to establish his own very successful business, the Sinden Optical company. Despite his pedigree David used to refer to himself as an amateur and always gave feely of his time and knowledge. Meeting David was an unforgettable experience such was the nature of the man. The attached image shows David (wearing a waistcoat) with the 72 inch mirror for the Helwan Telescope Egypt. To find out more about David and Grubb Parsons please have a look at my website: https://sites.google.com/site/grubbparsons/home Thanks for looking. John
  11. Hello, I am looking for a pitch at the Kelling star party including the main weekend. If you can't make it and would like to sell your pitch please contact me. Thanks, John
  12. Hi Rick, Good to see that you have resumed work on the mirror. Looking at your video I see that you are using a 13 inch lap, if you are parabolising the mirror I would recommend something around 10 inch in diameter. A 13 inch lap will be slow at adding correction. I usually use a 50 % (or even smaller) diameter lap for figuring which seems to work well. Also a 'w' stroke like the one you are using tends to be slower at adding correction than a stroke across the mirror with a slight offset so that the centre of the lap is not passing through the centre of the mirror. Good luck, will be watching your progress with interest. John
  13. That is true Damian. It always takes me back to my first visit to David Sinden's workshop......or was it my first visit to the local Indian restaurant? Either way great memories. John
  14. I have a copy of ATM Book 1 first edition from 1928, it is in very poor condition. It was given to me by an ex-employee of Grubb Parsons who told me that it was consulted regularly during the making of some of the companies large telescopes, it certainly bares the scares of heavy usage. I have to say that I love the smell of molten pitch!!!! Keep up the good work with the mirror Chris. John
  15. Congratulations on your first spectrum....glad you decided to have ago! Be careful you might get hooked. John
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