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The very latest of when, where, how and why of Amateur Telescope Making (ATM) section of the South East Queensland Astronomical Society (SEQAS).

Graham hosts weekly meetings of the SEQAS ATM Section at his home in McDowall, Brisbane. Graham has experience in spin casting mirror blanks up to 17 inches diameter as well as grinding and polishing. Graham has experience and notes on telescope construction particularly large truss style Dobsonian's. 

Optical testing is a important aspect of mirror polishing and Graham has a good quality Ronchi tester and the Knife edge tester. If you have bought a new or second-hand telescope it is always good to get an opinion on the quality of the mirror. Guidance can be given on the interpretation of the test results which are not always clear.

Grinding and polishing mirrors can be awkward for mirrors over 12' (300mm). SEQAS houses a hydraulic automated grinding/polishing machine which can save some effort.

John Stuart has developed a rotary kiln, now housed in Graham's workshop. The kiln heats the glass then rotates it to help attain a curved surface. This process saves much of the grinding effort.  Each mirror is moulded to a cone shape which gives a lightweight blank, being 33% the weight of a full thickness blank. Spin casting allows the sagitta to be set between f3 and f8,  according to the users requirements.

Links to other clubs/societies...

Home  Last updated : 9/11/2000