Q: Can you supply me with a mirror-making kit?

A: In gerneral, NO. We are a non-profit organisation, not in the business of selling materials. Thus, we band together and make bulk purchases specifically for our ATM class. People in outlying areas that cannot attend the class should preferably form their own group to similarly make bulk purchases. However, in rare deserving cases, we can perhaps be a little flexible - if you think you fall into this category, talk to us directly.

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Q:  Where can I get my mirror aluminised?

A:  This depends on the size of the mirror. We have been very happy with the services of Walbac Tool & Die, who can handle mirrors up to about 12 inches (30cm) in diameter. For larger mirrors, you can try the CSIR in Pretoria or Eloptro in Kempton Park. If you are an ASSA national member, you can also try the SAAO in Sutherland.

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Q:  Could you possibly direct me to somebody that will be willing to grind me a mirror, and how much would this cost?

A:  The number of hours and the effort plus attention to detail, are what the amateur can bring to his mirror - he doesn't count these as being a cost, and thus can make a scope "cheaply". Any realistic level of quality can be achieved merely by putting in more (skilled!) effort. If however one is to make a mirror for someone else (i.e. specifically to sell), then time suddenly does become a true cost and commercial mirrors may even have the edge. What value any arbitrary person would place on his/her time, it not something one can reasonably estimate; it needs negotiation on a case by case basis. But every now and then, people are willing to part with either a complete telescope or parts thereof, as they progress in the hobby. Our suggestion is that you come to the Telescope Making Class and enquire in person about such possibilities. Also, keep an eye out for adverts on our front page.

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Q: Where can I get the raw material for grinding a 12"?

A: This is not easy in South Africa. For the advanced amateur, bringing in glass for a big scope is probably the way to go. We have had great success in using recycled glass cast for us into disks. However, this is only effective to a maximum of 9 or 10 inches diameter. Beyond that, the quality of the blanks tend to be unsatisfactory.

25mm float/plate glass used to be made here in SA, but was discontinued long ago - now 19mm is the thickest available locally. 19mm float glass has been successfully used to make mirrors up to 10" diameter, but needs great care in the grinding, polishing & figuring stages to get a good figure, and must then be properly supported in use by a floatation system to avoid warping.

Occasionally we find old portholes or other thick material; these arrive from the strangest places, without warning. They are usually 32mm thick (which is very suitable for larger mirrors), though are often chipped on the edges. If you have a source for thick glass, please let us know! (Note that laminated glass is not suitable, due to internal stresses that affect the figure over time.)

All this having been said, be advised that you need to make several smaller mirrors to build technique, before you tackle a large one, and for that the recycled blanks are fine.

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