Aluminizing in the Field
Story & Photos by Rick Kelsch
The week before Starfest, Rosemary and I attended a regular meeting
of the South Simcoe Amateur Astronomers (SSAA) in Tottenham. We were
pleasantly surprised to find that the evening's speaker was Alan Ward,
of MOONWARD Vacuum Coatings, specialists in metallic and dielectric thin
films for optical surfaces.
Alan gave an entertaining and informative talk on optical coatings,
and passed around a circular piece of glass which had been treated with
anti-reflection coatings; the glass appeared to be a torus shape, but
upon close inspection, the "hole" which appeared to be in the middle was
actually not a hole, but rather a multi-layer dielectric coating designed to
be totally anti-reflective, as compared to the "donut" which was uncoated
for comparison purposes. We were all, to be sure, very impressed!
After the meeting, Rosemary was speaking to Alan, and he told her that he'd
like to do an aluminizing demo at Starfest, and that it would, as far as he
knew, the first time anywhere that an aluminizing was to be done in the
field (literally!). In order to do it, they would require both electric
power and a source of cold running water. Rosemary volunteered our trailer
site as having both, and the result is shown in the following images.
John Moon explaining the equipment set-up & process
Interested spectators watch as both mechanical & diffusion pumps are started up
Aluminum vapour being deposited on the glass substrate
Vacuum released, John waits to remove bell jar |
Close-up of bell jar with safety cage removed |
John and Alan removing heavy (~ 3/8" thick) bell jar
Aluminized surface (reflecting the grass below the apparatus) of glass substrate
Alan, holding the freshly aluminized mirror and answering questions.
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