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[ATM] An intriguing toy
Hi all,
I've just picked up a curious item on eBay that seems to hold a certain
promise as a TM project. When I say "just" I actually mean that I
picked it up on an opportunistic bid back in early January but have only
just gotten it home today. The item is an early model "three gun" video
projector weighing about 80kg (176lb) - it was listed as pick up only
and was situated across the other side of the continent.
Getting my booty home proved somewhat problematic and it often seemed
that my $52 "bargain" was going to come back rapidly and bite me rather
savagely with exhorbitant private shipping charges and the projector
mysteriously going missing for a couple of days when it arrived on my
side of the continent. In the end though, I was able to get it
delivered to me for a shade under $100 and with the help of some
understanding colleagues.
What attracted me to this projector was that it was a rarity as such
items go - the optical sets utilize a Schmidt configuration rather than
the more familiar refractor style. It was listed as non-working, which
suited me perfectly, but the seller advised me after the close of the
sale that he had been able to identify the fault and that it was now
functional. It's not often you think "d*mn, what a nuisance" when
delivered that sort of news.
Anyway, I got the projector home today and have verified its working
status, but I was much more keen to lift the cover and inspect the
optical sets, so here goes a basic description. Each of the optical
sets is comprised of a 7.5" tapered primary and a 6.5" corrector (clear
aperture ~6.25"). These are spaced apart by four threaded rods with the
distance from the rearmost surface of the primary to the front of the
corrector being 9.25". The primary mirror has a barrel fan attached to
its rear that blows air directly onto the CRT through its central hole.
The central obstruction by the prime focur assembly is huge (about
4"!). This assembly is comprised of a 2.5" diameter CRT that pokes
about 4" into the unit and an 8" long tapering nose cone (which hides a
large valve) protruding from the front. The prime focus assembly is
supported by an externally mounted four-vane spider and appears to be
operated by a toothed rubber belt runs around the spider mounting
points, though I can't see a motor that is used to operate this function.
All-in-all it looks like an intriguing proposition. It appears as
though the optical assemblies could be readily converted for
astronomical use, even if it be just for photographic purposes, but I'm
wondering if anyone else has come across this type of system or has any
advice to offer.
The projector was made by Projection Systems in New Jersey and
apparently converted for PAL use by Speywood Comm. in England. The
original eBay listing can be viewed at
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=5741329319. I've
also a handful of photos showing the optical assemblies that I can make
available on my website if necessary.
Cheers,
Bevan
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