Re: [ATM] Cheap Optics for Public Terrestrial Telescope?

["Robert Mohr" <rmohr@tiwcorp.com>]

David,

I have seen small erecting prisms, as well as eyepiece kits (lens sets) at 
Surplus Shed.

Bob Mohr

> Hi Folks:
> 
> First of all I'd like to thank the people who responded to my question about
> a cylindrical cage-style tube for a 16" Newtonian. Their suggestions were
> helpful.
> 
> Regarding my current question, In addition to my interest in telescopes, I'm
> a volunteer building a hiking trail on a 1,000-foot mountain at the edge of
> our neighborhood here in Moreno Valley in Southern Calif. It's my daily
> exercise, and I've been working on it for 6 years. As the trail has grown in
> length, access to the mountain top has become easier. When I started, I'd
> see maybe 1 or 2 sets of fresh footprints per week. Now hardly a day goes by
> when someone doesn't hike to the top, and on weekends, I see entire families
> making the climb just to enjoy the spectacular view.
> 
> >From the top you can see all over Southern California. To the South and the
> East are Mt. Palomar and Mt. San Jacinto. To the West and Northwest, Mt.
> Wilson and Mt. Baldy, and to the North, Lake Arrowhead and the San
> Bernardino Mountains, and to the East, the 12,000-foot peak of Mt. San
> Gorgonio.
> 
> This past week it occurred to me how nice it would be to have a
> permanently-mounted terrestrial telescope up there that hikers could use to
> look at the many points of interest around them. I'm thinking something
> heavy and "clunky-looking" that wouldn't be worth stealing, but optically
> good enough to provide a nice view.
> 
> I have a machine shop, so I could make it myself, and I'm thinking that I'd
> probably make it from PVC plastic pipe, put it on an alt-azimuth mount made
> of galvanized steel pipe, and use inexpensive optics to keep the cost down.
> I'd make the eyepiece drawtube the simple slide-focus type with a stop on
> the inner end. Then I'd glue the whole scope together so it would be
> weather-proof, and so that you'd have to cut it apart to get the lenses out.
> I'd weather-seal the slide-focuser with greased o'rings.
> 
> The optics I'm thinking I'll need will be an achromatic objective from 50 to
> 80mm. in diameter, achromatic lenses suitable for making a Plossl-style
> eyepiece (1-1/4" would be o.k., but lenses for a 2" eyepiece would be even
> nicer), and an erecting prism, and I'd like to make the magnification in the
> 10X to 20X range.
> 
> Regarding the fate of the telescope once it's in place, I'm guessing that if
> I make it homely-looking, that will discourage people from trying to steal
> it. About 6 months ago I put up signs asking people on motorcycles to avoid
> riding on the trail (motorcycles were becoming a problem), and both I and
> the neighbors have been pleased with how well the people who use the
> mountain are now respecting those signs. If I include an appropriate sign on
> the telescope, I think there's a pretty good chance that people will respect
> it too.
> 
> In surfing the net today, I've found numerous good deals on objective
> lenses, and potential eyepiece lens sets (I could even cannibalize a Rini
> eyepiece), but I'm striking out on the unmounted erecting prisms. All
> suggestions on sources for cheap objective lenses, eyepiece lenses, and
> erecting prisms will be greatly appreciated.
> 
> Regarding the optics, with the understanding that the scope might be stolen
> or damaged, and that I'll eventually want to make another, it would be nice
> to find sources where I could buy replacement lenses and prisms if needed.
> 
> Finally, I've seen a new scope sold by Apogee. It's called a "Beer Bottle"
> telescope, and because the ads all say it can be used as a spotting scope,
> I'm guessing that it has a built-in erecting prism. But I can't find any
> descriptions of this scope that verify my assumption. With its 50mm.
> objective and its 18X magnification, it might contain all the optics I need
> in one package, and though it's physically smaller than what I'd like, with
> its low internet price of $19.95, it's certainly cheap enough. Anyone looked
> through one of these? Any opinions on the Apogee Beer Bottle scope would
> also be appreciated.
> 
> Dave Sleeter/Moreno Valley, CA
> 
> 
> 
> 
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> 



Robert Mohr
Director of Technical Services
TIW Technology, Inc
rmohr@tiwcorp.com
See our web site at www.tiwcorp.com
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