Re: Re ATM Light Pollution Filters

["B. Pepin" <atmjedit@conceptsnet.com>]

Yes! That's the spirit!


----- Original Message ----- 
From: Philip J. Tramdack <tramdack@TCNJ.EDU>
To: Peter Jones <pmjco@email.msn.com>
Cc: ATM Mailing List <atm@shore.net>
Sent: Wednesday, September 13, 2000 7:07 AM
Subject: Re: Re ATM Light Pollution Filters


> 
> I have been observing mainly from my backyard outside of Pennington in
> Hopewell Twp NJ since mid '92. Although semi-rural this is about 7 miles
> west of Princeton and 4 miles north of Trenton. Limiting magnitude on a
> good night is about 4.5 directly overhead. On the best of nights the
> Milky Way in Cygnus is visible as a very light band. On one occasion I
> saw granulation in the Milky Way (in 8 years). Across the street my
> neighbors have an unshielded motion-detecting security light to protect
> the junk cars. Since they come and go until sometime after the bars
> close, all nights of the week, the light is going on and off until 2:30
> most nights. My other neighbors occasionally leave the porch light on
> etc., and this is annoying as well. There is a shopping center .5 miles
> away.
> 
> I experimented with a semi-permanent octagonal light shield about 8'
> across and 7' high in a corner of the yard for about 5 years. It was
> made of UNGLUED 1" or so PVC pipe and canvas tarp stretched around and
> guyed out. Unglued so that in a high wind it could blow down rather than
> break up. This worked great as often I could see 5 mag stars overhead;
> also it shielded from the wind in the winter and reduced dewing. The
> theory here is that if you can shield your eyes from direct view of even
> far-away lights (like street lights) and you use a heavily shelded red
> reading light, you can extend your dark adaptation considerably. It goes
> without saying that lighting up the old seegar every 10 minutes won't do
> at all.
> 
> I gave that up because it limited my views of the whole sky enough to be
> a pain. Now I keep the telescope (10" f/6) in its rocker box in a
> Rubbermaid shed ready to go and wheel it out with a hand truck. The 5
> miniute set up definitely helps me keep my 50+ observing sessions per
> year schedule.
> 
> I did however miss the light shielding benefits of the canvas shelter,
> so this July I made a new portable shelter that also works great. It has
> three ripstop panels 9' x 5' stretched on 11' long 3/4" PVC pipe that
> cross in an X. The 11 footers are made up of lengths 6.5' and 4.5' that
> join in an X fitting also unglued. The top of the panel has a PVC cap in
> each corner; the bottom caps are at the ends of 2' of nylon line, so the
> panels are like sails stretched on the PVC Xs, about 7' off the ground
> at the top with about 2' clearance off the ground. The three panels can
> be set up at right angles with one side open, or as a triangular shelter
> with no sides open. They are more or less self-supporting. The whole
> thing breaks down into a pile of pipes and the three sails which fit in
> a stuff sack smaller than a sleeping bag. Set up is about 5 minutes. So
> far, this has worked great, being portable anywhere, stable in a
> moderate breeze (although guying out is a good precaution) and although
> not opaque, sufficiently proof against light that inside it I can see
> below 5th mag stars overhead when only 4th mag stars are visible in
> direct view of lights. I do not have a scanner so it is not convenient
> to post pictures but you get the idea. PJT
> 
> 
> -- 
> Philip J. Tramdack
> Associate Dean for the Library
> Roscoe L. West Library
> The College of New Jersey
> Box 7718
> Ewing  NJ 08628-0718
> vox 609-771-2343
> fax 609-637-5177
>