Page 18-19 lists an astigmatism issue with Herschelian telescope (with secondary flat mirror removed). Is this an issue with all folded newtonians, that do...
A folded Newt. is used on axis as normal, it is not an off axis configuration like the Herschelian so the aberrations are only those of a typical Newt. of a...
As long as the flat secondary is on the axis of the parabolic mirror, there is no astigmatism. It doesn't matter what angle the deflection to the side focuser...
Can anyone tell me where I could find a good source of Dob component parts, off the shelf? Specifically, aluminum 18 point floatation mirror cells, and C...
Hi Jeff Will you settle for used? Astromart and cloudynights classifieds are good sources. New, just google what you want and different manufacturers will...
Try www.webstertelescopes.com they sell floatation cells, altitude bearings and other Dob parts. John ... From: Jeff To: bigdob@yahoogroups.com Sent: Monday,...
Im in the process of designing an obsession style 16" truss dob. Ive been reading David Krieg's book and he basically says you can use almost any ply to make a...
The next best would be true marine plywoods. The have no voids and likely use even better glues/adhesives. Before Baltic Birch was imported into Canada, I...
Thanks for the reply. so you say true marine ply would be fine. That begs the question, what specifically is true marine ply? I mean, when i go to a large...
Bob is correct about marine grade ply. the main thing (in Ireland) is to double protect it from water. When I visited there, I enjoyed the hour a day of rain,...
I'm a cabinet maker in Canada. I agree that the high quality plywoods are best - from a looks and quality point of view. But, I agree with Bob Bunge that any...
The key piece if you are using a non-marine grade plywood is to at least use an "exterior grade" plywood. Exterior grade plywood uses water proof glue. Marine...
...of New Perspectives on Newtonian Collimation is now available. Information is available here: http://homepage.mac.com/vicmenard/telescopes/index.html The...
At the Texas Star Party (TSP) and at Riverside last year, myself and colleagues were extending invitations to northern hemisphere observers who would like to...
I have downloaded PLOP and inputted my mirror details. it has generated an 18 point design,but i have no idea how to find the dimensions of my mirror cell. im...
I already have the 1 1/4" UHC by Lumicon, but I really don't want to spend about twice that for the 2" UHC Lumicon filter or other filter costing that much or...
If I were you I would seriously consider the DGM Optics NPB Nebula Filter, see a review and other comments here; http://tinyurl.com/6ow28b I have had this...
Since the subject of plywood and weathering is being discussed, I'd like to get different opinions of how many coats of unthinned urethane people think are...
Ha!!! one guy at Okie-Tex explained to me he put urethane on until he was just too sick and tired of it to add another coat. Are you sick of it after 5 coats?...
While we're on the subject of urethane, I understand that Obsession (perhaps others) puts multiple coats of polyurethane on their Dobs after the stain. My...
Hi Dave, I refinished my 1991 vintage Obsession with spray MinWax urethane after the original coating started to degrade after about four years of heavy use. ...
Good quality spar varnish has UV protection built in since it is intended for exterior use (originally the spars and masts of sailboats). Pat [Non-text...
Urethane is frequently used simply as an overcoat to protect the sealed wood surfaces from solar Ultra violet damage. When so used, numerous coats aren't...
... From: Bob <gofast3@...> Subject: [bigdob] Re: Polyurethane vs. Spar Urethane To: bigdob@yahoogroups.com Date: Friday, November 14, 2008, 11:58 AM ...
... <What desert do you observe from? Our scope is soaked in dew nearly every night.> I'll assume for the moment that you did not read my exchange completely...
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