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Posts Made By: David Simper

September 14, 2006 02:12 AM Forum: Telescope Making

Flotate or not ?

Posted By David Simper
Dilemma: for a 12.5" thin (1") quartz mirror, at 6 points of support calculated by Plop for the material of this specific mechanical characteristics, would silicone gluing to 6 fixed pads (done right over spacers) be equivalent to a 3 lever 6-point flotation cell ?

October 27, 2006 11:17 PM Forum: Equipment Talk

Opinions HEQ5/Sirius mount

Posted By David Simper
I am finding surprisingly small number of reports about this mount. Anybody around has one esp. with the goto function ?

Thanks,

David

March 1, 2007 04:20 AM Forum: Star Parties

Any plans for Grand Canyon SP ?

Posted By David Simper
Are you planning to go ? Are you privy to some insider info, like will the side meadow be available on the South Rim this year, will there be less lights on the porch at the North Rim, are you considering combining it with a side observing trip (e.g. Canyonlands, Arches, Monument Valley ?)

David

March 31, 2007 12:22 AM Forum: AstroMart FAQ

Google has no barriers ?

Posted By David Simper
How come that Google spider can get to the >text< of the messages ? Normally non-members have to sign in to read the body of messages ...

Example:
http://tinyurl.com/2lgwq3

May 8, 2007 03:09 PM Forum: Refractors

Re: Vixen ED102SS f/6.5 = doublet or triplet?

Posted By David Simper
A doublet. Even with Moonlite focuser wink The third element in the drawtube is for photography only. And it has MUCH worse C.A. then NP-101.

October 16, 2007 04:51 AM Forum: Equipment Talk

Off topic but optical problem

Posted By David Simper
I need advice of local optical theory gurus.

I need to find out parameters for a paraboloid reflector to reflect all light radiated by a T5 fluorescent tube. T5 means the tube is 5/8" in diameter.

My current polished aluminium reflector for an aquarium tank has a primitive \_/ shape with only two bends
http://www.publiclogic.com/fish/DSC06698.JPG
and in fact is worse looking from the transport than the one in the picture, it resembles more |_| causing most of the light from the back of the tube to get lost ("re-strike" phenomenon).
This gave me an idea that when I will try to reshape it, I may better give it a paraboloid shape.

So the optical problem is like this - if you have a spherical focal plane of 5/8" what size and shape needs the reflector to be ?

As you can see in the photo, the tubes are rather crammed together so there is not much space for the diverging sides of the reflector..

March 16, 2008 04:48 PM Forum: Eyepieces

How bad are cheap zooms ?

Posted By David Simper
I need a eyepieces(s) for a friend who is starting astronomy hobby and is tight on budget. He got Celestron 80ED OTA. Would be one of the cheap zooms like Orion Explorer II 7-21mm Zoom Eyepiece ~$50 good enough or does it have severe limitations ?

June 20, 2008 07:06 AM Forum: Ask rating questions here

First negative ?

Posted By David Simper
I am considering first negative rating.
I responded to ad with "I will take it" and some clarification questions re details of the item.
During the day, his response was that he received so many inquiries that he should have ask more $$$.
Last email was that he sold locally.
I responded that I thought that "I will take it" means a commitment on AM.


October 30, 2010 08:53 PM Forum: Equipment Talk

Re: Dobsonian Makers

Posted By David Simper
Do you know about http://www.dobstuff.com ?

I have no experience with them but would try them to finish my never done scope, if I ever get it from Starbuckets.

That's the risk you take with going less tried route - that many years later you have no money, no Zambuto optics, no scope and no replies from the garage maker.

July 6, 2002 02:03 PM Forum: Telescope Making

Triplet or Doublet at decent price ?

Posted By David Simper
http://www.apm-telescopes.de/products/apm_achro/tmb_achromaten.htm

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