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Posts Made By: Dominic Di Leo

August 27, 2008 05:20 PM Forum: Telescope Making

virtual counterweight question

Posted By Dominic Di Leo
Guy,

Google "tom krajci virtual counterweight"

Email him and he will respond if you still need help.

November 10, 2008 03:10 PM Forum: Telescope Making

Triplet objective f/2.8 78mm??

Posted By Dominic Di Leo
Probably a Cooke triplet projection lens. Color corrected for a limited distance and not corrected for infinity. Usually these purpose designed assemblies don't do well for other applications.

January 17, 2009 05:08 PM Forum: Telescope Making

Selling Machine Tools

Posted By Dominic Di Leo
A good inventory with full model numbers is a must for starters. Palo Alto, Oakland Bay area, must have some used industrial machinery resellers that may make an acceptable offer for the lot. For a fee, she may be able to get everything appraised for fair market retail and sell items piecemeal on Craig's List.

April 7, 2009 11:31 PM Forum: Telescope Making

Folded Refractor

Posted By Dominic Di Leo
Nicely executed work. If you think a double fold requires preplanning and accurate alignment...........here is a clever triple fold constructed by Dave Bevel inspired by an original article on this design in S&T.

http://www.gate.net/~davebevel/Drumscope/

June 10, 2009 09:42 PM Forum: Telescope Making

Mirror cell for 17.5 inch f/4.5

Posted By Dominic Di Leo
The author of PLOP considers an rms error less than 4.3e-06 as being sufficient for most optics. Six points of support will work okay, whether it be Pyrex or plate. If that is a Coulter mirror with the original figure, then I am absolutely sure six points will do.
Mark Holm has done an extensive workup of different size examples and uses 2.5e-06 as a cutoff for acceptability. His work considers support for fine figured optics and can be viewed at:

http://www.atmsite.org/contrib/Holm/Plop_optimized_cells/index.html

July 23, 2009 03:51 PM Forum: Telescope Making

Stress testing mirrors

Posted By Dominic Di Leo
Probably a poor anneal if the glass is more than an inch thick. Commercial tempered glass rarely is more than 3/4in. You can cook it and slow cool to relieve it. Is it borosilicate or soda lime?
BTW, Schott is producing Borosilicate in 67mm thickness. It is hot rolled and the same material as Borofloat 33.

December 30, 2009 12:43 AM Forum: Telescope Making

Folded Refractor

Posted By Dominic Di Leo
I replied before when this topic came up.

"Have you considered a drumscope? There was an article about the design in S/T. Dave Bevel made a nice version of it and put up several very good pics on his website.
The topic string is in the ATM
archives: http://astro.umsystem.edu/cgi-bin/search_atm.cgi?query=drumscope&show_context=0&results=0

and Dave's site is:
http://www.gate.net/~davebevel/Drumscope/"

His entire project list is a worthwhile read. Open up his parent directory for more of his work.


January 4, 2010 09:58 PM Forum: Reflectors

new orion dobs

Posted By Dominic Di Leo
The 36 is for real. The sandwiched float lime glass mirror is fabricated by Jean-Guy Moreau and finished off by Normand Fullum. Bill Byrd who frequently posted on Astromart has one. You can find several pics and the discussion here:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=475590&poll_id=&news_id=&page=

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