130625

130625 SBAU Telescope Workshop, June 25, 2013
EdK, JerryW, TomW, TomT, DmitriiZ, TomK (~845p)

DZ- has put in 2 hrs since TW told him 6hrs more might be needed.  He will be polishing tonight with CeO2  http://www.ceroxid.com/html/cerium_oxide.html after settling in the tool on the mirror blank.  JW explained that during polishing glass is moved from one area to another, not removed.  Also, some of the CeO2 polishing compound will be embedded in the mirror.

DZ- TT email him for DropBox link to his downloaded YouTube videos of telescope making that TW will use for Westmont presentation & DZ will show at Tinker Fest.
JW- showing TW spreadsheet / MathCad for JW scope calculation for Foucault knife edge error.  Entered TW scope parameters / knife edge variables into JW form for calculation.
TW- showed JW upcoming presentation on mirror grinding and parabolizing with math for Westmont College Summer Science Institute students.

TK- plans on being at SBMNH Tinker Fest.  TW will bring 8” with Baader filter for sun viewing that day.
TK- discussed his solar scope plans (4”?)
TK- TT send him link to this blog http://sbautw.blogspot.com
JW- To correct aberration that causes coma use a ParaCorr by Televue http://www.televue.com/engine/TV3b_page.asp?id=61, maybe cheaper by Baader:   http://www.telescopes.com/telescope-accessories/photographic/baaderplanetariummpccmultipurposecomacorrector.cfm

130604

130604 SBAU Telescope Workshop June 4, 2013
TimC, TomT,TomW,JerryW,JoeD
-Javier gave TimC a donated 8” polished pyrex glass, with the requirement that someone reports on the final product telescope back to the donator.  TimC brought this in tonight and TomT took photos of the glass, Edmunds rouge, pitched tool for polishing, and some extra.  Mirror measured to be a f/8 with the Ronchi test showing a good pattern?

-JerryW patiently explained focal radius vs focal length to TomT.  Also mirror types for various types of cassegrain telescopes.
-JoeD 6” brought in his $300 astro-tech newtonian F/4 mirror, which measured to about F3.9 on TomW testing setup and surfaces were viewed with Ronchi and knife edge.
-TomW measuring his two 6” glasses, one is R-87” f/7, the other is f/4, and examining the surfaces with Ronchi testing, perhaps a tad high center on the second? with the pinched center of the Ronchi pattern.
-TimC grinding his 16” w 120 grit still, JerryW spherocity tester shows it very good already.
-Finally TomW 10” F3.3 was viewed and it was almost perfect for the Ronchi pattern.
-TomT took off at 9pm to go see the outreach at UCSB Ucen...it was very busy there with students.
Photos available soon here for both the TW and outreach:
http://www.flickr.com/photos/27241501@N03/sets/72157633980863507/with/8975222139/
Potluck this Friday.

130115

SBAU Telescope Workshop, January, 15, 2013

attendees:  tim c, jerry w, tom t

-12.5” Cave mirror in cast cell brought in by Tim C.,

looking to make tube for it

Cave Optical Co. #M737961

F6, 75 1/8” F.L.  January 5, 1973

 -discuss aspect ratio for tom t.  6:1, thickness of glass to diameter of mirror.

Jerry talked about glass sag at thinner glass ratio (10:1)

-Book (and Sky&Telescope article) by Albert Highe

“Engineering, Design, and Construction of Portable Newtonian Telescopes”

-advantage of laminated vaulted birch wood:  better for lower coefficient of expansion than aluminum

photos taken at meeting:

http://www.flickr.com/photos/27241501@N03/sets/72157632584126122/