130924

130924 Telescope Workshop notes 730-9p Tuesday evenings
Attendees:  JerryW, EdK, TomT, TimC, TomW, ChrisU, DmitriiZ










TomW- melting and pouring pitch for 9” tool to be used on EdK’s 12.5” mirror.  The pitch was poured into a release (isopropyl/detergent solution) coated silicone waffle pitch lap pad with 1/8” divisions between the .75” squares of pitch 1/4" deep (LM-4 "Perfect Pitch" Lap Mold
 https://home.comcast.net/~kevin.mccarthy137/Pitchlaps/index.html#top $56 shipped ). Two 3/4” plywood disks provided by EdK, which TomW glued together and sealed to waterproof, the now 1.5” thick disk, with Dap clear varnish (water based, that dries in about 10 minutes between coats, 6 coats used).  The disk was placed on the pitch while it was still hot & soft with a gallon of water placed on top for forming weight.  Thirty minutes of cooling time is then needed.  The waffle pitch lap mold was pulled off the pitch very gently and it released perfectly.  TomW then chipped off the pitch pieces that extended over the edge of the disk.  As a test, Tom placed the pitched disk directly onto the mirror and the fit was great.  A little polishing with the Cerium Oxide solution was done, and after washing it off, a few squares of the pitch was beginning to show the polishing compound, white, loading into them.









TomW’s Pitch is basically beeswax and pine sap purchased from Willmann-Bell that TomW has had stored for about 10 years.  TomW broke off some of this “new” batch to add to the pitch left in the pan.  JoeD gave electric heating pad and pitch pan to TomW some time ago.    Five pounds of pitch is about $60 from http://www.willbell.com/ATMSupplies/ATM_Supplies.htm








TimC-continued his work on donated 8” mirror grinding to f/5, now today with 220 grit.  TimC used the 8x loupe to check the surface at the end. 
DmitriiZ- continuing polishing his 12.5" mirror to improve characteristics (after forming his pitch to the mirror).








ChrisU- talking telescope supplies with JerryW and TomW.  TomW recommended  TMB, Tom Back, eyepieces, maybe an 8mm for ChrisU.  TimC has one he can test.  Chris will take photos of his setup so far that he is making, and next week maybe bring in for discussion.  http://www.tmboptical.com/
TomW will be teaching an optics class at Westmont and he discussed the textbooks available with Jerry (JW mentioned Kline, Rossi) http://scienceworld.wolfram.com/physics/Optics.html
See more photos / videos here: http://www.flickr.com/photos/27241501@N03/sets/72157635885172366/

Workshop on for Tuesday, Sept 24, 730pm

-------- Original Message --------

Subject:	Workshop
Date:	Sun, 22 Sep 2013 10:33:48 -0700
From:	Tim C
To:	Tim C

There will be a workshop this week September 24th.  The workshop is humming along now with activities. Come on by if you'd like to see many projects in different stages of progress. Bill , could you have the gate open please? Thanks!  I believe in the near future we will need advice on designing some Dobs now in progress. If you are in this category,  please consider coming by in the next couple of weeks. I have a sense we will be discussing  building of Sona tube type Dobs. Tom and Jerry have some very informative ideas of how to start, and progress through the building. Once we have identified who will be using this design I'd like to invite some of our woodworking friends in to assist with what you will need to continue.

T

PS-if you will need to bring in materials to the workshop we can help you to bring them in if they are bulky or heavy.  There are push carts I think we can use or we can meet in the parking lot or upper end near the side gate. We are allowed two cars to come to the Broder, and we can load your materials and bring them in and take them out at the end of the night. Let us know if you need assistance. 

130917

130917 Telescope Workshop notes
Attendees:  JerryW, EdK, TomT, TimC, TomW, ChrisU, DmitriiZ
TomW- brought in the actual book “Understanding Foucault” by David Harbour and TimC another book, “Making a Refractor Telescope” by Norman Remer.
TomW- also brought in his 8” concrete tube for his f/5, 6” mirror with his specially designed bearing wheel and cross supports that allow for the tube to slide within it.

TomW- continued polishing out EdK's 1968 Pyrex 12.5” f/5 mirror:  polishing 45min the raised center with a 6” and wider motion this time.  TomW set up the Ronchi tester, with the 100 line per inch grating, to check the mirror progress.  Foucault test was done also. Center looking better, but TomW thinks a larger polishing tool is needed to correct the surface as a whole.










TimC-continued his work on the donated 8” mirror grinding to f/5 with 120 grit.  TimC let TomT practice the grinding cycle/motions (1/3 over centers) with the mirror.  Since proper depth has been reached, the mirror glass blank and the tool were switched bottom/top positions about every 3 grinding cycles around.  At the end, TimC showed us the cleaned off surface of the mirror glass showing more evenly ground surface with his loupe.  JerryW looked at it and says another hour is needed to get the surface pits more even at 120grit.










DmitriiZ- formed the pitch to his mirror and was continuing polishing his 12.5inch to improve characteristics.

















ChrisU- showed us his paint grinding glass pestle that is used with a glass mortar.  Chris also brought in and shared a tasty treat.
More photos and vids here: http://www.flickr.com/photos/27241501@N03/sets/72157635818957903/

130910

130910 Telescope Workshop notes
Attendees:  EdK, TomT, TimC, TomW, Martin Meza, ChrisU

TimC-showed us the Kindle book “Understanding Foucault” by David Harbour [ http://www.amazon.com/Understanding-Foucault-David-A-Harbour/dp/1934916013 ] on his Samsung tablet.

TomW- on EdK's 1968 pyrex 12.5” f/5 mirror:  polishing 60min the raised center with a 6” and center only motion.  TomW also set up the Ronchi tester, with the grating, to check the mirror progress.  Foucault test was done also. Center looking better, but a lot of heat was coming from the mirror due to the polishing.

TimC-continued his work on donated 8” mirror grinding to f/5 with 120.  TimC let TomT practice the grinding cycle/motions (1/3 over centers) with the mirror.  Since proper depth has been reached, the mirror glass blank and the tool were switched bottom/top positions about every 3 grinding cycles around.  At the end, TimC showed us the cleaned off surface of the mirror glass showing a more evenly ground surface.

Martin brought in his 8” Dobsonian with a dovetail mount that he had purchased from Mike Farris.  The unit has a mirror that was aluminized in San Carlos, May 2008.  The focuser was donated to Mike by JerryW.  He will be offering this unit up to ChristopherU for $175 or so as CU has been looking for a finished 8” mirror.  Chris accepted the deal, and TomW bought the dovetail assembly from Martin.
More Photos/Vids here: http://www.flickr.com/photos/27241501@N03/sets/72157635600207075/with/9792371316/ 

130903

130903 Telescope Workshop notes
Attendees:  EdK, TomT, DmitriiZ, TimC, TomW, JoeD, NathanF, JerryW
EdK- 1968 pyrex 12.5” f/5 mirror: TomW showed EdK how to polish out the raised center with a 6” tool (TomW made for EdK) and center only motion.  TomW set up the Ronchi tester, with the diffraction grating, to check the mirror progress after 30 minutes and again after 15 minutes of polishing.  I think the mirror was improving a bit. EdK had a price list for a barn door type telescope mounting base ( http://www.equatorialplatforms.com/ ).










TimC-continued his work on donated 8” mirror grinding to f/5 but skipping to 220 grit from 80 grit since 120 grit was not available.  TimC let TomT and ChrisU practice the grinding cycle/motions (1/3 over centers) with the mirror.  TimC explained that once the needed depth of sagitta (curvature) of the mirror blank is reached by larger grit grinding, then the mirror glass blank and the tool need to switch bottom/top positions about every 3 grinding cycles around (or when the grit wears smooth?), so that the center and edges of the mirror wear down evenly.  At the end, TimC showed us the cleaned off surface of the mirror glass showing some imperfections from the unfinished grinding process.










DmitriiZ-working on his 12.5”, polishing the center down, DZ used TomW idea to form the pitch against mirror with a “washer of paper” at the edge, so the pitch extends a fraction more out in the center.  Later tested on TomW Ronchi tester, it was still high in center and TomW/JerryW giving ideas on how to polish out the  center. 










JerrryW talking a long time to NathanF & TomT about astrophotography, and types of camera sensors, noting that human eyes are most sensitive to green light. NF is looking to take good photo of M31 for one.  ChrisU asked JW about finding a finished 8” mirror that he can construct a telescope around and JW checked CloudyNights.

More photos and videos:  http://www.flickr.com/photos/27241501@N03/sets/72157635376717258/