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/

130827

130827 Telescope Workshop notes
Attendees:  EdK, TomT, DmitriiZ, TimC, TomW, JoeD, Nathan Fields (interested in astrophotography)

EdK-brought in 1968 pyrex 12.5” f/5 mirror blank  w/ Couder disks that had been polished and TomW set up his tester again to compare against his Ronchi patterns that he brought in for center and edge comparison.

DmitriiZ-working tonight on his 12.5”, polishing the center down, will test on TomW Ronchi tester. Still high in center and TomW trying to give ideas on how to polish out the  center.  Laser showed edge  not polished out.  TomW came up w/ idea to press pitch on mirror with a “washer of paper” at the edge, so the pitch extends a fraction more out in the center.  That will have to be done every 15 minutes as the pitch wears down smooth again.











TimC-continued work on donated 8” grinding to f/5 with 80 grit still.  Nathan observed the sagittal depth measurement with the drill bit and used the loupe to see the surface with TimC explaining.  Depth is getting close to desired.

JoeD-brought in Amateur Telescope Making Journal books vol. 1 & 2 containing various articles.  Also a book on woodworking to make chests and cabinets.  EdK took them home to read.
See more photos, videos:  http://www.flickr.com/photos/27241501@N03/sets/72157635269973582/

130820

130820 Telescope Workshop notes
Attendees:  EdK, JerryW, TomT, DmitriiZ, TimC, TomW, ChrisU


EdK-brought in 1968 pyrex 12.5” f/5 mirror blank  (also w/ couder disks  http://stellafane.org/tm/atm/test/mask.html) that had been polished and TomW set up his tester (1/4-80 threads on adjuster!) for Ronchi test and  resultant patterns in and at focal length.  TomW's verdict was center of mirror was not quite deep enough for perfection, but edges look good.  Foucault knife edge test did not show the problem in the center as well.   TomW recommends 6” tool to work on center to deepen it.  TomW will bring in a calculated Ronchi pattern chart from the focal length of 127” to use by EdK for finishing the mirror.

TomW says edges good

TimC-continued work on donated 8” mirror blank grinding to f/5 with 80 grit still.  Many “wets” or “charges” of the grit was used.  When the measurement of the sagittal, depth, is satisfied the smaller grits will be used.
TomW-brought in another crisp, this time rubarb, apple, peach, strawberry…delicious again.
ChrisU-has been looking for mirror blanks prefinished on the internet; JerryW recommended Cloudynights.com for its classifieds.  TomW showed him the tester and pin sticks describing the percent of light gathered at each pin distance across a mirror.
JerryW-has been working on his 10” Cassegrain, 14” Dahl-Kirkham, and 18” Newtonian at home…all have the grinding stage done.  He is currently grinding the 6” spherical secondary for the Dahl-Kirkham.
See all of tonight's photos and videos of mirror here: http://www.flickr.com/photos/27241501@N03/sets/72157635163404065/

130813

130813 Telescope Workshop meeting minutes August 13, 2013
TimC, TomW, JerryW, EdK, TomT, new member Christopher Ulivo (SBCC Art Prof) [see:  http://christopherulivo.com/ ]

 TC-Astrovaganza went well at the Broder Bldg, August 10, but Powerpoint timing seemed off and was not viewed that much.
TW-shared his large homemade apple crisp...delicious!

TC-discussing telescope making w/ CU, who is more interested in building the telescope mount than grinding out a mirror.

JW-using Edmund spherocity tester on his corrected Dahl-Kirkham secondary mirror.

JW-also showing Moonlite telescope accessories Dobsonian truss mounts to EK.
TC,TW-grinding 8”  donated mirror (80 grit) and TC describing  depth needed to CU.


















JW-showing CU that firsthanddiscovery.com sells mirror kits w/o tool

130722 TimC Subject: Tinkerers' Faire

130722  TimC:  Subject: Tinkerers' Faire

I just wanted to send a big shout out of THANK YOU!!!!! all of you who participated this past Sunday. I think it was a big success. We may get some hard numbers of the attendance sometime in the future. I will guess we had at least 400? I know some of you had to make arrangements or didn't feel tip top that day. I really thank you for making the effort to coming out. Justin C did a great job in organizing this event. The walk in with the carts was way easier than I thought it would be. I actually got all my stuff on one cart (almost). Javier was great to make arrangements for us to pick up the monitor. Dmitrii, I thought the presentation you created was perfection. I hope we can do it again this coming August for the Astrovaganza ( or someone can run it.). The pictures on the monitor were worth not having to explain certain aspects of mirror making and more. Customers could see it. Tom K said he had a whole bunch of kids. The idea to set up on the nearby bench was truly a good match for these little ones. Joe D was so helpful that day to me his help was indispensable. The prank to have the front desk ask me for I.D. was actually a good one. You got me. Tom T was a floater as well as Ed K. Tom thanks for handling the hand outs for me! Having free floaters I believe is a must. Tom W. and Jerry, what can I say? When I have any hard questions come at me, I automatically turn to find you two. Couldn't do it without you both. Hope you are feeling better Tom. Jerry, thanks for going the extra mile for us. Give Pat our best!( The dog needed a day off anyway;-) ). I was in the classroom with Jerry and mentioned how disappointed not having my good buddy Ed Edwards ' there was. I was really looking forward to him giving his take on old school amatuer astronomy to the customers. Jerry told me," You never know, maybe he got the message and he will be here any moment." Two minutes later, he walked into the lunchroom! Thanks to Gary R for dropping everything to help us get Ed's scope into the canopy area! Gary, I hope you got to see the Tour final stage that evening. (You too Ed K.) The visuals on the Arc de Triomphe were just the best!!! Last but not least I want to thank the AU for letting us use the new monitor. I will tell you, it was not money spent in vain! It is really cool! Just the right size! We will do it all again this August if any of you are up to it. Next month, I think we will be at the Broder Building to set up our presentation. Personally, I hope you can make it. You guys are just great. I was watching. I'd put you guys up against anyone, anytime, anywhere. Period. T