2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015
by Francis O'Reilly & Jay Drew
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Grind More, Worry Less
With the season changing and the Stellafane roads too muddy to support much traffic, we have moved to our winter home at Fletcher House in Chester, VT. Many thanks to Newsbank for providing this wonderful workspace.
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Kris' project ready to go.
12.5" Mirror/Tool Set
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Kris fine grinding with 15 micron Aluminum oxide with tool on top.
Kris Fine Grinding
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Holly made good progress hogging out her 8" f/6 mirror today, reaching a Sagitta of 0.62"
Holly Rough Grinding
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
The slurry of ground up carbo, glass, and water that develops after a good turn around the barrel using 80 grit.
Holly's Gritty Mud
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Long strokes with plenty of overhang are the key here. The coarse grit gets pretty noisy at this end of the workshop.
Bob Hogging His Curve
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Rough grinding is pretty straightforward, and Class Leader Francis is helping Bob fine tune his technique.
Francis' Helpful Hints
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Francis tests Jack's 8" mirror for complete polish. If a laser beam's reflection disappears into the glass, the mirror will be "polished out" to optical specifications.
Laser Test
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Jack's mirror is coming along nicely, but it still needs some polishing on the outer zones. He will do some Tool on Top work to accomplish this.
Jack & Francis Laser Testing
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Francis, Phil, and George discuss the progress on George's 8" f/6 mirror. He is grinding at 9 micron.
Fine Grinding Conference
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Grind More, Worry Less
Most of us purchase our supplies from Tom at gotgrit.com, but FirstHandDiscovery.com is another good source for ATM materials. George bought his grit kit from them and is happy with the results.
Grinding Supplies
TM Class TN's
A couple of pictures of folks on hand today.
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015TM Class TN's
Always positive and full of interesting ideas, Tom entertains us in one of the 5 identical NASA shirts his Mom provided.
Tom
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015TM Class TN's
STM Keith is figuring his 6" f/7 mirror.
Keith
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015TM Class TN's
Does the gentleman signing the poster look familiar? Francis shared this picture of his young son from 1988.
Vincent & Clyde
Making a Pitch Lap
A series of photos showing the process STM Glenn Jackson uses to create a polishing tool. Glenn was in charge of the Mirror Demo presentations at Convention this year and his hard work really paid off there. Here he gives a step by step master class in pitch lap making.
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Glenn has used our Easy Bake Oven to melt a pan full of Gugolz 64 pitch. He likes to pour his when it is relatively thick and sticky.
Melting the Pitch
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
A look at the consistency Glenn prefers.
Pitch in Pan
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Glenn has a dental stone tool ready to go, and taped a dam around the edge. The pitch is poured directly on top of the tool about 3/8" thick
Poured on the Substrate
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
After cooling for 15-20 minutes, Glenn ripped the tape dam away leaving a nice pitch disk stuck to the tool.
Tape Removed
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Glenn uses a dash of polishing compound to wet the mirror before placing it on top of the pitch and pressing in the curve.
Lubricating the Mirror
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Using body weight and keeping the mirror in motion, Glenn presses the originally-flat pitch surface into contact with the mirror.
First Press
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
The pitch flows slowly and us bigger ATMs have an advantage in weighing down the mirror. Resistance is futile.
Heavy Pressing
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
After maybe 5 minutes of pressing, Glenn takes a look at the result. Pretty nice.
First Look
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
As sometimes happens, there is a pretty big hole in the pitch near the center of the lap. See it?
Big Bubble Divot
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Rather than leaving this defect, Glenn drizzles in some warm pitch to fill up the hole.
Filling in the Concavity
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
It's a simple matter to press this new dollop of pitch into contact with the mirror. Poof! Divot gone.
More Pressing
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Making a Pitch Lap
Our new creation is ready to channel. Next step, polishing time.
Final Result
Polishing and testing in action
Class members enjoying the seemingly endless process of creating a perfect optical surface.
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Fran has been battling this very fast 12.5" Cassegrain primary mirror for some time, using a variety of sub- and full-diameter tools.
Fran Figuring
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Using very light pressure (note Fran's hands supporting the mirror rather than pressing downwards) to correct an outer zone.
Big Overhang
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Phil takes a turn on one of the student mirrors, demonstrating a corrective stroke.
Phil Phiguring
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
STM Dan working the lap. He began this mirror when he was a youngster and has recently returned to working on it.
Dan Polishing
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Jack uses the flux capaciter ray gun to fuse his mirror to the grinding table.
Jack and the Ray Gun
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Jack's laser test showed he still had some sweat equity to put in before his mirror is polished out.
Polish Polish Polish
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Caleb is a steady strong worker and is almost done with the polish.
Caleb Making Progress
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Francis checks Caleb's pitch lap. He has used a nylon onion bag to press in a couple million little microfacets, which helps the pitch flow and speeds the polishing action.
Micro Facets Galore
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
Moment of truth, is it done? Tom is still putting the final touches on his 8" parabola. The verdict? Still a little overcorrected. Tom will use TOT and a star lap to bring down some of the overcorrection.
Testing Tom's Mirror
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Polishing and testing in action
STM Dave's gorgeous Foucault Tester with Autocollimation Flat locked and loaded.
Tester: The Business End
Shaking out the grit
George and Holly help with cleanup at the end of the day. Time for some hot beverages.
2015-16 Stellafane Telescope Making Class Session 03 held on December 12, 2015Shaking out the grit
Working in the beautiful Fletcher House is a treat, but we're careful to lay tarps down to avoid getting grit, pitch, and cerium all over Newsbanks floors. George and Holly are kind enough to help us clean up the tarp for next month's adventures.
Folding the Tarp
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