Session 04 held on 2016-01-10

Grinding at Stellafane

Working in our winter home at Fletcher House in Chester, VT.

Session 04 held on 2016-01-10 Grinding at Stellafane The Fletcher House Conference Room stripped down and the floor covered with a blue tarp to catch the dripping grit.	Session 04 held on 2016-01-10 Grinding at Stellafane Barrels set up and grit is flying.	Session 04 held on 2016-01-10 Grinding at Stellafane Stephen is polishing in the grinding room, being careful of contamination. Glenn is working on a new project in the background.
Session 04 held on 2016-01-10 Grinding at Stellafane This little guy was the hit of the day.	Session 04 held on 2016-01-10 Grinding at Stellafane Ray is working on a 14.5" Quartz mirror. It is fairly thin, so to avoid flexure he has it attached to an aluminum backing plate using blocking pitch as glue. Hopefully this will prevent astigmatism from creeping in, but it is pretty heavy.	Session 04 held on 2016-01-10 Grinding at Stellafane Slinging that giant piece of glass around is tiring!
Session 04 held on 2016-01-10 Grinding at Stellafane Holly has completed hogging out her mirror and is ready to start fine grinding.	Session 04 held on 2016-01-10 Grinding at Stellafane Bob is also finishing up the initial curve generation with 80 grit carbo. It takes some effort.	Session 04 held on 2016-01-10 Grinding at Stellafane Ready for another session of amateur telescope making.
	Session 04 held on 2016-01-10 Grinding at Stellafane Ray, previous Mirror Class Leader and Francis, current Telescope Making Class leader, inspecting Ray's 14.5" mirror for consistent pits. Once they are happy with the surface Ray will move on to the next grit size.

Making Pitch Laps, Polishing, and Figuring

Some instructors and students going through the steps to polish out and figure their mirrors.

Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring The channels in Tom's pitch lap are closing up with all the pressing and work he is doing to finish the parabola, so he is using a razor blade to open them up.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Club member Glenn has got another project well in hand here.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Fran's 12.5" f/3.9 Cassegrain primary has been giving him fits with the final figuring stages. The surface is quite smooth, but has been stubbornly overcorrected with a tenacious turned down edge. Fran finally put it on his Mirror O Matic polishing machine and returned it to a nice sphere with a smooth edge. Time for another crack at the elusive parabola.
Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring We use old fashioned heat lamps to warm mirrors and pitch. Here Fran's big Cass primary is getting a sunbath in preparation for pressing a new pitch lap.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Reade is putting correction into his 6" mirror.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Warming up the mirror and lap for a nice pressing session. Keeping good contact between the mirror and pitch lap is important.
Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Keith is also in the figuring stage on his 6" mirror and here we find him screwing down wooden chocks to hold his mirror/tool in place on the barrel.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Francis shows his famous smile while hoisting one of the mirrors for his Stevick Paul system. Note the graffiti on the back.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Instead of keeping a traditional polishing log, Francis is tracking his progress right on the mirror. Saves a tree.
Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring George and Francis pour a pitch lap in the basement. They are using a "Perfect Pitch Lap Mold" from Kevin McCarthy in New Hampshire.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Everyone has an opinion on laps and many of us here at Stellafane like the ones we make using molds. There are lots of advantages and we'll try and do a photo spread on them soon.	Session 04 held on 2016-01-10 Making Pitch Laps, Polishing, and Figuring Dick's 12.5" Autocollimator and bench are in the background.

Optical Figuring Advice

A couple pictures of the master gurus in action.

Session 04 held on 2016-01-10 Optical Figuring Advice Different strokes for different strokes.

Session 04 held on 2016-01-10 Optical Figuring Advice Chasing the wild parabola.

Setting Up Our Portable Test Bench

We store this beast in the Fletcher House basement over the winter and drag it out for classes.

Session 04 held on 2016-01-10 Setting Up Our Portable Test Bench Our test bench is quite heavy so is split into two pieces. Here Tom and Keith are dragging the first half up from the basement into the testing room. The black face pointing towards the camera is the working bed of the bench, painted to reduce glare from the tester. You can see the two aluminum rails that hold the mirror and the blue tape we use to mark the position for different mirrors.	Session 04 held on 2016-01-10 Setting Up Our Portable Test Bench Keith, Tom, Dave, and Ray connect the two halves. We keep it nicely lined up square so that it's easier to test multiple mirrors with minimal realignment.	Session 04 held on 2016-01-10 Setting Up Our Portable Test Bench Keith sets up the canvas shroud that keeps light out of the tunnel. You can see the tracks that support our mirror stand. This can trolley along towards and away from the tester depending on the focal length of the mirror while staying in alignment with the light path. This feature really helps when multiple mirrors are up and down from the tester. Dave's magnificently machined aluminum Foucault Tester/Autocollimation flat can be seen on the left.
	Session 04 held on 2016-01-10 Setting Up Our Portable Test Bench Dave at the business end of his tester. His right hand is adjusting the Knife Edge fore and aft along the focal plane to examine different zones of the mirror under test. The wire running near his eye to his hand is a high output fiber optic line, a real upgrade to the standard Foucault tester lightsource. You can see the edge of his 12.5" Autocollimation flat to the right. This is a super flat on a cellular pyrex substrate that he figured himself. Resting on the right side of the tester you can see a Howie Glatter laser collimator. By placing this at the Light Source point, Dave can quickly align mirrors for testing. All the beautiful aluminum machining is Dave's own work: besides having a complete optical shop at home Dave is also a skilled machinist with all the metal working tools that make a Man Cave special.

A Rainy Winter Day

Turning our previous snow into icy slush and starting to flood the basement.

Session 04 held on 2016-01-10 A Rainy Winter Day That's some cold water!

Session 04 held on 2016-01-10 A Rainy Winter Day The Fletcher House cellar is prone to flooding, so we keep everything up on pallets over the winter.