What A Lovely Lawn (Almost!)
November -- a lovely season in New England -- and the underground electrical feed
is now in place, the building is mostly wired up, and the site has been graded,
graveled, stoned, and loamed (which they pronounce "loom" around these parts).
You can see the packed stone path, and the boss's wife at the door, in this
shot from the northwest. Anyone want to plant some grass?
Seeding
December 1st: we came out to install some optical fibers, and were greeted by
record high temperatures -- 70 degrees! So we changed plans and planted 50 lbs
of grass seed, along with the obligatory "starter fertilizer." There's Jason,
gently raking the seeded loam. Let's see what happens next spring.....
Roof Controller
Chris Laumann, a junior at Harvard, built this cute roof controller -- hardware,
software, the works. It lets you do things under manual or computer control,
such as "jogging" the roof, or moving it to Open or Closed positions. It also
tells you the roof position, and the temperature. Here it is, clamped in a
Panavise, in debugging mode. We'll have a shot of it, installed, after it's
installed!
Pretty on the Inside, Too!
Here's a shot of the panel and box wiring of Chris' controller; pretty neat.
The Telescope Mirror
Meanwhile, down in Pottsville, Arkansas, Ray Desmarais and his crew have ground,
polished, and tested the 72" mirror blank. Here's a shot of it, on edge; you can
see the cushion of "peanuts" used to distribute the load during figuring. That's
Ray, the proud parent, showing off his creation. Silvering is set for early
January, 2002.
Making the Mirror
Here are some shots of the mirror in its maternity ward:
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Here's Ray Desmarais, in front of his giant
kiln. He uses it to soften glass slabs onto
a spherical form.
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A closer view, with our 72" mirror on its form.
There are heating coils running all over the
floor, and around the wall. It takes a day or so
to soften the slab, and a week or more to cool.
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Here's the slab, just removed from the kiln. The
lifting bracket is facing the camera. That's
Chris, Ray's son, on the right; the other guy is
Mike, showing through a glass mirror darkly.
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Another view of the 6-footer, with various 6-footers
standing around it. From left -- Ray, Chris, Mike,
and Jim. Ray is messing with his diminutive 5-foot
kiln there in the back.
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The grinding machine, with a 48" tool doing its thing.
Chris is applying the grits.
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Here's Chris, again, slathering on the sand.
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The Drive
Here's my son, Jake, with the drive system he helped build for the telescope.
The REALLY BIG stepping motor on the left turns a half-inch hardened shaft,
which friction-drives the telescope's 24" precision-cut steel drive arc.
The shaft rides in ball-bearing pillow blocks; you can see the hefty monolithic
"Heli-Cal" coupling, and the Warner electric-release holding brake (on the right).
We overbuilt this thing, for reliability: heavy 3/8" bolts, extravagant torque,
solid alloy mounting brackets, blocks, and base slab.
Roof Controller -- Installed
Here's Chip Coldwell and Chris Laumann, admiring the roof controller and
motor power wiring, now installed inside the completed control room (13 Jan 02).
Controller Portrait
Hey, everyone's gotta have a portrait, right? Here's the controller's, showing
both the control electronics box (right), and the NEMA box holding the power wiring
(relays, motor driver board, breakers, meter shunt, snubbers, and so on). Notice
how the controller box displays the roof position and ambient temperature.
Hospitable Workbench
We loaded up Alan's truck with a big counter unit, some drawers, and a couple of
kids, and hauled them to the observatory. Here's the result, after a few hours'
work by the Sliski clan.
Snow Load -- No Problem!
We worried about snow loading, since you can add 50 lbs per square foot easily
enough with a deep wet snow in New England. Turns out we had an opportunity to
test this proposition on January 13 (a snowy Sunday), when we had about 6 inches
of fresh wet snow. The roof didn't even notice it! (We could tell by the motor
current, which was unchanged from its nominal 3A at 208Vdc). Better yet, within
a couple of hours it all just slid off the steep metal-clad roof. The happy gang
here consists of (left to right) Chip Coldwell, Chris Laumann, and the Sliski's:
Aaron, Alan, and David.
