At 05:01 PM 10/31/04, Richard wrote:
Oh my, I'm drooling... a 6" TaTakahashi I bet that scope will be used
more than the 16" Meade.
It's a beauty! Opened the boxes enough to ensure it wasn't damaged in
transit. We joke about it being the 16" Meade SCG "finder scope."
So if I understand you correctly, the new wedge will set the Meade off
center from the pier? By how much? The wedge must have a unique and
robust design to provide stability with the offset. I'd love to see a
photo of it if you can find the free time to take one. I wish I lived
nearby so I could take a peek. :)
The pier is offset inside the dome to accommodate a large scope with fork
mounts. Not an issue with outdoor pier mounts . . . doesn't matter much
where the scope ends up relative to the pier provided it's balanced. It is
an issue inside a dome. For this a fork mounted 'scope, the pier is
typically offset due south from dome center (in the northern hemisphere).
The geometry of the pier offset inside the dome was designed for the 14"
scope and its wedge . . . so that when aimed veritically the scope pointed
directly at the center of the dome. Moving the two-story concrete pier set
who knows how many feet below ground to match the new scope's geometry isn't
feasible.
;-)
The following is an ASCII-Art diagram of wedge and pier in fixed-pitch font
(it will look totally fouled up in a proportional-spaced font).
/
^ <- N / * S ->
/:\ / *
: /Wedge* ___
: ___/_______*___|___| <- weights
Dome C/L __|___|__ |___|
: | |
: | Pier |
For a fork mounted 'scope, the angle of the wedge face from the horizontal
plate is 90-latitude. The 'scope forks extend north from the wedge face.
The horizontal portion of the wedge is a rectangular plate with round collar
on its underside. The wedge collar fits into a round collar embedded in the
pier top allowing the wedge to rotate for azimuthal polar alignment of the
wedge. The wedge face is hinged at its base plate and its support struts
aretwo mondo jack-screws for latitude adjustment. The horizontal plate
extends to the "south" of the pier collar about a foot to hold
counter-balance weights (they're not small!). The old 'scope didn't have
anything piggy-backed except the small 8x50 finder. The weight of the two
new 'scopes on the forks and wedge will be significantly higher. That's why
it's a custom wedge, not the stock one Meade makes for the 'scope. The
wedgeitself is steel plate . . . with a couple small trusses under its base.
Didn't measure it, but it's definitely thicker than 1/2" steel and too heavy
for me to pick it up by myself (about a three-strong-man lift).
The pier is a completely independent structure from the building and dome.
It was constructed first and then the building was built around it. The pier
goes through a hole through both floors with about 1-1/2" clearance
completely around it. This is typical construction so that movement inside
the observatory building doesn't vibrate the pier. One can jump up and down
on the second floor right next to the 'scope without any effect on it. A
column of studs and wallboard surrounds it between the first and second
floors. On the upper floor inside the dome there's a lip around the hole
(inthe floor) with a fabric collar between the lip and pier to keep stuff
from accidentally dropping into . . . quite literally . . . the black hole
around the pier . . . never to be seen again.
I'll be in there several times over the next couple weeks and will try to
snag a couple photos of the inside.
-- John Lind
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