(ATM) PIER QUESTION
nc_anheier@ccmail.pnl.gov
Fri, 25 Aug 1995 09:13 -0700 (PDT)
Help! I'm building an observatory in my back pasture and I need some advise.
My problem started with the pier that holds my C8. Following the design in my
scope manual, I buried a six foot x 4" diameter schedule 80 pipe three foot
into the ground. About 350 lbs of concrete was poured around the pier and
inside the pipe. On top of the pipe I welded a flange that holds my fabricated
wedge. This wedge consists of a piece of 8" long x 2 1/2" diameter pipe cut
and re-welded at about 45 degrees (my latitude). On top of this I put a 1/4"
aluminum disk that has the appropriate bolt hole pattern matching my scope
base. Once assembled, I immediately noticed a horrible vibration problem. In
looking back at the design, the scope is placed off the pier axis quite some
distance, thereby creating a long lever arm. The next night I chucked the
custom wedge and bolted a Celestron wedge on top of the pier. This wedge
reduces the lever arm problem greatly. The vibration was somewhat less, but is
worse than the field tripod, wedge, scope combo! The vibration is bad enought
that it is hard to focus the scope. What gives? BTW I was using a 18 mm
eyepiece, barlow, and using Jupiter as the target. My goal of the pier is to
allow long exposure photography. My thoughts at this point are 1) put three
guy wires on the pier at 120 degree intervals, thereby placing the pier under
tension, 2) pour more concrete around pier, 3) yanking the damn thing out of
the ground with a very large tractor and start over with a better design.
Please let me know what your thoughts are.
Thanks in Advance
Norm Anheier (nc_anheier@pnl.gov)