Permanent Pier Design
by Jim Slay <JimSlayNTS
aol.com>
Also see Observatory Plans and Wedge Modifications
From: Jim SlayDate: Jan., 2001
The footing is the key element I believe.
I used a 16" diameter steel road culvert 12.5 feet long (cost $ 150.00) supported in a 60" by 60" footing by 60" to 65" deep (a lot of digging and concrete over 13 tons) I also used 3/4" rebar 10 feet long with most of it pounded into ground at various angles, total of 200#lbs. The culvert was set 5.5 feet deep or to the bottom of footing and had six sections of rebar set inside, the culvert was filled to with in 1.5 foot of top and later a four post 3'x3' structural steel leveling pad was added that added another 4 feet of height to pier.
In use, the only vibration observed has been from a heavy truck going down the street, but very rarely in the night. I can walk and move around observatory and see no vibration in eyepiece (12 mm with 3X Barlow = 762X used for drift alignment) or when dome turns 1 deg. every 4 minutes. Pier is isolated from observatory 100%, if I pull on pier or kick pier I will see some movement but very little.
See photos below:
 |
 |
 |
 |
