Observatory Piers - whats your experience

[h0ughy]

Ok, where am I coming from - looking at what type of pier to construct in the back yard. But before I do, I was wondering what the other Pleabians of IIS have to say with theirs.:D

[Lester]

G'day Houghy,

In my observatory I have a cement pier which goes into the ground 3 feet to solid granite. Up to ground or floor level it is 2 feet square and from there up moulded from old icecream tins about 10" diameter and 2 feet high. The cement has weldmesh in it. Protruding from the top of the pier is a 4" diameter by 1/4" thick pipe that the G.E mount fits into.

[h0ughy]

thanks Lester, you ate yourself to happiness!

[Lester]

Yes Houghy I use to be a icecream-aholic.

[astroron]

Hi Houghy my pier is a 90mm pipe filled with sand 1mt above the ground and 1mt into the ground and a 50cm concrete caseing, andis isolated from the surrounding floor by a 12mm thick rubber spacer:thumbsup:

[h0ughy]

Ron
was the steel pipe ok or not stable enought and that is why you concrete encased?

[astroron]

No HOughy, even with the pipe filled with sand it still vibrated quite noticably even when the wind blew, that was before I built the observatory.
A metre out of the ground even with the pipe filled with sand the scope still took quite a few seconds to stop vibrating. cheers Ron:thumbsup:

[Striker]

You have seen mine...the bigger the better....you never know what scope you will put on it in a year down the rack....lol

But I hope I never move as it weighs around half a tonne. filled with river sand sealed and welded.

[rogerg]

Houghy,

I have a steel pier, 1m into the ground, 1m above. Originally sat in a 1x1x1m cube of concrete but now at it's new home only 70cm deep because I hit rock.

The pier is in 2 halves, bolted together with 8 x 3/4 inch bolts. I did this because I knew I'd be moving it a few years after construction, has worked well.

The pier is about 210mm diameter, 12mm steel pipe. Same above and below. The top half is filled with sand so reduce high frequency vibrations. The top has an adjustable plate

I don't have any problem with vibrations or movement, I'd consider anything stronger excessive. The vibrations in my setup are entirely relating to the telescope's mount and wedge, not the solid lump of steel/concrete it's mounted on :-) :)

I would consider concrete instead of steel, you have absolutely no concern of vibration then, providing it's big enough.

Tips:
- get the height right
- make sure you don't have rock where you want to put it (may alter your design)
- give it lots of footings
- seperate from the rest of your observatory floor
- consider wiring conduit up the centre of the pier
- consider attach points for hooks etc for controllers, mini shelves, whatever.
- don't go overboard, we don't want the earth tipping on it's side because of a 100 tone block of concrete :)

Pics of mine:
http://www.rogergroom.com/rogergroom/esh_rog_gallery.jsp?Item=218

Roger.

[h0ughy]

:( :prey: Help, I cannot handle looking at things I cannot Have....................striker, you must be ready to sell yours, $5 ok!

Roger, wow, you moved the observatory. Tell me do you still operate in Alt az mode? What was your peir design, yes it looks very solid!

[rogerg]

Houghy,

I operate in equatorial - that link was to the construction pics, I didn't have a wedge for the first year or so, since about 2003 I've had a wedge, and the observatory is decked out much nicer :-) See newer pics:

http://www.rogergroom.com/rogergroom/esh_rog_gallery.jsp?Item=185

and

http://www.rogergroom.com/rogergroom/esh_rog_gallery.jsp?Item=219
for the move.

When I get home tonight (about 8 hours yet - work :( ) I'll hopefully remember to PM you the design drawings for my pier that the engineer used to make it, that'll explain the design to you.

Roger.

[rogerg]

Oh and it helps to know how much things cost... I don't know how it compares to others here... but the steel bit (both pieces) of my pier cost about $450, and the concrete including the 1x1x1m and the 6x3m pad around it cost me about $1100. Not sure how much for just the block sorry, but it was done in 2 pours such that they were seperated, which added significant cost to the project.

Oh and the steel is galvanised. I have never got around to painting it. :)

Roger.

[h0ughy]

ROger I will PM my work email and my home email address! Thanks