Casting a concrete pier

[MarkS]

I've decided to go for concrete piers in the observatory - cheap, solid, deflection and vibration free.

What's the best way to cast one?  I've seen 300mm diameter steel duct in 1.5m lengths on eBay.  To my mind that seems ideal.  Any better suggestions?

Is a cubic meter of concrete under each pier necessary or will 0.5 cubic meters be sufficient?

I laid my North/South line last weekend using Pole Star and verified by solar noon sunshine.  So soon I can mark out the plot, remove the kiddie's climbing frame and start digging.

Mark

[The Thing]

You can get cardboard tube used for casting pillars, you can cut it off afterwards. Or see if your local carpet fitter has some old inners!

[MarkS]

Cardboard tube sounds like a good idea.  But I think I would leave the cardboard in place to help with thermal insulation - don't want warm air currents rising up from the pillar when planetary imaging.

[mickw]

warm air currents rising up

I thought the observatory was going to be in the UK   

[MarkS]

I'm thinking about those summer nights following hot sunny days with stifling shed temperatures.

Well, I can dream can't I?

[The Thing]

Cardboard tube sounds like a good idea.  But I think I would leave the cardboard in place to help with thermal insulation - don't want warm air currents rising up from the pillar when planetary imaging.

I have come across people (on the web) who carpet the concrete pier so that it hurts less when collided with in the dark, also it's a nice warm covering available in a variety of colours and patterns to match the rest of the decor

[MarkS]

It'll have wall to wall carpet so it might as well have carpet on the concrete piers as well ...

[mickw]

Altair Astro suggest about 1/2 sq M for their Skyshed pier

[Carole]

Well when I installed mine, every-one kept telling me 3' deep, and 2' 6" x 2'6" square which is what I have got.
I have the Skypod Pier.

No idea what that is in Sq M

Carole

[mickw]

No idea what that is in Sq M

Nearly a Sq M

[Carole]

Ah, just worked it out. Comes to roughly 1.5 Sq metres.

Carole

[mickw]

Actually 0.53 sqM

Can't be bigger than 1 because of sides less than 1 metre

[Carole]

Thinking back to my school days, don't you multiply 2'6" x 2.6" x 3' to get the cubic measurement?  Not had to do these sort of calculations since then.  I converted it to yards first, which is why I said approximately, couldn't be naffed to also convert to metres as yards are pretty close. 

Yes I think I worked it out in cubic yards instead of square metres, in which case no idea how to do that!!!

Never mind I don't need to do these sort of calculations any more so will leave it to the experts. 

Carole

[mickw]

 
Hardly the right person to be called an expert - I hate maths, but................

Calculate in feet then divide by 27 to give yards (which is close enough to metres)

That was the long way - this is the easy way

http://joshmadison.com/convert-for-windows/

[Mac]

an easier way is to measure in meters first, no conversion then.