Concrete or wood..does it matter?

[pinkflyd99]

Hi guys. I built an obs. without a pier(dont ask) Now of course I want one. It would be much easier to use a 4x4 or 6x6 wood post instead of a concrete pier. If I use wood. I understand that polar alignment wont be perfect all the time, but I would assume it would be better tathn on a tripod. I have an LXD75 sn8 and a AT66. Any suggestions

[neilfleming]

I'd vote for concrete. Wood would flex and shift too much. My second choice would be your tripod on a concrete base that was independent of the wooden floor.

...Neil

[Bob_riggs]

Hi PF!

Welcome to AstroClassifieds!

Neil is certainly correct with concrete (and steel) for imaging. I would add that for visual a seasoned beam sized for your equipment, maybe an 8 x 8 or even larger, would be sufficiently steady. I'd go with treated material, or soak it well in a good preservative, hand compact 6" of gravel in the bottom of the hole for drainage, and fill the hole around it with concrete. If you and your ob move, a chainsaw will make it disappear.

Heck, if you go into imaging, you just might find it is quite adequate, as the LXD75 is a well balanced mount.

As compared with a tripod, the beam would get my vote in a heartbeat.

[Jim Fusco]

This is very interesting. http://www.oregonvos.net/~jgarlitz/thermal.htm I know it's about wood truss. http://darkwing.uoregon.edu/~struct/...lecture27.html
This is showing dry wood has half the thermal COE of concrete or steel. here brick is showing the best http://www.supercivilcd.com/THERMAL.htm.
If you are going to use wood I would glue layer together with the grains facing opposite direction. And it would need to be dry and sealed well. As with everything expands and contract, the issues you want to avoid is a twist or curve. Metal will do this too. However if you are going wood consider the superbeams like gluelam or composite used in construction in new houses/ buildings. There is no grain but must be sealed well and has a lower COE than concrete or steel.