Telescope pads - construction advice.

[neilcreek]

Hello folks!

I'm the astrophotography section head at Mount Burnett Observatory in Victoria. We're a large community astronomical society and we are on an historical site with a former Monash University telescope and dome.

My goal is to make astrophotography a major activity at MBO and to use society resources to provide support for members to practice their astrophotography. The site is on old farmland and the ground is quite uneven. All of us spend a good portion of our setup time levelling our tripods and getting them pointed roughly South.

I would like to be able to construct a series of powered telescope pads with firm, level surfaces with North/South lines marked to speed up setup and make it more comfortable to use. What would the best way to go about this?

I originally considered using 1x1m pavers, but couldn't find any of that size, and I worry that individual pavers would tilt/separate over time. I have thought about pouring cement but since the land is leased they may have to be removed at some point, and I also worry about radiant heat after a sunny day.

What kind of material would you recommend for a firm, stable pad which could be removed with relative ease, not affect seeing, be comfortable to use and stay level?

MBO astrophotographers will thank you for your advice! :D

[glend]

Bunnings has a fine assortment of pavers suitable for mounts. Just dig a hole the same shape and put some sand down as a base. I used pavers for years before I built my observatory.

[Wilso]

A cheap alternative to paving is to use crushed dolomite or crushed granite.
Compacts down very well and almost sets like concrete if you wet it down while using a compacting plate (vibrating plate). Remove any grass or loose topsoil first.
Dolomite has a high salt content so use plastic over the top if you decide to pave or concrete later.

Good luck:thumbsup:

[troypiggo]

The best solution may vary depending on the subgrade material. Assuming you'll be stripping any grass/vegetation/topsoil, but is the material under that fill or natural; sandy, clay, silt, gravel, or rock? Sand/gravel/rock will be pretty stable, but clay or wet silty material can be reactive (shrink/swell with seasonal moisture variations) or cause issues when it's wet.

So paver type solution may be ok for sand/gravel/rock, but you might want to put down a slab if you're expecting some movement.

[JA]

Hello Neil,

Given the parameters you specified: size, flatness, stability etc... you should go for concrete (1m x 1m Pad) and put up with some difficulty if removal is required sometime in future years ( a couple of guys and a few hours with a jack hammer and bin). Concrete paving slabs tend to max out at around 600mm square x 40 thick, which is not going to do it for you for a typical astro tripod base size.

If you're concerned about heat build up - You could do it Greek Style ;) ..... paint the concrete white (and keep it clean) to increase reflectance / decrease absorptivity. Even go crazy and try a space blanket or reflective pad cover which you could remove in the early evening at setup time.

Best
JA

[doppler]

+1 for the 1m x 1m concrete slab / pad, 100mm thick and leave out the reo mesh, a small 1m slab shouldn't crack and without reo will be a lot easier to remove later.

[axle01]

Neil check out the video on this thread.
Townsville Astronomy Group has just put down a 10x20 meter pad, we will be extending it another 20 meters.

http://www.iceinspace.com.au/forum/showthread.php?t=166550

Al

[lazjen]

I assume you're going to be putting tripods on these pads?

You could go much smaller and just have the legs on small pads (so 3 little ones per setup). You can then set them up to be closely polar aligned too.

These pads can then be cheap "garden pot" concrete bases (maybe 30cm across or less?). Easy to carry and put in place.

I did this for a while until I got my obs setup.

[muletopia]

The picture shows what I did here for my wife's tripod. Just a small refinement on LewisM's idea.
Use pipe into which the feet just fit, no cement required,no rush.
Orient and level the tripod,set the south foot to the required level.
Place the east pipe and set its height to have the tripod level south to east legs.
Place the west pipe and set level.
The pieces of pipe are about 20 cm long.
It has worked for us.

Chris