Dave's DiY Observatory - Chapter 1

[centroid]

To build on this section of the Forum, making it a 'one-stop' location on the 'board', where anyone contemplating an observatory build, canc see how others have gone about this, here's my contribution:

Having decided that for me, and observatory was going to be essential, if I was going to continue in this hobby, I considered all the options, and decided on a design. The construction of a Roll-off-Roof (RoR) observatory got under way in January 2002.

At this time, the obsy was to house an 8" Celestron SCT, on an EQ5 GEM.

The basic structure was a 6'x6' wooden shed (experience has shown that a minimum of 7'x7' would have been a better option). A purpose built (stronger than that of a normal shed) gable ended, RoR.

The main structure comprised a 1.5"x1.5" wooden framework, with 1.75"x1.75" timbers for the roof, and tops of ths obsy side walls, on which the track for the roof section would be attached.

The roof would run on 8 fixed castor wheels (4 on each side). These would be fixed to the side beams of the roof, and run on 30mmx30mm aluminium angle track. The track would be fixed to the top on the shed's side walls, and would be extended to the rear of the obsy on a 4"x2" wooden support framework, onto to which the roof would be rollled when open. The walls would be clad with redwood shiplap cladding, and the roof with felt.

I approached a local engineering company, with my design for a pier, and this was made from 8" dia, 1/4" thick steel pipe, with plates welded top and bottom. A separate, and identical plate was made, onto which the GEM would be mounted. This would be attached to the pier top-plate by M12 studding, thus allowing levelling adjustments to be made.

Having decided on a location for the obsy, the first step was to cast a concrete block in the ground, for the pier base.

I excavated a hole 18"x18"x18", with 12"x12"x12" hole at the bottom of it.

There has been lots of discussion on the size of concrete block for a pier base, with some people casting 1m cubes or larger. However, with my concrete block, I've never sufferer any vibration or movement problems in nearly eight years of use, and the pier currently supports a 12" SCT, an 80mm APO, and a ZS66.

Having made a template of the pier base-plate and its fixing holes, I cast the concrete block, with four galvanised fixing bolts held in position by the base template.

Dave

To be continued: