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These pages feature extensive construction details for my observatory completed in the summer of 2001 for a Meade LX200 10" f/10 Schmidt-Cassegrain telescope

page 2


The pier

A friend is manager of a local scrap yard and he generously gave me a 0.5" thick walled 11" diameter steel tube and some 0.5" thick steel plate. The optimum height of my Meade tripod was 32" with myself comfortably seated. This took into consideration objects near the horizon and zenith. I wanted at least this amount in the ground embedded in concrete. The concrete around the pier was also to be isolated from the concrete pad with a 0.5" gap between them, and with the surface of the pier concrete 0.5" lower than the surface of the pad so that flooring could be placed on the pad and over the top of the pier concrete. In this way no vibrations from walking around in the observatory should impact on the pier and the telescope. They don't!

To allow for levelling (not really that important with a 2-star alignment) and aligning the scope on the north-south axis  and also making sure that I could fit a wedge in the future, I designed a system that involved two 14" steel mounting plates and lots of stainless steel nuts and bolts. One plate is welded to the top of the pier. It has a 14mm (9/16") hole drilled in the centre to allow a 1/2"-13 thread set screw to pass through (and eventually up into the scope's "Azimuth Attachment Hole" (Meade manual Fig 13 p53)). It also has four 0.75" holes UNC threaded on diagonals 7" away from the centre hole. Through these will be threaded 0.75" stainless steel set screws locked with nuts and washers underneath.

Telescope mounting plates image

Telescope mounting plates

The second plate - the top plate - has a similar 14mm centre hole. There is another 11mm (7/16") hole drilled 3.5" away (centre to centre) towards the centre of one side. This will allow a 2" long 3/8"-16 stainless steel set screw to thread into the "Wedge Attachment Hole" opposite the power panel (Meade manual Fig 13 p53) clamping the scope to this steel plate. This means that this side of the plate will face south.

Both plates were coated in several layers of rust converter paint that reacts with rust forming a tough black coating. On top of this they were 'anodized' with several coats of smooth black Hammerite paint. It has formed a solid and rust-proof finish.

Pier and plates cross-section image

Pier and plates cross-section

The idea is that the top plate sits on top of the four 0.75" set screws solidly mounted through the pier plate welded to the pier. The scope sits on this and is attached to it with the "Wedge Attachment Hole" set screw. There is about a 2" gap between the plates. In the pier wall 4" below the pier plate is an access hole cut with the welding torch when the top plate was welded on. Through this I can insert a 4.5" long 1/2"-13 stainless steel set screw up into the scope's "Azimuth Attachment Hole" through the two centre holes in the plates. With a builder's level mounted on the scope's tube, the top plate can be adjusted for level using the four large set screws which can be locked into pace with nuts. The scope is aligned on the north-south axis by having the power panel facing north as usual, setting the altitude or declination to that of Polaris, setting the RA to zero and locking the RA axis, and then sighting Polaris (through the finder scope then using an eyepiece) by rotating the top plate on which the scope sits. When aligned the centre set screw can be locked into place clamping the scope to the top plate and the top plate to the pier with 3 nuts. Funny enough it all works and is rock steady :-)

In all this I allowed for the fact that someday I might get into photography and buy a wedge. No changes should be necessary as the wedge should bolt straight onto the top plate.

 

Copyright 2002-2010 Mark S Baines All Rights Reserved     -     Last updated: 04 03 2010