Framing the Gantry Section
Whether you chose to install a full cement footing as an extension to the observatory floor, or you used sono tube piers, or a combination of the two, at this stage you will find it necessary to locate the gantry post supports precisely in their saddles.
To assure an effortless roll-off, the gantry and its track must be precisely in line with the observatory track section. This requires no deviation in height or angle, maintaining precise parallel supports for the steel castor track installed later. To fabricate such an arrangement requires careful attention to alignment and construction.
The first step involves temporarily placing the 6″ × 6″ posts in the four saddles now firmly set in concrete, and bracing them with 2″ × 4″ supports until each post is plumb (perfectly vertical). Use a carpenter’s level to plumb the posts, then lightly nail the posts through the saddles just enough to hold them in temporary position.
When you are satisfied the framework of posts is square and “true,”...