Kevin's ATM equatorial Mount Page

Page Created: 1998 October 02
Page last updated: 2010 March 08

equatorial Mount

So I had Callisto, my first 7" f4.5 dobsonian telescope, which is normally an altitude-azimuth (alt/az) tracking motion. I wondered how hard it would be to build an equatorial mount for this scope. So I set to build one. The base portion had to be heavy enough so the whole assembly would not tip over in operation. The angle of the mount relative to the base had to be fixed at my local latitude (about 45 degrees north). Basically it looks like a standard dobsonian mount, with a baseboard and feet on the bottom, and a rotating upper plate on top, seperated by teflon pads.

The biggest problem came with the amount of torque of the tlescope mass when resting in the cradle, the top portion tended to pull away from the bottom. The only solution I found was to have the centre bolt keeping the two parts together, really really tight.

Equatorial dobsonian style mount mark I. Realized that the telescope balance point would be way too far to the rear so decided to move it.

Moved the mount forward on the base and added in the upper mounting piece.

Edge on view to show main rotation axis and the 3 nylon supports.

There were some operational issues with the first design above. So some modications were made (see below). The bottom plate was made longer with a wide stance and adjustable feet for balance. Two nylon/teflon supports were added to the bottom of the circle, to help take someof the load off the centre bolt. Turning the scope was still pretty easy and smooth. I was thinking of adding a clamp at the top with teflon facing down to assist in keeping the top plate in contact with the bottom plate.
9811a22 The new base with a longer bottom plate, 2 adjustable feet in the rear, 2 nylon supportson the bottom of the top circle, and higher side panels for the mounting point.

9811a23 Front view showing 45 degree angle support. This is currently fixed. If I start to travel enough it may have to be modified to become adjustable.
The mount has three feet, spaced as widely apart as possible and use hockey pucks with bolts through them.
This unit was shelved before it got a lot of use as the callisto telescope it was designed for was torn down with the intent to redesign it with a sonotube enclosed OTA... but that was never completed.