A Dobsonian telescope which employs roller bearings in lieu of teflon pads will have far less friction. This is desirable for the motorized system. However, for manual mode (which I still use), balancing the telescope could become a major problem. Although my telescope was well-balanced, there was some room for improvement.

It is generally recommended that the scope be balanced in the 45º position, so that moving it up or down would not affect it to a great extent. This really depends on how your telescope is built. My telescope has heavy altitude trunnions, which created a balance problem as indicated in the figures below.

In this figure, with the scope at 45º, the altitude trunnion weight is distributed evenly around the balance point. This is shown as a checkerboard pattern (50% to the right of the balance point) and the non-checkerboard area (50% to the left of the balance point).

However, move the scope down to the horizontal position, and you can see that most of the trunnion weight is behind (mirror side) of the rotation point, shifting the balance to the rear and causing the crown to drift upward (figure below). Also, more weight on the mirror side of the balance point is contributed by the mirror box itself.

This is exactly what was happening to my scope. In addition, with the scope vertical it would tend to move downward due to the shifting weight of the trunnions (figure below).

The obvious solution to this is to make the trunnions of minimum weight. In my case, the trunnions were solid wood that were 1-5/8" thick. Instead of building new ones, I removed portions of the trunion to reduce weight, but not affect its structural integrity. In addition, I made some cuts in the mirror box to further reduce weight that shifts from one side of the balance point to the other when moving the scope from 0º to 90º (figure below).

Below is a photo of my mirror box after the cuts were made. Wood sections that were removed are indicated by arrows. You can also see the wedges removed from the trunion. These improvements helped reduce the balance problem of the scope, and will improve both the motorized and manual modes of operation.