The SF1 German Equatorial Mount
The smaller of the two equatorial mounts for the Starfinder, the SF1, isn't as small
as it's name may suggest. Lets first have a look at the body of the mount as a whole:
Note: The foot rule in the above picture has 20cms long legs, this is almost exactly 8 inches!
Have a look at the foot -rule and You know, how big the mount is in reality. First, we take a look at the pole block:
If You loosen both screws, the big one and the small one below, You can adjust the polar height
of the mount. The axis cross' movement in polar height is very smooth and without any wobbling.
If You fix the pole block by fastening both screws, it doesn't leave the previously fixed position.
The readout of polar height is a bit silly cause the angular scale is just a sticker and the smaller
screw below should work as a pointer. It's better, to put a goniometer a long the Dec-axis to
determine the correct polar alignment.
But, if once fastened, the polar height won't move, no matter, what You are doing with the mount.
The pole block is machined from a massive piece of metal and screwed to the 4inch steel column
with three very stable feet. So this setup is extremely solid: If it stands, it stands!
The next point to look at are the right ascension axis, setting circle and the tracking drive. Here we
can mostly find out good things as well!
The setting circles are very easily adjustable: just push down the ring with the numbers a bit and turn
it to the desired position, independently from the scope's position. The only bug: The pointer is, again,
just a sticker. It's not too big a problem, but an engraving in the mount perpendicular to the Dec axis
would have been the better solution.
The RA-drive is a quite interesting thing: a quartz controlled motor drives the RA axis directly via a
clutch. The scope will permanently and unvisibly be tracked. nevertheless, it can manually be positioned
whenever You want by just moving the scope. You don't have to loosen any fixtures for the axis. All that's
done automatically by the clutch. If You leave the scope untouched, it will at once be tracked again. The
torque of both the motor and the clutch make an additional setscrew for the RA-axis unnecessary. Quite
a good thing!
Now, let's have a more detailed look on the declination axis:
This axis is motorized via a tangent arm, which can be seen silver-coloured
in the above picture. The knob at the axis housing is for fixing the declination
Above picture shows, how the tangent arm is driven by a spindle.
Here You can see the drive moving the spindle for Dec positioning.
The SF1 can be battery driven by 6 Mignon cells (6x1,5V = 9V)
Hereby, the Dec drive has so less power, that it can only move the scope
if it is totally perfectly balanced. If You power the SF1 by vehicle battery
or a 12V supply, however, the Dec motor has enough power.
This declination drive - on the one hand a bit noisy on the other limited
by the tangent arm principle - is the most unprofessional feature of the SF1.
In Dec as well as in RA, the Axes can be driven in 32x, 16x, 4x and 2x
A last weak point are the steel straps for fixing the tube on the wedge which
imply a certain potential of vibration.
Furthermore, the straps are tightened by 2 little screws, which are
very hard to grip. Replace them by two 1/4" nuts.