ATM 3 or 4 vane spider

[doug kniffen <dk@usmo.com>]

One thing that hasn't been mentioned on this subject(recently?) is where
the spikes are.  Remember the last ring plane crossing of Saturn? Preceding
the event the rings became ever more difficult to see due to the presense
of the spikes. So the day before the crossing I re-mounted my 4 vane spider
at an angle that allowed viewing the rings between the diffraction spikes.
The result was definitely worth the effort. It is also much easier to work
around four spikes than six spikes. Why didn't I just rotate the tube?
Because the Dec. counter weights (GEM) were also being used for radial tube
balance. 

While an event that occurs once every fifteen years may not seem to be much
reason for choosing a mechanical support with more diffraction, I'll
mention that there seemed to be a subtle improvement of Jovian cloud belt
visiblity. Should one try observing double stars, a 3 vane spider is 50%
more likely to hide a faint companion star under a spike. After
experimenting with welding rod diffraction on my SCT, I decided that
decreased spike location is more important than slightly increased spider
diffraction.

Doug K