Mounting the dome
As your telescope slews and tracks it's way about the stars, you
need the ability to move the dome slot with it without excessive effort. At
first you can do this by hand, just pushing the dome around as the telescope
moves. If the your telescope is motor-driven, then later you can fit a motor
drive to the dome and synchronize the two. Your imagination has no limits.
This is a task that requires patience, a lot of tinkering and
fine tuning. At this stage the dome is getting a bit too cumbersome for one
person to maneuver so be careful of your fingers and your back. I thought I
would get the top ring of the walls fitted with rollers and adjusted while it
was still on the ground. This would be extremely difficult to attempt on top of
the walls.
Make sure you get sturdy wheels for this. I got mine from a
hardware store pretty cheap. I had to make up my own mounts for some of them.
Use your own initiative here and try a few ideas.
To stop the dome from rolling off to one side, the guide wheels
need something to guide. On the inside edge of the dome support ring, I screwed
a two-part band made of a long strip of particle board and strips of 5mm grey
plastic sheet. A bit like Perspex only softer.
A wise fellow named Steve Quirk who owns Frog Rock Observatory
at Mudgee, NSW (http://www.hwy.com.au/~sjquirk/index.html)
gave me some good advice. "Make sure you secure the dome from being lifted by
high winds". To that effect, I welded up some brackets out of, (strangely
enough), more brackets. These are bolted onto the support ring and overhang the
guide band of the dome. Leave some clearance so the dome does not get caught on
them. I used four which I think is plenty. The damage done to the dome would be
one thing if the wind got hold of it, but can you imagine what may happen to
your precious telescope and camera equipment?
Lifting and Positioning of the dome on top of the building was
done utilising my father's backhoe. There is nothing that man can't do, bless
him! This trial lift and position is just to check for fit and adjust before the
final fibreglassing is done. Once I am satisfied that this is the way it will
go, we will lower the dome to the ground again and coat it in fibreglass. I
installed four "U" bolts around the perimeter of the dome to tie on some ropes
for lifting. Make sure you tie on some rope to use as a "tag line" so you have a
little more reach and control while remaining safe. If you are going to leave it
on for more than a day, make sure you tarp it or the wood will spoil if it gets
wet through rain or even nightly dew.
NOTE I found that the rollers I
have used are too stiff and great effort is exerted to rotate the dome by hand.
This will only get worse as I add the weight of the fibreglass on top.
Therefore, I have come up with the idea of using a metal ring, (band) and a few
specialist rollers on bearings to free it up a bit. See the update on
Support Ring page. Take a look at this movie of the dome rotating: