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Above is pictured an observing adjustable chair for use at the telescope
eyepiece. When looking into the eyepiece for long periods of time and in
the standing position – you tend to sway a bit and lose you view through
the eyepiece. A big improvement is the addition of a chair, especially one
that is adjustable in height so you can sit comfortably at the eyepiece without
straining your neck or your back.
As you can see by the three pictures above the chair is adjustable
to the heights nominated by the grooves (notches) cutout in the side rails
of the chair. For people who have read Phillip Harringtons 1994 book –
“Star Ware”, you may have seen a similar type of chair with four legs.
However, this is a four-wheel drive version that can be set on uneven terrain
and remain stable because it has only three legs similar to a telescope
tripod.
Detail of the all terrain observing chair (ATOC) can be seen in this
next photo of the notches in the hard wood timber and the aluminium support
rod which runs through to the other side of the chair.
A close up of the chair locking mechanism is seen here showing the
rear aluminium rod running in the groove that runs the length of the side
rails.
As seen in this rear close-up shot of the seat assembly, there is
now way that the seat can move once it is in the locked position when sitting
on the observing chair. To readjust is to simply lift up the front of the
seat, it will pivot out of the notches, and then the seat can be easily
moved to a different height.
The above picture shows the hinge assembly for the one rear leg used
to support the chair. It is kind of a bulky looking set-up, but it works.
It is designed to keep tension on the support leg so that it will remain
in place if you happen to move the chair while you are sitting on it. If the
rear leg could swing freely, it could have the potential to topple you over
because the leg may swing towards the front legs and create an unstable position
for the occupier when he or she leans back again
The yellow rope shown keeps the rear leg at the correct distance from
the front legs so on level ground the seat is in the horizontal position.
Has potential to cause the dreaded “splits” if rope is not installed in
the correct manner, with the result of the previously-comfortably-seated-amateur-astronomer
now flat on the ground and seeing more stars than usual.
The chair in full view, folds up fairly flat for transport in a car
and does not weigh a whole lot – about 10 kilograms actually. If I made
another one, it could be even lighter by a few kilos, with some careful
thought. I guess you would need a moderate level of woodworking skills to
construct one of these and perhaps for the metal worker, a steel chair would
be fine too.
This particular chair is designed for viewing an equatorially mounted
Cassegrain or Schmidt Cassegrain type of telescope, where the eyepiece exits
the back of the optical tube assembly. I suspect it would also work just
fine on a refractor or a Newtonian. The minimum and maximum heights of the
seat of this particular chair are 300mm to 800mm respectively.
The All Terrain Observing Chair is a very comfortable addition to
make observing that much more pleasurable.
Peter Sayers
