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In 2008 I decided to erect an observatory. After some
research I decided to opt for a
SkyPod These are manufactured in Canada and imported to the
UK by Altair Astro in Norwich.
The first stage of the installation requires the preparation of the
ground and the foundations for the pier to support the telescope. For
this I dug a hole about a metre deep and a metre across, like an inverse
stepped cone. Here is a picture of the hole.
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Around this I built the frame for a deck to go around
the pier. This used 4"x4" posts concreted in the ground to support a
frame made from 4"x2" timber. This is shown in the image. The
grass beneath was sprayed with sodium chlorate to kill it off and then
covered in weed repellent fabric.
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The hole was then filled with
concrete. I did this by first casting about 30cms in the bottom and
embedding in this three vertical wooden battens. These were cut to
length so that the tops were level with where the base of the pier would
be. Once this had set, further concrete was added until about 20cms from
the top of the battens. At this stage the four J bolts need to be cast
in the concrete - these have threaded ends to which the pier will be
bolted. To set these in the correct position I made a wooden template
from MDF and fixed the bolts at the correct spacing. Further concrete
was poured in the hole to the top of the battens and the MDF template
with J bolts pressed in place. The level was checked with a spirit level
(see image). This is then left for the concrete to set hard - at least 3
days (and covered if rain is expected). |
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I bought a pier from
Altair Astro that has a
levelling table at the top, thus overcoming the need to get the pier
absolutely vertical to optical standards (something that would be very
difficult to do) - but it is fairly easy to get within a degree of the
vertical. More information on these piers can be found
here.
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Next
the MDF template can be removed and the pier set in position on the
protruding threads of the 4 J bolts. I mixed up some wet cement and put
a layer about 5mm thick across the top of the cast concrete before
setting the pier in position. This allowed me to set the pier in
position and check it was level (with the wet cement I had a chance to
adjust the level slightly). I then left it for 2 days for the cement to
set before tightly bolting down, inserting washers between the nuts and
the flange in the pier. I then wound some cling-film on the protruding
nuts and bolts to protect them. I then decided to pour some more
concrete over the flange of the pier, burying it about 75mm deep. I felt
this would further stabilise the pier. This was still below the level of
the deck and carefully designed not to foul the deck framework.
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Finally the deck was completed,
making sure the deck frame and planks do not touch the pier (to prevent
any vibration from the deck floor disturbing the pier) |
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The POD
landed on 29th August when Ian from Altair Astro delivered it to my
home. We started the assembly as soon as Ian left. The first step was to
join the two halves of the primary dome |
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Sealing the
two halves of the primary dome |
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The primary
dome complete with the running track |
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The six wall
panels connected together very easily. |
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Assembling
the secondary dome - yes and more sealant ! |
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Primary dome
and wheels in position |
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Secondary
dome slotted in position |
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By the end of
that day my wife Anne and I had it up and finished in the garden.
The final result,
some 5 hours later ! |
