After the "microbe" and the dobson 114/900 which you
maybe saw on various sites, I present you the crobson (contraction
of "microbe and Dobson") or still named "Baby Dob". Almost everything is
garbage :
The mirror cell is constituted
by a triangular aluminium base and a support of mirror made with
2 hard disks glued with exopy. 3 screws + springs allow adjustment
of the primary mirror.
The bottom of tube is an piece of steel cylinder. Given the weak
weight of the primary mirror, that allows to move the centre of gravity near
the mirror.
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The primary mirror is 80/400 mm extract
from a spectrophotometer. It was not planned for imaging
(only photometry) and shows regrettably optical defects.
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The secondary mirror was cut in a
flat mirror founded in a scanner. Small axis is 20mm. The
spider is an assembly of thread stalks (3mm diam.),
a piece of PVC tube (20mm diam.) and some screws and
nuts.
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The upper ring is
a piece of 100mm diam. PVC tube. Eyepiece holder is made
with 2 pieces of PVC tubes. One slides easily in
the other one to make adjustment.
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The joins for the cage
and the bottom of tube were cut from a piece
of aluminium valley. It was regrettably
necessary to buy aluminium tubes (twice 1m, 6mm
diam.)... extravagant!
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Assembly of joins, then tubes.
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The rocker box is cut from a plate
of PVC. Altitude bearings are still hard disks. PTFE pads
measure approximately 5x6x7mm. Given the thoughtlessness
of the instrument, It is easily unbalanced in the
slightest change of ocular. I thus have to equip it
with a brake which we can see on the side of the rocker
box.
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Here is the beast, waiting for the night on my window...
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... and fixed on the mount of its big brother.
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