Shown to the left is the 16" f3.75 Dream Astrograph owned
by Tenagra Observatories. 16801 CCD chip and 10 position, 50mm
square filter wheel, as well as a standard 4" coma corrector
make up the imaging train. |
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Upon arrival at Tenagra the physical position of each component
was logged and collimation was checked with all three collimation
tools. |
The M2 sub assembly was removed and the focuser's tip/tilt was
given a slight adjustment in the tube axis only. M1 coincidence
with the telescope tube was then ascertained and adjusted to
be coincident. |
The M2 sub assembly was re-installed, then mechanically and optically
aligned. The optical system was then adjusted so collimation
tools showed perfect alignment. Then an altitude-only test was
conducting while looking through the AutoCollimator tool to judge
telescope rigidity (how well the optics stay aligned with an
angle change to the telescope). The same was then done adding
RA to the telescope angle (a compound angle). High stiffness
was observed and documented. |
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The imaging train was added back in, included a 10-position filter
wheel that the client wanted had not been able to obtain functionality
with in the past. I was able to fix the focuser's mechanical
interference problem, as well as remove, clean, blackened and
replace all of the customer's filters (see photo comparison link
below). The full system was then tested under the stars over
the course of two nights. |
It was determined on the first night that the CCD chip had a
tilt error of 550 microns (0.55mm), as if one corner of the chip
were too high by 550 microns. Since the depth of field of a f3.75
system is around 30 microns, this amount of error far exceeds
the remaining errors in the system. It was also determined that
the back focus, the distance between the corrector and the focal
plane, was not correct. |
The system was shimmed, for both tilt and z, near the focal plane.
Subsequent testing showed I could obtain round stars across the
entire 16801 CCD chip (52mm image circle) while at zenith. |
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