OPTICS
APO140 is an Aplanatic Oiled Triplet refractor with ED glass (FPL-53) as a middle element. The
color correction is optimized for visual use with focus shift less than 0.02% from 436nm to
1000nm. Calculated Strehl for
e-line (546nm) is 0.99.
Intereferometry of the first run
lenses showed that the aver-
age Strehl is close to calculated
with a very smooth wave front
and RMS less than 1/50.
The oiled design has only two
air-to-glass surfaces. The result
is a higher contrast image
because of much less scatter
and veiling glare due to inter-
nal reflections comparing to
air-spaced objectives.
The outside surfaces of front
and rear lenses are coated with 7 layers of
antireflective
coating, that reduce light reflection to the
average 0.25% in range of 400-700nm.
Shown on the left is a sample of interferome-
try of typical objective with appr. RMS less
than 1/50 and wave front error less than
1/10. The lenses are tested during manufac-
turing with different methods including: test
plates, autocollimation test with an artificial
star, interferometry,
however we do not
supply test results to avoid any kind of
misinterpretations or “numbers” com-
petition between customers.
Each objective assembled in precision
thermocompensation cell (1), that contains:
Three Lenses Sealed Construction (2) with
a special oil between lenses and Threaded
Ring (3). The Threaded Ring of each objec-
tive is engraved with serial number of OTA.
The optics are collimated at the shop dur-
ing assembly and do not require any addi-
tional adjustments. Collimating, assembling
and sealing require special equipment and
techniques and must be done only by quali-
fied technician.
WARNING: NEVER TRY TO DISASSEM-
BLE THE OBJECTIVE! DISSASSEMBLY
OF THE OBJECTIVE WILL RESULT IN SERIOUS DAMAGE
TO THE MOST EXPENSIVE PART OF YOUR TELESCOPE - THE OPTICS!
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