Takahashi FOA60-K Instruction Manual page 16

◆ Extender 1.7XR
The Extender 1.7XR with 2-group 4-element
can be installed in between the main tube
and the focuser unit, unlike conventional
types. The Extender 1.7XR can extend
the focal length and at the same time it
can better correct the center aberration. In
addition, it can correct the edge aberration,
making the field practically flat.
This can extend the focal length of the
FOA-60 to 900mm (f/15.0), offering highest
optical performance of all Takahashi optical
systems. Over the full range of the visible
light transmission, it can produce images of
99% Strehl ratio across the field of a DSLR
camera.
It is very compact, and with its long focal
length and flat field it is well-suited to take
magnified images of the corona or the
prominence in the total eclipse. With almost
no vignetting, it is also suited for imaging
lands as a super telephoto lens.
For accessory connections, please refer to
the system chart.
Main Tube
Main Tube
Extender 1.7XR
3
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▼Imaging System
with the Extender 1.7XR
Effective Focal Length : 900mm
Effective Focal Ratio : f/15.0
Image Circle : φ 44mm (100% illuminated)
φ 88mm (reference)
▼Attaching the Extender 1.7XR
1. At first, remove the main tube. Holding
the focuser unit and the tube, turn them
counter-clockwise to separate them.
2. Attach the Extender 1.7XR to the focuser
unit by turning it clockwise until attached.
Be careful not to attach it crooked or
slanted to the focuser unit.
3. Then, attach the tube onto the Extender
1.7XR by turning it clockwise.
1
Focuser Unit
2
Focuser Unit
Extender 1.7XR
Focuser Unit