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Different releases: The Helinear Focuser
Some of the ESPRIT 150 series are delivered with a different focuser: the
Helinear focuser
.
Focusing with the Helinear focuser
•
Unlock the locking screw below the focuser
(1)
.
•
Slowly turn the focus knobs
(2)
one way or the other,
until the image on the eyepiece or the camera sensor is
nearly sharp.
•
To finely focus the image turn the 1:11 knob one way or
the other until the image is perfectly sharp
(3)
.
•
Lock the screw below the focuser
(1)
.
The image usually has to be finely refocused over time, due
to small variations caused by temperature changes.
Before doing prime focus imaging
Before installing the field flattener onto the drawtube of the Helinear
focuser, the 2" ring adaptor
(2)
needs to be unscrewed and removed.
In order to easily unscrew the ring, the blocking thumbscrew
(1)
at the
end of the drawtube needs to be tight to lock the rotating end cap.
Framing a picture with the Helinear focuser
When the object you want to picture is in the middle of the circular 44mm field, most often its
orientation on the rectangular camera sensor is not what you expected (figure A). You can easily
reframe the picture on the camera sensor by unlocking the thumbscrew at the end of the focuser
drawtube and turning all the optical train until the framing suits your needs (figure B). When done
relock the thumbscrew, and you are ready to picture the sky.
