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FOCUS MOTOR FOR SCT & EDGEHD INSTRUCTION MANUAL
6 I ENGLISH
When changing direction of the focus motor, you may
notice a little bit of backlash in the telescope’s focus. This
means that the motor is turning a bit before the focus of
the telescope changes. This will typically manifest itself
when critically focusing on a star using the slowest motor
speed rate. You can compensate for this backlash with
the backlash setting.
In the Celestron hand control, the backlash setting can
be found by pressing the MENU button, then selecting
“Focuser,” then “Backlash.” For the Celestron Focuser
Utility Program or Celestron PWI, there is a Backlash
Settings slider in the user interface. The backlash setting
can be set from 0-99.
To find the best backlash setting, first acquire a bright
star in your telescope’s field of view and roughly focus it.
Next, set the motor speed rate to its slowest setting and
defocus the star using one of the hand control’s SCROLL
buttons, or the MOVE IN or MOVE OUT command from
the computer program. Defocus the star until you can
To best protect the focus motor, keep the tethered covers
on the ports when not in use. When the ports are in use,
the covers can be hooked onto the posts on the side of
the focus motor to keep them from dangling.
clearly see the out-of-focus “doughnut” star image. Now,
reverse direction of the focus motor. If the defocused
star image immediately starts becoming smaller, then
the backlash setting should remain at 0 (i.e. the default
setting). If you notice a bit of time elapsing before the
image begins changing, then increase the backlash
setting. Repeat this procedure until the focus of the
telescope immediately changes when changing direction
of the focus motor. If you set the backlash setting too
high, you will notice the focus rapidly changing as soon
as you change directions, and it may “overshoot” your
desired focus. If this occurs, decrease the backlash
setting.
BACKLASH SETTINGS
PORT COVERS
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