Pec - Vixen Starbook-S User Manual

Tips on setting values of backlash compensation
Watch how the telescope moves when you increase the values. Start with setting an initial
reference value (10 for example), and double this value after checking the telescope movement
with the initial value. If the second value (20) is too small to compensate for the backlash, enter
the number doubled (40) the second value. Likewise, increase the number by doubling the value
if necessary.
Example: Enter 20 for setting the backlash compensation. If this value is too weak for the
compensation, increase the value to 40. If it generates too strong compensation as a result,
decrease to the value halfway between 20 and 40. If the value of 30 is still somewhat large for
the compensation, decrease to 25. On the contrary if 30 is somewhat small, increase to 35. In
this way you can adjust the mount for the most effective backlash compensation.

PEC

Equatorial mount (with drive motors) is designed to precisely track the motion of celestial objects.
With the equatorial mount you may notice that starts in the field of view of your telescope are
moving back and forth very slowly over a period of time (e.g. 10 minutes for GP2 and GPD2).
This is a result of viewing them at very high magnification. It is unavoidable since the
equatorial mount is driven via gear wheels. However, it may be annoying when you are
observing at high magnification.
The PEC (periodic error correction) function electrically rectifies this phenomenon in the
equatorial mount. You can correct a drifting motion of the equatorial mount with manual
operation of the buttons on the controller and memorize it in the STARBOOK-S. It will enable
you to make more precise tracking by using the recorded motion*.
* The tracking accuracy relies on how you correct irregular motions. The tracking may
deteriorate if the correction is made inaccurately.
Start the PEC recoding
(1) Position a guide star you want to use for the PEC recording in the center cross hairs of your
guiding eyepiece. (You can use a Vixen GA-4 illuminated guiding adapter or a Vixen Or-12.5mm
with illuminated reticle as a guiding eyepiece.) Use an eyepiece which yields a magnification of
approximately 200 power.
(2) Confirm the current screen is in SCOPE MODE. Pressing the Chart key will change the
screen to SCOPE MODE when you are in CHART MODE.
(3) Press Menu to display the System Menu. Move the cursor to PEC with the keys and
press Select to enter the PEC screen.
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