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Figure 20.
Using the optical axis offset screws move Polaris
halfway to the eyepiece's center.
correction (PEc)
Using the PEC functions requires an illuminated reticle eye-
piece capable of producing at least 300X magnification when
used with your telescope. For best results, the true field of view
should not exceed 10 arcminutes.
Periodic errors are inherent in almost all worm gears due to
slight eccentricities and misalignments. The PEC (Periodic
Error Correction) Training function provides a manual correct-
ing method to reduce the amplitude of the worm gear errors. By
recording a full cycle of guiding actions, the Sirius EQ-G can
compensate for drifting in the R.A. sidereal tracking caused
by periodic errors. The following instruction will lead you on a
step-by-step procedure for performing the PEC.
Note: The PEC training function is recommended for advanced
users with interest in long-exposure astrophotography only.
Careful guiding is required. Standard sidereal tracking is suf-
ficient for all casual visual applications of the Sirius EQ-G, and
PEC training is not required.
PEc training
1. Perform an accurate polar alignment using the polar axis
finder scope.
18
2. Manually point or electronically slew the telescope mount-
3. Activate "Sidereal Tracking" from the Setup menu (see
4. Rotate the reticle eyepiece in the focuser (or diagonal) until
5. Move the guide star designated in step 2 to the center of
6. On the hand controller, select PEC Training in the Utility
Note: Utility Functions can be accessed by pressing the
UTILITY quick rererence button on the hand controller.
7. Select the R.A. guide speed for the PEC Training. You have
8. The Sirius EQ-G hand controller will display the current
9. Using the left or right direction button only, move the tele-
The Sirius EQ-G hand controller will record the manual guid-
ing actions for 8 minutes in order to characterize the periodic
errors. Pressing ESC will immediately stop the recording and
exit from the PEC Training function.
Note: Guiding actions are recorded even when the PEC train-
ing is stopped midway. The PEC + sidereal tracking will not be
accurate until a full cycle of the PEC Training is performed.
The Sirius EQ-G will emit a "beep" sound and display "Record
completed" when the training time is up. Press any button to
exit from the PEC Training upon completion.
Figure 21.
Drifting caused by periodic error.
ed on the Sirius EQ-G to a star with a small value Dec.
coordinate (Dec. between +10° and –10°). This object will
be used as the guide star.
"Setup Functions"). Once tracking has initiated, press ESC
to return to the Setup menu.
the R.A. movement of the star becomes parallel to one of
the illuminated crosshairs
the eyepiece field of view using the direction buttons.
Functions and press ENTER.
two guide speed choices: 1) 0.25X and 2) 0.5X. Press the
numeric button 1 to choose a guide speed of 1.25X or
press 2 to choose a guide speed of 1.5X.
time once the guide speed has been selected, indicating
the recording has begun.
scope so the guide star remains centered in the eyepiece
field of view (Figure 21). Repeat as necessary.
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