Vixen Sphinx SXP - Manual (Page 76)

Chapter 5 APPLICATION
PEC (Periodic Error Correction)
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Equatorial mounts with drive motors are designed to precisely track the motion of celestial objects. With the use of a telescope mounted on
the equatorial mount, you may notice that stars in the field of view of the telescope at high magnification are drifting back and forth very slowly
over a period of time (e.g. 480 seconds with SXP mount) in the direction of R.A. This is caused by the motion of the tracking gear wheels and
it is part of the design of equatorial mounts. The PEC (periodic error correction) rectifies this phenomenon on the equatorial mount and
records the correction electronically.
The tracking accuracy varies in irregular motion and must be corrected as precisely as possible.
The SXP mount does not detects a start point of the PEC recording until the R.A and Declination axes are rotated electorically at an angle of
one degree and more. Pay attention to it if you start the PEC recording immediately after you turn on the mount.
A cycle of the PEC recording ends with another chime as soon as the 480 seconds has elapsed, but the duration of the recording continues
until you stop it. The PEC recording is renewed in each cycle.
Note: You can complete the PEC recording per cycle and it must be started from a defined starting point. If you can't start the PEC
recording right after turning on the power of the SXP mount, rotate the mount electrically more than one degree in both R.A and DEC to
detect the starting point.
The P-PEC (permanent periodic error correction) allows you to save corrections and you can use the same correction from your last
observing session.
Choose “Equatorial with Polar Setting” in the Mount Type described on page 83. Accurately polar align the mount.
Prepare an eyepiece with crosshairs such as a Vixen OR-12.5mm with illuminated reticle. Put a guide star on
the center of the crosshairs in the eyepiece. Go to high magnification with an eyepiece as high as 200x and
more.
In the “Mount Setting” menu, choose “PEC” with the or direction key and press the key to call up
the dialog box.
In the “PEC” dialog box, choose “Rec Start” with the or direction key and press the key (or the key)
The PEC recording starts with chimes after counting down 3 seconds. Tracking the guide star very carefully as your corrections during
manual operation are recorded.
On starting the PEC recording, the speed of correction is fixed at 0.5 times of sidereal rate
regardless of an enlargement or reduction of the star chart. The • zoom keys allow
enlarging or reducing the star chart on the screen during the PEC recording.
During the PEC recording the count number is displayed in red
at the left corner of the information bar on the bottom of the
screen. The counter starts from 479 and counts down every
second to 0 and repeat.
Starting the PEC Recording
The period of time for the PEC recording is 8 minutes (480 seconds).
What is P-PEC?
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Tracking ON PEC on recording (red)
Centering the guide star Centering the guide star
Guide Star Guide Star
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