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PART XI : ADVANCED FUNCTIONS
11.5 Periodic Error Correction (PEC) for EQ Mount
The periodic error correction function applies to an equatorial mount only.
All equatorial mount has periodic tracking error which is not critical for visual observing but
might lower the picture quality of long exposure astrophotography. The SynScan hand con-
trol has the periodic error correction (PEC) function to improve the tracking performance for
astrophotography.
Depending on the model of the equatorial mount, there are two types of PEC. One is soft-
ware based PEC (SPEC), which applies to Sky-Watcher's EQ3/EQ5/HEQ5/EQ6 Pro mount.
The other is permanent PEC (PPEC), which applies to Sky-Watcher's AZ-EQ6 GT mount and
EQ8 mount. The SynScan hand control can detect the mount model and choose the corre-
sponding PEC algorithm.
The PEC function is a training-replay process.
PEC Training:
Polar align the equatorial mount accurately, and then perform a star alignment.
1.
Choose a star close to the celestial equator, point the telescope towards it and start the
2.
mount tracking. Center the star in the telescope's eyepiece.
UTILITY FUNCTION\PEC Training
Access the menu "
3.
will display "
Select Speed: 1)0.125X 2)0.25X
sition of the star in the FOV of the telescope when a user presses the
tion key on the SynScan hand control. Choosing a 0.125X sidereal rate is recommended
for a smaller FOV of telescope, and a 0.25X sidereal rate is recommended for a wider
1
FOV of telescope. Press the "
" or "
step.
The screen will display the elapsed time. Use the
4.
trol the mount and keep the star at the same spot in the FOV of the telescope until the
SynScan hand control stops displaying the time. The total time for this training process
depends on mount models.
PEC Replay
Once PEC training is completed, access the menu "
ENTER
the
key to start the PEC replay, that is, start to compensate the period error. Choosing
Setup\Tracking
other items in the menu "
Notes:
•
It is recommended to use a high-power telescope and a reticle eyepiece for the PEC train-
ing. A digital eyepiece with a computer is preferred.
•
For the equatorial mounts that support PPEC (such as the AZ-EQ6 GT and EQ8 mounts),
an autoguider can be used to replace manual guiding in PEC training process. In such
cases, it is recommended to turn on the autoguiding for at least one minute before starting
the PEC training process. The total time for the PEC training of these mount can be as long
as two cycles of the period error.
ENTER
" and press the
key, the screen
". This is the speed used to adjust the po-
Left
Right
or
2
" key to make a selection and proceed to the next
Left
and
Right
direction keys to con-
Setup\Tracking\PEC+Sidereal
" will turn off the PEC.
38
PEC can only compensate tracking errors on the R.A. axis. Therefore, a precise polar
1.
alignment is still required to track minor errors on the Dec. axis.
2.
After turning on the PEC replay, it is recommended to wait for at least one cycle time
of the period error before taking a picture.
3.
To re-use the PEC data on a mount which supports SPEC, users should park the tele-
scope before shutting off power
the mounts which support PPEC.
11.6 Calibrating Auto-Home Offset
Some Sky-Watcher's equatorial mounts (ex. the EQ 8 mount) has the Auto-Home function
which can set the mount to a standard home position after turning on the power.
The offset of the home position can be calibrated and compensated with the following
procedures:
Polar-align the equatorial mount accurately.
1.
Turn off the power, and then turn it on again, and then initialize the hand control.
2.
When SynScan hand control asks "
3.
to-home process.
Finish the subsequent initialization steps.
4.
At the end of the initialization, choose 1-star alignment to align the mount.
5.
direc-
At the end of the 1-star alignment, the hand control will ask "
6.
(The "
•
Press "
•
Press "
position offset.
" and press
(refer to Section
Auto-Home?
H.P.O.
" means Home Position Offset).
1
" key to keep the original Home Position Offset.
2
" to use the results obtained from the 1-star alignment to calibrate the home
39
PART XI : ADVANCED FUNCTIONS
11.1). This limitation does not apply to
", press the "
1
" key to execute the au-
Update H.P.O? 1)No 2) Yes
"
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