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12. Close the camera's shutter.
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PEC for short, is a system that improves the tracking accuracy of the drive by reducing the number of user corrections needed to keep a
guide star centered in the eyepiece. PEC is designed to improve photographic quality by reducing the amplitude of the worm errors.
Using the PEC function is a three-step process. First, the CPC needs to know the current position of its worm gear so that it has a
reference when playing back the recorded error. Next, you must guide for at least 8 minutes during which time the system records the
correction you make. (It takes the worm gear 8 minutes to make one complete revolution, hence the need to guide for 8 minutes). This
"teaches" the PEC chip the characteristics of the worm. The periodic error of the worm gear drive will be stored in the PEC chip and used
to correct periodic error. The last step is to play back the corrections you made during the recording phase. Keep in mind, this feature is
for advanced astrophotography and still requires careful guiding since all telescope drives have some periodic error.
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Once the telescope has been polar aligned using the EQ North Align (or EQ South for southern hemisphere) method, select PEC from the
Utilities menu and press ENTER to begin recording your periodic error. Here's how to use the PEC function.
1.
Find a bright star relatively close to the object you want to photograph.
2.
Insert a high power eyepiece with illuminated cross hairs into your telescope. Orient the guiding eyepiece cross hairs so that one
is parallel to the declination while the other is parallel to the R.A. axis.
3.
Center the guide star on the illuminated cross hairs, focus the telescope, and study the periodic movement.
4.
Before actually recording the periodic error, take a few minutes to practice guiding. Set the hand control slew rate to an
appropriate guide rate (rate 1 = .5x, rate 2 = 1x) and practice centering the guide star in the cross hairs for several minutes. This
will help you familiarize yourself with the periodic error of the drive and the operation of the hand control. Remember to ignore
declination drift when programming the PEC.
Note: When recording PEC only the photo guide rates (rates 1 and 2) will be operational. This eliminates the possibility of moving the
telescope suddenly while recording.
5.
To begin recording the drive's periodic error, press the MENU button and select PEC from the Utilities menu. Use the Up/Down
scroll buttons to display the Record option and press ENTER. You will have 5 seconds before the system starts to record. The
first time each observing session that PEC record or play is selected, the worm gear must rotate in order to mark its starting
position. If the rotation of the worm gear moves your guide star outside the field of view of the eyepiece, it will have to be re-
centered before the recording begins.
Helpful
Hint
Once the worm gear is indexed, it will not need to be positioned again until the telescope is turned-off. So, to give yourself more time
to prepare for guiding, it is best to restart PEC recording after the worm gear has found its index.
6.
After 8 minutes PEC will automatically stop recording.
7.
Point the telescope at the object you want to photograph and center the guide star on the illuminated cross hairs and you are
ready to play back the periodic error correction.
8.
Once the drive's periodic error has been recorded, use the Playback function to begin playing back the correction for future
photographic guiding. If you want to re-record the periodic error, select Record and repeat the recording processes again. The
previously recorded information will be replaced with the current information. Repeat steps 7 and 8 to playback the PEC
corrections for your next object.
Does the PEC function make unguided astrophotography possible? Yes and no. For solar (filtered), lunar, and piggyback (up to 200mm),
the answer is yes. However, even with PEC, off-axis guiding is still mandatory for long exposure, deep sky astrophotography. The
optional Reducer/Corrector lens reduces exposure times making the task of guiding a little easier.
When getting started, use fast films to record as much detail in the shortest possible time. Here are proven recommendations:
•
Ektar 1000 (color print)
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