39
4.
Thread the T-Ring onto the Radial Guider.
5.
Mount your camera body onto the T-Ring the same as you would any other lens.
6.
Set the shutter speed to the "B" setting.
7.
Focus the telescope on a star.
8.
Center your subject in the field of your camera.
9.
Find a suitable guide star in the telescope field. This can be the most time consuming process.
10.
Open the shutter using a cable release.
11.
Monitor your guide star for the duration of the exposure using the buttons on the hand controller to make the needed
corrections.
12.
Close the camera's shutter.
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(
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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.
Using Periodic Error Correction
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.
Summary of Contents for 11074-XLT
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Page 51: ...51 APPENDIX F MAPS OF TIME ZONES...
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