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MANUAL for the AUTO GUIDER of the AIP 70cm TELESCOPE



1.
Follow the instructions in the telecope manual. If everything is fine, turn your attention to the auto guider. (Don't forget to switch on the second PC and monitor if not already done.) If you see the pull-down menu, don't be afraid - essentially you will need only two menu points.

2.
Set temperature
[Camera -> Setup -> Setpoint]

Adjust the reference temperature of the CCD.
This has to be done in consecutive steps!!!


(Problem: The heat sink is to small. When the difference between reference temperature and actual temperature is to big, the heat sink can't get rid of the produced heat, hence the cooling element takes more power and produces more heat. An effective cooling of the CCD is no more possible.)

Check the actual temperature (lower right corner on the screen). If it doesn't fall and the power consumption of the cooling element reaches 100 percent (the value in brackets), set the reference temperature to a higher value (make the difference between actual temperature and reference temperature smaller). Once the reference temperature is reached, set a new reference temperature. The actual temperature needed depends on the stars in the FOV of the guider. If there is a bright source, some degrees below zero are sufficient.

3.
Select guide star and exposure time
[Track -> Autoguide ]

Exposure time:
Select the exposure time. The actual time depends of course on the brightness of the guiding star. Start with 2 seconds, check the image and - if it's necessary (that means not enough counts for the guiding star) - choose a longer exposure time.
Once the exposure time is fixed, select your guiding star with the white rectangular cursor on the image. Press the "Enter" button twice and everything is fine. After each exposure, the counts and the relative motion in pixel values of the guiding star are shown. The pixel values should stay below +/-1.0 (see below). In the case of clouds, the guider loses track and has to be re-initialized.

4.
Solve problems
[Track -> Autoguide -> Parameters] or
[Track -> Autoguide Parameters]

The auto guider moves the telescope via the mechanical telescope drive mechanism. This mechanism has an immanent and an age-dependent tolerance, which makes it hard to calibrate the guider exactly. Another problem is the non-linear motor activity of the drive for small motions as used by the guider. This makes it sometimes necessary to adjust the guider parameters manually - if the relative motion of the guiding star is growing after each exposure (in x or y) or highly fluctuant. The parameters of interest are Aggressiveness,
Relay--(+/-, x/y)--Speed and Minimum/Maximum move. (By the way: x means RA and y means DEC). The aggressiveness mainly gives the reaction time of the guider. High aggressiveness means a fast reaction even if there is only a small difference in pixel values of the guiding star between two successive exposures. Low aggressiveness means a lazy behaviour of the guider. If the relative motion of the guiding star grows after each exposure, choose a higher aggressiveness. If the relative motion is big but highly fluctuant (+/-), decrease the aggressiveness. Minimum/maximum move gives the allowed time for motor activity in milliseconds. The maximum move should always be greater than 1000.

(Written by J. Vogel)


Last change 2007/02/15