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Guiding the telescope

Verify that tracking is enabled. Shift to the guiding camera section and select an exposure time of 1 second. Press exposing to obtain continuous read-outs from the guiding camera. The field of view images now by the guiding camera is indicated as the small square in the Sky Graphics Window (Fig. 15).

Figure: Left: Selecting a "fit frame", Right: The telescope operating in "guide mode".
\includegraphics [width=7.75cm]{fit_frame.ps}
\includegraphics [width=8cm]{guiding.ps}

Select a guide field: Search for a reasonably bright star by moving the guiding camera field of view (GFOV). Press buttons + or - of the guiding field control unit to move the GFOV (Fig. 14 and 15).

Set the camera into ``guiding'' mode: Move the mouse pointer to the center of the star in the guiding camera display, press the right mouse button, and select fit frame with the left mouse button. A small section around the star is now displayed (Fig. 7). If you are not satified, switch back to the full frame by pressing the right mouse button in the guiding camera display and by selecting total image. You may search now for another guide star. If satisfied, select an exposure time from 3 to 7 seconds (with button exptim), and press guiding.

Judging the guide quality: A two-dimensional Gauss-Fit is applied to the brightness distribution of the star and is displayed as ellipse in the guiding camera display. The Gauss-Fit parameters are displayed in a Gauss fit parameter display at the top of the guiding camera display. Given are background and amplitude, x-position and full width half maximum (FWHM) in x-direction in arcsec, y-position and y-FWHM in arcsec, and offsets from the center position of the first exposure in arcsec. Make sure that the intensity (amplitude) of your guide star has a level higher than 100. Offsets from the center position of the first exposure should be $<$2 arcsec, unless the seeing is much greater.


next up previous contents
Next: A typical observing night Up: olt_manual Previous: Flat-fielding   Contents
Dieter Engels
2003-01-15