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Focusing the guiding camera

Now 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 (Fig. 7).

Select a guide field: To focus the guiding camera shift a reasonably bright star into the guiding camera field of view (GFOV). Press buttons + or - of the guiding field control unit to move the GFOV. The GFOV is displayed as the small square in the Sky Graphics Window (Fig. 14 and 15).

Set guiding camera into ``focusing mode'': Press misc and select focusing with the left mouse button. Proceed as in the Section 3.1 before to obtain Gauss-Fits to the brightness distribution of your star.

Set a starting focus value: The focus is set in the guiding camera focus control unit of the guiding camera section (Fig. 14). The focus is changed by pressing the buttons + or -. A good starting value for the guiding camera focus is 19.0. The values are in arbitrary units.

Make a guide focus imaging sequence: Change the focus stepwise, while the guide camera is in ``focusing mode'' and record the FWHMs displayed. The best focus is the one where the FWHMs are minimized. Again, you may choose step sizes of four. A reasonable FWHM for a well focused guiding camera should be similar to the FWHM obtained for the main camera.


next up previous contents
Next: Calibration exposures Up: Focusing telescope and guiding Previous: Focusing the telescope   Contents
Dieter Engels
2003-01-15