Locating guide stars at Prime Focus

A star will be bright enough for autoguiding if it is visible on the finder with 4 frames of integration at full TV gain. Avoid very bright (6) stars. Proceed as follows:

1. Move the rotator to your required position angle with e.g.:

   ROTPOS 180

2. Slew the telescope to your object to be observed; confirm with a GLANCE exposure.
3. Press the FINDER button on the Grinnell panel.
4. Press the DIRECT button on the Grinnell panel.
5. Press the BEAMSWITCH A button on the Control Desk.

   The guide probe field will now become visible on the finder; stars should appear to move along the major axis of the chip as the beamswitch takes effect.

   If nothing happens, check at the User Interface (with AD/T) that the aperture A position is correctly defined: it should be 0,-590. If it is not, then type:

   AP/A 0 -590

   in order to define the aperture position, and press A again.

6. Select the Grinnell function GET GUIDE STAR. A display of the field accessible to the probe will appear on the screen.
7. Move the cursor to your chosen guide star in the permitted area and press ENTER on the Grinnell joystick control box.
8. Finally press the BEAMSWITCH NOM button on the Control Desk and press DIRECT on the Grinnell panel.

The telescope is now pointing to your object, which should be positioned close to the centre of the CCD detector, while the guide probe is positioned such that the guide star is at the centre of the acquisition area. Subsequently, the guide star will have to be acquired with the guide probe, by going through the field - acquire - guide - loop/enable sequence described below in section .