Vixen AGA-1 - Manual (Page 9)

2. Setting the right ascension and declination accurately on the
monitor screen.
To correctly set the right ascension and declination displayed on
the monitor screen, center the guide star and bring into focus.
After centering the guide star on the cross, press the stop key of
the motor drive. At that time, look at the direction of the guide star
movement. The direction of the guide star movement is the right
ascension. Put the guide star upon the horizontal line of the cross
by turning the CCD video camera.
3. Select a motor drive speed which is appropriate to the focal length
of your telescope for photography. The longer the focal length,
the slower the speed you set to allow for finer adjustments.
4. Checking brightness of the guide star
If you press the “Level Check” key, AGA-1 will begin to check if
brightness of the guide star you selected is good. The middle
green indicator goes on and off during checking.