Ultrastar C handbook Issue 1, August 2015
The settings shown above are generally satisfactory as a starting point, although some will probably
need refinement for best results. In the example shown, the ‘autoguider socket’ on the Ultrastar C is
providing the control signals to the mount, but you might alternatively use the ‘LX200’ mode via the
serial port of the computer, if this is preferred. The Guiding Parameters are set to 6 pixels per second,
which corresponds to the typical drift rate of a 1000mm focal length guide telescope when the mount is
guiding at 0.5x sidereal speed. Longer focal lengths and/or higher guiding rates will require a larger
value to be set so as to avoid excessively fast corrections, which can cause erratic guiding or even
oscillation of the guiding errors to either side of the guide star.
Once the defaults have been set to values which you think will be approximately correct, save the
settings and open the ‘View’ menu. In this you will see an option called ‘Max palette stretch’. Open
this and check the ‘Activate stretch display’ check box. This will automatically boost the image
brightness so that faint guide stars can be easily seen – if necessary, you can adjust the slider for the
best results.
Now click on the camera icon to open the Ultrastar C control dialog, as below:
The image box will be empty at this point, but we need a frame to select the guide star from, so use the
guiding options to select a suitable exposure time (say 1 second) and press the ‘Start’ button below the
image box. A sequence of images will be shown and you can refine the image focus and centring as
required. Before attempting to guide, it is wise to check that you have control of the telescope drive via
the Ultrastar C software. This is easily done by pressing the ‘Move Telescope’ buttons at the lower left
of the control box. Check that pressing the arrow buttons causes the star field to drift left, right, up and
