Starlight Xpress CoStar - Manual (Page 3)

CoStar handbook Issue 1 May 2011
The CoStar attached to an 80mm F5 guide ‘scope
The focal length of your guide telescope is not especially critical for good guiding, as the guiding
software searches for the ‘centroid’ of the guide star image and can resolve shifts of far less than 1
pixel. Using a guide scope with a relatively short focal length (between 300 and 500mm) makes guide
star finding very easy and this is a recommended setup for general purpose guiding.
The control of your telescope mount will depend on what inputs are provided. The CoStar output
connector supplies 4 pull-down lines and a common return line to simulate an ‘ST4’ style autoguider
output. The lines are isolated from the CoStar electronics by opto-isolator chips and so there is no risk
of damage when connecting the outputs to mounts with unprotected electronics. A standard ‘RJ12’
style output lead is supplied with the CoStar and this may be connected to any ST4 compatible
autoguider input socket on the mount. It is also possible to guide by using serial data from the computer
to an RS232 input on the mount, but this will be covered later and is less effective than the direct
hardware connection.
The guiding mode is fixed at 1x1 binned, as Cmos imagers cannot operate in a true 2x2, or higher,
binned mode.