Guider
An SBIG SG-4 autoguider was added to the Moore Observatory CDK20 in October 2009. It is mounted on the bracket originally designed to hold a Nikon DSLR and wide-field lens under the telescope. However, in that position, the guider will not clear the mount as the telescope rotates in declination. The bracket was moved to the "top" of the telescope and secured to the central truss ring by two 1/4-20 stainless steel allen-head cap screws. The Nikon attachment plate has a rib on the underside that reduces flexure.
The guider is presently used with a Takahashi 60 mm diameter apochromatic refractor with a focal length of 355 mm. The assembly is held by a Takahashi tube mount, and bolted to the Nikon plate with a single 1/4-20 screw. The strength of this attachment derives from the large contact area.
The SG-4 requires a serial connection to the control computer and 12V DC power. On the Moore telescope, the 12V is supplied by a powerbrick that is carried on the OTA and connected to the web powerswitch "Camera" control. The serial line is connected through a DB9 and 6-foot serial extension cable to a Cat5 cable with DB9 adapters that goes to pegasus, the Sirius dome computer.
Pegasus runs with a Siig PCI serial card that adds two ports to the machine. These ports appear as ttyS4 and ttyS5. (To see the port assignments, use dmseg | less and search for tty.) On the Moore telescope the ttyS5 port is used for the guider connection. This is set in the prefs.guider file.
The guider in this location tracks with an accuracy of at least 1.5 arcseconds full width at half maximum in 60 second exposures. One of the first images taken with this system was of M42 on the night of October 28-29, 2009.