TopBox User Manual


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Fig. 1. Left: Telescope with the TopBox attached to the tailpiece.   Right: Electronics control unit mounted on the W side of the telescope pier.

The RRRT TopBox is an automated combination polarimetry module and offset guider. It consists of a single enclosure containing a movable diagonal pickoff mirror followed by two filter wheels and the mount for an imaging CCD camera. The first filter wheel holds a pair of Savart plate polarization analyzers, and the second filter wheel holds bandpass filters. The pickoff mirror is attached to a focuser with an autoguider camera which may be interchanged with a video camera or a standard eyepiece for visual observing without disturbing the focal plane detector setup. The two Savart plates are oriented at 45 degrees to each other in the converging beam to produce a pair of optically corrected double images yielding independent measurements of both linear Stokes parameters for point sources in the CCD field of view by differential photometry. The system is designed to be mounted on the tailpiece of the RRRT to place either an SBIG STL-1001E or an Apogee Alta U42 CCD camera in the optimum focal plane, with options to move the guiding and polarimetry optics out of the beam for unguided or direct imaging.

Fig. 2. TopBox with mounting flange and W side panel removed, showing autoguider mechanism (focuser, linear positioner, and pickoff mirror) and filter wheel module.

The control electronics are mounted on a subpanel housed in a utility cabinet which is mounted on the west side of the telescope pier. Three stepper motor drivers on a single daisy-chained serial control line operate the two filter wheels and the linear slide which carries the autoguider assembly, and another driver unit on a second serial control line operates the autoguider focuser.

Fig. 3. TopBox control electronics unit mounted on the telescope pier.

An ASCOM driver program using the two serial lines controls the TopBox and allows it to be addressed within the RRRT automated observatory control system, which includes TheSky for telescope control, MaxImDL for camera control and autoguiding, ACP as a hub for integration of these subsystems together with the dome, telescope focus, and weather monitor, and ACP Scheduler for fully robotic operation.

Last modified: Oct 3, 2012
David McDavid