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Current Telescope Control System. Big Bear Solar Observatory Pointing and Tracking Guiding Light Beam Control. Introduction. Current telescope control system has evolved since 1969. Very little of telescope is computer-controlled. Light beam control system is unique to this telescope.
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Current Telescope Control System Big Bear Solar Observatory Pointing and Tracking Guiding Light Beam Control
Introduction • Current telescope control system has evolved since 1969. • Very little of telescope is computer-controlled. • Light beam control system is unique to this telescope.
Pointing and Tracking • Equatorial mount: RA & Dec axes. • RA axis, ring gear, worm, transmission • Preload motor -- replaces weight • Slew motor. • Tracking motor -- originally synchronous motor, now stepper motor • Set / guide motor
Declination • Preload spring. • Slew motor. • Set / guide motor.
Computer Control System • High-level control: sundial. • Low-level control: pcguider, tracking motor controller.
Software languages, interface to hardware • Sundial: Tcl/Tk, C. • Pcguider: C. • Motor controller (internal). • Interface: serial ports.
Light Beam Control • Sundial also handles light beam control. • Interface to hardware LBC through digital I/O board (imitates old PDP11 DR11 cards). • Interface to cameras is either serial or TCP/IP socket interface
Other hardware • LBC system also controls some other hardware. • Zeiss H-alpha filter • Filterwheel(s)
PC Guider • Directly controls stepper motors for guider stages. • Communicates with telpos part of PDPRP on sundial.
Tracking motor control • LBC computer communicates directly to tracking motor controller to set RA tracking speed. • Needed primarily because of variable lunar motion (photoelectric guiders correct for solar variations).
Photoelectric guiders • Small telescope forms image of Sun on quad cell. Quad cell is on motor stage controlled by PC guider. • Quad cell generates error signals in RA, Dec. • Analog servo operates telescope guider motors to minimize error signal.