Phase 1 of the computer control upgrade to the McMath-Pierce main spectrograph is now completed. The grating turret slew and stepper drives are now controlled by a VME-based computer running VXworks. The new hand paddle allows both manual and automatic movement of the grating. In manual mode, the user can select either slew or stepper motor control, as well as three pre-defined speeds. As the grating is moved, the ASCII display indicates the current grating angle, wavelength and grating order.
In the automatic mode, the user enters the desired wavelength, or grating angle and the grating order, and presses "go." The software will then position the grating, using the appropriate combination of slew and stepper motor motions. The spectral line will appear at the photoelectric port. For quick optical setups, there is also a zero-order function. In both the auto and manual mode, the user may also enter an offset angle to shift the desired spectral feature to the photographic exit port.
Phase 2, due to be finished this spring, will allow users alternate methods of control as well as a grating rock function for spatial/spectral flat fielding. A standard command language will allow users to control the grating over an RS232 serial port, an ethernet port, or remotely via a Web GUI interface. The serial/ethernet access was implemented to allow users who bring their own computers and instrumentation to control the spectrograph directly. The GUI will allow users in the main observation room to run the grating without the hand paddle, as well as provide support personnel with a means to remotely troubleshoot the spectrograph operation.
Lonnie Cole, Dave Jaksha, Carole Leiker
Jan Schwitters, Ed Stover