Deployment of the mx spectrometer

The MX Spectrometer is a remotely controlled multiple object fiber optic spectrometer head. Mobile fiber probes provide the capacity to obtain simultaneous spectra of many objects. Our experience with the Medusa aperture plate fiber optic spectrograph led us to design and build the MX with automated fiber positioning in the telescope focal plane. 32 stepper motor driven probes in a fishermen-around-the-pond arrangement position 64 fibers in the 45 arcminute field of the Steward Observatory 2.3m telescope. An onboard Z-80 microprocessor interfaces to 64 intelligent stepper motor controllers. The intelligent controllers allow simultaneous motion of all the probes for rapid field alignment. All fibers can be moved from one target pattern to another in less than 90 seconds. Two arcsecond diameter fiber apertures can be moved in steps as small as 0.1 arcseconds (10 microns). Probe collisions are prevented by software which maps the footprint of each probe in the focal plane. A failsafe electronic hardware system stops all motion in the unlikely event that two probes touch or encounter a foreign object. A second Z-80 with floppy disk drives is stationed in the control room to interface with the observer. This support microprocessor provides mass storage for coordinate lists as well as serial communications with the instrument microprocessor. We describe here both construction and actual operation of the MX Spectrometer at the telescope. The ability to record spectra of 32 objects plus additional sky spectra will greatly enhance our ability to study clustered systems of stars or galaxies.