Telescopes I've Used - MMT

MMT Observatory, Mount Hopkins, Arizona

MMT enclosure

MMT originally stood for Multiple-Mirror Telescope, made from what amounted to 6 independent 1.8-m telescopes on a single mount bringing light to a common (very small, because of differently tilted light paths) focal plane. The primary mirrors were surplus from the cancelled USAF Manned Orbiting Laboratory (MOL) prject in the 1960s, which was to have been essentially a series of crewed photoreconnaissance satellites. I went along for an observing run on a project with Rogier Windhorst while the telescope was still in its original multiple-mirror configuration. It was hard to get a good view of the old MMT because the enclosure hugged the telescope so closely. We used the MMT spectrograph to measure optical spectra of radio galaxies, selecting the most promising targets for further UV observations using IUE. Now the MMT (with the same acronym but different words, now it's Magnum Mirror so they wouldn't need new stationery) is in service as a 6.5m single-mirror instrument.

Part of the old MMT structure Observing at the MMT

The MMT was first touted as a path to new telescope technology, using laser metrology to constantly align the individual mirrors and give the equivalent light grasp of a 4.5m telescope at a fraction of the cost of traditional designs. What the MMT really taught us, though, was from its minimalist enclosure - that astronomers had been causing much of the atmospheric image degradation that vexed them, through domes so large and massive that they caused serious thermal effects. The laser alignment system had problems with the insect population on Mt. Hopkins, showing a tendency to run away from proper position when moths flew through the beams. Real stars were more useful for aligning the optics, which needed to be done every half-hour or more. The bottom image shows the displays as such an alignment was in progress.

Aligning mirrors of the MMT on a star

The MMT appears near the image splice in this USGS aerial photo from Terraserver.

In 2012, we had a night (plus additional service observations) for Aparajita Sengupta's dissertation, using the Hectospec fiber instrument for spectra of hundreds of galaxies in and behind the cluster (more pickily, supergroup) Abell 1882 at redshift z=0.14. Here's the new improved telescope tightly fitted into the same building. Our visit was the evening after the 20 May 2012 solar eclipse; one picture shows the eclipsed sun behind a filter past the MMT enclosure. From Mt. Hopkins, the partially eclipsed Sun set just about behind Kitt Peak.

MMT enclosure with eclipsed Sun New MMT, telescope view MMT 6.5m primary mirror

Setting eclipsed Sun over Kitt Peak from Mt. Hopkins

Telescope Collection

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