The summit of Mt. Hopkins sits at 8,500 feet above sea level, in the Santa Rita Mountains south of Tucson. It's home of the MMT, or Multiple Mirror Telescope, part of the Fred Lawrence Whipple Observatory.

PHOTO: Courtesy of FLWO
MMT, from neighboring Mt. Wrightson.

On most nights, the summit has a clear view of the night sky, making it perfect for astronomical observation. But this week, two nearby fires have had a negative effect on operations at the MMT.

The fires, one near Nogales, the other near Sonoita, have sent clouds of smoke over the mountaintop this week. The smoke not only affects observations, but the telescopes themselves. Sean Moran, a researcher at the MMT, says the smoke can leave a layer of ash on telescope mirror.

PHOTO: Mark Duggan
Smoke from the Bull Fire drifts toward the observatory.
PHOTO: Mark Duggan
The single mirror of the MMT replaced its former multiple mirror array.
PHOTO: Mark Duggan
Control room at the MMT.