It was interesting to visit Kitt Peak and see large human-built structures oriented to the sky, after seeing large human-built structures oriented to the sky in Chaco Canyon.
The big solar telescope is used to study the structure and spectra of
sunspots. It has a very long focal length--the slanted shaft of the
optical tunnel extends 200 feet from the tower to the ground, and another
300 feet into the mountainside. Unlike distant stars, the sun
is bright, so the light does not need to be so concentrated--rather, the
large size of the main mirror at the top (2.1 m across) and the long focal
length allow for high spatial and spectral resolution. Looking down
the optical tunnel from inside (right), you can see one of the secondary
mirrors.
The 4-m Mayall telescope is one of the largest optical telescopes in
the world. It is used to view dim objects in the visible and infrared
wavelengths. White paint reflects sunlight, and the vents at the
top take in ambient air--thermal engineers must be clever to prevent warm
drafts from distorting the viewing.
The main mirror is 4 meters across and weighs 15 tons. It is mounted
on a massive cement pier that is completely separate from the building
and the dome, to isolate it from vibrations. It was hard to
capture the enormous size of the telescope in a photograph, so I swiped
this one from the Kitt
Peak website. The blue "horseshoe" moves the 92-foot telescope
in an arc to follow the stars through the night.
The telescope known as WIYN is nearly as large, with a 3.5-m mirror.
Newer honeycomb-molding technology was used to manufacture this mirror,
so it is much less heavy, and the infrastructure to support and move the
mirror can also be smaller. Actuators on the back of the mirror have
little motors that constantly tug and tweak the shape of the mirror by
microscopic amounts to keep its surface optimized for viewing.
The technology that I found most captivating was a nifty robotic detector.
The robot can move some 100 tiny prisms to place them precisely in the
focal plane of the telescope. A steel plate is mounted.at the focal
plane, and the prisms are held in place by magnets and connected to optical
fibers. Thus each prism is positioned to collect the focused light
from a single star within a large star field, then send it through the
optical fiber to a spectroscope and CCD detector. The robot then
computes new positions and moves the prisms to new locations, all without
tangling the optical fibers, to gather the next 100 star spectra.
In this way, individual spectra from a large number of stars in the star
field can be collected simultaneously and automatically.
I didn't take these photos, either. WIYN excels at images, such
as this one (left, in false color) of a spiral galaxy that is 20 million
light years away and 70,000 light-years across. Another spiral
galaxy is seen side-on, looking from the edge of the disk. Our own
galaxy, the Milky Way, is also a spiral galaxy, but we can't take pictures
of it since we're inside it.
I bought a beautiful Tohono O'odham basket at the gift shop, with a
design of spiraling arms made from yucca fibers, similar to this one made
by Alice Andrews. The coiled design is traditional, but also reminds
me of how the tribal people have shared their mountain so that we can all
see distant spiral galaxies.
