Date: 4 February 1995
Subject: A Shrine to Curiosity about the Universe
From: Ingrid Siegert Tanghe <ist@america.net>
MOUNT PALOMAR OBSERVATORY: A SHRINE TO CURIOSITY ABOUT THE UNIVERSE
BY BRIAN MASON
I did remember to bring a jacket; but I was hardly expecting snow in
Southern California. Then at 4,000 feet above sea level on my way
up Mt. Palomar I passed a highway department sign warning of snow plows
ahead. This was still 1,500 feet below the summit, home to Palomar
Observatory and the venerable 200-inch Hale Telescope. At 5,000 feet
I hit snow and wondered just how inadequate my jacket would prove. I
needn't have worried. In the excitement of seeing the Hale Telescope I
forgot all about the cold.
With the dramatic Hubble Space Telescope images flooding the astro-
nomical world it may be difficult to appreciate the enormous contribution
of the 200-inch Hale. After all, its grandeur is more subtle. The
machinery, unless you understand its perfection, is not outwardly
impressive. And the observatory itself is a mere 5,550 feet above sea
level. The lights of Southern California even compromise current research.
My visit to Palomar was strictly as a tourist. I joined the throngs
of visitors on a recent Sunday afternoon. I was happy to see the crowds.
It was a reminder that astronomy holds a special place in the public
imagination. From overhearing conversations I could tell that few
visitors understood exactly what they were seeing, or even how
significant was the work coming from this telescope to our understanding
of basic cosmology. Yet, they came. Even without full comprehension
people are drawn to this as if it were a shrine. In reality, it is.
I definitely felt as though I were walking on hallowed ground as I
stepped through the front door, past the bust of George Ellery Hale,
and up the curving steps to the public gallery. My reaction stems from
the knowledge that under this dome began the serious exploration of
Edwin Hubble's expanding universe. No mean feat for a pile of gears and
glass.
I have a feeling, though, that this observatory has been hallowed
since the moment development began in 1928. The evidence lies in the
series of nineteen exquisite drawings made by Dr. Russell W. Porter over
a period of twelve years during the conceptual development and
construction of the instrument. Machinery alone cannot inspire such
beautiful work. These drawings were obviously inspired by awe. They
are an attempt to communicate and come to terms with a force that
Dr. Porter knew would revolutionize science. This spirit lives, as
attested by the crowds who made the arduous trek up winding roads, past
stinking cattle farms, and the long walk from the parking area through
mud and slush to see a telescope which began operation fifty years ago.
The visitors' gallery offers a fine view of the instrument. The
massive yoke mount, of course, is most imposing. Next to its giant arms
and the huge horseshoe-shaped bearing at the north end, the telescope
itself appears insignificant. Some 530 tons of moving weight is supported
by the two giant bearings. The large horseshoe at the north is so
shaped to allow the telescope to be pointed at the celestial north
pole without obstruction. The horseshoe glides on a film of oil pumped
continuously against the bearing at a pressure of 300 pounds per square
inch. The contact is so free of friction, and the telescope so
delicately balanced, that only 1/12 horsepower is needed to track the
stars. The telescope itself attaches to the yoke through two trunnions.
The method of connection is surprising. It is secured to the declination
trunnions through a scaled-up system of bicycle spokes. These spokes
allow for flexure and ensure smooth contact with the ball bearings.
With all the imposing girders, beams, and bearings, it is almost
possible to over-look the mirror. The true size of the mirror is best
appreciated in the adjacent museum where an actual size concrete blank
now enables guests to rest their weary feet. It is enormous. The glass
version, 200-inches across and nearly two feet thick, rides on 36
independent counterbalances. Like most everything about the telescope,
these mirror supports were revolutionary in their day. Amateur telescope
makers might take solace in the knowledge that eight years of grinding
were needed to remove some 4.75 tons of glass to achieve the correct
figure.
Occasionally, the giant mirror is removed from the telescope and
recoated. For this operation, an enormous vacuum chamber on steel rails
plucks the 60-ton mirror and its cell from the telescope. After the
surface of the mirror has been cleaned the chamber is sealed and the air
is pumped out. Then tungsten filaments, previously coated with a minute
quantity of aluminum, are heated allowing the vaporized aluminum to
settle on to the mirror. This entire operation may be completed in only
two days.
Most observing work nowadays depends on CCDs and spectrographs. But
in the old days, observing with the Hale must have been a real gas.
Astronomers once actually rode inside the telescope, suspended at the
prime focus. A precarious elevator tracking along the inside of the dome
carried the observer to a narrow walkway. Then the telescope tube would
swing around allowing the observer to step from the walkway into a rather
spacious chamber at the prime focus. One can only imagine what it was
like using an eyepiece on the ultimate light bucket.
Prime focus is not the only point of observation. Indeed, the
versatility of the instrument marks the genius of its designers.
Light may also be routed to a Cassegrain focus, a five-mirror Coude'
system through the south polar shaft, or through the hollow east
declination trunnion (remember the bicycle spokes). The focal ratios
available in various configurations are f/3.3, f/16, and f/30. At the
f/30 focal point, an image of the moon is nearly five feet across!
In shear massiveness, the 200-inch Hale Telescope is about as
technologically distant from the Hubble Space Telescope as would be
possible. Yet, they have much in common. The space telescope represents
the ultimate extreme in technical finesse. If anything, its flawed mirror
emphasizes the degree to which our technology was pushed. The Hale
Telescope, on the other hand, represents the brute force method of great
achievement. In its own way the Hale instrument was as great a risk as
the space telescope. Just for size, the 200-inch mirror was DOUBLE
anything that had previously been attempted. Even the dome weighs 1,000
tons. The telescope tube weighs 150 tons. Final figuring of the
mirror was done by hand over a period of a year. In all, twenty years
were invested in engineering and construction.
Now, having visited this shrine to curiosity about the universe, I am
grateful to George Ellery Hale and Russell W. Porter for their courage in
making the 200-inch telescope their generation's equivalent of our space
telescope. Similarly, I respect the designers and builders of the space
telescope for their courage in dramatically pushing spacecraft and optical
technology to new extremes in a quest to learn more about our universe.
About the author -
Brian Mason is a Systems Engineer for a computer company by vocation,
a historian of science by training (MA, Virginia Tech) and dabbles in
astronomy, radio (KO4LK) and photography by avocation. He says his
real work is in raising his three young daughters.
REPRINTED FROM THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF
THE ATLANTIC, February 1995 - Vol. 6, No. 7. Copyright (c) 1995 - ASA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- T o d d E. V a n H o o s e a r -
``'''vanhoose@lalaland.cl.msu.edu - vanhoose@msu.edu - vanhoose@lalaland.cl.msu.edu
(._.) Michigan State University - East Lansing, MI USA
(_) Computer Laboratory - Department of Communication
`---' <A HREF="http://lalaland.cl.msu.edu/~vanhoose/">My Home Page</A>
"I.R.S.: We've got what it takes to take what you've got!"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~