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Telescopes and the equipment that go along with them are very analogous to
human eyes and brains. The advantage of telescopes is they have considerably
more light gathering area.
Telescopes have to do (only) a few things:
- Focus the light from objects onto a detector
- Point to various places on the sky``Track'' objects as they drift across the sky
At the end of the last century, the biggest telescopes had mirrors
with diameters of around 40 inches (1 meter) and observations were
``visual''. There was a steady increase in mirror size and mechanical
sophistication up through the 1950's when the Palomar ``200 inch" (5 meter)
telescope went into operation. The Soviets built a 6m mirror telescope
that never worked very well. The Palomar reigned as the biggest useful
telescope will 1994 when the first of two Keck telescopes was completed
which had a 10m (400", 33.3 foot) diameter mirror.
- Q. How much more light does the Keck 10m telescope
gather than your eye with it light collecting diameter of 0.5 inch?
Ratio of light gathering AREA:
Note: used same units for Keck and eye diameters
- It is hard to get a feel for these big numbers sometimes.
A 2 candlepower light on the moon would give 9 photons per minute
with Keck and 1 photon per 46 days with your naked eye. This is why
we build big telescopes.
- Go outside on a dark night an look up. There are about 3000 stars visible
to the ``naked eye'' and 3 galaxies. With the Keck telescope, there are
billions of stars visible and billions of galaxies.
- Where are these telescopes?
- Mt Hamilton (3m and 1m) is the site for Lick Observatory with
headquarters on the UCSC campus.
- Kitt Peak National
Observatory (Arizona) and the
- Cerro Tololo Interamerican
Observatory (Chile) are the main
US national facilities (4m, 2m, 1m)
- On top of Mauna Kea on Hawaii there is a whole community of
telescopes including the
Keck 10m telescopes
, an 8m Japanese
telescope, radio telescopes, the Canada-France-Hawaii
telescopes and soon, an 8m national facility telescope.
- European Southern Observatory, Canary Islands, Australia --
there are an amazing number of telescopes out there.
- Why always put telescopes on top of mountains?
- The Hubble Space Telescope - higher than your average
mountaintop. Why spend 2 billion dollars on a 90" telescope?
- HST gives very high spatial resolution
- HST has ``darker'' skies
- HST opens up new spectral windows (more later)
- What is the US budget for astronomy?
~ $250 million/year = 70 cents per year per person.
One Keck telescope runs about $80 million to build and $10 million to run.
Wed Jan 14 21:53:00 PST 1998