Telescopes

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:

1. Point to various places on the sky

2. "Track" objects as they drift across the sky

3. Focus the light from objects onto a detector

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 until 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 (~400in) telescope gather than your eye which has a light collecting diameter of 0.5 inches?

  Ratio of light gathering AREA:

  (	400	)	2	=	600,000
  	0.5

  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 and 3 galaxies visible to the "naked eye".
  With the Keck telescope, there are billions of stars and billions of galaxies visible.

Where are these telescopes?

Mt Hamilton (3m and 1m) is the site for Lick Obs. with headquarters on the UCSC campus. (photo © UC Regents/Lick Observatory)

Kitt Peak National Observatory, Arizona (photo © AURA/NOAO/NSF)

and

Cerro Tololo Interamerican Observatory, (Chile) are the main US national facilities (4m, 2m, 1m) (photo © Krzysztof Z. Stanek)

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. (Photo © W.M. Keck Observatory)

European Southern Observatory (ESO) (Photo © Krzysztof Z. Stanek)

There are also telescopes in the Canary Islands, Australia... -- there are an amazing number of telescopes out there.

Why are all the telescopes always put on top of mountains?

The Hubble Space Telescope - higher than your average mountaintop.

Why spend 2 billion dollars on a 90" telescope?

1. HST gives very high spatial resolution

2. HST has "darker" skies

3. HST opens up new spectral windows (more later)

Check out these images taken by hst.

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.