WHERE: AT EXPLORIT Science Center, 3141 5th Street, Davis.

Telescopes through the Ages!
Saturday, November 12, 2005
7:00 to 10:00 p.m. at Explorit
Hosts: Vinita & Calvin Domier (530) 756-0191, vcdomier@yahoo.com

Join us Saturday evening, Nov. 12, at 7:00 p.m., when we will discuss different types of telescopes astronomers have used to "see" into the vast universe. We will also look at planets, stars, and other deep sky objects in the night sky, weather permitting.

On a clear night far from city lights, we can see about 2000-3000 stars with our naked eyes. We see the stars and other celestial objects because of light emanating or reflecting from them. To see millions of stars and other faint objects, we have to use telescopes or binoculars as they collect and magnify more light than our eyes can.

The first telescope is believed to be invented in 1608 by Hans Lippershey in Holland. This spyglass had two lenses in a tube and could magnify distant objects. Galileo Galilei used Lippershey's idea in 1609 to make telescopes with 8, 20, and 30X magni-fications. Galileo was the first person to use telescopes for astronomical purposes: he ob-served mountains and craters on the Moon, saw countless individual stars in the seemingly continuous Milky Way, and dis-covered the four largest moons of Jupiter.

Galileo's telescope was an optical one as it magnified light we see. Besides visible light, there is a lot of invisible radiation coming from stars and other deep sky objects. All these different types of radiations are part of the electromagnetic spectrum in which the waves travel at the same speed but at different frequencies. This speed is referred to as the speed of light (c=3x108km/s), and nothing in the universe moves faster than light speed.

Elecromagnetic waves are classified as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays, with radio waves having the lowest frequencies and energies and gamma rays having the highest. Earth's atmosphere lets in near ultraviolet, visible light, some infrared, and most radio waves, but blocks out the other types of electromagnetic radiations.

Optical telescopes capture and magnify visible light and are refracting if they are made of lenses (like Galileo's), and reflecting if they have mirrors (like Isaac Newton's). Some telescopes have combin-ations of lenses and mirrors (like Schmidt-Cassegrain). American Grote Reber made the first radio telescope in 1936 with a parabolic dish to collect radio waves. Many modern radio telescopes are electronically connected to greatly enhance their resolu-tion so as to show more details.

Ground-based telescopes cannot "see" the other electromagnetic radiations. Their "seeing" is also affected by atmospheric conditions. With the advent of the space age, we can overcome these limitations by sending orbiting telescopes into space, high above the Earth's atmosphere.

The Hubble Telescope (launched in 1990) is the most famous space-based optical telescope. The Cosmic Background Explorer (1989) studied microwaves, the Compton Gamma Ray Observatory (1991) studied gamma rays, the Chandra X-Ray Observatory (1999) studies x-rays, and the Spitzer Space Telescope (2003) studies infrared.


Besides talking about telescopes, we will also look at Mars. It made another historical nearest approach to Earth on Oct. 29. Next time Mars will be this close is 2018. Mars (mag. -2.2, in Aries), is the bright orange-red object high in the eastern sky, rising around 7pm and setting after sunrise. It is optimally situated high in the sky for viewing all night. We will also look at beautiful and bright Venus (mag. -4.2, in Oph.), setting around 8:30pm. Jupiter (mag. -1.5 in Virgo) sets around 6pm and Saturn (mag. +0.3 in Cancer) rises after midnight. Mars is in Opposition on Nov 7, 2005.

Moon phases:
New: 11/1 & 12/1,
First Qrt: 11/8 & 12/8,
Full: 11/15 & 12/15,
Last Qrt: 11/23 & 12/23.

To Receive These Bulletins via E-mail Contact Explorit at: Explorit Science Center

The Astronomy Club is for everyone - adults, children, knowledgeable or ignorant. Come to listen, look and learn, or to share your expertise or experience.