Telescopes continued…

Why is bigger better?

Two reasons…

(1) Light-gathering power

• Depends on the area of the objective mirror (or lens)

• Compare 16-inch to our 10-inch scopes:

(2) Resolution of telescopes• Angular resolution depends on telescope

diameter (D) and signal wavelength (λ):

Rayleigh criterion: Θmin ~ λ / D

Some numbers …For optical wavelengths, Θ in arc-seconds, and D in inches it

works out to Θmin ~ 4.5 / D

Example: for your 10-inch telescopes,

Θmin ~ 4.5/ 10 = 0.45 arc-sec

(note garage sale signs…)

Above for diffraction-limited situations like space telescopes. Our atmospheric limits actual results.

Overcome atmospheric limits with active optics.

Mayal 4-m

McMath solar telescope

Wynn

•Near Tucson

•Tax supported with other consortia, too

•Nice public program

•Tucson: good lighting

Kitt Peak National Observatory

Mayal 4-meter

McMath solar telescope

Originally separate mirrors as shown here

Whole building rotates

Operated by the Smithsonian Institution, founded with funds from British scientist James Smithson, who bequeathed his fortune to America for the creation of an institute for the “increase and diffusion of knowledge.” Now looks like ….

The MMT (Mt. Hopkins, SE AZ)

New MMT 6.5-meter

Also on Hopkins: LBT

• Large Binocular Telescope

• Twin 8.4-m mirrors

• Optical interferometry

• Will image extrasolar planets

And: VATT & SMT

• Vatican Advanced Technology Telescope

• Univ. Arizona Sub-Millimeter Telescope

Mauna Kea , Hawaii – Keck, Gemini, Suabaru, NASA, and others

Gemini (North) 8-m Telescope …

8-meter spin-cast mirror

Twin Keck 10-m Telescopes

Keck segmented primary mirror

European Southern Observatory (Chile)

Why the shift to southern hemisphere?

VLT four 8-m’s

European Southern Observatory 3.6-m

Cerro Tololo nearby with the Blanco 4-m, a twin to Kitt Peak 4-m

DuPont 2.5-m also there

Supporting this closed Mt. Wilson 100-inch

Gemini South and SOAR on nearby Cerro Pachỏn

Gemini South

SOAR = Southern Observatory for Astrophysical Research

How’s it coming?...

UNC-CH (17%) and others

PROMPT …