Russian 6-m

•Nasmyth focus platforms

•Problems: 17-ton mirror has thermal time constant of a few days; location based on politics.

• Note alt-az mount

Enormous telescopes of the Future

• TMT = Ten Meter Telescope (US)

• OWL = Overwhelmingly Large telescope, 100m

The rest of the spectrum

• Space-based observatories needed

• Radio requires special telescopes

IRAS = InfraRed Astronomical Satellite – early NASA

IUE = International Ultraviolet Explorer—another…

Russian 6-m

•Nasmyth focus platforms

•Problems: 17-ton mirror has thermal time constant of a few days; location based on politics.

• Note alt-az mount

NASA’s Great Observatories

HST = Hubble Space Telescope

Compton Gamma Ray Observatory (GRO)

• Mission now over

Chandra X-Ray Satellite

SIRTF = Space Infra-Red Telescope Facility

• launched a year ago

• Renamed the Spitzer Space Telescope

James Webb Next Generation Space Telescope

•> 20-ft diameter

• Named after 2nd NASA administrator; built by TRW

•L2 Lagrange point for Earth-Sun system (thus 106 times closer to us than sun – mass ratio…), or 940,000 miles from us. (Sun-stationary)

Karl Jansky’s Rotating Antenna (Bell Labs, 1931)

Saw a sidereal period (~23h56m) signal

Typical Radio Astronomy Telescope

Why so large? ….

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 8-inch telescopes,

Θmin ~ 4.5 / 8 = 0.56 arc-sec (note signs…)

Schematic

Today: a computer

Green Bank, WV

aricebo

Interferometry

VLA = Very Large Array (NM)

VLBA = Very Long Baseline Array

PARI = Pisgah Astronomical Research Institute