1. Telescope Basics
ASTR101 Mini-Lecture

2. The Electromagnetic Spectrum

3. Ground based observatories are typically “Visible” or “Radio.”
Interestingly human eyes are tuned to the visible spectrum.

4. VISIBLE - Discuss a bit of RainBOW

5. Visible Light/Spectrum
Also called “optical” (Rainbow Spectrum)
Frequency: 430 – 770 Tera-hertz (Thz)
Wavelength: 390 to 700 nm (~ cm)
This is the spectral range where the very long history of astronomical observations are made (until this past century when modern technology enabled other spectral range)
Now: imaging, photometry, spectroscopy and polarimetry

6. 3 basic types Refractor Reflector Compound (Catadioptric) ss
Early Galilean type was ground breaking, but eventually a very limited built.
Reflector
Newtonian concept
Compound (Catadioptric)
Schmidt-Cassegrain ss

7. Refractor Telescope
This is the earliest type and the simplest construct using a (magnifying) lens, plus a 2nd eyepiece.
Earliest patent by Hans Lippershey (German-Dutch) in 1608
Galileo built his own version, but definitely not of original idea
Already a compound system with 2 pieces.
Geometrical Optics (with the focus as the key “spec”) had already been well-established since its early start in 1300’s.
Geometrical Optics as the underlying principles (rules) – “focus” is an importance spec (a number)
Some basic rules
Match the two foci
Magnification is equal to M= fo/fe
Add an illustration

8. Infrared – NOT mUCH Here!

9. RADIO

10. Radio Waves Frequency: 3 kilo-hertz to 300 Giga-hertz (Ghz)
Wavelength: 100 kilometer (km) to 1 millimeter
Typical AM radio stations ~ 1000 khz  wavelength is 300 meters

11. Radio Sources
Sun is not a strong radio source, but it is the closest star
Jupiter’s strong magnetic field
The Milky Way galactic center
Radio pulsars (rotating neutron stars)
Extra-Galatic Radio Galaxies

12. Radio Telescopes/Receivers
“Antenna” or “Dish”

13. Arecibo Observatory, Puerto Rico – a single 300-m Radio Dish (single)
Many discoveries, including Crab Pulsar and other rotating neutron stars

14. The Very Large Array (VLA) Socorro, New Mexico
27 radio dishes; 25 m each
Interferometry-based
The site of the movie Contact (1997) starring Jodie Foster and Matthew McConaughey

15. Space Telescopes
Hubble space telescope (HST) arguably initiate a new era of space-borne observations, primarily in the Optical/Visible range
James Webb Space Telescope (JWST) is the next legacy but in Infrared range
Recall that Infrared observations is difficult from the ground.