Astronomy 1
Fall 1998

October 19 Lecture

Telescopes and Astronomical Instruments

Text Chapters (Chaisson) = #5 (Read, Look at Figures and READ the CAPTIONS)
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NOTICES
- 1 Hour Test - Next Wednesday: October 21 
   In Class Test (Chapters 1-5, Text part of chapter 5 only) plus time and coordinates
- REVIEW PAGE 


- Observation Session - Sponsored by Blomidon Naturalists Society
Open to the Public
Place: Stile Park (top of Highland Avenue)
Time: 8 pm Friday Oct 23 (If cloudy try Saturday Oct 24, same time)
	Telescopes Viewing of Celestial Objects + Constellation Identification
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Astronomical Event:
Oct 20 (Tuesday) New Moon
Oct 23 (Friday) Saturn at Opposition
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LECTURE  
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Resolving Power of all types of radiation telescopes (not just optical)
	l = wavelength
	a (radians) = 1.2 l/D 		radian = 206,300"arc
	a ("arc) = 0.25  l(micrometer)/D(m)
EXAMPLE:
Microwaves l = 1mm = 1000 micrometers
How big a radio telescope does it have to be to resolve 1"arc?
D(m) = 0.25 l(micrometer)/a ("arc) = 0.25 (1000 )/1 = 250 m

Types of Telescope Designs
	-Refractor 
	-Newtonian Reflector
	-Cassegrain
	-Schmidt
	-Schmidt-Cassegrain
	-Maksutov
Mounts
	-Equatorial
	-Alt-Azimuth (New computer controlled large telescopes)
		Smithsonian Astrophysical Observatory on Mt Hopkins
		Mulitple-Mirror Telescope
		also -- Keck telescopes on Mauna Kea (Hawaii)

READ THE TEXT WHICH HAS GOOD DISCUSSION OF TELESCOPES
	active optics, multiple mirror telescope, 
	adaptive optics, interferometers

Detectors:
(Visible, Near UV, Near IR)(300nm - 1000nm)
1. The Eye (see also Oct 7 Lecture)
	Convenient - insensitive - Not Quantitative
	Resolution 1' arc at fovea centralis (cones)
		Colored vision less sensitive and in the cones 
		by a factor of 100
	Resolution away in the rods = 5-10' arc		
	Only B&W at low light levels (peak at 500 nm) Rhodopsin in rods
		(Dark adaptaton 20-30 minutes)
		1-10 photons required to trigger detection
	Use averted vision because cones not at center of eye (rods are)
	Sensitivity (400-700 nm)

2. Photographic Plate
	Wide Angle (large format)
	Huge amount of information on one photograph
	Wavelength Sensitivity (400 nm - 800 nm)
	Long history - records for over 100 years
	Non-linear response to light

3. Photomultipliers and Photodiodes
	Very Sensitive 
	No imaging
	Used for photometry 
	Fast and used for short time events.
	
4. Charged Coupled Device 
(CCD) Cameras [Santa Barbara Group example]
About CCD's SBIG
	Very linear photo response - time exposure
	Very efficient (as high as 75% quantum efficiency)
	Precise 2 dimensional measurement
	Digital output - easy to analyze results
	Small Format (centimeters)
	Used all observatories and becoming popular with 
		amateur astronomers	

-- Other Telescopes: --

Radio and Microwave
	No imaging - single detector
	Must scan to produce an "image" = contour map of intensity
	Single - Steerable (Penticton - Green Bank)	(Large area for sensitivity)
		Fixed (Arecibo)	(Much Larger area but limited pointing)
	Interferometers		(Increase resolution)
	Very Large Base Line or Very Large Array Interferometers

EXAMPLE: wavelength = 1 m 
              baseline = 1000 km = 106 m
	a" = 206,300 (1/106) = 0.2 " arc
at wavelength = 1cm , a" = 0.002"arc using the VLBI

X-ray and Gamma Ray
	Difficult to make a refractive or reflective surface. 
X-ray 
	Use grazing angles to get reflectance and focusing
Gamma rays 
	Tracks in Photographic Plates
	Counters

Satellite Observatories (above the atmosphere to detect UV, X-ray, Gamma Rays
Hubble Space Telescope (See Interlude 5-1) 2.4m dia optical 
Hubble Space Telescope Overview

In orbit 1990, repair 1993,Correction of Optics

IRAS (Infrared Astronomical Satellite) 1983 (no longer working but produced important survey)
IUE (International Ultraviolet Explorer) 1978-
EUVE (Extreme Ultraviolet Explorer) 1992
HEAO (High Energy Astronomical Observatories)  - Einstein Observatory (1979)
ROSAT (Roentgen Satellite) 1990
GRO (Gamma Ray Observatory) Compton Observatory 1991
AXAF (Advanced X-ray Astrophysical Facility 1999)

Spectrum Photos in the Text

RIVUXG
(Radio - Infrared - Visible - Ultraviolet - Xray - Gamma)
See Table 5-1 READ