ModernObservational/Instrumentation

TechniquesAstronomy 500

Andy Sheinis, Sterling 5520,2-0492sheinis@astro.wisc.eduMW 2:30, 6515 SterlingOffice Hours: Tu 11-12

Class Website:Handouts, .ppt lectures and HW will be postedhttp://www.astro.wisc.edu/~sheinis/~500class

Homework:There will be a 5-6 problem sets, one dueapproximately every other week. I will either post, orhandout solutions. I encourage you to discuss theproblems with your classmates, but you must eachwrite up your own solution.

There will also be a Midterm and Final exam as well asan “Observational” project, which may or may notinclude a laboratory exercise.Grading:Approximate grading distribution will be:

HW 40%Project 20%Midterm 20%Final 20%

Texts:

Required:Walker, "Astronomical Observations", Cambridge Univ. Press.Schroeder, "Astronomical Optics", Academic Press

Recommended:Kitchin, "Astrophysical Techiques", Adam Hilger, LtdBevington&Robinson, "Data Reduction and Error Analysis for thePhysical Sciences", McGraw-HillGray, “The Observation and Analysis of Stellar Photospheres”,Cambridge U. Press

Other Useful References:McLean, “Electronic Imaging in Astronomy”, WileyRybicki and Lightman, “Radiative Processes in Astrophysics”, WileyCox, “Allen’s Astrophysical Quantities”, Athlone Press

chapters

Date title W K S G R & L

1/22/06 Introduction to the course. Basic Observables 1 6

1/23/06 Photon Fluctuations, Fundamental noise sources, S/N 2 4

1/29/06 S/N in aperture photometry 2 4

1/30/06 Detection Limits/ Signal-to-noise/ time estimation 2 1.1 16

2/5/06 Planning an Observing run

2/6/06 Basic Processing

2/12/06 Basic Processing

2/13/06 Intro to Optics: Fundamentals/ radiometry 2 5 1

2/19/06 Intro to Optics: Paraxial Optics, Wave Optics 10

2/20/06 Detectors revisited 8 16

2/26/06 Telescopes 3 4, 7 ,8, 10

2/27/06 Telescopes 3 4, 7 ,8, 10

3/5/06 seeing, speckles and scintillation 4 5

3/6/06 seeing, speckles and scintillation 4 2

3/12/06 Direct imaging resolved and unresolved source photometry 2.1, 2.3, 3

3/13/06 Direct imaging resolved and unresolved source photometry 2.1, 2.3, 3

3/19/06 Spectrographs: Basics 7 4 13, 15 3

3/20/06 Spectrographs: Basics 7 4 13,15 3

3/26/06 Spectrographs: Specialized, MOS, IFU 4

3/27/06 Midterm

4/2/06 spring break

4/3/06 spring break

4/9/06 Spectoscopy: Processing techniques 7 4

4/10/06 Measureing spectral Continuum 7 10

4/16/06 Measureing spectral Lines 7 12

4/17/06 Student Presentations

4/23/06 Student Presentations

4/24/06 Polarimetry: Nordsieck 5.2

4/30/06 Fabry-Perot: Reynolds

5/1/06 Radio: Eric Wilcots 1.2

5/7/06 Radio: Eric Wilcots

5/8/06 Review.

* W=Walker

K=Kitchin

S=Schroeder

G=Gray

R&L=Rybicki and Lightman

Astronomy is Different

• Universe is the laboratory• We can only observe, no interaction• Limited to phenomena, occuring in the past• Must take interpret a “snapshot”• Have only the properties of light• Cannot measure directly, must infer from the

measurement of light.

Properties of light

• Intensity, flux, irradiance, amplitude• Angle of arrival, position, image• Wavelength, frequency, color• Angular momentum, spin, polarization• time variation (in some cases)• Phase (interferometry, radio, AO)

LargeTelescopes

• Only two (Keck I and II) available in the 90’s• Several available at the turn of the century (the 4

VLT units, Gemini North and South, Subaru, HET)• One more in 2005, SALT!• others under construction (LBT, GTC)• and plans already for 30-100m telescopes...

Telescopes• Name Diameter Nationality of Sponsors Site Built• (SALT) 11.0 m South Africa, USA, UK, Germany, Poland, New Zealand South African 2005• (GTC) 10.4 m Spain Roque de los Muchachos Observatory, Canary Islands 2005• Keck 1 9.8 m USA Mauna Kea Observatory, Hawaii 1993• Keck 2 9.8 m USA Mauna Kea Observatory, Hawaii 1996• (HET) 9.2 m USA, Germany McDonald Observatory, Texas 1997• (LBT) 2x8.4 m USA, Italy, Germany Mount Graham Arizona 2004• Subaru (NLT) 8.3 m Japan Mauna Kea Observatory, Hawaii 1999• VLT 1 (Antu) 8.2 m ESO Countries (European + Chile) Paranal Observatory, Chile 1998• VLT 2 (Kueyen) 8.2 m ESO Countries (European + Chile) Paranal Observatory, Chile 1999• VLT 3 (Melipal) 8.2 m ESO Countries (European + Chile) Paranal Observatory, Chile 2000• VLT 4 (Yepun) 8.2 m ESO Countries (European + Chile) Paranal Observatory, Chile 2001• Gemini North 8.1 m USA, UK, Canada, Chile, Australia, Mauna Kea Observatory, Hawaii 1999• Gemini South 8.1 m USA, UK, Canada, Chile, Australia, Cerro Tololo Observatory, Chile 2001• (MMT) 6.5 m USA Fred Lawrence Whipple Observatory, Arizona 1999• Magellan 1 6.5 m USA Las Campanas Observatory, Chile 2000• Magellan 2 6.5 m USA Las Campanas Observatory, Chile 2002• BTA-6 6 m Russia Zelenchukskaya, Caucasus 1976• Large Zenith Telescope (LZT) 6 m Canada, France Maple Ridge, British Columbia 2003• Hale Telescope 5 m USA Palomar Observatory, California 1948

PIC: SALT outside nowSALT Telescope

WIYN Telescope

Total E/t= Luminosity, L

!

dE = L(t)dt

dE = L" (t)d" dt

dE = L#(t)d# dt

Ln = specific luminosity

Flux

Flux is energy incident on some area dA of the Earthssurface. Flux is not conserved and falls of as R-2.

!

dE = f" dAd" dt

dE = f" (4#R2)d" dt = L" d" dt

$ f" =L"

(4#R2)

Flux

• Flux is measured in Janskys in the radio• 1Jy=10-26 W m-2 Hz-1

• In the visible flux is measured in apparentmagnitudes

!

m1 "m2 = "2.5log10f1

f2

#

$ %

&

' (

m = "2.5log10f1

f0

#

$ %

&

' (

Flux: absolute magnitude

• Absolute magnitude is the apparent magnitude thatwould be observed at 10 pc.

• A is the total extinction due to intersetllar dust inmagnitudes

!

m" #M" = 5log10 d # 5 + A(")

Qf1

f2=

d2

d1

$

% &

'

( )

2

For small changes in flux

!

"m = 2.5(log10( f + "f ) /(ln10) =1.086"f

Q f1 / f2 =1#"f and "f <<1

Standard choices for reference flux

• Vega system: apparent Magnitude ofVega = 0 in all bands.

• Convenient, but non-physical• A-B magnitude system:• F0=3.63e10-23 W m-2 Hz-1, flat spectrum• Agrees with Vega at 548nm (center of

V-band)

Interesting magnitudes (V-band)

• Sun: m=-26.7• Full moon: m=-12.6• Sirius: m=-1.5• Naked eye limit: m=6• Brightest stars in Andromeda: m=19• Present day limit: m~29• Night sky: m=21.5 (best sites, dark time)• Night sky: m=18 (bright time)

Intensity

• Finite size source (subtends a real angle)• Specific intensity• Brightness, surface brightness• Specific brightness• Units: (Jy sr-1) or (W m-2 Hz-1sr -1) or (erg cm-2

Hz -1) or (m arcsec-2)• What happens when the source is not

resolved?

Intensity

• Omega measured in RA and Dec• v= frequency• t= Integration time• P=polarization• Location where you are receiving the light.

!

dE = I" (#,",t, p)d#d" dt dA

Where I will depend on:

Observation

• E=energy received during measurement• R=energy from the sky• F= filter function!

E = " I# ($,#,t, p) r($)F(#)d$d# dt dA

E = A%t " I# ($,#,t, p) r($)F(#)d$d#

3100Å is the UVatmospheric cutoff

1.1µ siliconbandgap