Ay122aLecture 1 - Measurements

Spectrum of the AO star Vegabasis for the UBVRIJHK calibration

Photometric Passbands

Photometric Passbands (2)

“Op:cal”&(0.381&micron)&Filters&

Standard&filters&for&use&in&calibra:ons&rela:ve&to&Vega,&but&not&really&intui:ve&for&anything&but&stars&at&z=0&

SDSS&filter&system:&!  “square”&bandpasses&!  &AB&calibra:on&

!  &e.g.,&m(u’)8m(r’)=0&means&constant&flux&density&in&fν&units&

Terrestrial Background

Light Pollution

!Op$cal!Sky!Background&Signal&from&the&sky&background&is&present&in&every&pixel.&&&Because&each&instrument&generally&has&a&different&pixel&scale,&the&sky&brightness&is&usually&tabulated&for&a&site&in&units&of&mag/arcsecond2.&

˝&(mag/& 2)&

Lunar age

(days)U B V R I

0 22.0 22.7 21.8 20.9 19.93 21.5 22.4 21.7 20.8 19.97 19.9 21.6 21.4 20.6 19.710 18.5 20.7 20.7 20.3 19.514 17.0 19.5 20.0 19.9 19.2

NaD&OH&

Hg&

Optical Sky Background

IR Sky Background

OH&can&be&resolved&

Zodiacal&light&

atmosphere&

IR!Sky!Backgrounds&

OH line Background

Line&intensi:es&vary&on&:mescales&of&~208200s&(as&well&as&spa:ally)&&

Sky Background Variation TestsSky Background Variation Tests

17

(P200/Triplespec 220 x 600s exposures over 5 nights in April 2009

Wavelength

time

11 April 2011 MOSFIRE PSR v1.5

Sky Background Variation TestsSky Background Variation Tests

18

(P200/Triplespec 220 x 600s exposures over 5 nights in April 2009

H-band continuum spectral pixel vs. time (e-/sec) OH line pixel vs. time (e-/sec)

11 April 2011 MOSFIRE PSR v1.5

Atmospheric Transparency

Atmospheric Transparency

IR Atmospheric Transparency

IR Atmospheric Transparency & FiltersGround8based&Filters&

IR&broad8band&filters&are&designed&to&match&the&atmospheric&windows&

Galactic 100um Cirrus EmissionGalac:c&100&micron&“Cirrus”&Emission&(IRAS&satellite,&1980s)&

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Source

Galaxy

Atmosphere

Filter

Telescope + Instrument

Poisson Distribution

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