PHOTOMETRY (the dirty little secret of photometry)

 

UBVRI  Johnson & Cousins-Kron Filter System

 

 

 

 

 

 

 

 

 

 

 

 

 

Strömgren uvby

 

 

 

 

 

 

 

 

 

Correcting Photometry for Atmospheric Extinction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Extinction         (mag / air mass) at Mauna Kea

 

310                    1.37

320                    0.82

340                    0.51

360                    0.37

380                    0.30

400                    0.25

450                    0.17

500                    0.13

550                    0.12

600                    0.11

650                    0.11

700                    0.10

800                    0.07

900                    0.05

 

 

 

Effect of Atmospheric Extinction & Stellar Spectral Shape on Bandpasses

 

 

 

Change in the shape of the U band transmission as a function of zenith angle

Change in effective central wavelength of the B and V bands with temperature of the Stellar Photosphere

 

 

 

 

 

 

 

 

 

Calculating the Extinction Coefficients

 

 

 

Calculating the Transformation Coefficients

 

 

 

 

 

 

For Spectroscopy, you have to do the same thing, except you need to do it at every wavelength you are measuring!!!

 

 

 

 

 

 

 

Some “Old-Fashioned” Photometers

 

 

 

 

 

 

 

 

 

 

 

Arrangement for a Star/Sky Background Photometer

Two-Star Photometer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A Modern Imaging Instrument – The Infrared Array Camera (IRAC) on the Spitzer Space Telescope

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Image of the Helix Nebula, taken with IRAC (blue) and MIPS (red)

 

How does one convert images taken at “invisible” (or other) wavelengths into RGB? Visit Hubble’s Color Toolbox!: http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/toolbox.php

 

Want to calculate signal/noise ratios for IRAC?  Go to SENS-PET  http://ssc.spitzer.caltech.edu/tools/senspet/