photometry

Photometry

Aperture Photometry

Difference Image Photometry

CCD/CMOS

CCD: charge-coupled device

CMOS: Complementary metal–oxide–semiconductor

estimate background

substract

count photon

mode count

PSF

PSF matching

intensity matching

precise (subpixel) alignment

extended source photometry

SNR

noise

SNR=Snet-√S

Signal-to-Noise Ratio

dark current

read noise and digitization error

Sky

σB^2=B*ns^2/nb^2

Nd=dark current

S=Stotal+σB^2+Nd+ns*Nr

Nr=read noise

Snet = (S+B) – Bestimated – dark + ϵ

Magnitude

M=C-2.5lgN+2.5lgt

F=N/t

Differential photometry

instrumental zero point magnitude

Mt(target)-Mt(standard) = Mi(target) - Mi(standard)

complications

Atmospheric extinction

Instrumental to Standard Magnitudes

x=secz

mins=m--kx