# Photometry

• Process of measuring apparent brightness of stars

## 5-step Magnitude Scale

• Based on apparent magnitude ($m$)
• 1 --> 6
• Brightest --> dimmest
• Larger magnitude --> less luminosity
• 5 steps in magnitude equals 100 times in luminosity
• 1 step in magnitude is 2.512 times in luminosity

## Equations

• The following equation allow us to calculate the difference in brightness of stars
• $m_1 - m_2 = 2.5 \log(\frac{b_2}{b_1})$
• $\frac{b_2}{b_1} = (100^{\frac{1}{5}})^{m_1 - m_2}$
• $m_1$ and $m_2$ are magnitudes of stars
• $b_1$ and $b_2$ are the brightness of stars