# 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

Astronomy Physics