Basics of Photometry

Using the infrared detector, we can measure the number of photons collected from a given star in our field of view. If we can get the number of photons as a flux coming from the star, we can determine the apparent brightness of the star. The flux from our star can be calculated from Equation 2.²

$$F_{\nu} = \frac{N h\nu}{At \Delta\nu \eta_{\nu}}$$ (2)

However, it is very hard to determine $A$, $\eta_{\nu}$, and $\Delta\nu$ for our telescope, so we need to use a method which does not require us to measure these values.