Below you will find instructions on how you can complete your analysis of photometric data. Below we will guide you through the process of converting your instrumental magnitudes into calibrated magnitudes that can be submitted to the AAVSO for long-term storage.
What you will need:
A list of instrumental magnitudes for your variable star
A list of instrumental magnitudes for at least two comparison stars (six preferred)
An internet connection (to lookup catalogue values)
Excel or OpenOffice Calc
Computing Calibrated MagnitudesRead more
Photometry by itself answers a single fundamental question: “How bright is it?” and if you do photometry over time you can answer another fundamental question: “How does brightness change with time?” These answers to these simple questions can be obtained from just visual inspection of a light curve, or through more advanced techniques, but the main reason why we do photometry is to gain additional insight to the behavior of various astronomical objects. In this tutorial we focus on stars, but the same approach we discuss here can be applied to planets, asteroids, comets, or even galaxies.
Measuring the Brightness of Stars
If you have observed the night sky, you have noticed that some stars are brighter than others. The brightest star in the northern hemisphere winter sky is Sirius, the "Dog Star" accompanying Orion on his nightly journey through the sky. In the constellation of Lyra the Harp, Vega shines the brightest in the summer sky. How bright is Sirius compared to its starry companions in the night sky? How does it compare to Vega, its counterpart in the summer sky? How bright are these stars compared to the light reflected from the surface of the Moon? From the surface of Venus?
Wondering what a light curve is? Sadly, it's not a cool weapon from Star Wars (although I imagine Jedi would find them useful for fighting around corners). Light curves are a fundamental tool for variable star astronomy. They are relatively simple and easy to grasp. They are simply a graph of brightness (Y axis) vs. time (X axis). Brightness increases as you go up the graph and time advances as you move to the right.
Here is a light curve of epsilon Aurigae from its last eclipse:Read more