Equipment and resources
The essential kit you need for a productive night of observing variable stars
Red light
An essential bit of kit! White light will destroy your night vision and distort your magnitude estimates. Your eyes must be dark adapted when you’re observing variables.
Binoculars or a small telescope There are a few naked-eye variables, but many hundreds are in the range of binoculars or a small telescope. A selection of low- to medium-power eyepieces is also useful.
Comparison charts
It’s essential that the correct star charts are used for magnitude estimates. You can get charts from the British
Astronomical Association (britastro. org/vss) or the American Association of Variable Star Observers (aavso.org). The charts provided by these organisations have carefully chosen comparison stars listed. Each chart has its own name (called a chart sequence). Magnitudes of the comparison stars on AAVSO charts have no decimal point (which could be confused as a star), while the magnitudes of stars on BAA charts are given by letters to prevent bias.
A notebook
You’ll need to keep a record of your magnitude estimates for each variable star you observe. You should include: the name of the variable star, the date, time
(in Universal Time), the chart sequence of the chart containing your comparison stars, your estimate and the deduced magnitude of your star.
A laminator
Laminating your charts will protect them against dew and save you from printing a new chart every clear night.
Online resources
Check out the BAA at britastro.org/vss and AAVSO at aavso.org. Both organisations allow you to download charts and generate light curves. There’s help with different aspects of variable star observing, and you can upload your observations as you make them.