Give it a go
Now let’s try a real example. Imagine now is July. High up at this time of year is the constellation of Draco, the Dragon. The stars you’ll need are marked on it in the image below. It’s a constellation meandering between the two bears, Ursa Major and Ursa Minor, and it has a distinct pattern of four stars marking its head, known as the
Lozenge. We’re going to estimate the magnitude of one of those stars, Grumium (Xi (ξ) Draconis). The comparison stars we’re going to use are Etamin (Gamma (γ) Draconis) and Kuma (Nu (ν) Draconis), at magnitudes +2.2 and +5.0 respectively.
The constellation of Draco is high this time of year. Use the stars Gamma (γ) and Nu (ν) Draconis to estimate the magnitude of Xi (ξ)
Observe carefully and try and work out where the brightness of Grumium lies between our two comparison stars. You should see that it’s roughly two-thirds of the way from Etamin towards Kuma, which will then give you a rough estimate for this star’s magnitude of about +4.0.
With your newfound skill you’ll be able to work out the brightness of a host of different objects, including variable stars. You’ll also be able to use binoculars or a telescope to estimate the brightness of really faint objects such as minor planets or comets.
Make sure you record your findings in a log book – you never know what you might find.