Association of Falkirk Astronomers

By Dr Russell Cockman

Stimulated by the concept of the 'Messier Marathon' where, during a brief period in March, it is possible for favourably placed observers to see all 109 Messier objects in a single night, I have examined whether any other classes of object can be the subject of an observing marathon.

I have found that there are very few classes of celestial object that can fit the bill- one of those are stars of the first magnitude. First magnitude stars are those brighter than magnitude 1.5 and there are 24 such stars in the sky. Seventeen of these are visible from the UK whilst seven, namely, Canopus, Achernar, Rigil Kentaurus, Hadar, Acrux, Becrux and Gacrux are too far south to be visible at all from our shores. Using Redshift3 I have discovered that for a few days around the 8th of January it is theoretically possible to observe all 17 first magnitude stars in the one night from the latitude of Central Scotland (and without optical aid!). I emphasise the word 'theoretically' because two of the stars will demand clear, haze-free horizons to have any chance of seeing them. I have named this observing schedule the 'The First Magnitude Marathon'.

Let's make a start. If it is clear on the 8th January hurry home and put on your winter woollies because the marathon starts as twilight fades. At 5:50pm look to the SSW horizon to spot Fomalhaut, the most southerly first magnitude star visible from the UK, just before it sets. Binoculars will definitely be helpful here, if detection of the star by naked eye is difficult! As the sky darkens Capella will be prominent high in the north east with Castor and Pollux lower down. Betelgeuse and Rigel are rising due east and Aldebaran is above. In the west the 'Summer Triangle' remains visible with Altair low down and Deneb and Vega above. That's ten already!

By 7pm, Procyon has risen and during the next hour Sirius rises in the SE and Regulus in the E. An hour later Adhara (' Canis Majoris, the faintest first magnitude star) starts to climb above the SE horizon. Fourteen and counting, but there's more to come! Around midnight Arcturus becomes prominent in the NE and by 2am Spica makes its appearance in the SE. That's sixteen- one to go! For the last, you will have to wait until the morning twilight begins to lighten the sky. At 6:50am Antares creeps above the SE horizon to make its brief appearance before being overwhelmed by the light of the impending dawn (again binoculars will help here).

So that's it- all seventeen first magnitude stars observed in the one night (weather permitting of course)'and that's The First Magnitude Marathon.