The Star Book: Stargazing throughout the seasons in the Northern Hemisphere. Peter Grego

Draco

       Dra / Draconis

       Highest at midnight: early July

      Despite sprawling across a huge portion of the northern circumpolar region, Draco is not the most prominent of constellations. Its traditional outline can be traced from its head (marked by Beta Dra and Gamma Dra) just north of Hercules, along a winding path to Alpha Dra (Thuban) at the constellation’s narrowest part, around to Lambda Dra near Draco’s western border. Around the time that the Pyramids were constructed, Thuban (magnitude 3.7) was the brightest star near the north celestial pole; precession will grant it this distinction again in more than 21,000 years’ time.

      Mu Dra is a close telescopic double star with white components of magnitudes 4.9 and 5.6; the pair is slowly moving apart, and they can now be comfortably resolved with a 100mm telescope, and are a good test for a 60mm telescope. Psi Dra is much easier to resolve; binoculars will reveal the yellow stellar duo of magnitudes 4.6 and 5.8. Binoculars can split the two wide components of 39 Dra (magnitudes 5 and 7.4); a telescope will show the magnitude 8 companion of the brighter star.

      The Cat’s Eye Nebula (NGC 6543) is a small but bright planetary nebula with a distinct bluish hue. A 150mm telescope will show it as a small ring surrounding an eleventh-magnitude central star.

       The Cat’s Eye Nebula in Draco, imaged using a 105mm refractor and astronomical CCD camera.

       Cassiopeia

       Cas / Cassiopeiae

       Highest at midnight: early October

      With its prominent five-star W asterism, Cassiopeia is one of the easiest constellations to recognize. Gamma Cas, the central star of the W asterism, is an irregular variable star that fluctuates, at unpredictable intervals, between magnitudes 3 and 1.6. Eta Cas is a nice double star with a magnitude 3.5 yellow primary and a red magnitude 7.5 companion, easily visible through a small telescope.

      Cassiopeia is a joy to scan with binoculars, as a bright section of the Milky Way flows across the constellation, engulfing the W. A treasure trove of bright open clusters lies within its boundaries, most of which lie east of the W. Containing around 30 stars, the bright compact cluster of M103 is best seen at higher magnifications. The Owl Cluster (NGC 457) is a loose assembly of around 100 fairly bright stars arranged in distinct lines; its two brightest stars shine like an owl’s eyes. NGC 663 is a beautiful binocular cluster containing around 80 stars. On the far western side of Cassiopeia, the compact Scorpion Cluster (M52) contains around 100 stars, the brightest of which form a splendid S shape. The Bubble Nebula (NGC 7635), a faint diffuse nebula visible through a 200mm telescope, lies just half a degree southwest of M52, so that the two objects can be viewed in the same low-power field of view.

       A delightful alignment of stars known as Kemble’s Cascade can be found in the circumpolar constellation of Camelopardalis, east of Cassiopeia.

       The Bubble Nebula in Cassiopeia, imaged using an 80mm refractor and astronomical CCD camera (filters used).

       Perseus

       Per / Persei

       Highest at midnight: mid-November

      Crossed in the north by the Milky Way, Perseus is a magnificent constellation containing a number of bright stars and open clusters. Near Alpha Per (Mirfak) lies Melotte 20, a large loose star cluster made up of a snaking chain of bright stars; it is a stunning sight through binoculars and at low magnifications.

      Beta Per (Algol) is a famous eclipsing binary. Every 2.87 days it drops from magnitude 2.1 to 3.4, changes easily monitored with the unaided eye. The Spiral Cluster (M34) can just be discerned with the unaided eye some five degrees west of Algol. It contains a number of star chains, with some of its brighter stars paired up.

      Eta Per is a nicely coloured double star, easily resolvable through a small telescope, with an orange magnitude 3.8 primary and a blue magnitude 8.5 companion.