Binocular tour

Cancer, Hydra and Monoceros point the way to the best binocular highlights in March

1. Cancer Minor

10x 50

The 16th-century Flemish astronomer Petrus Plancius defined many constellations that still survive, but his Cancer Minor, the Little Crab, lasted only a few decades. This may be because it appears like a longer and fainter version of the constellation Sagitta, and almost nothing like the crab it represents. Still, it is a pretty asterism of coloured 5th magnitude stars that extends nearly 7° from 85 Geminorum to 68 Geminorum.  SEEN IT

2. 14 Canis Minoris 15x 70

Canis Minor may not top lists of interesting constellations, but it does have one treat for binocular astronomers. 5.5° southeast of Procyon (Alpha (α) Canis Minoris) you will see a pair of orange stars. The fainter, westernmost one is 14 Canis Minoris, an easily splittable triple star, with its mag +9.3 and +9.7 comites (companions) lying 101 and 136 arcseconds away to the east and southeast respectively.  SEEN IT

3. The Missing Messier

10x 50

Charles Messier incorrectly catalogued the position of M48, but it was more than 150 years after Caroline Herschel re-discovered it in 1783 that astronomers realised she’d found the object matching Messier’s description. This open cluster lies 3° southeast of Zeta (ζ) Monocerotis, appearing as a condensed patch of stars. With 10x50 binoculars, you can resolve a few brighter stars against the background of fainter stars.  SEEN IT

4. The Hydra’s Head 10x 50

The head of this nemesis of Heracles is defined by six stars between magnitudes +3.1 and +4.4, but curiously only the faintest of the six, Sigma (σ) Hydrae, retains a common name, Minkhir al-Shuja (hydra’s nostril), that relates to the Hydra in Greek mythology. Binoculars of any size enable you to enjoy the wide variation in colours, from the intense white of Eta (η) to the yellow-orange of Zeta (ζ).  SEEN IT

5. VZ Cancri

15x 70

If you’d like to watch a star complete its cycle of variability in a single session, this is the one for you. VZ Cancri varies between mag. +7.2 and +7.9 over a period of 4 hours 17 minutes. You’ll find it midway between 49 and 36 Cancri. VZ is an RR Lyrae variable; it has a steep rise in brightness followed by a gradual dimming. The inset chart shows the magnitudes of some comparison stars.  SEEN IT

6. X Cancri 10x 50

Just over 2° east of Delta (δ) Cancri is a 1° line of three 6th and 7th magnitude stars. The middle one is X Cancri. This red star is a semiregular variable carbon star which has a main period of 180 days and a magnitude range of +5.7 to +6.9. Semiregular variables are giants or supergiants whose main period is overlain by irregular changes in magnitude.  SEEN IT

✓ Tick the box when you’ve seen each one