Binocular tour

1. Praesepe, M44 10x 50

Just above Asellus Australis (Delta (δ) Cancri) is what in pre-telescopic times was called ‘Nephelion’ (the Little Cloud), which describes a naked-eye view. Praesepe is a close and populous cluster, making it ideal for binoculars, which reveal that it appears brighter in the middle. This results from conservation of momentum in interactions between heavy and light stars; the latter must move faster, and hence further from its centre.  SEEN IT

2. M67 10x 50

Just under 2° west of Acubens (Alpha (α) Cancri), your binoculars unveil a misty patch that brightens towards the centre. M67 is about the same apparent size as the Moon and hosts about a hundred stars of a similar type and age as our Sun. As it is fairly nearby (2,700 lightyears), M67 is one of the most studied open clusters because of the number of proxies for the Sun it contains.  SEEN IT

3. Regulus 10x 50

Most multiple stars with components of very different magnitudes are difficult to split, so it’s pleasant to find an easy one! Regulus (Alpha (α) Leonis) itself shines at mag. +1.4, nearly five hundred times brighter than its companion. Fortunately, they are separated by nearly 3 arcminutes, allowing even small ‘compact’ binoculars to show the companion star. This is a true multiple star, not a chance line-ofsight pairing.  SEEN IT

4. Vesta 10x 50

Asteroid 4 Vesta starts March at mag. +6.1, less that two degrees east of Chort (Theta (θ) Leonis). It brightens slightly as it moves towards 51 Leonis, before fading by about half a magnitude at the month’s end. It will be brighter than any star near its path, so it should be easy to tell which is the asteroid but, if you are unsure, it moves each night.  SEEN IT

5. Iota Cancri 15x 70

You should be able to identify Iota (ι) Cancri with your naked eye. This is a double star; the mag. +4.0 primary is a yellow giant, and the secondary is a white main sequence dwarf that shines at mag. +6.0. Only 31 arcseconds separate them, so you’ll appreciate the 15x70s when you try to split this true binary star, which has an orbital period of 65,000 years.  SEEN IT

6. NGC 2903 15x 70

You’ll need dark transparent skies for this month’s most challenging target. First, identify Alterf (Lambda (λ) Leonis). A degree south of it are a pair of fainter stars about half a degree apart. Our target galaxy is just south of the fainter, more easterly one. Try using averted vision by directing your gaze back on Alterf, but concentrating your attention on the location of the galaxy.  SEEN IT

✓ Tick the box when you’ve seen each one