Almach (γ And) is one of the finest colour contrast double stars in the sky. To the naked eye it appears as a single bright star of mag. +2.10 but scopes resolve it into an outstanding double consisting of a bright yellow or slightly orange primary and a fainter deep blue secondary. It's widely regarded as the second best colour contrast double in the sky, surpassed only by Albireo (β Cyg) in Cygnus.

Almach (credit - Mount Lemmon Observatory)

Almach is located in the eastern part of Andromeda. It's the the 3rd brightest star in the constellation and is comparable in magnitude to Polaris and the main stars of Ursa Major. To locate Almach the Great Square of Pegasus is a good starting point and in particular its northeastern star Alpheratz (α And). With an apparent magnitude of +2.07, Alpheratz is marginally brighter than Almach. From Alpheratz imagine a line moving in a northeastern direction towards Perseus. The line first passes through delta And (δ And - mag. +3.3) followed by Mirach (β And - mag. +2.1) and then onto Almach.

Any small scope will split Almach. For example, a 80mm (3.1 inch) refractor at 75x will easily transform the star into two colourful Suns separated by 9.4 arc seconds. The colour contrast is stark, the brighter star is a K3 type giant that shines orange yellow while its companion is a hot blue B9 type main-sequence star. Depending on your eyes and seeing conditions you may perceive slightly different colors. It was German physicist and astronomer Johann Tobias Mayer who first identified the star as a double in 1778.

The blue secondary star is actually a triple star and through large amateur scopes on nights of good seeing can be split into components of mag. +5.1 and +6.3. The separation is a measly 0.3 arc seconds and requires apertures of at least 250mm (10-inch) to accomplish. German astronomer Wilhelm Struve in October 1842 discovered it was a double star. In addition, the brighter member of the pair is also a spectroscopic double making this a four star system in total. It's located 358 light-years distant.

Almach is a wonderful double star for all types of telescopes. It's best seen from northern latitudes during the months of October, November and December.

Finder Chart for Almach (credit - freestarcharts)

Finder Chart for Almach - pdf format (credit - freestarcharts)

Almach Data Table

Henry Draper Catalogue (HD)12533
Hipparcos Catalogue (HIP)9640
BayerGamma Andromedae
Flamsteed57
Struve205
NameAlmach
Distance (ly)358
RA (J2000)02h 03m 54s
DEC (J2000)42d 19m 47s
Apparent Mag.2.10
A/BC Mag. 2.3 / 5.0
A/BC Separation (arc secs)9.4
A/BC PA (deg)63
B/C mag. 5.1 / 6.3
B/C Separation (arc secs)0.3
B/C PA (deg)185
Other Name SpellingsAlmaach, Almaack, Almak, Almaak, Alamak
Notable FeatureFour star system. One of the finest colour contrast multiple stars for amateurs.

Sky Highlights - March 2017

Comet
Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury
Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
Evening
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Midnight
Southeast:- Jupiter (mag. -2.3 to -2.5)
Morning
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
Evening
West:- Venus (first half of month), Mars, Uranus
Midnight
North:- Jupiter
East:- Saturn
Morning
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Telescopes:-
Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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