First Light Guide #12: Gamma Andromedae

Gamma Andromedae

A detailed guide to finding / observing the double star

First Light Guide 12 graphicFirst Light Guides #12 is a detailed written and video reference to finding and observing the double star Gamma Andromedae in the constellation of Andromeda. This star's proper name is either Almaak or Almach. This guide is ideal for beginners, but many advanced amateur astronomers may find it useful. It is designed to help you locate this double star with almost any telescope. There is a video to using a magnified finderscope, red dot finder, or setting circles along written tips on observing Gamma Andromedae.

Visitors who are new to this site may wish to get started here, while more advanced observers can search the First Light Guides by constellation, or by right ascension

Find Gamma Andromedae in the sky

Gamma Andromedae is a rather interesting double star within our own Milky Way galaxy. First, the primary is a very yellow star, and the secondary an intense blue. At over 350 light years distance, the light from these stars reaching us today left not long after Christian Huygens proposed that Saturn had rings... in the 1600's! But the star gets even stranger. The dimmer blue secondary is itself a double star, averaging a Sun/Neptune distance. Stranger still, the primary of THAT system is ALSO double! So Gamma Andromedae is really a quadruple star system. 

For almost any type of telescope, learn how to find Gamma Andromedae here:

Observing tips:

Gamma Andromedae, also known by it's ancient Arabic name Almaak, is a lovely double star that is easy to split into a pair in most any telescope. Additionally, while many deep sky objects are devoid of color, Almaak offers up a wonderful contrast in colors: A brighter, yellow primary star, and dimmer, pale blue star. 

Separated by 10 arc seconds, medium-to-high magnification provides not only a better split of the two components, but also deeper color contrast. This is not as true with smaller telescopes because the will often show the color quite well. But in larger telescopes - 150mm or larger - the hues may stand out a bit more with greater magnification. This is because colors of stars can get 'washed out' somewhat due to the large light-gathering of larger telescopes. When the magnification is increased, the color can become more apparent. Try various magnifications, depending on the eyepieces available, and see what works best. 

Fun fact: Slightly de-focusing the star can actually show the colors more clearly, as they are spread out more for the eye to view. Due to the close separation, do not defocus them very much, but try it and see how the colors appear to you. Intentionally not dark adapting can also be useful. 

Useful filter(s): None needed or required.

What should I see?

Below is an approximate view of Almaak (Gamma And) as seen with a 70mm telescope at 150x magnification, and a 0.35 degree telescopic field of view. (The separation at this magnification is easier to see in a telescope than the graphic shows due to the size of the primary star here.) Demonstrates how view would look with the double star on the meridian using a refractor telescope and a star diagonal.  Other telescopes or object sky positions may incur a differing view.  Various magnifications, eyepieces, telescope focal lengths and other variables may alter the view compared to this one.  This is a representation only intended to help the observer get some idea what they may see at the eyepiece.  

Approximate view of Almaak as seen in a small telescope

Details of Gamma Andromedae

Type: Double star

Distance: 350 light years, ± 30

Apparent separation: 10 arc seconds

Apparent magnitude: 2.2, 5.0

Right ascension: 02h 03m 54.0s

Declination: +42 19' 47"

Because telescopes and observers are all different, here are some alternate sketched/drawn views of Almaak:

fowlmouth76, 72mm telescope at 108x

fowlmouth76, 110mm telescope at 110x

The constellation: Andromeda

General information about Andromeda, the Chained Princess, where Messier 31 and Messier 32 are located. This will help you know where to find the constellation in the sky and be able to locate and identify its brightest stars.

Name of constellation: Andromeda

Abbreviation: And

Genetive form: Andromedae

Common names: Andromeda, The Chained Princess

Associated asterisms: One star forms the fourth point in the "Great Square of Pegasus"

Original 48 of Ptolemy: Yes

Area by size: 722.28 square degrees

Relative size: 19 out of 88 (Camelopardalis is next larger, Puppis is next smaller)

First Light Guide objects: Messier 31, Messier 32, 56 Andromedae, Gamma Andromedae

Brightest stars, in order of magnitude 

First lists the Bayer designation, then the "traditional" star name (often Arabic, but not always - see each star's notes for details).

  • α (Alpha) Andromedae (Alpheratz, Sirrah) magnitude 2.06, the 55th brightest star in the sky. It represents Andromeda's head in Western mythology, however, the star's traditional Arabic names – Alpheratz and Sirrah, from the phrase surrat al-faras – that means "navel of the steed". This is a reference to this star partially forming an asterism known as the "Great Square of Pegasus" with three more stars in Pegasusαβ, and γ Peg

  • β (Beta) Andromedae (Mirach) magnitude 2.06, is the 56th brightest star in the sky. Its name comes from the Arabic phrase al-Maraqq meaning "the loins" or "the loincloth".

  • γ (Gamma) Andromedae (Almach, Almaak) magnitude 2.15, is 62nd brightest star in the sky. Almach was named for the Arabic phrase ╩┐Anaq al-Ard, which means "the earth-kid", an obtuse reference to an animal that aids a lion in finding prey. Gamma Andromedae is one of the Suburban Astronomers Catalog objects; it's object-locating guide is here.