Telescope Reviews: Binocular Icon 38 : The Andromeda Spiral M31.

Of all galaxies, M31 is perhaps the most famous and the most observed one. With an integrated magnitude of 3.5, the Andromeda Galaxy is even visible to the unaided eye on clear nights as an obvious elongated smudge of light. M31 is, besides M33, the remotest object to be observed with the naked eye. Even at a distance of 2.4 million l-y, the Andromeda Galaxy still covers almost 4° of the night sky. M31 forms together with M33 and our very own Milky Way, the main core of the Local Galaxy Group. I once read that our Milky Way and M31 are on a collision course with each other.
In general, binoculars are not the preferred instrument to study galaxies. But what an amazing view has the Andromeda Galaxy to offer in a pair of binoculars! The large central bulge of M31 can be seen with direct vision. The nucleus appears star like. The elongated halo fades slowly away in the background. With averted vision, the halo can be followed for 1 ½° on each side of the central bulge. While nucleus, central bulge and halo are visible as distinct features, they happen to be merged together as one solid body. The NW side of the galaxy is tilted towards us. Here is where multiple dust lanes absorb the soft glowing light of the galaxy in our line of sight. That is why the NW side of the galaxy appears ‘bordered’, while the SE side shows a softer edge. I did have the impression that another dust lane could be seen on the SE side of the galaxy, or just behind the central bulge. If the dust lanes don’t look obvious to you at first, try to gently rock the binoculars. The motion will stimulate your night vision. As if the Andromeda Galaxy isn’t interesting enough to observe, there is more to go after: satellite galaxies! One of M31’s satellites is M32. It can be found just S of the central bulge. It appears like a small star that is put out of focus. The other satellite galaxy, M110, can be found at ½° NW of the central bulge. M110 looks like a faint isolated cloud when seen with averted vision.
The view of the Andromeda Galaxy and its satellites in my 15x70 TS Marine binoculars was impressive! When I finished my field sketch, I sat back and enjoyed the naked eye view from my observing site in the French Alps. I had never seen M31 so clearly. Much to my surprise, I noticed that M31 had company from two other deep-sky objects, visible between Andromeda and Triangulum. The most obvious object was the open cluster NGC 752. The other was the utterly elusive galaxy M33, at a distance of 2.7 million l-y!

Site : Le Castellard Melan, France ( 44° N )
Date : September 28, 2008
Time : around 23.00UT
Binoculars : TS Marine 15x70
FOV: 4.4°
Filter : none
Mount : Trico Machine Sky Window
Seeing : 2/5
Transp. : 4/5
Sky brightness : 21.33 magnitudes per square arc second near zenith (SQM reading).
Nelm: 6.5
Sketch Orientation: N up, W right.
Digital sketch made with Corel Paint Shop Pro X2, based on a raw pencil sketch.

(Note: if the sketch does look too dark on your monitor, try to darken the room.)

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Rony

My Astronomical Sketches

My Binocular Sketches

Callibrate your Monitor with this little strip.

Edited by rodelaet (10/08/08 05:42 AM)