Constellation of the Month - Andromeda, Triangulum & Perseus

Steve Crouch

The Far North

This month's Constellation of the Month will be a bit different than usual in that it actually encompasses three constellations: Andromeda, Perseus and Triangulum. The reason for doing this is that this time of the year is the optimum time to view all three of these Northern constellations, and the post-Christmas barbecue viewing site offers a good northerly horizon (although a little light polluted). I have therefore provided a selection of objects spread around this area of the sky. Most are fairly easy, but it has to be said that you need good transparency and seeing conditions because you are observing these objects through a very thick layer of atmosphere.

We start in Andromeda. The best known object here is undoubtedly the great spiral galaxy, M31 (RA 00h 32.7m Dec +41deg 16'). It is easily seen with the naked eye but is better in binoculars. Slightly more optical aid will show the companion galaxies M110 (RA 00h 40.4m Dec +41deg 41') and M32 (RA 00h 42.7deg Dec +40deg 52'). M32 is somewhat easier. My C8 with a 55mm Plossl eyepiece shows all three in the same field.

Andromeda is also the home of a good planetary nebula, NGC7662 (RA 23h 25.9m Dec +42deg 33'). My observations show a uniform blue disk about 30" in diameter with no central star visible. Another galaxy is NGC404 (RA 01h 09.4m Dec +35deg 43') visible 6.5' to the NW of Beta And as a fairly bright hazy spot. The only double star in Andromeda that I will mention is the famous Gamma And (RA 02h 03.9m Dec +42deg 20'). The 2.3 magnitude orange-yellow primary has a 4.8 magnitude bluish-white companion at a separation of 9.7" Finally in Andromeda, the 10th magnitude edge-on spiral NGC891 (RA 02h 22.6m Dec +42deg 21m) - Peter Bobroff's 50cm gave a fine view of this object about two years ago.

The next constellation in this northerly selection is the small constellation of Triangulum, and I will only mention the Triangulum galaxy M33 (RA 01h 33.9m Dec +30deg 39'). This object has long had a reputation of being difficult, but it is actually quite easy, even in binoculars. The problem that some people have with it, I think, is that they don't realise that it is a fairly large low surface brightness object and use too much magnification. While observing M33, check out NGC604, a bright star forming region. This object is similar to the Tarantula nebula in the LMC, as a recent Hubble image shows, but is, of course, much more distant.

Finally to Perseus. A good object, which given its size, is probably more effective for small telescopes, is the open cluster M34 (RA 02 42.0m Dec +42deg 47'). Also worthy of a glance is Algol, the prototype eclipsing binary star (RA 03h 08.2m Dec +40deg 57'). Double star fans can try Struve 425 (RA 03h 40.1m Dec +34deg 07') which consists of yellow 7.6 magnitude components 2" apart. The challenge object for the pre-Christmas observing night, the California Nebula NGC1499, is also located in Perseus (RA 04h 00.7m Dec +36' 37'). All I will say about this object is that, under the right conditions and using the right equipment, it is easier than the Horsehead Nebula.