Constellation of the Month - Grus

Michael Nelmes

Grus the crane is formed by a very distinctive curved cross, high in the early evening at this time of year. It's one of the few constellation that, with a little imagination, you can almost pick the shape of - at least, you can imagine the crane's wings and body formed by a prominent cross. I always associate Grus with galaxies. I recall a friend counting six galaxies of the Grus Cluster in one field through his 8-inch Newtonian. Here's my selection, based on Hartung.

NGC7213 (Position 22h 6.2m, -47deg 25min). This galaxy is small but has a fairly bright core, with very faint extensions. It fits with 2nd magnitude Alpha Guis (Alnair) easily in a low power field.

Pi Gruis (22h 19m, -46 12'). This is supposed to be a "double double", but after staring at each star for some minutes (in average seeing) I still couldn't make out any companions. The colour contrast is very noticeable though, one being a deep orange and the other yellow. Magnitudes are both about 6 although the orange one is slightly variable, separation 4 arc minutes. The latter star's companion is mag. 11 at 2.7 arc seconds, the yellow star is mag. 12 at 4.7 arc seconds.

NGC7410 (22h 52.1m, -39 56'). This edge-on spiral galaxy appears as an elongated fuzz with a noticeably off-centre nucleus.

Theta Gruis (23h 4.1m, -43 47'). A binary of magnitudes 4.5 and 7, separation 1.2 arc seconds. Use the Oddie! I couldn't split it.

Dunlop 246 (23h 4.4m, -50 57'). An attractive, easy pair of 6th and 7th mag. yellow stars at 8.6 arc seconds separation.

NGC7552 (23h 13.5m, -42 53'). A barred spiral galaxy of the Grus Cluster. The bar is quite visible but I couldn't make out the arms.

NGC7582, 7590, 7599 (23h 16.2m, -42 34'). A group of edge-on spiral galaxies, one angled to the other two. (There's a similar grouping in Leo). As I mentioned above, there are actually several fainter ones to look for in the field. The three were visible the first time I tried, and recently, even with light cirrus and a 60% Moon about 30 degrees away to contend with, one was visible. A good one for those with light buckets.

There are no excuses for not having a look through Grus now that the weather is warming up. Happy viewing!