Observing the Southern Sky
It may seem strange starting off an article on observing the Southern Skies by talking about observing in the Northern Hemisphere but that is exactly what I am going to do. I guess that it will help to provide some background into how this article came about as well.
I had occasion to travel to the USA in April last year to visit a friend in Rye, NY for three weeks and took the opportunity to purchase a second hand Sky Window binocular observing aid. The one that I purchased is the product from Trico Machine (www.tricomachine.com) and is a great little toy for observing the sky with binoculars. It is simple device with a swivel mirror that sits on a tabletop and allows one to have the binoculars fixed in position and held steady whilst observing. It's great for something to do whilst the autoguider is allowing you to do some "hands free" imaging.
During my time in the USA I was in email correspondences with David Wagner, your newsletter editor, and on my return David asked very nicely if I would like to contribute to the newsletter by way of an article. Of course when he suggested that the subject for the article should be about observing the southern sky, how could I refuse? What a chance to gloat about the brilliance of the southern Milky Way which can be so bright on a clear moonless night that you can even cast a shadow from its light.
Now getting back to my USA trip and northern hemisphere observing, given that I had not been to the northern hemisphere since having become interested (obsessed!) in amateur astronomy it was a great opportunity to observe objects that cannot be seen from my location in Australia. I live 250km (160 miles) west of Sydney at latitude 33.15 degrees south and was therefore very keen to observe some objects around the northern celestial pole. To achieve this, my friend and myself drove from Rye, NY to the Catskill Mountains and spent a night in one of the lodges not far from the ski fields. This was around mid April and there was a quarter moon at the time but the observing was still excellent and the lodge site was located in a valley with reasonable dark skies.
I concentrated my observing on objects around the northern celestial pole and started by identifying some of the constellations in that area (Ursa Major, Ursa Minor & Draco in particular). After observing the double stars Mizar and Alcor in Ursa Major, I moved on to what was definitely an observing highlight for me, which was to look at M81 and M82 in the binoculars using my new observing aid. Fantastic it was and I was very impressed with the clarity of the image particularly considering the quarter moon would have reduced the contrast somewhat. I could definitely see the shape and orientation of the two galaxies and had great pleasure in telling my friend we were looking at entire galaxies over 10 million light years away. Of course we then got on to conversations about life, the universe and everything as one does at these times. It wasn't a late night and I gave it away around 12:30 a.m. when frost started to form on my sky atlas.
Now of course I am back in Oz and can once again enjoy the beauty of the southern sky. I note a comment that I heard recently that one of the benefits of the southern sky, apart from having a great list of wonderful objects, is that the effect of light pollution is not as bad due to the fact that there is less heavy polluting industry. This results in less dust particles and reduces the effect of any light pollution that may be present. I admit to not tracking down the source of this observation or confirming its feasibility but I like the argument anyway.
My observing location (and also my home) is in a little village called Wattle Flat (Pop. 250), New South Wales and is approximately 250km (160 miles for those you in the USA) west of Sydney Australia and is at an elevation of 920 meters or roughly 3000 feet. This location is very good for dark skies with the only real source of light pollution being the city of Bathurst, which is 35km to the south. The light from this city intrudes approximately 20 degrees above the southern horizon and is not normally a problem for observing.
Three years ago I purchased a second hand Losmandy GM-8 and Celestron 9.25" SCT that is now housed in an observatory that sits proudly in the back paddock behind the house. The observatory building project is probably another article in itself and those of you wishing to see more details can pick up some information on my web site at: http://www.ryderhome.com.au. Click on the "Star Gazing" icon on the home page and then follow the links to the observatory construction page. The observatory is a real bonus and it is great being able to just stroll out the back and be observing within five minutes.
So what is so special about observing the southern sky? Apart from the fact that I live here of course, there are many wonderful and varied objects to observe and photograph. In stopping to think about a few objects that are easily observed from my location, the following list resulted (to name just a few...):
- Large and small Magellanic clouds
- Eta carina nebula
- Coal sack dark nebula
- Centaurus A
- Omega Centauri
- Tarantula nebula
- Jewel box cluster
- 47 Tucana
The constellation Crux (a.k.a. Southern Cross) of course appears on the Australian National Flag as you can see on the facing page.
The familiar "kite shaped" pattern is very well known to Southern observers and I have to admit that the sight of the Crux on a dark/clear night nestled in amongst the southern Milky Way is very inspiring. The area in the sky around Crux can keep ones observing log very busy for many nights as well. At an average declination of -60 degrees, Crux is almost circumpolar from my location at Wattle Flat. The following photo that I have taken of an area of sky around Crux is a good example of the many different and interesting objects that can be found here. This photo is a combination of two photos taken with my 55mm Canon F1 lens on Fuji Provia 400f transparency film. Exposure time for both photos was 20 minutes.
Apart from the constellation of Crux, how many other deep sky objects can you spot in the photo? You should be able to see at least the following: IC2602 (Southern Pleiades) open cluster, NGC 3372 (Eta Carina nebula), NGC 3532 open cluster, NGC 3766 open cluster, IC 2948: nebula, and the coal sack nebula.The above objects and this general area are absolutely stunning to observe in binoculars particularly with any observing aid that helps with keeping them steady such as the unit that I brought back from the USA with me. The Coalsack nebula is an interesting story as well. This can be seen in the above photo below alpha and beta Crucis toward the corner of the photo. Against the background of the bright Milky Way it is quite distinctive and if you look closely you may notice that there is an extension to the dark area that protrudes out from the nebula just underneath alpha crux. It is easy to imagine that the Coalsack nebula is actually the head of a bird and that the part that protrudes is the bird's beak.
The ancient Australian aborigines named an area of dark nebula in the Milky Way starting from the Coalsack nebula, traversing the Milky Way almost all of the way to Scorpius as the "Emu" because of its likeness to the Australian flightless bird, the Emu. The Coalsack nebula with its protruding beak is the head of the Emu and the body extends along the Milky Way and is comprised of the dark areas of sky against the Milky Way background. It is sort of like looking at a negative image though it is so very obvious once it is pointed out to you. I strongly recommend putting it on your hit list of objects to observe the next time you have the opportunity to travel south.
So I guess whilst were talking about Crux, this is probably a good springboard into talking about the Southern Celestial Pole and how to use Crux to find it. In the southern hemisphere we do not have the benefit of a bright star like Polaris to assist with locating the celestial pole as the nearest bright (sort of) star that we have to the SCP is sigma Octans which at a brightness of 5.4 does not exactly leap out of the sky at you. I can see sigma Octans from my observing location but only by using averted vision.
There is an old boy scout trick to assist with finding due south and it also works for finding the southern celestial pole as well. That is to draw an imaginary line in the sky along the long axis of Crux and to draw another imaginary line starting from midway between alpha and beta Centauri and where these two imaginary lines cross the SCP is located.
I have included this star trail image taken of the area around the SCP. This is a 1.5 hour exposure taken with a Canon F1 28mm lens using Kodak Max 400 negative film. It is possible to see the "fogginess" left by the Magellanic Clouds. At around the 10-11 o'clock position there is a smudge left by the Large Magellanic Cloud and at around the 2 o'clock position there is a smudge left by the Small Magellanic Cloud.
One of the first things that I did after installing my C9.25" SCT in my observatory was to start trying my hand at astrophotography. Being somewhat impatient I tried a short photo of a few minutes of the famous globular cluster, Omega Centauri. The photo below was taken with my Canon F1 (yes, that's correct a 1971 vintage manual SLR and a great camera at that!). I had purchased a T-ring and adapter and tried a prime focus shot that was unguided. In the overall scheme of things I think that the photo came out reasonably well with a bit of processing in Photo Shop to set the levels.
There are probably two objects that inspired my initial interest in amateur astronomy. One is the shown below and the other is the well-known M42, the Great Orion Nebula. I will never forget struggling with my first telescope, a 4.25" Tasco Newtonian reflector sitting on an equatorial mount of dubious quality and using the Collins Stars and Planets Field Guide to star hop my way to Omega Centauri. When it appeared on the telescope eyepiece for the first time I was beheld with a feeling of wonder, awe and amazement that is impossible to describe in words but I know that the readers of this article will understand. It is that feeling that makes you want to get back out there on a clear dark night when the air is crisp and you can enjoy being at one with nature and the night sky. Great stuff is all I can say.
That's probably all I can say for now as well for this article and I would like to extend my warmest regards to my northern hemisphere astronomy colleagues and wish you all the best of clear, dark skies.Published in the October 2006 issue of the NightTimes