Lucky us! This little gem of a constellation is only visible south of the equator! Circinus represents a compass and once you have a look at all the neighbouring constellations it all makes sense I suppose. The great ship Argo is near by although it’s known as it parts these days (eg, carina the hull). When I say compass though I am talking about the drafting and mapping tool, not the magnetic type. The cincinnus was designated in the 18th century Nicolas de Lacaille.
Circinus has no messier objects and only a few deep space objects, but within its borders are a few binary stars worthy of a look. When looking for this just draw a line back from beta cent to the famous double alpha cent and it’s directly behind. There are only 3 bright stars here the brightest being alpha Circinus at 3.2 mag, it is also the nearest star 53.5ly from earth.
Circinus
1. dun166- 3.18/ 8.47 15.7"/ a good start to unfamiliar territory. I pleasant wide double easily obtainable at low magnifications consisting of a bright white star and a dimmer red looking star. A fine start to a long time from binaries.
2. wfc153- 6.10/ 9.90 distance unknown?/ the software I use to find these seems to be out of date. It shows a 1947 dist of 34" and closing at a rate of 2" every 5 years which puts it about as close as the previous binary. Anyhow this one has the same colouration of the previous (being white primary and reddish secondary) but is dimmer.
3. rss369- 7.46/10.24 43.6"/ Took a little finding this one. For some reason my goto started going wrong so I had to use my chart.... a fair distance apart and easy to split the primary is yellow and the dimmer secondary look blue.
4. coo186 7.6/10.61 7"/ Forming the tip of a triangle this double looks great at low mags. The alpha is white and the beta is a nice red. The red is more distinguishable for the previous doubles.
5. cpo16 7.03/7.98 2.4"/ this yellow and white pair sitting on the outskirts of the constellation needs a little more magnification than the previous binaries. It’s a pretty one tho and well worth the stop. I used a mag of about 166x
6. jsp649 8.30/10.30 1.3/ a pretty hard split and due the awkward angle my newt was at hard to determine colours too. I am fairly sure the primary is orange.
7. hj4714 7.89/8.54 22.6"/ session 2 (only 2.5 months later) brightish pair that are easily split. They are about the same brightness but are distinguishable from each other. Conditions didn’t allow for proper colours but they look yellow or orange and possibly blue. Still quite nice to look at....
8. hrg107 8.39/9.06 getting towards the limit of my 8" scop on a near full moon and bad seeing and bad transparency, this couple form the centre dot of a 3 dot line. The stars themselves while being close are still easy to split even in the worse conditions. The colours look to be 2 yellows.
9.hds2145 8.58/10.58 6.2"/ just about at my limit of vision and the telescope with a near full moon the secondary is just about an averted vision object. Still, it’s worth adding to the list and quite a challenge for small scopes in bad conditions. The primary looks to be yellow and I am not sure about the secondary (pos. yellow too).
A terrific write up Ving -- congrats. As soon as I started browsing your article, I pulled out my log to see if I'd seen any of these and surprisingly I've only seen 1! And, I've only got 7 entries for the whole of Circinus!
Gotta do something about that!
Anyway, here is my observation of Dun 166 with 25cm from 1996:
x138 21' TF. Mags 3.4 8.0 Sep 15.6 PA 229. Pretty with a substantial mags difference. A at mag 3.5, B is est mag 7.5 about 20" distant at PA 230. A is off white/creamy. B is deep yellowish/orange.
