Hi All,
Tonight was the first clear night in a week-odd and luckily we had excellent conditions for the open-night to commemorate the 400th anniversary of the discovery of Jupiter's moons at Sydney Observatory.
After it was all over and was almost home (about an hour's drive) I stopped at a park just down the road from where I live and spent about 5 minutes making a quick naked-eye estimate of Eta Car (as you do ...). Using SAO 238343 (Mag 5.08) and SAO 251090 (Mag 4.56) which are very handy orange stars each about a degree from Eta Carinae, I thought it virtually the same as the latter placing it at about 4.5 - 4.6.
More interesting stuff here:
http://www.iop.org/EJ/article/1538-3...0278.text.html
and here:
http://www.universetoday.com/2009/11...ed-eye-enigma/
quite technical but fascinating:
http://articles.adsabs.harvard.edu/c...;filetype=.pdf
and here:
http://www.etacarinae.iag.usp.br/
and some general stuff about the most massive Milky Way stars (inc Eta) is here:
http://www.tim-thompson.com/bright-stars.html
Best,
Les D