The nebula NGC3372 is often called "Eta Carinae" although that is really the name of the orange star at its center. The nebula is big (covering about 4 square degrees of the sky and having a true diameter of about 460 light years at 8800 light years distance) and bright (easy naked eye visibility) with plenty of detail in dark conditions. Its at 60° south so you really need to be in the southern hemisphere to see it. Some detail can be seen even in binoculars, and its absolutely magnificent in a wide field telescope (its huge so lowest magnification is essential).
The central star is very massive, bright and unstable. At one point (in 1843) it was the second brightest star in the sky. Currently the star is below magnitude 6 but it was magnitude 4 when first discovered and has been as low as 8 in the past. It is one of the most massive and luminous stars known with a mass of 100 times the sun and brightness 4 million times greater!
The Eta Carinae nebula is really a collection of bright and dark nebulae in the same general area of the sky. A famous component is the Keyhole Nebula which is a dark area embedded in a bright part of the larger bright nebulosity. Most of the nebulosity is emission nebula but there is also a cluster and an associated reflection nebula. The nebulosity immediately surrounding the star itself is the result of an explosion of more than 10 solar masses of material 150 years ago and is expanding at 2 million km/h. The distance to Eta Carinae is 7000 light years. Exact position is RA 10h 43m 48s, declination -59 52' 00"
Its almost impossible not to find this nebula because it is so bright and big, but if you need to get oriented to the right area of the sky just use the Southern Cross (Crux) which you can locate using the pointers (Alpha and Beta Centauri). Just follow a line along the short axis of the cross and off at about a 45° angle as shown above. You will notice plenty of nebulae and clusters in this area - along with Sagittarius its the richest area in the sky.
This photo shows the area around the Eta Carinae nebula. To the left of the nebula is NGC3532, a large bright open cluster. On the extreme right is another open cluster, NGC3114 which is magnitude 4. Above the nebula is the small cluster NGC3293, also magnitude 4. Other small clusters and nebulae can also be seen in this image.
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