An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.
The NGC 2451 Open Cluster probably discovered by Giovanni Battista Hodierna before 1654 andJohn Herschel in 1835. In 1994, it was postulated that this was actually two open clusters that lie along the same line of sight. To the Naked Eye, a cluster usually is seen as one star due to the distance from earth. However, mindful observation allows you to see many stars combined together as in a powder puff.
The open star cluster NGC 2451 in Puppis (click) will be well placed for observation during January and beyond. It will reach its highest point in the sky at around midnight Sri Lanka time. Refer below Map and the red circled area. Click on image to enlarge.
At a declination of -37°58', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 32°N.
From Sri Lanka, it will be visible between 19:54 and 04:30. It will become accessible at around 19:54, when it rises 15° above the south-eastern horizon, and then reach its highest point in the sky at 00:14, 45° above the southern horizon. It will become inaccessible at around 04:30 when it sinks to 15° above your south-western horizon.
At magnitude 2.8, NGC2451 is visible to the naked eye, but best viewed through a pair of binoculars.