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Continuing south from Leo you will see a long meandering string of not particularly bright stars called Hydra. Leon's brightest star Alphard is only magnitude 2. Magnitude is a system developed in ancient times to describe the brightness of stars. Stars were classified from 1 as the brightest to 5 for stars that are just visible to the naked eye. You will need the ideal conditions of a moonless night and no interfering artificial lighting to be able to see magnitude 5 stars. Thanks to modern instruments the brightness of stars much dimmer than magnitude 5 can be measured. With binoculars you can easily see stars of only magnitude 6, 7 or even 8. On the other end of the brightness scale, the brightness of objects such as Venus, the Moon and the Sun have been accurately measured and produced negative numbers indicating that they are very bright.
Alphard is from the Arabic "al-Fard al-Shuda" - the serpent's solitary one.
Corvus