As part of the zodiac, the “Water-pourer” Aquarius is known since ancient times. It is, however, a very faint constellation, since none of its stars are brighter than 2.8m. Nevertheless, it contains a number of interesting objects for amateur astronomers, including two planetary nebulae. The extended Helix Nebula appears in the binocular as a patch of light, while the Saturn Nebula (NGC 7009) is only an object for telescopes. However, it was the first planetary nebula which was recognized as such – in 1782 by Herschel.
M 2 can be seen in binoculars only as a small patch of light or a faded star of 6.3m, yet its 100,000 stars make it one of the most luminous globular clusters in our galaxy. Its diameter is about 150 light-years, and it is not quite spherical, but appears slightly flattened. M 2 is only about half as large as Omega Centauri, the largest globular cluster in our galaxy. 30,000-50,000 light-years separate us from M 2.
The Helix Nebula (NGC 7293) is only 450 to 700 light-years away, yet this planetary nebula is no small challenge to the observer. Its overall brightness of 7.3m is spread over an area of 12 × 16 arcmin, which corresponds to approximately half the full Moon – the Helix has a correspondingly low surface brightness. In a pair of 10 × 50 binoculars you can find it under a very dark sky as a dim, gray patch of light, while it is a very challenging object in brighter regions. The 13.3m central star is a challenge even for telescopes – the 180,032° F (100,000° C) hot stellar remnant remains invisible in binoculars.