The constellation is faint, covering a large area of 980 square degrees. An easy way to locate Aquarius for the first time with the naked eye is to find the large square of Pegasus, then moving south locate theta Pegasus in the head of the horse, directly east you will see the “Y” shape of the water jug described below.
As early as the Babylonian times Aquarius was seen as a man pouring water from an urn. In Greek mythology Aquarius was a shepherd boy, Ganymede, who was the wine waiter to the gods from Mt Olympus.
The most distinguishing region of the constellation to the naked eye is made up of Alpha (α) the magnitude 2.9 super-giant and the stars of the urn which form a “Y” shape. Gamma (γ) a blue-white mag 3.9 star, Zeta (ζ) a binary of 4.4 and 4.6 magnitude white stars with just over 2 arc seconds of separation which orbit each other every 760 years, Eta (η) mag 4.0 and Pi (π) mag.4.6 complete the asterism. (I was able to split Zeta on a night of moderate seeing with 406 x magnification with my 5 inch refractor – with better seeing they can be split with lower magnification.)
The western end of the constellation holds most of the gems of Aquarius.
M 2 (NGC 7089) is a 6.5 globular cluster visible with binoculars as a small hazy ball. I located it using alpha Aquarii as a marker, then looking southwest I located a line of 5 stars between 6 and 8 magnitude pointing to M 2 which made it easy to locate. It is located 5°46’ north east of beta Aquarii. With my 5” (128mm) refractor at 130 x I was able to resolve the outer stars, and at higher magnification a larger sprinkling of stars was evident, the center was condensed with irregular wisps of stars extending from it giving the cluster an uneven spherical shape
NGC 7293 (Caldwell 63) “The Helix Nebula” is the largest (12’ x 10’) and nearest (522 ly) planetary nebula to us, taking up ½ the angular diameter of the moon with a magnitude of 6 – 7. The Helix is unkike most other planetary nebulae, it is quite large and more nebulous. Because the light of the Helix is spread over a large area it has a low surface area brightness. Therefore observations are best made with binoculars or low power and large field of view with a telescope to condense the nebula’s light, and increase the contrast between it and the background sky. I first located it as a faint fuzzy patch of light with 7 x 50 binoculars using delta (δ) Aquarii as a starting point. It sits just west of magnitude 5 Upsilon (υ) Aquarii. With my 5” refractor at 40 x it had a very transparent appearance, like a misty elongated cloud with faint background stars visible behind it. With closer observation using averted vision, it appeared grayish in colour with slightly more condensation around the edges and more transparency in the central region. The central star of magnitude 13.4 should be visible in dark skies with a 4” telescope or larger. If you have never observed the “Helix” it is definitely time to track it down!
NGC 7009 (Caldwell 55) “The Saturn Nebula” at magnitude 8 it appears as a blue green ellipse. It is brighter, but much smaller (44”x23”) in comparison to the Helix and lies further away at 1,400 ly. The central star is magnitude 11.5. The nebula falls on a line between Epsilon Aqr. and (approximately 10° southwest of) delta Capricorni, just 1 ¼ ° west of Nu (n) Aquarii.
With binoculars I could not distinguish the nebula from the surrounding stars. At low power of 40x and then at 61x with the 5”there was a hint of bulging of the star to suggest it was the nebula. The ring like extensions (the ansae) that give the planetary it’s name “The Saturn Nebula” were first described in 1850 by Lord Wm Parsons Rosse based on observations with his 72” reflector. At least a 10 inch telescope is required to allow the ansae to be glimpsed. Larger telescopes bring out the brilliant green colour.
M 72 (NGC 6891) an irregularly round 9thmagnitude globular cluster approximately 4° northeast of Epsilon Aqr. 3° WSW of the Saturn Nebula. It is classified as an open globular. This faint Messier globular is much smaller than M2, about 1’5 across and can be resolved with a 20 cm scope. It will appear as a nebulous spot in a 10 cm scope. It is best suited for a large telescope with high magnification.
M 73 (NGC 6994) is a small Y-shaped asterism of 4 magnitude 10 stars aligned in an east- west direction. The small group are approximately 1.5° north-east of M72. It is surprising that Messier included this in his list of objects as it doesn’t appear nebulous at all. Messier’s description of M73 ‘Amas de trios ou quatre petits etoiles, qui ressemble a une nebuleuse au premier coup-d’ oeil…’ (Cluster of three or four small stars, which resembles a nebula at first glance…’)Maybe we are just fortunate that our telescopes are much better than one Messier was using at the time.
References: Collins Stars & Planets 2nd Ed., Ridpath & Tirion; Deep Sky Companions: The Messier Objects, O’Meara; Deep-Sky Companions: The Caldwell Objects, O’Meara; Hartung’s Astronomical Objects, 2nd Ed, Malin & Frew; Star Atlas Pro V6.2: Photos from Digital Sky Survey www.ngcic.org/dss, Burnham’s Celestial Handbook 1966.