The source of this galactic river lies adjacent to the star Rigel in Orion and its meandering form is concluded by the bright star Achernar. Quite aptly, Achernar is the Arabic word for 'end of river'.
The whole constellation is the sixth largest in the sky with Hydra being the largest. Despite its considerable size, there seems to be a lack of bright stars and it is easy to find in a dark sky with the river being between two bright stars.
Deep sky objects in Eridanus consist mainly of spiral galaxies but there are some examples of stellar death such as NGC 1535 and the reflection nebula, the Witch Head Nebula.
Casting her venomous gaze at the heroic Rigel, it almost seems as if this stellar witch is concealing herself with an invisibility cloak as it is difficult to see the silhouette of the witch against the dark blue nebula. The witch's head is more easily seen in images that are rotated 180 degrees.
The silhouette of the witch head is caused by stellar winds that might emanate from the nearby Orion OB association. In fact a star of Orion, Rigel, is responsible for illuminating the gas and dust. The blue colour is a direct influence of Rigel's intense colour and another contributor is that the dust reflects blue light more efficiently than any other colour.
Probably the most spectacular barred spiral galaxy in the sky, NGC 1300 joins many other southern barred spirals as vying for the place of the greatest barred spiral. It is curious that many of the most exquisite barred spirals are found in the southern sky.
It is a massive galaxy and even at its 75 million light year distance, it is still quite large through amateur scopes. The dimensions of the galaxy even exceed our home galaxy, the central bar is longer than the Milky Way at an incredible length of
150 000 light years!
Dark brown rivers of dust flow through the centre of the two spiral arms. Many star clusters are found at the parts where the arms originate from the bar.
A planetary nebula that is more obscure, larger and fainter than the classic
NGC 1535. An OIII filter greatly increases visibility but astrophotography is the best way to see the green disk. Near the top, the gas is interacting with the interstellar medium and a bright shock front is apparent. This is reminiscent of limb brightening found in other planetaries.
The central star is bright blue and the thinning of the gas allows background galaxies to be visible through it, this is a trait shared with other obscure little known planetary nebulae such as PK164+31.1 in Lynx and Abell 36 in Virgo.
This object is found near the border with Horologium towards the middle of the vast river that is Eridanus. Fortunately there are no bright stars in the vicinity to overwhelm it with unwanted glare but as a downside, the faint stars might be challenging to use as stepping stones to find it. This planetary nebula was discovered in 1971 by Lubos Kohoutek.
