Fish-Eye and Hammer-Aitoff Projections as a Function of Longitude
The top panel shows a 3D view of the sky as seen from Earth.
In both projections the origin of the map of the sky
corresponds to the position of the Sun in the sky.
Fisheye Map
In this map the distance to the origin corresponds to solar elongations,
defined as the angle between a position in the sky and the position of
the Sun. This map is useful for heliospheric studies since radial structure
(e.g., radial outflow) from the Sun translates to radial structure in the
skymap.
Hammer-Aitoff Map
The Hammer-Aitoff map is an equal area projection of the sky: areas in the sky
with the same area will have the same area in projection on the map.