Sky projection description Projection
" orthographic" , " Hammer-Aitoff" or " cylindrical equal area"
.
The Projection value is purely descriptive and does not affect the celestial
coordinate system represented by the SkyFrame in any way. If it is set to a
non-blank string, the description provided may be used when forming the default
value for the SkyFrame’ s Title attribute (so that typically it will appear in
graphical output, for instance). The default value is an empty string.