Technical data

Chapter 5 Starmap 24
The Names option can only be enabled when the corresponding object has been selected. The constellation names and
lines may be enabled independently if desired.
The Default button sets all of the options to their original default values, The Clear button removes all of the
selections. This is useful when making major changes to the options.
When new objects are added, only the new items are redrawn on the existing starmap. If an existing item is removed,
the entire starmap is redrawn.
Projections
The Starmap is normally drawn in a Spherical projection. That is, each point is calculated in X,Y, and Z then
projected (mapped) onto a sphere. This projection produces a display that has minimal distortion at the center of the
display, independent of the actual position of the object on the celestial sphere.
The spherical projection requires a substantial amount of processor time to generate a map, but the final results far
outweigh the small increase in display time. Other simple projections are sometimes seen in other programs. These
are used to increase the apparent rendering time of the map, but they introduce significant amounts of distortion.
Autostar Suite uses only the most accurate display techniques.
A variant of the spherical projection is the Azimuthal Equidistant projection. This projection differs from the
spherical in that the Z coordinates of the point are projected onto a flat plane, rather than onto a sphere. The resulting
projection gives a more satisfactory display of the entire sky, especially near the horizon. However, the objects at the
center of the map are somewhat smaller than objects near the horizontal. Use this projection when trying to find
constellations or to orient yourself with the sky, but use the Spherical projection when zooming into a smaller area of
the sky.
The R.A., Dec. and Dist. values shown in the Coordinate Display are correct in either projection.
Precision
To increase the display speed of the planets, comets and asteroids, the Precision menu allows you to choose the
precision that best suits your requirements. The lowest precision gives the fastest rendering time. If you are interested
in animating the motions of the all of the objects, choose the Low precision mode. If you are animating only the