Adjustable illuminated astral map - has light behind transparent baseplate with negative of constellations and datum scale

摘要

The adjustable astral map has a central axis of rotation (A) representing one of the poles. It has annotated constellations (36) in the northern or southern hemisphere, the equatorial zone, and part of the other hemisphere, also peripheral annotated scales (30,32,40) for setting the observation time. Seen in the viewing direction, a light with a switch is mounted behind a transparent baseplate (12). There is a non-translucent mask over most of its surface. It forms a negative of the constellations and of an annotated circular datum scale (30) with daily and monthly calibrations enclosing them, in turn enclosed by an unmasked ring (26) of radius R and width b. A transparent covering sheet bearing against the baseplate turns on the axis and is of dia. equal to or greater than 2x(R + b), and is masked at the constellation area apart from the elliptical cut-out portion representing the horizon of the observation point. At the radius R this has an annotated 24 hour calibration (40). USE/ADVANTAGE - Adjustable low cost astral map is easy to read, even in the dark.