Technical data

Index 42
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Glossary
absolute magnitude - the apparent magnitude an object would have if it were moved to a distance of 10
parsecs.
angular diameter - the apparent diameter of an object expressed in angular measure i.e., deg, min, sec.
aperture - the diameter of the objective lens or primary mirror of a telescope.
apparent magnitude - the observed brightness of an object without any correction for distance.
astrometry - the branch of astronomy concerned with the precise measurement of positions and motions
of celestial objects.
coma - an optical defect that affects only image details away from the center of the field of view causing
stars to appear flared, like tiny comets pointing inward from the edge of the field.
focal length - the distance from the lens or mirror to the focal point.
focus - the oint in an optical system where all the image components are brought together.