Kleiner Hinweis am Rande, die Sternkarten, die normal in Kataloge etc sind, erlauben durch ihre Projektion keine gerade Rückverlängerung der Bahnen zum Radianten. Das sind dann unterschiedliche Bögen. Geraden entstehen nur auf Sternkarten in gnomonischer Projektion
Hallo "Speul" und Forum,
Herzlichen Dank für diesen klärenden Hinweis! Ich benutzte für meine "Darstellung" den SKY ATLAS 2000.0 und George Lovi (von S+T) schreibt in der Einleitung dies:
"In planning
Sky Atlas 2000.0, particular attention was paid to constructing its charts not only with great accuracy, but also on map projections that produce minimum distortion of constellation figures and asterisms — a situation far from universal with other star atlases. The accompanying diagrams, by Wil Tirion, show the geometrical principles behind the
secant conic (top two) and
secant cylindrical (bottom) projections used in his atlas. They are so named because the projection surface cuts through the sphere. The cartographic term for the circle of intersection is "standard parallel"; here they are actually declination circles and are indicated by horizontal dashed lines. Along these circles the distortion is zero, because the hour-circle spacing with respect to the declination circles is the same as in the sky. To the immediate right of each diagram is a one-hour right-ascension segment showing the approximate declination range of each chart group as well as the amount of distortion. The solid vertical lines (which are straight) are the hour circles in the atlas, while the dashed ones wearing in and out represent the same coordinate line on the celestial sphere. The close correspondence of the two is a very good indication of how closely the Tirion atlas matches the sky. And the fact that the dashed lines depart from the solid ones by virtually equal amounts on both sides shows how well the projections split what differences there are."
Mein Scan stammt von Karte Nr. 11 und entspricht laut
Introduction Kommentar somit einer
secant cylindrical projection.
Herzliche Grüße,
Bernd
