Re: [guide-user] Add a trail - analemma
Bill J Gray Jun 28, 2004
Hi Markus,
I'd click on Overlays... Toggle Overlays on/off, then on "Planet trails
from animation." My bet would be that they're on, but only shown at
(say) fields of view between 1 and 60 degrees... that is, not at 90
degrees. Adjust this, and your trail will suddenly appear.
But what will show up is _not_ an analemma. The sun doesn't actually
move in an analemma-like figure eight relative to the stars; it just
moves around the ecliptic, slightly faster in January than it does in
July. To get an analemma, you'd have to get Guide to (say) show the
path of the sun in alt/az coordinates. (This would be a bit confusing.
The sun is now in Gemini; if you showed an analemma-like path starting
at the current time, the sun would drop down into Canis Minor and/or
Monoceros, then down into Canis Major. Basically, you would be
combining a star chart based on celestial coordinates with an object
trail based on alt/az coordinates.)
Weird as this combination would be, it does have some uses aside
from the analemma: for example, charts showing the visibility of
Venus or Mercury or comets at morning or evening twilight. So I may
add something like this... with the warning that the results will
just give a general idea of the path of an object, one that "drifts"
relative to the stars.
-- Bill