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From: Carlos Roberto Raba<E7>a <rabaca@nova.ov.ufrj.br>
Reply-To: rabaca@nova.ov.ufrj.br
Organization: Observatorio do Valongo - UFRJ
To: Stephan Kulow <coolo@kde.org>
Subject: Re: Moon tool
Date: Fri, 20 Oct 2000 17:10:39 -0200
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Stephan,
 
> In KDE2 I implemented free choice view angle, so I could also slide
> it some degrees off to see it like I see it here :)
 
It is nice to hear that! Unfortunately, I still use KDE 1.1.2.... By the way,
when is the final release o 2.0?
 
> But if you're an expert, I would like your advise on the correct
> terms. Where on the earth you see the moon in the the default view
> you can see on web pages etc.?
 
As you know, the moon keeps always the same face turned to earth (the so called
near side). This is a composition of its period of orbital motion and rotation:
they are approximately the same. The moon's orbit is inclined with respect to
the equator by (only) 5 degrees, and for our purposes, keeps the polar
orientation in the sky unchanged. This means that the angle that you
see the moon in the sky changes by a composition of two factors only: 1)
latitude of the observer, and 2) time of the day that you look at the moon. If
you look at the moon over many hours, the change of orientation in the sky is
moon's orbital plane is close to the equator (as I said before) the discussion
of orientation looses any meaning. At these positions, the passage by the
meridian happens very close to the top of your head. So, I can be facing east
and move my head up to see the moon, or I can be facing west and move my head
up. Which rotation should I addopt? That is why I told you to use 0 or 180
degrees. Otherwise, you would need to incorporate in your code many otherif he
relations, including the latitude of the observer.he will see the first quarter
moon as a C and the last quater moon as a D (see
> The current kmoon uses the pictures of this site:l) when the moon is over
> http://timbeauchamp.tripod.com/moon/, but a (german) colleague ofes over his
> yours pointed out that the images are mirrored horizontally, son is reversed.
> we corrected that (the larger craters appear on the left ontor. Since the
> the moon I see in the sky, while they are right on the web).
 
My colleague is correct. The east-west sides in the pictures are wrong, so you
should flip them sideways. For an observer in the northern hemisthere this is
all you need to do. For an observer in the southern hemisphere, you need to
rotate this new set of images by 180 degrees. Keep in mind that in the sky if
north is up east is to the left, if south is up east is to the right. You can
easily see this if you lay down ;-/ on the floor with you head/legs pointing to
the north/south line. Now, try to point your left arm to the geographic
east while facing up.
 
I hope this helps you. If you like more info, it will be a pleasure to
help. Best wishes,
 
Carlos
