Thanks Robert for this answer. Ok, than the world is again as it should be :) . Yes, the ecliptic changes with precession and nutation over 25800 years, right. But WHY does ist pretend to do a daily 25800-cycle? I mean, what needs to be different from the polar projection except the coordinates which would be given in Alt-Az instead of Ra/Dec? Why this tumbling around.
Ok, here my problems: 1. when I want to see if there are other coordinate data in the information board for the moon in Alt-Az and Ra-Dec, and let the software search for the moon in the toolbar, the coordinates are centered +00°00' and 24h00m00,0s (in polar projection). But the moon is on the other end of the sky. How to fix this. 2. on the 21. July 2010 at 00:15.00 the moon completely disappeared below the south-western mountain-horizon. When I simulate this time then the moon in Alt-Az-projection (because in polar alignment I can't see the mathematical horizon) is already displayed below the mathematical horizon. What is wrong here? The difficulty is that I can't imagine to create a proper local horizon with these obstacles - I mean, one evening the moon rises above a mountain and on the following night the moon rises above the same horizon but is displayed much below or above the already created horizon line from the previous night. Thanks very much for help! Luzius --- In [email protected], Robert Vanderbei <r...@...> wrote: > > The ecliptic does not move with respect to the celestial sphere (the > background stars) over short time scales. Hence in equatorial mode it > remains fixed. But the ecliptic and the stars do move from moment to moment > and from day to day (at a given time of day). Hence, in alt-az mode you will > see changes. Not sure if this is the source of confusion. Hope. It helps. > > Sent from my iPhone > > On Jun 28, 2010, at 11:05 AM, "luzius.thuerlemann" <luzius.thuerlem...@...> > wrote: > > > Hi John > > > > Yesterday I realised that the ecliptic moves during a single day. Sounds > > stupid, but I've never realised that before. I thouhgt that it changes only > > during long periods over months and seasons etc. But over a single day?! I > > know the change of the seasons and the motion of the sun over a year etc., > > but I really cannot explain this motion over 24 hours. When I animate the > > daily motion it looks to me as if it was an exaggerated motion of the > > earth's precession. I just don't get it. > > The seasonal changes etc. are no problem, but these not obvious > > short-term-things seem to be. > > > > But this should not affect the creation of a local horizon in CdC. When I > > write down the time when the moon just rises above or sets below the > > horizon, and subtract the moon's radius from the local altitude, then I > > should get the horizon altitude at the moon's azimut at that time and I can > > simulate the horizon altitude there. > > But my problem is that the setting moon was displayed much closer to the > > mathematical horizon compared to the already simulated > > rising-horizon-mountain in the south-east (it was as if the western > > south-mountain is half or a third as high as the south-eastern one) - > > although the two mountain's altitude would not have created such an obvious > > difference...they're pretty much of the same height, and the observing > > position was also the same. > > > > It's really strange. And all because of this strange > > daily-eliptic-precession. I don't get it. > > > > > > Thanks for your help! > > > > Luzius > > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > >
