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" <[email protected]> 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 > > >
