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    Default The suns path along the Ecliptic



    A few nights ago, I noticed that the moon was at due south in the sky but it had not reached its zenith. According to this,Current night sky over New York City - AstroViewer, the sun is also running along a line that will see its zenith at South West. It also seems to have risen towards south and sets past west towards the north. Is this due to the tilt of the earths axis and will it change?

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    Default Re: The suns path along the Ecliptic

    Your question is hard to understand, possibly because you may be using the wrong words. "Zenith" is the point in the sky directly overhead, 90 degrees from the horizon in all directions. From NYC, neither the Sun nor the Moon will EVER appear at the zenith, since you are too far north. Furthermore, for any celestial object, its highest altitude above the horizon that day (technically, when it transits your local meridian) is always mid-way through its daily passage. For instance, the Sun ALWAYS transits the local meridian at local apparent noon. And yes, the altitude of the Sun at local apparent noon does vary with the season, being lowest around December 21/22 and highest around June 21/22. I suspect you are either mis-reading AstroViewer, or there is is something badly wrong with it. Wrapping your brain around this spherical geometry and celestial sphere stuff can be hard at first, but it's really satisfying as you realize you are beginning to actually understand it all. Good luck!

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    Default Re: The suns path along the Ecliptic

    By "zenith", do you mean its highest elevation for a specific day? The term is normally only used to indicate the spot in the sky that is directly overhead.

    The Sun's rising an setting will be symmetrical around the north-south line. In summer, it rises in the north-east and sets in the north-west. This time of year, it rises in the east and sets in the west. In winter, it rises in the south-east and sets in the south-west. It will never rise in the south and set in the north-west.

    It is possible that your compass is reading incorrectly. Are you adjusting properly for magentic variation?

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    Default Re: The suns path along the Ecliptic

    Aha! I see what is going on. You are mis-interpreting what the ecliptic repressents.

    The ecliptic is not the daily path of the Sun. It is its path throughout the year relative to the stars. The Sun, the red line repenting the ecliptic and the stars all move together across the sky during the day. The Sun rises roughly due east (right now), follows a curve through its current position as shown on the chart, and then sets due west. The red ecliptic line moves with it.

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    Default Re: The suns path along the Ecliptic

    Yes. My mistake. Instead of zenith, I meant to say highest point which, as it turns out, is "transits the meridian". So in reference to the Moon, would it always transit my local meridian due south? When I say DUE SOUTH I mean dead on south. Not south/east or south/west. Thats my first question. It seems that the moon rose at 1PM and reached the point in the sky that was due south by 4-430. So I figured that it had to go further west to reach its highest point. And then start its downward path.


    As for Astroviewer. I don't understand what the red line is supposed to represent because it changes once the sun is off of the map.

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    Default Re: The suns path along the Ecliptic

    Your local meridian starts at the north celestial pole (roughly where the star Polaris is), crosses through your zenith, and then drops down to the horizon due south of you. The Sun, Moon and planets are, by definition, due south of you when they cross the meridian. The highest point of any object is when it crosses your meridian, due south of you.

    The red line on the astroviewer is the Ecliptic. It is a projection of the Sun's yearly motion onto the sky. Each day, the Sun will be about one degree farther left on that red circle.

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    Default Re: The suns path along the Ecliptic

    Yes. Thanks. I'm starting to get it now. I don't know if I was seeing something and interpreting it wrong when I saw the moon still creeping upwards after it hit the transit. I'm looking at the moon now as it approaches the meridian. Luckily I have a tree in front of me which will help me see its upwards motion towards the transit and then the slow decent as it moves west.

 

 

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