Crossing The Border – No Wall Needed

   Tuesday November 1st the innermost planet, Mercury, crosses the ‘border’ (the ecliptic) moving south toward its greatest southern declination next month on December 1st. All planets with an orbital tilt, or inclination, relative to the Earth’s orbit (the plane of the ecliptic) will cross the border at two points along their respective orbital path.
    These intersections between the ecliptic and a planets orbital path are called nodes, and Mercury is an example of a planet at its descending node. The opposite of this is the ascending node. With either node the planet has a range of ‘travel’ relative to the ecliptic that takes it to a north or south maximum separation from the ecliptic measured in degrees.
   Venus, for example, reaches its greatest southern declination on the 22nd. This is significant, if you are into this sort of thing, because with a southerly declination and its current orbital path Venus will pass by M-8, the Lagoon Nebula on the 8th as illustrated with this graphic showing a view with 10×50 binoculars.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

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