Chris Peterson wrote:waterfeller wrote:Of course. With the amazing star background, it is easy to forget that the camera was pointed in a different direction for each picture so we are seeing a different part of the Mars plane, making the "up and down" motion understandable.
Regardless of exactly where the imager had his camera aimed, all the images have been registered against the star background, so effectively we are seeing in just one direction over the entire period of time. In fact, it's because the view isn't changing that we see that up and down motion so clearly.Out of curiosity, what is the angle between the two planes and when during our year do they intersect?
Mars is inclined 1.85° to the ecliptic. To calculate the intersection dates, you need to look at the orbital elements for both Earth and Mars, specifically the longitude of the ascending node. Of course, the Earth crosses Mars's orbital plane exactly twice a year; by my calculation around May 10 and November 11. Obviously these crossings are almost exactly 6 months apart, given the very nearly circular orbit of the Earth.
I'm not that good at math. According to http://spider.seds.org/spider/Mars/mars2012.html , here are the nodes during the previous, current, and next apparitions of Mars (ascending node is when Mars passes from south to north of Earth's ecliptic plane, descending node is when Mars passes from north to south of Earth's ecliptic plane):
20 August 2009 ascending
7 September 2010 descending
8 July 2011 ascending
25 July 2012 descending
25 May 2013 ascending
11 June 2014 descending