Is the "Equation Of Time" the Only Difference Between Solar and Star Movement?

In principle, the eccentricity of earth's orbit would affect the apparent rotation of the star field, but the orbit is so small in comparison to stellar distance that this would scarcely be measurable.

The sun is close enough for this to make a difference. The figure-eight "analemma" shows how the day varies depending on where the earth is in its orbit. In particular, it shows the apparent lead/lag of sunrise/sunset at various times of the year. It factors into celestial navigation, but my course in that is so long ago that I have forgotten the details.

Now I gotta look up the Wiki on "analemma"....

Thank you for the very quick reply and the word "analemma" I just couldn't remember it.

Brian

So have most cartographers over the past 30 yrs. One just doesn't see it on new maps anymore.

You are generally right.

http://www.astro.cornell.edu/academics/courses/astro201/sidereal.htm

If the time period is long the movement of the axis of the earth itself(precession of equinox) introduces a parallax shift to the star field. The pole star was not always the pole star.

http://csep10.phys.utk.edu/astr161/lect/time/precession.html

The sunitself moves along in space. This also factors in if the period is long.

http://hypertextbook.com/facts/2002/StacyLeong.shtml

The earth circles the sun so I guess that the speed that it moves across the sky seasonally is different than the speed that the stars move across the sky. Just the writing down and asking the question helps me visualize it! The answers are a bonus. Thanks

And I finally "got" that due to its proximity, the sun goes up and down on the celestial sphere over the seasons but the stars do not.

The Earth's axial tilt varies between 22.1° and 24.5° (but see below), with a 42,000 year period, and at present, the tilt is decreasing. In addition to this steady decrease, there are also much smaller short term (18.6 years) variations, that is also affected by Sun's gravitation in its depleting angle relative to Earth's, known as nutation....from wiki

What this means is that the celestial north and south poles have never been exactly pinpointed nor an astronomical time constant established without daily re-calculation. Navigators using sextants always tried to factor in where the sun should be at a precise time on the following day. Any discrepancy needed to be averaged to maintain course.

Hello

1. Equation of time has nothing to do with precession (change in the direction of tilt of earth axis, as well as change in earths tilt angle. If I am correct, it is the equation to count the effect of varying rotational speed of earth around Sun. The earth rotates around Sun in elliptical orbit. It rotates fast when it is closest to Sun around 3rd July and slowest when it is far away from Sun around 3rd January. I will elaborate this in couple of days. ext two days, I may be too busy to put these details in simple language.

2. The precession period is not 42000 years. It is 26000 years. This means that the direction of pole of the earth is now towards pole star. This direction goes on changing. It changes slowly. In few more thousand years, our ancestors will see some different star as pole star (such as Vega). But after 26000 years, again human beings (if they maintain this earth and are alive) will see same pole star what we See now.