## star motions

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• Fixed star motions answered Posted by: Arthyr awc99@mindspring.com kaldu4you Date: Fri Sep 1, 2006 11:11 am (PDT) Arthyr sent: In my opinion we use
Message 1 of 2 , Sep 1, 2006
star motions

Posted by: "Arthyr" awc99@... kaldu4you
Date: Fri Sep 1, 2006 11:11 am (PDT)

Arthyr sent:

In my opinion we use precessional motion of one degreee every 72 years. . .
just looking for confirmation. . .
===============================================
Precession is 0 deg 0 min 50.23 secs a year

Rule of thumb, 5 minutes of a degree every 6 years

1 full degree every 71.67 years (72 is fine as an average)

As for stars' proper motion, it is extremely slow and each star has its
own - there's no "average"

Last May, I sent an inquiry to Mark Pottenger on behalf of a friend who
was trying to figure out celestial motions - here's what he wrote about
precession:

What is moving in precession is the Earth.

If Earth was perfectly upright in its orbit, the ecliptic and equator would be the same great circle and the ecliptic pole and the equatorial pole would be the same.

Since the Earth is tilted from that perfect upright position (currently about 23.5 degrees, varying over time from 22 to 24), the equatorial pole precesses around the ecliptic pole and the equator moves around the ecliptic.

Stars do not move with respect to the ecliptic except for the very small effect of Proper Motion, which is only significant for the closest stars.

Mark Pottenger
====================
Love, Diana

• Thank you Diana, Are you all right with all that rain? At 10:25 PM 9/1/2006 -0400, you wrote: Fixed star motions answered     Posted by: Arthyr
Message 2 of 2 , Sep 1, 2006
Thank you Diana,

Are you all right with all that rain?

At 10:25 PM 9/1/2006 -0400, you wrote:

Posted by: "Arthyr" awc99@... kaldu4you
Date: Fri Sep 1, 2006 11:11 am (PDT)

Arthyr sent:

In my opinion we use precessional motion of one degreee every 72 years. . .
just looking for confirmation. . .
===============================================
Precession is 0 deg 0 min 50.23 secs a year

Rule of thumb, 5 minutes of a degree every 6 years

1 full degree every 71.67 years (72 is fine as an average)

As for stars' proper motion, it is extremely slow and each star has its
own - there's no "average"

Last May, I sent an inquiry to Mark Pottenger on behalf of a friend who
was trying to figure out celestial motions - here's what he wrote about
precession:

What is moving in precession is the Earth.

If Earth was perfectly upright in its orbit, the ecliptic and equator would be the same great circle and the ecliptic pole and the equatorial pole would be the same.

Since the Earth is tilted from that perfect upright position (currently about 23.5 degrees, varying over time from 22 to 24), the equatorial pole precesses around the ecliptic pole and the equator moves around the ecliptic.

Stars do not move with respect to the ecliptic except for the very small effect of Proper Motion, which is only significant for the closest stars.

Mark Pottenger
====================
Love, Diana

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