Burnhams and Uranometria 2000 discrepancy

Newbie question. After a couple of hours of binocular study of Auriga,
I sat down with Burnhams and Uranometria 2000 to identify the things
I'd seen (lots of surprises in Auriga if you haven't looked before -
it was great fun, even though I had to peek through gaps in clouds to
get a view).

While poring over the books, I discovered something puzzling.

There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams? Dec is OK, but everything is
moved over by 1 grid in U2000.

They can't BOTH be right! What gives? Or am I reading U2000 wrong?

Thanks
Beats

On 9 Oct 2003 00:30:59 -0700, (justbeats)
wrote:

There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams? Dec is OK, but everything is
moved over by 1 grid in U2000.

Precession slowly changes the coordinate system. The positions in the
tables in Burnham are for 1950. The positions in Uranometria 2000 are
for 2000. You will notice in Uranometria there are extra crossmarks
in the corners of the charts. Those marks anchor the coordinate grid
for 1950 positions. This is explained in the introduction to
Uranometria 2000.

I would imagine it's because the coordinates given in Burnhams are
Epoch 1950.0.

Scotty

On 9 Oct 2003 00:30:59 -0700, (justbeats)
wrote:

Newbie question. After a couple of hours of binocular study of Auriga,
I sat down with Burnhams and Uranometria 2000 to identify the things
I'd seen (lots of surprises in Auriga if you haven't looked before -
it was great fun, even though I had to peek through gaps in clouds to
get a view).

While poring over the books, I discovered something puzzling.

There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams? Dec is OK, but everything is
moved over by 1 grid in U2000.

They can't BOTH be right! What gives? Or am I reading U2000 wrong?

Thanks
Beats

(justbeats) wrote in sci.astro.amateur:


They can't BOTH be right! What gives? Or am I reading U2000 wrong?


Isn't Burnham 1950.0?

--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

justbeats wrote:

Newbie question. After a couple of hours of binocular study of Auriga,
I sat down with Burnhams and Uranometria 2000 to identify the things
I'd seen (lots of surprises in Auriga if you haven't looked before -
it was great fun, even though I had to peek through gaps in clouds to
get a view).

While poring over the books, I discovered something puzzling.

There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams? Dec is OK, but everything is
moved over by 1 grid in U2000.

They can't BOTH be right! What gives? Or am I reading U2000 wrong?

Thanks
Beats


Precession of the Equinoxes
http://scienceworld.wolfram.com/phys...Equinoxes.html

Burnham's Celestial Handbook is based on epoch 1950.0

Uranometria 2000.0 uses equinox 2000.0. Uranometria 2000.0's stellar
data base was augmented to include the 50 nearest stars and the 25
greatest proper motion stars no matter how faint. Those stars'
positions known in 1950.0 coordinated were processed to equinox 2000.0.

"justbeats" wrote in message
m...
Newbie question. After a couple of hours of binocular study of Auriga,
I sat down with Burnhams and Uranometria 2000 to identify the things
I'd seen (lots of surprises in Auriga if you haven't looked before -
it was great fun, even though I had to peek through gaps in clouds to
get a view).

While poring over the books, I discovered something puzzling.

There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams? Dec is OK, but everything is
moved over by 1 grid in U2000.

The positions in Uranometria are for epoch 2000; those of Burnham, 1950.

The epoch of a position is the date (year) for which the r.a. and
declination are calculated.

Because of precession (a steady change in the direction of the earth's
axis), R.A. and declination are constantly changing all over the sky. The
rate of change is about 3/4 degree per century, if I recall correctly.


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

(justbeats) wrote in message
There's an apparent 4 minute RA discrepancy between objects plotted in
U2000 and positions given in Burnhams?

Doh! Thanks folks.

Beats