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Re: (IAAC) position angle



Mark,
Its the angle subtended by the major axis of the galaxy referenced to North,
moving counter-clockwise towards East, and then South.  The maximum PA can
be no larger than 179.999...  degrees.  Example:  A galaxy whose major axis
is East-West has a PA of 90 degrees.  A galaxy whose major axis points
halfway between North and East has a PA of 45 degrees.  If a galaxy's major
axis points halfway between East and South, then it has a PA of 135 degrees.
Hope this helps,
/Bob
---------------------------------------------------------------
"I feel a lot more like I do now than I did
when I got here." - Chevy Chase
---------------------------------------------------------------
Bob Erdmann - Core Team Member & Webmaster
The NGC/IC Project - http://www.ngcic.org
e-mail: bobe@ngcic.org
----- Original Message -----
From: "deepsky" <deepsky@usmo.com>
To: "IAAC Discussion List" <netastrocatalog-announce@jovian.com>
Sent: Thursday, June 08, 2000 1:07 PM
Subject: (IAAC) position angle
> I observed 2 galaxies last night that were
> oriented north east to south west.  Megastar
> listed both of them with a p.a. of about 35
> degrees.  I assume the p.a. means position
> angle.  Am I right?  How do you determine the
> position angle of a galaxy?  I see this
> terminology frequently when reading the reports
> of experienced observers and would be interested
> to learn more about it.
>
> Mark
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