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Porrima is a binary with an orbit
of 168.7 years. At the moment the stars are near to their closest approach and will be
difficult to separate for the next few years. This gives an excellent oppertunity to
observe real change in the separation and position angle of a double.
Both stars are of almost equal brightness: magn. 2.7 and 2.8 (Hipparcos 1997) or 3.5 and
3.6 (Tycho 2 2000) which makes them difficult to split when they are around or less than
1" separated, but which also makes the pair a brilliant double when their separation
is larger again.
These images gives an indication,
note that different sources give different values:
 
I have observed
Porrima the last few years, and it's becoming a real challenge:
| Scope |
Date
|
Separation
|
Remarks |
| CG11 |
May 2001 |
~1.4" |
Reasonable seeing, just separated
with 280x, easy with 560x |
| CG11 |
April 2002 |
~1.1" |
Moderate seeing, snowman with
140x, indication with 185x, separated with 280x, easy with 400x |
| MK67 |
May 2002 |
~1.1" |
Moderate seeing, elongated with
180x, separated with 360x |
| CG11 |
March 2003 |
~0.9" |
Less-than-moderate seeing,
reasonably well separated with 280x |
Images and
measurements by Steve
Bodin,
using a C8 and video-camera:
The motion of Porrima,
composite image from images of 2001, 2002 and 2003:
Near minimum distance; the 2005 image:
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