Stars in stereo

[bercov@xxxxxxxxxxx (John Bercovitz)]

There was some discussion recently about whether or not the stars 
can be seen in stereo.  I just now recalled hearing in a class a 
long time ago that Rigil Kent (alpha Cen.) has a parallax sensible 
using earth's orbit as a baseline and that that was how its 
distance was established.  So let's do a quick calculation.  8-)  
Earth's orbit is 1000 seconds across.  Rigil Kent is about 4 light 
years away (if memory serves, and it often doesn't) and at piE7 
seconds per year, it's 1.26E8 seconds away.  Divide that by the 
baseline of 1000 seconds, and you have a parallax of one part in 
1.26E5.  Now the best stereoacuity I know of is 3" of arc.  Three 
seconds of arc /(3600 sec/degree)/(57 deg/rad) = .0000145 the 
inverse of which is one part in 6.9E4.  So it looks like we can't 
quite see the parallax with the "naked eye" using earth orbit as 
the baseline but if we magnified the views 2X (observed from half 
the correct distance from the views), and we did indeed possess a 
stereoacuity of 3" of arc, we'd have it made; we could see Rigil 
Kent standing out from the other stars.  Since 3" of arc is 
unusually good, it might be better to magnify 10X instead.  Of 
course, this means the view is no longer ortho, a very bad thing.  8-)

John (Orthoman) B


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