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star color with binoculars



 
 
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  #1  
Old March 14th 08, 03:04 AM posted to sci.astro.amateur
brucegooglegroups
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Posts: 168
Default star color with binoculars

On occasion I see color in stars when viewing with binoculars. For
example, Arcturus is white with some blue and red. Is this true color
or chromatic abberation?

Bruce
  #2  
Old March 14th 08, 04:01 AM posted to sci.astro.amateur
Chris L Peterson
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Default star color with binoculars

On Thu, 13 Mar 2008 19:04:44 -0700 (PDT), brucegooglegroups
wrote:

On occasion I see color in stars when viewing with binoculars. For
example, Arcturus is white with some blue and red. Is this true color
or chromatic abberation?


What you describe is chromatic aberration. Binoculars will help you see
the actual star color as well, mainly in the core of the image. Stars
nearly always show colors with low saturation. In the absence of
chromatic aberration, they will show as a single color. If you see
multiple colors, it's CA. Some of that will be from the binoculars, but
some may be from atmospheric refraction as well- especially if the star
is low in the sky or the seeing is very poor.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #4  
Old March 14th 08, 02:22 PM posted to sci.astro.amateur
brucegooglegroups
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Default star color with binoculars

On Mar 14, 12:37 am, canopus56 wrote:
brucegooglegroups wrote in news:ccd8d894-
:

On occasion I see color in stars when viewing with binoculars. For
example, Arcturus is white with some blue and red. Is this true color
or chromatic abberation?
Bruce


The short answer is, yes, it's real. For example, compare Arcturus and
Sirius. Everyone can agree that in binoculars or to the naked-eye, they
have a different color. The problem is that there is so much individual
variation in the responsiveness of the human eye, that not everyone sees
the same colors. This caused endless disagreements among prominent
historical astronomers during the 1700s and 1800s before the widespread
distribution of useable spectometers. There's a good discussion of this in
an older book, Colours of the Stars by David Malin and Paul Murdin (1984).

- Canopus56

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Posted via a free Usenet account fromhttp://www.teranews.com


In the same evening I would see "normal colors" ( white or orange-
yellow) and only see the red, blue, colors on a few stars- such as
Arcturus or Izar. I will read the book.
Thanks.
Bruce
  #5  
Old March 15th 08, 11:01 PM posted to sci.astro.amateur
canopus56[_3_]
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Default star color with binoculars

brucegooglegroups wrote in
:

On Mar 14, 12:37 am, canopus56 wrote:
brucegooglegroups wrote in
news:ccd8d894-
:


snip all
In the same evening I would see "normal colors" ( white or orange-
yellow) and only see the red, blue, colors on a few stars- such as
Arcturus or Izar. I will read the book. Thanks. Bruce


Like Chris said, there is also an optical fringe component in binoculars.
But those can be backed out because the color fringe in optics is well
understood. This leaves individual vision response. I did a short
illustration of this at a public star party last fall using Arcturus. I
had a wide age range of attendees at my scope at once (7 to 70 years old)
and asked each to describe the colors that they saw in a color contrast
double. Everybody saw colors, but nobody saw the same color, including me!
- Canopus56

--
Posted via a free Usenet account from http://www.teranews.com

 




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