Why do the bright stars appear to have four points?

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sheilab8
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Why do the bright stars appear to have four points?

Post by sheilab8 » Mon Aug 09, 2010 10:16 pm

Why do the bright stars appear to have four points in the photographs? Is it an effect of the telescope or camera?

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neufer
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Re: Why do the bright stars appear to have four points?

Post by neufer » Mon Aug 09, 2010 10:32 pm

sheilab8 wrote:Why do the bright stars appear to have four points in the photographs? Is it an effect of the telescope or camera?
It is not uncommon to use four struts to secure the secondary mirror:
Image
Art Neuendorffer

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owlice
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Re: Why do the bright stars appear to have four points?

Post by owlice » Mon Aug 09, 2010 10:43 pm

Sheila, welcome to Asterisk! Yes, they are from the telescope. They are called diffraction spikes, and more information about them can be found in this Wikipedia article.
A closed mouth gathers no foot.

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BMAONE23
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Re: Why do the bright stars appear to have four points?

Post by BMAONE23 » Tue Aug 10, 2010 2:39 am

They can also be utilized to point out some near by binary stars as these could have split diffraction spikes
similar to Pluto/Charon

http://www.google.com/imgres?imgurl=htt ... CCYQ9QEwAw

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neufer
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Re: Why do the bright stars appear to have four points?

Post by neufer » Tue Aug 10, 2010 3:07 am

Art Neuendorffer