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Author Topic: Stellar Haloes  (Read 3157 times)

Offline ghh

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Stellar Haloes
« on: 10/10/2006 20:54:09 »
Browsing through the image libraries, I have noticed the large number of images which display “haloes” around stars.
One has been accustomed to the lack of clarity in highly magnified images, but there is a curious consistency in this phenomenon, however there is no commonality in the optics of the telescopes, nor in whether they are ground or space based,  or in the processing, whether photographic or CCD, and surely all these options cannot be due to gas clouds – so are we looking at a real effect?
The strange thing is that these images are biased to the blue, rather than red as predicted by space curvature. [nofollow] [nofollow] [nofollow] [nofollow]
The most telling of these is the image from the AAT of Supernova 1987A [nofollow]
In this photograph the image of the supernova has been superimposed by a negative (black) image of the stars before the explosion. The curious thing is that the haloes now reflect the brightness of the supernova, rather than an aberration of the stellar image.
What is the astronomer’s explanation of this phenomenon?



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Re: Stellar Haloes
« Reply #1 on: 10/10/2006 22:53:22 »
Not an astronomer - but I would first suspect atmospheric effects upon the image – unless you have any images from a space based telescope that has a similar effect.


Offline Soul Surfer

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Re: Stellar Haloes
« Reply #2 on: 11/10/2006 00:05:18 »
The haloes round the brighter stars in the images are functions of the telescope design and the wave nature of light.

The image produced by an ideal point source in an ideal telecope consists of a bright peak surrounded by a set of diffraction rings that are slightly different sizes for different wavelengths of light.  Any disturbance in the atmosphere tends also to make these rings move so in photographs you see them as blurred haloes but wuth a good telescope and good seeing conditions you can see them with your eyes.  the pointy bits on the images are also diffraction effects caised by the supports of secondary mirrors in reflecting telescopes.  The obscuration effectivlely causes the resolution of the elescope to be degraded sin that direction.  refracting telecopes do not have support structure in them and tend not to suffer from this problem.

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Offline Zeig

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Re: Stellar Haloes
« Reply #3 on: 13/10/2006 03:35:08 »
not an astronomer eighther but isn't that from the disturbence of the light from gasses,dust,polution,ect when going through our atmosphere (makes stars look like they twinkle) and just dust and gasses in space that do that?

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Re: Stellar Haloes
« Reply #3 on: 13/10/2006 03:35:08 »


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