Re: Comet thought experiment.

From: Hilton Evans (hiltonevans_at_dont_spam_me.net)
Date: 01/12/05 

Date: Wed, 12 Jan 2005 12:21:31 GMT

"GD" <alfa@melb.something.au> wrote in message news:Xns95DCC0D3736A9alfamelbsomethingau@203.87.95.150...
> Upfront I'll say that I dont have any of the bits of equipment required
> to try this idea, all my astrophoto stuff is film based. Not a CCD or
> laptop in sight.
>
> On the topic of comet hunting:
> It seems that there is such a thing as a "typical comet spectrum". Doing
> a google search on the topic seems to bear this idea out anyway.
>
> What I had in mind was taking a few CCD images of the same patch of sky,
> each image taken through a different filter (UHC, Swan Band etc...).
> Then a bit of software would look though the images and display a view
> based on how similar the intensities of each pixel in those images
> represented the intensities expected by a comet.
>
> You'd calibrate and set it up using filtered images of known comets of
> course.
>
> If this idea worked for *most* comets, and imaging only took a minute
> or so, and the computer analysis was quick, then I imagine a heap of sky
> could be scanned quite quickly for new comets since you arent looking for
> movement, just the right spectrum.
>
> Thoughts?

    It's a lot easier and much more efficient to
    image the same part of the sky and look for
    day to day movements of fuzzy objects.

    To acquire a spectrum, you must spread the light
    over an extended area. This reduces the
    sensitivity greatly. For an extended object,
    like a comet you would need a slit which
    reduces the sensitivity even more.

    Finally your software would have to sift
    through the haystack of stellar spectra
    to find that needle of a comet spectrum. 

-- 
Hilton Evans
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