Comet thought experiment.

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?

On 12 Jan 2005 18:28:48 +1050, GD wrote:

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.

This could work in some cases, but it probably wouldn't be as efficient as you'd
like. First of all, to get good spectral resolution you would need to use fairly
narrowband filters, which means you would be throwing away a lot of light and
your individual exposures would have to be quite long. Second, it is very easy
to automate a search for movement. It is only when the comet is still very far
out that the movement is small and harder to detect, but when it is far out it
also isn't showing much secondary emission from solar radiation, and the
distinct spectrum you are looking for isn't there.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Much easier would be to take the photos and compare them for things that
move between the images. Stars don't move and comets and other such debris
floating about in the solar system do.

--
Why isn't there an Ozone Hole at the NORTH Pole?

Chris L Peterson wrote in
:

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.

This could work in some cases, but it probably wouldn't be as
efficient as you'd like. First of all, to get good spectral resolution
you would need to use fairly narrowband filters, which means you would
be throwing away a lot of light and your individual exposures would
have to be quite long. Second, it is very easy to automate a search
for movement. It is only when the comet is still very far out that the
movement is small and harder to detect, but when it is far out it also
isn't showing much secondary emission from solar radiation, and the
distinct spectrum you are looking for isn't there.


Thats cool. These things were issues that I'd already though of, but
wasnt sure if anybody has actually *tried it* yet.

So... if anybody reading this needs a reason to go outside tonight, I'd
love it if somebody could take some images of any recently discovered
comet, using perhaps 3 different narrowband filters (one for each image),
and email them to me. I'd then throw a bit of software at them to see
if anything about the comet spectrum stood out as distinctive compared to
the background stars (or not).

cheers...