On Sun, Nov 09, 2014 at 09:12:25AM +1100, Greg Chalik wrote:
> Bruce, thank you for the explanation.
> What other filters are there aside from the RGB?

There are 80 filters applicable between two different sensors.

> So what would the image look like to the naked eye?

That's hard to say without using filters that gather data suitable for
approximating the eye's spectral response.  Since most of these sorts
of astronomical phenomena tend to have low luminance, probably "black"
or at best "a faint grey smear that you can barely see if you look
slightly away from it".  The article suggests that with a telescope
that gathers a lot more light than naked eyes can, it would look
pinkish.

> And, why is studying these clouds in a given filter so important?

Our eyes suck at frequency discrimination, as do the raw, unfiltered
sensors.

Filters allow specific wavelengths to be studied and compared, giving
much more detailed information about the processes that produced the
light.  E.g. relatively cool thermal radiation (at "only" a few
thousand K) tends to have a broad, smooth spectrum of a known form.
At higher temperatures we tend to see only the visual/UV part of the
spectrum, often dominated by ionization and recombination lines at
specific wavelengths, and so on.

- Tim