> On 8 Nov 2014, at 23:16, Tim <xxxxxx@little-possums.net> wrote:
>
>> 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.

Many thanks Tim. That's a really helpful (and clear!) explanation.
tc