Re: [APML]: Color Film and Filters

[sdilling@ford.com (Stephen Dillinger)]

> So again I ask,  does pointing this filter up into the night sky
> somehow validate all the phony colors?
>
> js
>

The short answer is "yes."

Here's why.  All of the strongly colored objects in the night sky are emission
objects.  The purpose of a wide band filter is to remove areas of the spectrum
where there are artificial sources of light but not remove any of the normal
emission lines, such as O-III, etc.

As for non emission objects, ie stars and reflection nebulae,  they emit so
much of their light outside of the blocked wavelengths that their color is not
affected very much.  Also, as someone pointed out, the wide band filter blocks
most of it's light on the long side of the H-beta line, thus the effect you
notice with oranges will be very pronounced.

A simple visual test would be to look at a *white* card in sunlight and see
what sort of tint you notice.  Strongly colored objects shining by reflected
light are not representative of the night sky.

................. Steve