Re: [APML] OIII line color

["Mike Cook, AF9Y" <mwcook@concentric.net>]

Tony's right, we've had the color discussions several
time on APML.  For the new folks, here's a repeat of
my posting showing the proper colors:

The correct color for the two OIII lines, Hb, Ha can be
shown on a chromaticity chart.  Here is the chart with
circles showing the color of those lines:

http://www.af9y.com/chrom.jpg

This example also shows the mix of Ha/Hb required to
produce the sometimes seen pink/violet type color.
Note that it takes a mix of  2.5 parts Ha to 1 part Hb for
this color range.

You can experiment with other emission
line mixes using the following CIE calculator:

http://www.flatnet.org/glossary/ciecalculator.htm


Mike Cook
AF9Y


>From:           	"Tony Hallas" <tonyhallas@foothill.net>

> Chris,
> 
>    This is an ongoing debate about the correct color for OIII... it really should be half
>    green, half blue... something like a green-cyan color I guess. Most color films cannot
>    capture this green color... it shows up better in tricolor attempts... regular color
>    films show this color only as a blue but there is a green component to it. The SBIG
>    filters capture the OIII line with more green than blue... hence the dramatic color.
> Believe it or not, that green is actually toned down a bit from what came up on the
> image... I took some of the yellow out. But I would rather work from this end (reduce the
> green) than not have it... anyway... there are other filter sets that give different
> versions of this line... maybe when I recover from the expense of the camera I'll try
> another set.
> 
>      Tony



Mike Cook, AF9Y
http://www.af9y.com
mwcook@cris.com




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