Re: [APML] OIII line color

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

Jerry,

   Although what you say about monitor space is true, the chart
itself is translated to the best representation within the color
or printer space.  So the color shown on that chart for the OIII
lines is MUCH  more accurate than a typical filter set can produce.
For example, there is no doubt that the lower OIII line is a lime
green.  It is not a blue green.

Mike Cook
AF9Y


Date sent:      	Wed, 17 Jul 2002 02:33:07 -0400
To:             	astro-photo@seds.org
From:           	Jerry Lodriguss <jml@astropix.com>
Subject:        	Re: [APML] OIII line color
Send reply to:  	astro-photo@seds.org

> Hi Mike,
> 
> I think one problem is that the locations of the two OIII lines lie outside 
> of the Maxwell triangle that would define any monitor's color space. So, 
> while these two spots are plotted correctly on the diagram as pure spectral 
> colors on the spectral locus, they can't be correctly displayed on a 
> monitor, neither on the CIE chromaticity diagram they are plotted on, nor 
> on any RGB emissive display of a deep-sky image.
> 
> So the green they would look like visually can't be displayed correctly on 
> any monitor, no matter what you do. You can't make an accurate color print 
> of them either.
> 
> Sorry. <G>
> 
> Jerry
> 
> 
> 
> At 10:22 PM 7/16/2002 -0400, you wrote:
> >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
> >
> >
> >
> >
> >--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
> >              Unsubscribe at <majordomo@seds.org>
> 
> 
> Astronomical photography: http://www.astropix.com
> 
> 
> 
> --  APML Archives at <http://astro.umsystem.edu/apml/>  ---
>              Unsubscribe at <majordomo@seds.org>
> 



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




--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
             Unsubscribe at <majordomo@seds.org>