----- Original Message -----
From: "Michelle Stone" <tac4mstone@No-Spam>
To: "The Astronomy Connection" <sf-bay-tac@No-Spam>
Sent: Friday, January 30, 2004 4:20 PM
Subject: [TAC] True Color (was: Most Beautiful AstroPhoto!)
> I've often wondered about this "true color" thang.
>
> If you could fly up to within a 10 light years or so to say M17, would you
> see the red colors? I imagine not.
>
> So true color only appears when you use a long exposure device. I see
that
> rendering true color is important for scientific reasons... but for me, I
> really enjoy the artistic panache that imagers use to draw out the detail
> and pull us away from this planet.
I think that "true color" is what people came to become accustomed to seeing
based on color film photography, or at least that is as good of an
explanation as any. Some folks "calibrate" their color balance based on
particular stars that are in the image whose spectrum is well known. The
cool thing about emission line or non-optical imaging using false color is
that you can do whatever you like when it comes to combining for color: what
color should XRAY radiation be? What about Deep IR or 1420.4MHz Neutral
Hydrogen? When I split the red spectrum into three emission lines of [SII],
[NII] and Ha, what color should be red? They are all red in nature.
(http://www.rdcrisp.darkhorizons.org/m1_crab_nebula_S2_N2_ha_page.htm)
Usually I have seen the longest wavelength be assigned to red, the next
longest gets green and the shortest goes to blue. So you could have an
interesting multiband image of 1420.4MHz Hydrogen, Near IR and XRAY being
assigned to RGB respectively. Is that "true" color?
One of the most awesome images I have ever seen is that MultiBand image of
the Crab
( http://chandra.harvard.edu/photo/2002/0052/0052_xray_opt_radio.jpg ) that
I appropriated into my recent morphing animation
(http://www.rdcrisp.darkhorizons.org/crab_morph_page.htm). It used XRAY,
Optical and Radio. The optical was just a "luminance" shot of many
wavelengths. My image that was integrated into the morph was [SII], Ha and
[OIII], which is Red Red and Teal (Blue-Green), respectively in nature.
Bottom line it is all about visualization and what is pleasing to the eye
best I can tell. And what looks good to me doesn't look so good to someone
else. I have no problem whatsoever with green hydrogen nebulosity; a la
Hubble "Pillars of Creation", so I use it extensively in my emission line
images. To others, it looks as offensive as cat hair on a dog.
Geez, I wish we could have some clear nights with good seeing soon!
rdc
