RE: [APML] Color of Objects (was Astronomy Magazine M8)

["Richard Klappal" <klappal@xnet.com>]

This discussion has gone around several times in the past.  Why has no one
considered (that I recall) a spectral scan of the object, followed by
amplification of the intensity until the rods/cones would respond
appropriately.

Alternatively, wouldn't the B-V and related spectral info give a reasonable
approximation?

A photo of a green pastoral scene is still green, regardless of how dark the
room is! All that is needed is to boost the effective intensity.

Rich


-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of Glenn Ray
Sent: Wednesday, December 05, 2001 3:36 PM
To: 'astro-photo@seds.org'
Subject: [APML] Color of Objects (was Astronomy Magazine M8)


It certainly makes for great philosophy, this discussion of "What color is
it? or "What does it really look like?".  One might as well ask: "What color
is an emerald in a very dark room?"  While we're at it, how about, "If a
tree falls in the forest, does it make a sound?" <g>

But seriously, it's quite true that if one is limited to naked eye viewing,
"bright" objects like M8 and M42 (heck, even the Milky Way) are just shades
of grey.  The low quantum efficiency of our light receptor cells, combined
with the low ratio of cones (color) to rods (light) -- about 1:20 -- means
that we can't detect color in low light.

Color only happens once the light is amplified (i.e., with a telescope) and
the greater the amplification (through aperture, not magnification), the
more color is perceived.  I'll never forget the first time I saw M42 through
a 24" dob...I didn't know that much color was visually perceivable.  I can
only imagine that it's amazing at larger apertures...

The fascinating fact is that, no matter how much closer we could get to
these bright objects, they would still appear (to our naked eyes) as patches
of grey.  While the inverse square law would apply, an object's apparent
size would also increase proportionally such that the apparent brightness
would remain the same.  We already know of examples like this in our sky
(ex., compare Ring vs Helix nebulae).

All we're doing (with film, CCD, image processing) is reveal what our eyes
cannot see alone.  Hopefully, we'll get a result that would be similar to
looking at the object with an immensely large telescope.  My feeling always
has been that an accurate rendition along those lines is always very
artistic.

Glenn Ray
Cypress, TX


-----Original Message-----
From: Matt BenDaniel [mailto:matt@starmatt.com]
Sent: Tuesday, December 04, 2001 12:59 PM
To: astro-photo@seds.org
Subject: Re: [APML] Astronomy Magazine M8


We know that M8 and most other diffuse emission nebula are actually grey
with the slightest pink tint.  But because we produce art (and not
scientific data), we take liberties when we curve.  Most of us saturate
and stretch images in a way that reveals structure and coloration in a
way that we hope is aesthetically pleasing to others (as well as to
ourselves).

Many many times on the APML and elsewhere the question has been asked,
"What does it really look like?".  The answer is that it (e.g. M8) looks
like a faint grey indistinct cloud.  But how relevant is that to our
final product (i.e. art)?

Also, I don't fault any image because it includes wavelengths that
cannot be seen by the naked eye.

However, I do object to many of the Hubble ST image renderings because
they seem to have be excessively far away from anything that could be
considered natural.  For example, the famous "Pillars of Creation" in
M16.  Orange with purple stars? Echh!
--
Matt BenDaniel
http://starmatt.com

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