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RE: [APML] Color of Objects (was Astronomy Magazine M8)
Obviously, but a 'spectral scan' would have to be recorded on something in
the first place.
I don't have the resources for an appropriately sensitive spectrometer -- My
Project STAR spectrometer backed up afocally with a 35mm camera won't cut
it. I guess I'll scan some of the observatories and/or catalogs at ADS to
see what spectral info there is and see what I can simulate manually.
-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of Stosh
Sent: Thursday, December 06, 2001 3:22 AM
To: astro-photo@seds.org
Subject: Re: [APML] Color of Objects (was Astronomy Magazine M8)
Greetings,
Without using some kind of a recording medium like film or CCD, there is no
possible way to amplify the brightness of an image to your eye. The inverse
square law that was mentioned that keeps the brightness the same as we
approach an
object also applies to magnifying it with a telescope. The brightness you
can see
an object with your naked eye is actually slightly brighter than what you'll
see
in a telescope because of light losses from different surfaces. A telescope
can
only magnify an image, it cannot increase its brightness. Your eye can only
open
to a max of approx. 7mm. If you observed orion through a huge aperture
telescope
without increasing the magnification, you'll get a huge light cone which
cannot
fit into your eye. So you boost the magnification which drops the
"brightness"
until the light cone can fit into our eye. At that point the brightness is
the
same as naked eye, or a previously mentioned, slightly dimmer. A larger
aperture
telescope is a waste to your eye unless you boost the magnification to
match.
The great thing about film and CCD is that there is no limit to pupil size.
You
can use a huge telescope with no magnification and increase the images
brightness.
later,
Stosh
Richard Klappal wrote:
>
> 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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