How much aperture for technicolor?
Posted 24 February 2013 - 10:02 AM
I'm guessing its impossible and that the contrasts and such are too skewed artificially to ever reveal the like even through a mirror miles across. Another limitation would seem to be image scale and exit pupil. If here were such a thing as a 10,000 foot aperture the magnification even with huge oculars custom made would be gargantuan and that not to say you could even see all the exit pupil.
It would seem, unless I've got it wrong there is a cap on aperture for say, a 150x view of M51.
Thanks in advance.
Posted 24 February 2013 - 10:25 AM
Is it ever possible though to have aperture large enough m42 or even the horse head vividly shows those deep crimsons and such.
Absolutely not. The intensity of light coming from most of M42 is too low to stimulate color vision -- period. A telescope can only make the intensity lower, not higher.
The upshot of it all is, how big a mirror do you need to finally collect enough light to equal the CCD and photo images?
That's not the right way of looking at this question. CCDs and human eyes see things differently. CCDs will always see more details in faint objects. Which one is better or more aesthetically pleasing is a matter of preference.
It would seem, unless I've got it wrong there is a cap on aperture for say, a 150x view of M51.
Right. You will get no gain from a telescope producing an exit pupil larger than your eye's pupil. Taking 7 mm as a taking human pupil, that means that the maximum useful aperture for 150X is 150 x 7 mm = 1050 mm -- still within the range of (very large) backyard telescopes.
Posted 24 February 2013 - 10:31 AM
Theoretically in presence of color contrast, color perception benefits from the angular size of the differently colored features. So the surface brightness and exit pupil considerations may not always be limiting. How this translates to practice - what objects, apertures, and magnifications - I have no idea.
Posted 24 February 2013 - 11:32 AM
Posted 24 February 2013 - 01:11 PM
If I recall correctly, Steve Aggas reported here a while ago, that the core of some bright galaxies were a wonderfully golden hue. I can't remember, if it was M31 or M51, but I think it was one of them.
Posted 24 February 2013 - 01:38 PM
Posted 24 February 2013 - 02:44 PM
The point is that is as bright an image of the object as can be obtained with the eye, at a scale large enough that color should be visible if it is going to be visible. The color is still muted.
I'm with Tony on this one. I think the surface brightness of most of M42 (let alone other objects) is just too low for technicolor to result. Muted color in some parts yes.
Besides stars, the most brilliant colors I see from objects in my scope are in planetary nebula. Some of them have very high surface brightness, and the blueish green color in them can be quite vivid.
Posted 24 February 2013 - 03:46 PM
Back in 2001 or so a bunch of us(during TSP) had the opportunity to observe all night with the McDonald observatories 82" Otto Struve scope. It was a mind blowing peak experience for a lot of us!!! Most striking was the colour ALL of us saw on objects like the Cats eye and Ghost of Jupiter. We saw totally obvious pastel greens and blues!! We had sub arc second seeing that night but I don't recall anyone seeing colour in the core of M64 (although the structure in the dark lanes was amazing!!).
I'm not sure if they still do nights on the 82" but it seems they still have special nights observing:
All I can say is that night gave us all an incureable case of aperture fever!!
Posted 24 February 2013 - 06:19 PM
From my own limited experiments, color detection requires a surface brightness of 18-19 magnitudes per square arcsecond. Many planetaries, few diffuse emission nebulae, many galaxy bulges and numerous globular cluster cores qualify. I doubt if any galaxy spiral arms or reflection nebulae are sufficiently bright.
For continuum sources such as galaxy and globular cores, the colors are subtle, being comprised of stars which collectively are yellowish.
For emission sources, bluish-green dominates because of the eye's much higher sensitivity to O-III and H-beta than H-alpha. To appreciate this, consider: Even though the red H-alpha in IC434 (against which the Horsehead is silhouetted) is of considerably higher intensity than the blue-green H-beta--as amply evidenced by any color image ever made--which filter do you bring to bear; H-beta or H-alpha? Even for such a brilliant nebula as M42, through an H-alpha filter the view is but a shadow of that through either the H-beta or O-III, even though in most parts the H-alpha is as as intense or more so.
This vast imbalance in the the eye's sensitivity to the emission components of glowing nebulae must always be borne in mind.
As we all know, aperture by itself does not alter surface brightness nor contrast; it merely changes image scale for given exit pupil. Once an object has been magnified (via sufficient aperture) to the point of revealing color, larger apertures can improve the perceived color intensity by covering more of the retina. But it cannot ever bring into view color which is of insufficient surface brightness to begin with.
Posted 24 February 2013 - 10:30 PM
It does make sense too in that a greater telescope visually will never give MORE light than is present. Galaxies particularly in the film days would need a simultaneous population of SN kicking off to light up like that .
Interesting stuff and thanks.
Posted 24 February 2013 - 11:21 PM
The Merope Nebula shows as blue with a 4.5" Newt with a large exit pupil of 5mm+.
And here is another DSO object I saw color in:
"Hi everyone, I managed to get another look at IC 418 tonight around 8:00pm with the C6. A 19mm eyepiece was used for a power of ~87x. At this power IC 418 appeared to be an out of focus star that fluctuates from light purple to orange and then to pink depending on the seeing. Perhaps even more interesting is that tonight at this power the central star was visible. Upping the power to ~425x greatly enlarged the PN but the central star disappeared completely as did the color seen at lower power. This is indeed a very cool PN!"
Posted 24 February 2013 - 11:41 PM
Clear skies and clean glass,
Posted 25 February 2013 - 01:47 AM
Posted 25 February 2013 - 06:43 AM
Posted 25 February 2013 - 07:07 AM
Posted 25 February 2013 - 09:31 AM
I wonder if the perception of blue in the Merope nebula wasn't influenced by the bluish light of Merope itself. The surface brightness of this nebula probably doesn't top 22 MPSAS, which would be fully 3 magnitudes below the color detection threshold.
In order to see color, the subject must have sufficient surface brightness to *easily* see with direct vision. The Merope nebula always requires averted vision for me. And I've never seen it as anything other than quite colorless.
Posted 25 February 2013 - 05:10 PM
I don't think that any aperture would produce "technicolor". The human eye just does not gather light in that manner.
However, using Tom Clark's 36 inch f/5 Newtonian many years ago we were blessed with a terrific evening. Using a 27mm Panoptic eyepiece, M 33 was amazing. I could see the two populations of stars. By that I mean that the core was sunshine yellow and the arms were a light blue-white with LOTS of mottling. We all climbed up and down the ladder several times to marvel at the detail and color. You know that one reason a big Newt provides better views is that at the eyepiece you are closer to the stars;-)
Clear skies to us all;
Posted 25 February 2013 - 09:48 PM
Posted 25 February 2013 - 11:22 PM
Orion Nebula-Bluish Green
Planetary Nebula-Grayish Blue Green
Galaxy-Gray or White.
Posted 26 February 2013 - 05:30 AM
Posted 26 February 2013 - 02:32 PM
The most vividly coloured DSO I've seen is the Homunculus Nebula surrounding Eta Carinae. It is a vivid orange in my 8" and 12" scopes. Following that, the Ghost of Jupiter presents a distinct bluish hue and several other bright high surface brightness PNe are an obvious greenish/bluish in colour. Beyond these objects though, no real colour can be seen in DSOs in amateur scopes, except for the brightest emission nebulae which might appear greenish.
Well, try IC 418 for a change (a definite reddish tinge on its edges is seen at low power in my 10 inch Newtonian). Up here "in the north", we also have the planetary known as "Campbell's Hydrogen Star" which also looks a reddish-orange color. In a 30 inch at the Nebraska Star Party, the core region of M31 had a faint yellowish-orange hue to it, as did some globular cluster stars in that same scope. Clear skies to you.
Posted 26 February 2013 - 11:53 PM
I've red a lot of comments on "green" M42 starting from 8" aperture, however I couldn't see neither in 8", nor in 24". So far the only deepsky objects that are color for me - are planetary nebulas.
That's interesting as I find it the other way around. Minty grey green in M42 - subtle but regularly visible under mag 6 sky's or better in the 8 and the 10 I had. I would guess with the right exit pupil the C6 would give a glimmer too. Planetary NEB to me are more challenging your color owing probably to the lesser apparent surface area visible.
In the best moments the green in M42s central wedge appeared minty green reminiscent of breaking open a chocolate mint candy to the green inside. At its peak obviousness this color has startled me. This at 140x by the way. For the most part cursory glancing gives just monochrome grey, a little attention, that grey grey faint green - then in the spectacular instances - wow. With the 8" it could be amazing.
Posted 27 February 2013 - 01:25 AM
As for the planetary nebulas, central part of M57 was obviously green for me and my friend in my 8" SCT, however I haven't informed him that it's green. Another color planetary for me was beautiful NGC 2438 in open cluster M46. I think that Cat's Eye will also be colored for me, will need to check this. My explanation to colors in planetary nebulas is their compact size.