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How much aperture for technicolor?

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#26 HellsKitchen

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Posted 27 February 2013 - 04:30 AM

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.


IC 418 has always been whitish to me, never succeeded in seeing the red in my 12. This is from my suburban backyard though so maybe I'd have a better chance from a dark sky location.

#27 Sarkikos

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Posted 27 February 2013 - 10:54 AM

Pete,

I get that we use skotopic vision in deepsky visual observing for the most part and that our retina/brain in low light is part of the reason we see blue, green and greys. Is it ever possible though to have aperture large enough m42 or even the horse head vividly shows those deep crimsons and such. I've seen top artists produce deepsky drawings through huge observatory aperture but always shades of grey. 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?


I'd say forget about it for the Horsehead. But I've seen light-red tinges in M42, M27 and M57 in my 10" f/4.8 at a yellow zone site. Contrast effect or real color from the object? I'd say real color.

One of the most colorful views of M27 and M57 I ever had was a couple years ago at my dark site. Another "observer" was doing AP. He invited us to come over and look at M57. I thought he meant through his eyepiece. No sir. He meant on his laptop connected to his telescope. He had all kinds of white light glaring out from that screen. Our eyes were promptly blasted back to photopic.

APers. Eh... :foreheadslap:

Now when we walked back to my 10" Dob to see the same objects, I could see those same reddish fringes just as in the APer's image. My wife and daughter also saw these colors. I don't suggest that we shock our eyes with white light at a dark site to see colors in bright nebulae. I'm just saying that I've seen it for myself.

I've seen plenty of bright greens and blues in the brighter planetary nebulae in my 10". M42 and the bright BN's in Sagittarius and elsewhere appear green to me. Only the dimmer nebulae look gray or white.

I'm not surprised that the reflection nebulae in M45 would have a slight tinge of light-blue. That's how I've seen them. After all, they are reflecting light from white-blue colored stars.

Mike

#28 GlennLeDrew

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Posted 27 February 2013 - 12:26 PM

Leviathan,
Seeing color in M57, but not in M42 surprises me. M42 has both much higher surface brightness and larger size, factors which really help in color detection.

Because the color receptors must be stimulated, this is photopic vision light levels, and hence one need not be dark adapted to see color in extended objects. All that matters is that the surface brightness be at least as high as about 19 magnitudes per square arcsecond.

Any nebula in which I've seen color presented this to me immediately upon stepping out from a well lit indoors or after exposure to bright light. If color is not evident then, it will not be even after good dark adaption. Actually, prolongation of deep darkness is counterproductive, for colors become de-saturated after a time. A dose of white light for a spell (not just a brief flash) 'resets' my color sensitivity.

#29 Sarkikos

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Posted 27 February 2013 - 12:40 PM

Glenn,

Any nebula in which I've seen color presented this to me immediately upon stepping out from a well lit indoors or after exposure to bright light. If color is not evident then, it will not be even after good dark adaption. Actually, prolongation of deep darkness is counterproductive, for colors become de-saturated after a time. A dose of white light for a spell (not just a brief flash) 'resets' my color sensitivity.


Exactly. IME, a few seconds of white light up to half-a-minute is sufficient. But this is not a good trick to play at a dark site - unless you're the only one at the dark site! And even then I wouldn't do it on purpose. I'd rather focus on the faint fuzzies and dimmer nebulae, the ones I can't see at home.

:grin:
Mike

#30 leviathan

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Posted 27 February 2013 - 02:12 PM

Leviathan,
Seeing color in M57, but not in M42 surprises me. M42 has both much higher surface brightness and larger size, factors which really help in color detection.

Because the color receptors must be stimulated, this is photopic vision light levels, and hence one need not be dark adapted to see color in extended objects. All that matters is that the surface brightness be at least as high as about 19 magnitudes per square arcsecond.

Any nebula in which I've seen color presented this to me immediately upon stepping out from a well lit indoors or after exposure to bright light. If color is not evident then, it will not be even after good dark adaption. Actually, prolongation of deep darkness is counterproductive, for colors become de-saturated after a time. A dose of white light for a spell (not just a brief flash) 'resets' my color sensitivity.

In both cases (M57 and NGC 2438) I could see green color after at least 20 min of adaption in grey zone.

Like I said, I think the key (at least for me) is compact size with low surface brightness.

#31 GlennLeDrew

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Posted 27 February 2013 - 07:46 PM

If a small size and lower surface brightness were to improve color perception, then smaller apertures would be better than larger. :grin:

#32 aatt

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Posted 27 February 2013 - 10:29 PM

I have seen green, blue and a faint hint of salmon in M41 in my 15" using a 34mm 2inch ES.The blue snowball planetary was definitely blue. Other than that, grays and greens.

#33 leviathan

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Posted 28 February 2013 - 01:37 AM

If a small size and lower surface brightness were to improve color perception, then smaller apertures would be better than larger. :grin:

Well, larger aperture gathers more light without loss of brightness at high magnification. At the same exit pupil larger aperture will give higher magnification.

#34 azure1961p

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Posted 28 February 2013 - 06:13 PM

And with that larger image scale can be a whopping difference in detail detected . I've never found small and faint desirable for the most detailed views. Even when its enlarged and dimmer I see more. Jus throwing it out there.

Pete

#35 GlennLeDrew

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Posted 28 February 2013 - 06:52 PM

Leviathan,
Ahhh, I must have misinterpreted. You wrote "compact size with low surface brightness", which I thought to mean "compact size and low surface brightness", where I now see you meant as "compact size when surface brightness is low". Meaning, of course, a lower magnification so as to obtain a larger exit pupil and hence brighter image.

#36 leviathan

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Posted 01 March 2013 - 02:07 AM

Leviathan,
Ahhh, I must have misinterpreted. You wrote "compact size with low surface brightness", which I thought to mean "compact size and low surface brightness", where I now see you meant as "compact size when surface brightness is low". Meaning, of course, a lower magnification so as to obtain a larger exit pupil and hence brighter image.

Yeap. ;) Sorry for my english )






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