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...Next summer, try for color in the Dumbbell (M27). when it's at the zenith, the "bow-tie" sometimes appears greenish, and the "football" (the fainter sections at right angles to the "bow-tie") appear rose-colored.

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From:

The color of night: Surface color perception under dim illuminations
JOEL POKORNY,1 MARGARET LUTZE,1 DINGCAI CAO,1,2 and ANDREW J. ZELE1
1 Depar tment of Ophthalmology and Visual Science, University of Chicago, Chicago, Illinois
2 Depar tment of Health Studies, University of Chicago, Chicago, Illinois

Visual Neuroscience ~2006!, 23, 525–530. DOI: 10.10170 S0952523806233492

"At the lowest illumination levels ... the reported colors can be associated with the relative scotopic luminance for the samples: samples seen as blue-green-gray are predominantly associated with high relative scotopic luminance, samples seen as red-orange are associated with intermediate relative scotopic luminance values..."
"...some of the visible samples when presented in the context of the other samples were identified as red or orange, whereas when presented individually each was identified as blue-green".

PS it seems to me that the fainter sections of M27 are dominated by OIII and are actually green, whereas it is the brightest part to be red (exactly the opposite of visual perception which tells reddish the fainter part and greenish the brightest) http://www.astrodon.com/oldsite/M27OIIIHAStarsRGB.jpg

Edited by Mauro Da Lio (11/24/07 06:51 PM)

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