Saturday, July 17, 2010

Dumbbell nebula under averted vision - NGC 6853

Sketch of the Dumbbell nebula (M27, NGC 6853)
9 July 2010, 21:31 UT
200mm SCT f/10, light pollution filter
80x, seeing 7/10, trans 3/5

This is my first sketch of this splendid Dumbbell Nebula (M27, NGC 6853). Seen from its poles (compared to an equatorial view from the Earth), we would probably see a round nebula similar to the Ring Nebula M57.

Under direct vision at a magnification of 80x, M27 appears as a large, diffuse rectangular patch of weak light surrounded by a background of scattered stars.

After some time observing under averted vision, the nebula shows a non-uniform glow, which I tried to bring out in my sketch. The intensity sketch drawn at the telescope brings out this distribution of this intensity within the nebula. On the upper left side the intensity seems to taper off rather abruptly in comparison to the opposite side of the nebula which shows a more uniform, but lower intensity. A faint star is visible at this tapering edge.

Combining these two regions of the nebula is a diagonal stretch of weak illumination. Using a light pollution filter, some faint intensity appears in the remaining space of the rectangular nebula.

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