The Cocoon
is a favorite target for astrophotographers but is often overlooked
visually because it is quite faint. Burnham's fails to mention it
all and Houston only mentions it in passing. Oddly, it is included
the the Caldwell Catalog, Patrick Moore's list of objects visible in
modest amateur instruments.  This
field contains a combination of HII region (red) and reflection
nebula (blue), cut by dark lanes of dust. All this makes for
beautiful color photographs such as the one above. This image was
created by combining red and blue images of the second generation
digital sky survey. Unfortunately it is not nearly so impressive in
the eyepiece.
A
dark sky is probably the most important factor in observing this
nebula. That, and using a wide field eyepiece. It appears as a
diffuse round glow. An OIII filter increases the contrast some but
does not make the nebula appear more visible. In larger instruments
hints of dark lanes can be glimpsed against the otherwise smooth
haze. An H-beta filter is said to very much improve the visibility
of the Cocoon.
The
field in a 10-inch f/10 at 63x. North is down and east is right.
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