The Cocoon Nebula
Diffuse Nebula in Cluster
IC 5146, OCL 213
Integrated Visual Magnitude: 10
Apparent Diameter: 20'

Minimum requirements to view: 6-inch telescope and very dark skies

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/4.5 at 75x. North is down and east is right.
 
Millennium Star Atlas Vol III Chart 1104
Sky Atlas 2000 Chart 9
Uranometria 2000 Vol I Chart 86

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