Campbell's Hydrogen Star -- Planetary Nebula in Cygnus
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A Strange Planetary Nebula
Campbell’s Hydrogen Star (HD 184738) shines at magnitude 11.3 in the constellation of
the Swan.  It is a WC star which are strange siblings to Wolf-Rayet stars.  The main
difference is that Wolf-Rayet stars are rich in Nitrogen with some Carbon in their
atmospheres while WC stars are rich in Carbon and Oxygen with little or no Nitrogen.  This
may not sound very exciting but the Planetary Nebula (PK 64 + 5.1) produced by
Campbell’s Hydrogen Star is not your usual Planetary Nebula.  The standard nebula filter
for enhancing Planetary Nebulae is the Oxygen-III, but it has no effect (that I can tell) on this
one.  The Hydrogen-Beta filter does help at higher powers, but it too is limited.  

This Planetary Nebula appears very small in the telescope.  At a size of 5 arcseconds it
requires high power before it becomes visible around its central WC star.  At low or medium
magnification, it is overpowered by the central star and since it refuses to brighten with an
OIII filter, it therefore can be a challenge to locate.  A nice bonus is that Campbell’s
Hydrogen Star is not far from the magnificent blue and gold double-star
Albireo and the
pretty double star provides a nice starting place to star hop to the small but strange
Planetary Nebula.