M17 is a large emission nebula
in Sagittarius, similar to that in
Orion, but viewed edge-on
instead of face-on. Its rather
complex and irregular shape has
spawned a variety of descriptive
monikers, including: Swan
Nebula, Omega Nebula,
Checkmark Nebula, and
Horseshoe Nebula.

The nebulosity extends out
considerably more than this
image shows, but
I wanted to
concentrate on the central
portion, which is richer in the OIII

Small scale detail is preserved
(and enhanced) in this
completely narrowband version
of M17, whereas it often appears
relatively washed out in other
M17 versions that use broadband
data. Of course, it helps that our
image scale at CTIO is 0.4"/pixel,
and the FWHM of 30 minute
integrations routinely approaches
1.0" (before any deconvolution or
other sharpening)!
16" RCOS @ f/11.3
Planewave 200 HR

Apogee U9 imager
SBIG 402 guider
Astrodon F

a & OIII Bicolor:

Ha=   30 min x 16, 1x1
OIII=  30 min x 16, 1x1

Data acquired at

Processed with Maxim,
, Neat Image,
and Adobe PS
        M17-- the Swan Nebula
      Click on image to enlarge

Click HERE to see a 2002 version
of M17 from my backyard -- it's
nice to keep these older, albeit inferior
images, to help document that there's
no substitute for experience!