The Eagle Nebula
Nebula in Serpens
Instrument: 12.5" f/5 Home made Newtonian
Platform: Astrophysics 1200 QMD
CCD Camera: SBIG 10XME NABG with Enhanced Water Cooling
Guider: SBIG ST4
Exposure: Ha+RGB = 30:10:10:10
RGB Combine Ratio: 1: 1.05: 1.11
Filters: AstroDon RGB Tricolor
Location: Payson, Arizona
Elevation: 5150 ft.
Sky: Seeing FWHM = 5 arcsec (Maxim DL - 10min subframe), Transparency 8/10
Outside Temperature: 60 F
CCD Temperature: -30 C
Processing Tools: Maxim DL, Gralaks Sigma, Photoshop, PixInsight, Starizona Debloomer.
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The seeing held steady for
this rendition of the famous Eagle Nebula, shot during a one
day lull in the constant supply of hard rains and thick clouds
that fill our skies during the monsoon season here in Arizona.
With only an hour of exposure time before the heavy dew shut
me down, I paid critical attention to collimation and focus to
get the best images possible. And this is the result of that
One of the brightest
nebulosities in the Summer sky, M16 is the star cluster you see
just above center, and at a bright 6th magnitude, contains nearly
600 known cluster members in an area of 6 arcminutes. The large
red hydrogen nebulosity here is actually IC4703, traditionally
listed at half a degree in size. This field which is just over
half a degree wide reveals that the nebula is considerably larger
than the cataloged size. The colors of the stars in this image
are nearly all yellows and reds. The lack of blues emphisizes
the fact that there is a huge amount of obscuring dust in this
part of the sky, and shorter wavelenths are severely attenuated.
this nebula provides some unique challenges. The central dark
nebulosity, known as the "Star Queen" or more recently
as Hubbles "Pillars of Creation" are low contrast against
the bright nebula. Applying the normal gamma curve function to
bring up the dim areas of nebulosity results in lowering the
contrast even more. Here, I settled on a compromise between the
visibility of the Star Queen and revealing the outermost nebulous
30 minutes of
unbinned RGB data was supplemented by another 30 minutes of 6nm
Halpha images. The goal in combining the Hydrogen data into the
RGB data was to keep accurate G2V stars, and keep the rosy pink
nebulosity as close as possible to the original RGB coloration.
The red channel was removed from the processed RGB image, and
combined with "lighten" with the Ha data at 100 percent.
Next, to capture the Hbeta data that is also present in the original
RGB data, we combined 10% of the Ha data into the blue channel
with lighten. By recombining the three channels as a new RGB
image, we were able to keep the stars at their proper brightness
and colors, while tastefully importing additional hydrogen data
into the image. A final note on adding the Ha data into the blue
- add only as much as it takes to obtain the same shade of pink
in the original RGB image, here about 10%. NO noise
reduction was used on this image.