click on image to enlarge
[OIII] = Red, Ha = Green, [NII] = Blue (shortest to longest wavelengths)
click on image to enlarge
[NII] = Red, Ha = Green, [OIII] = Blue (longest to shortest wavelengths)
click on image to enlarge
Ha = Red, [NII] = Green, [OIII] = Blue
Taken on February 6 and 7, 2004 from my backyard in Castro Valley, Ca. under a near full moon.
--One of the problems created by using emission line filters is the loss of star intensity. This planetary nebula has a faint but very hot central star that emits strongly in UV. The narrow passband of the filters used do not capture much radiation from this star so the star is dimmed considerably from an RGB image. To see good examples of RGB images of this object, refer to the links below:
Al Kelly's Amateur image that introduced this object to me
Al Kelly's LRGB image and Richard Crisp's [NII]Ha[OIII] image data combined:
Al Kelly did the combination processing and writes:
"All processing was in AIP4WIN.
Luminance was processed from a mean stack of my unfiltered images (18 x 5 min)
with your OIII, Ha, and NII images. Processing was a merger of gamma-log
stretched, non-unsharp DDPed, and histogram shaped versions, with modest
background smoothing applied. No sharpening or deconvolution applied.
Chrominance assignment was R : G : B = R+NII : G+Ha+B+OIII : B+OIII"
Arnie Rosner's Dream Machine/Mewlon 300 image
A nice history of the nebula (in German) with image in same filter set
Equipment used and exposure details:
Astro-Physics AP155EDF imaging scope @1085mm focal length (f/7)
SBIG ST10XME imaging camera @ -30C
Astro-Physics 80mm guide scope
SBIG ST7E Guide control camera @-10C
FLI CFW 1 filter wheel
Custom Scientific Narrowband Emission Line Filter
[Nitrogen II] 658.3nm 3nm FWHM
Hydrogen alpha 656.3nm 3nm FWHM
[Oxygen III] 500.7nm 3nm FWHM
Exposure details:
7 exposures of 15 minutes for Halpha binned 2x2
7 exposures of 15 minutes for [NII] binned 2x2
7 exposures of 15 minutes for [OIII] binned 2x2
5 hours 15 minutes total exposure time
Maxim DL used for ST10XME control
CCDSOFT 5.00.71 used for ST7E control
Sigma prebeta 11 used for darks, flats, biases and light combine
SGBNR used for smoothing
Photoshop CS used for final touch up