M27 – The Dumbbell Nebula

Here are our attempts at M27, the Dumbbell Nebula, the first through an SCT at f/10, and another through an APO refractor at f/7.

M27 in Natural Light

[See M27 in narrowband light]

The goal for this image was to collect as much luminance as possible to reduce background noise. With nearly three hours exposure, the image looks better than earlier attempts. The following night I got an hour apiece for the color images unbinned, and that worked fairly well. (It would have been better to bin the color frames 2x2 for this LRGB image. Doing so would have collected more color data, providing a better signal-to-noise ratio.)


Equipment Celestron 9¼" at f/10 on a Celestron CGE equatorial mount
SBIG ST-8XM camera
SBIG AO-7 adaptive optics at about 4Hz.
Optec IFW filter wheel with Astrodon TruBalance LRGB filters
Optec TCF-S focuser
Imaging and autoguiding with MaxIm DL 4.04
Luminance   2.8 hours (34 x 5 min.), unbinned, -15°C
Red   1 hour (12 x 5 min.), unbinned, -15°C
Green   1 hour (12 x 5 min.), unbinned, -15°C
Blue   1 hour (12 x 5 min.), binned 1x1, -15°C
Processing Master dark frame: 4.25 hours (51 x 5 min.), sigma-reject combined
Dark and flat frame reduction in CCDSoft
Luminance images combined in Ray Gralak's Sigma Clip pre-Beta 11
Color images average-combined CCDSoft
Processing and LRGB-combined in Photoshop CS
Date and Location 15 & 16 October 2004
Montpelier, VA    N 37° 49' 12", W 77° 42' 06"

M27 - The Dumbbell Nebula

M27 in Narrowband Light

[See M27 in natural-color light]

This narrowband image reveals the extent of M27's ionized gas with 30-minute sub-exposures (now that our differential flexure problem is resolved). Notice how the nebulosity visible here covers a much larger area than in the natural-color image above, especially above and below the main nebula. For example, the green texture in the lower-right corner is a patch of ionized hydrogen gas, and another patch (mixed with ionized oxygen) is visible at the top-center.

This image assigns sulfur-II to the red channel, hydrogen-alpha to the green channel, and oxygen-III to the blue channel (this is the same palette used by the Hubble Space Telescope for its false-color images).


TMB-130SS APO refractor at f/7 on a Losmandy G-11 equatorial mount
SBIG ST-8XM camera
SBIG CFW-10 filter wheel with Astrodon filters
Guiding: 60mm f/5 refractor and ST-402 camera
Imaging and autoguiding with MaxIm DL 4.57
Red (Sulfur-II)   3 hours (6 x 30 min.), unbinned, @ -20°C
Green (Hydrogen-alpha)   5.5 hours (11 x 30 min.), unbinned, @ -20°C
Blue (Oxygen-III)   3.5 hours (7 x 30 min.), unbinned, @ -20°C
Processing Dark and flat-frame processing in CCDStack
Channel sub-frames statistical-combined in CCDStack
Levels, curves and color-combined in Photoshop CS3
Date and Location 29, 30 & 31 October + 3 &4 November 2007
Montpelier, VA    N 37° 49' 12", W 77° 42' 06"