M8 - The Lagoon Nebula in Hydrogen-Alpha light


Copyright 2008 Hap Griffin

The nebula gets its name from the fact that the main cloud is bi-sected by a dark region in its middle resembling a lagoon on an island.  The young open star cluster NGC 6530, here seen to the left of the "lagoon" was formed from the gas and dust comprising the nebula.  The numerous dark knots in the nebula are areas where the hydrogen cloud is collapsing on itself in the process of forming new stars.  These knots of denser gas are known as Bok Globules.  It is thought that our sun and solar system formed nearly 5 billion years ago out of such a cloud.

This image was taken through a narrowband Baader hydrogen-alpha filter.  Hydrogen gas, when excited by radiation to the point where it emits its own glow emits a deep red light at a wavelength of 656.3 nano-meters.  The filter used here passes only that wavelength and a very narrow window of wavelengths on either side...thus it is essentially a single color image and reproduced here as shades of gray.  One advantage to shooting these emission nebulae through such a filter is that increased detail can be seen that is sometimes lost in the maze of colors in a full color image.  Another advantage is that such photographs can be taken in full moonlight that would spoil a full-color image.  This was captured with an almost full moon high in the sky..  

M8 lies at a distance of approximately 5200 light-years. 


Date/Location:    April 16, 2008   Griffin-Hunter Observatory near Bethune, SC
Instrument:    Canon 40D Digital SLR (modified)  through Orion 10" Newtonian w/ Baader MPCC
Focal Ratio:   F/4.7
Guiding:    Auto via SBIG ST-402 through Orion ED80 refractor
Conditions:    Clear and cool 
Weather:    29 F
Exposure: 100 minutes total (20 x 5 minutes @ ISO 800)
Filters:    Baader 7 nm HA filter, Baader UV/IR block filter internal to camera
Processing:    De-bayering, calibration, selection of red channel data, alignment, stacking, Digital Development, Richarson-Lucy Deconvolution in ImagesPlus 3.0 .  Finished in Photoshop CS3.