The Lagoon Nebula in H-Alpha + RGB

The Lagoon Nebula in H-Alpha / RGB

The Lagoon Nebula in Sagittarius

For comparison, below is the pure RGB image

The Lagoon Nebula in RGB

And below is the pure H-Alpha channel:

The Lagoon Nebula in H-Alpha

Discovered by Hodierna about 1654. The Lagoon Nebula Messier 8 (M8, NGC 6523) is one of the finest and brightest star-forming regions in the sky. It is a giant cloud of interstellar matter which is currently undergoing vivid star formation, and has already formed a considerable cluster of young stars.

This object has been discovered by Giovanni Battista Hodierna before 1654, and classified it as "nebulosa," i.e. of intermediate brightness. It was independently noted as a "nebula" by John Flamsteed about 1680.

According to Kenneth Glyn Jones, the Lagoon Nebula has an apparent extension of 90x40 minutes of arc, which is 3 x 1 1/3 the apparent diameter of the full moon, and corresponds to about 140x60 light years if our distance of 5,200 light years should be correct, which is a bit uncertain; newer sources have 4850 (Glyn Jones) to 6500, but David J. Eichler gives the value of 5,200 light years (Eichler 1996).

One of the remarkable features of the Lagoon Nebula is the presence of dark nebulae known as 'globules' which are collapsing protostellar clouds with diameters of about 10,000 AU (Astronomical Units). Some of the more conspicuous globules have been cataloged in E.E. Barnard's catalog of dark nebulae.

Within the brightest part of the Lagoon Nebula, a remarkable feature can be seen, which according to its shape is called the "Hourglass Nebula" (see our detailed photos). This feature was discovered by John Herschel and occurs in a region where a vivid star formation process appears to take place currently; the bright emission is caused by heavy excitation of very hot, young stars, the illuminator of the hourglass is the hot star Herschel 36 (mag 9.5, spectral class O7). Closely by this feature is the apparently brightest of the stars associated with the Lagoon Nebula, 9 Sagittarii (mag 5.97, spectral class O5), which surely contributes a lot of the high energy radiation which excites the nebula to shine.

Scope: Astro-Physics AP155EDF w TCC (flattener / reducer)
Camera: StarlightXpress Trius SX814 w Astrodon GenII H-Alpha filter
Mount: Paramount MX guided w SBIG ST-402ME / Borg 60mm piggyback
8 x 15 min in H-Alpha
22/18/12 x 5 min RGB
Acquired with TheSkyX and CCD-Commander
RGB acquired with TheSkyX and CCD-Commander
Data reduction and RGB processing in PixInsight
H-Alpha sharpening and H-Alpha combine w RGB in Photoshop CC 2018

Click on each image to see it 3x this resolution and to resize it in the browser.

Lucknow, Ontario
July 2018