Hemisphere:  Southern  ·  Constellation: Orion (Ori)  ·  Contains:  Horsehead nebula  ·  IC 434  ·  NGC 2023
The Horsehead Nebula, 


            Joshua Bury
The Horsehead Nebula
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The Horsehead Nebula

The Horsehead Nebula, 


            Joshua Bury
The Horsehead Nebula
Powered byPixInsight

The Horsehead Nebula

Technical card

Imaging telescopes or lenses: C9.25

Imaging cameras: SBIG ST-4000XCM

Mounts: CGEM

Guiding telescopes or lenses: Orion 50mm GuideScope

Guiding cameras: SBIG ST-i Mono

Focal reducers: Celestron f/6.3 Focal Reducer/Corrector

Dates:Oct. 23, 2011

Frames: 80x180" (4h)

Integration: 4h

Avg. Moon age: 25.68 days

Avg. Moon phase: 15.87%

Basic astrometry details

Astrometry.net job: 101208

RA center: 05h41m08s.4

DEC center: -02°2526

Pixel scale: 1.228 arcsec/pixel

Orientation: 90.533 degrees

Field radius: 0.427 degrees

Resolution: 1882x1648


Hit 'L' on your keyboard for a MUCH better view.

You've probably seen this one before but there's actually a lot going on here! To start with, the large red swath going across the field of view is a Hydrogen emission nebula. This is Hydrogen gas that is glowing (à la neon lights) due to ionization from nearby stars. The distinctive Horsehead is actually part of a larger cloud of dark dust that's silhouetted in front of the background nebula. You'll notice that there's far fewer stars in the lower half of the image than the top. That's because most of them are obscured by the same dark nebula that the Horsehead is part of.

Wouldn't it be great if it were possible to 'see' more of that dark nebula (besides a silhouette and lack of stars)? What would it look like if we could shine a really bright light on it? Well, wonder no longer because there's a star in the lower left of this shot that's illuminating a large portion this nebula. Notice how blue the dust looks. Turns out that it appears blue for the same reason that our sky is blue (on a clear day anyways). The physics behind this is called Rayleigh Scattering and it's also responsible for the deep orange of the setting sun (and moon). Here's the gist: when you have a volume of particles of a certain size and shine full-spectrum light on it it reflects (or scatters) the blue part of the light and allows the red part of the spectrum to pass through. In the lower-left of this shot we're looking at starlight reflected off the dark clouds of interstellar dust.

The Horsehead is normally a Winter treat but since I don't see much of the stars in the Winter months in Western Oregon I thought I'd sneak it in

Hope everyone's having a great weekend!

Technical info about the image:

Object: Barnard 33, The Horsehead Nebula

Sky: 20.8 mag/arcsec^2

Mount: CGEM

Imaging scope: C9.25 at f/6.3

Imaging FL: 1480mm

Imaging camera: SBIG ST-4000XCM

Lights: 80x180s (4h)

Calibration: 9 sky flats, 47 darks (-20C)

Guide scope: Orion 9x50 finder scope

Guide camera: Meade DSI I (2s intervals)

Other details: Images acquired with CCDOPS v5, guided with PHD (using GPUSB), calibrated and stacked using Deep Sky Stacker, post-processed in Photoshop CS5.


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The Horsehead Nebula, 


            Joshua Bury