The Rho Ophiuchus Complex

Finally, I've been able to get myself to image the most magnificent part of the entire sky, the Rho Ophiuchus Complex. This complex extends into two constellations; Scorpius and Ophiuchus. This region of the sky is a subset of the Antares in Scorpius - Mk II image.

I'm a bit upset that Jupiter was causing internal lens reflections when it was just out of frame; I had wanted to capture more of the red nebulosity on the left-hand side as it contains another pretty blue star, Tau Scorpii. So, I decided to keep Jupiter in the frame. Next year, Jupiter would have moved away into another constellation along the ecliptic so I shall try again.

As for what's in this image:

The red nebulosity on the left-hand side is the emission nebula, RCW129.

The bright orange star towards the left is Antares. Antares (Alpha Scorpii) is one of the brightest stars in the sky which shines at a magnitude of 1.0. It is a red giant located approximately 600 light years away from our Sun. It is a double star, whose companion is a magnitude 5.4 star located just 2.5 arcseconds away. It is quite difficult to split from Antares, however, under ideal conditions (steady skies) and using a telescope of moderate aperture (6" and above) with very fine optics (sometimes with a aperture mask) it is quite easy to split. The companion is a grey-green coloured star. The companion circles the primary approximately every 900 years.

The bright orange component of this image is a dark nebula, IC 4606. It is being illuminated by the shine of Antares.

If you look carefully towards the bottom of the orange portion of nebulosity, you will see a very dense small clump; this is NGC 6144, a globular cluster.

Below the orange nebulosity of IC 4606 is a beautiful globular cluster. This is the Cat's Eye (M4) cluster. It is about 10 billion years old and about 7000 light years away. M4 may actually be the closest globular cluster to our own solar system. Antares is about 1.5 degrees from M4, which makes it difficult to see with the naked eye. Binoculars show that M4 is a very bright and round cluster. The cluster's core is loosely concentrated with a string of 10th magnitude and fainter stars running across the centre. The cluster is somewhat obscured by dark interstellar cloud. A beautiful object in any instrument.

Towards the bottom is some gorgeous faint red nebulosity. This is a combination of an emission and dark nebula called Sh2-9 and Ced130.

The blue nebula to the right of the IC 4606 is IC 4605 which is a reflection nebula.

The grey-green nebula under the 'V'-shaped nebula is IC 4603, a reflection nebula. The stars in this region form part of an open cluster, called Gras1.

The blue nebula towards centre-right is IC 5604, a reflection nebula. The dark patch in this region is B42, a dark nebula. The stars in the centre of this region form the Rho Ophiuchi multiple star system.

Lastly, the bright nuisance at the top right is Jupiter. Still, it's turned out quite alright.

I'm stoked.

This composite consists of one set of images; one set of 35 images taken at ISO-400.
Each individual image was a 240 second exposure.
IRIS was used to calibrate each image (dark subtraction [median combined master dark] and flat field division [median combined master flat {lights and darks}]), to register, align, and finally stack.
Photoshop CS2 was used to adjust levels, curves, frame and resize the final composite.

Target: The Rho Ophiuchus Complex in Ophiuchus
Date: Friday, July 13th, 2007
Time: First image: 10:43 PM
Time: Last image: 01:05 AM
Location: Lake Bathurst, NSW, Australia
Camera: Canon EOS-350D (modified: Baader UV/IR filter)
Lens: Nikkor ED 180mm F/2.8 (stopped down to F/4.0)
Focal length: 180mm
Mount: Takahashi EM-200
Exposure: 35 x 240 seconds (2 hours and 20 minutes) @ ISO-400 (RAW)
Software: IRIS: Calibration, registration, stacking; Adobe Photoshop CS2: post-processing and framing