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Deep Field Scorpius A Hydrogen Alpha mosaic

This deep hydrogen-alpha mosaic covers approximately 50 degrees of sky as assembled from more than 80 individual image tiles taken with a CCD camera and wide field astrograph. It contains numerous astronomical objects including stellar nurseries, ancient super novae remnants, dark molecular clouds, clusters of stars, and planetary nebulae. It represents only a small segment of the Milky Way's equatorial plane.

Deep Field Scorpius
Click on the link below or copy and paste the URL to your Browser for a high resolution, interactive version of the mosaic using the GigaPan viewer.

http://www.gigapan.com/gigapans/c755274737556194a9a6cfef2eceb091

The destination doesn't define the journey

It would seem I've been collecting data on this part of the southern Milky Way since 2014. In fact it started with a single tile and grew over time. Slowly the pieces have been coming together to make up this amazing vista around the southern most portions of the constellations Scorpius and Sagittarius. Seasonal changes, bad weather, broken equipment, and life in general often get in the way of completing projects. This is just one of many mosaic programs in progress from the Australia remote observatory. When the weather is good, and the equipment is working, each completed image tile comes together with a wide field telescope and specialized CCD camera. The observatory, located in Coonabarabran, Australia, is fortunate to be under some of the best night skies in the world and is remotely operated from California. With minimum interference from air and light pollution, this enables the telescope and camera to reveal large scale structures on our line of sight toward the Sagittarius spiral arm of our home galaxy.

RRO, Rainbow Remote Observatory

What is Hydrogen Alpha?

The visible spectrum and H-alpha emission line.

Great clouds of gas and molecular dust are prevalent along the galactic equator of the Milky Way, mostly comprised of hydrogen emission nebulae. These are clouds of partially ionized gas called HII regions. Think of this as a mix of electrons and ionized hydrogen that is consistently recombining into hydrogen atoms. If we visualize the hydrogen atom like a small solar system, the excited electron will move outward from one orbit to the next. When energy is lost, the electron will cascade back to the original "orbit", emitting this energy in the form of visible light isolated to a very narrow spectral emission line at 656nm. Long exposure astrophotography through a filter narrowly isolating the 656nm emission line reveals these faint and diffuse H II regions, otherwise lost in the broad visible spectrum.

Sky Coverage

This 360 degree image was created using the all-sky Milky Way map produced by Douglas Finkbeiner from data collected by the WHAM, VTSS and SHASSA hydrogen-alpha surveys. The rectangle identifies the photographic field of the Scorpius mosaic. Notable HII fields have also been identified.

Source: Douglas Finkbeiner WHAM, VTSS, SHASSA

Mosaic Planning

Developed by David Lindemann, a beta version of SkySurveyor software is used to perform mosaic sequencing and automated image acquisition. The software aligns mosaic tiles along lines of RA and Declination. The overlap is 40 arc minutes for each of the tiles for mosaic assembly. Each tile has an accumulated exposure time of 180 minutes.

SkySurveyor plot. Background image source: Wisconsin Hydrogen Alpha Mapper Survey

Mosaic assembly is enabled through Micorsoft's Image Composite Editor (ICE). A freeware that does quite well handling numerous large files. These are individual 16bit, 32gb files.

ICE Assembly

Technology

System resolution is 3.5 arc seconds per pixel, with the telescope and CCD array covering a field of 3.98 degrees.

  • Camera: FLI Proline KAF-16803, 9um pixels, 4096 x 4096
  • Telescope: Takahashi FSQ-N, 106mm f/5 fluorite quintuplet optics. 80mm flat field image circle
  • Mount: Software Bisque, Paramount ME
  • Filter: AstroDon 5nm narrow band-pass Hydrogen-alpha. 50mm square filter
  • Software: TheSky X, MaximDL v.6, SkySurveyor beta, Microsoft Image Composite Editor, Adobe Photoshop CC
  • Location: Rainbow Observatory, Coonabarabran, NSW, Australia

The Scorpius OB1 Association

Scorpius OB1, (refers to a grouping of hot, giant stars of spectral types O and B), located at a distance of about 1750 parsecs, is surrounded by the diffuse nebula RCW 113. This cavity is a large shell of gas where ultraviolet radiation and stellar winds have blown away most of the material in this area.

The core of the association is the star cluster NGC 6231, also called the "Northern Jewel Box", which is embedded in the Prawn Nebula, RCW 116. In the same region as Scorpius OB1 is RCW 119, a wind blown bubble surrounding prominent X-ray eclipsing binary HD 153919. To the south and in the foreground at 1500 parsecs is RCW 114, which is probably a ring nebula surrounding the Wolf-Rayet star WR 90, expanding into a pre-existing supernova cavity - SNR 343.0-06.0. Source: Galaxy Map

The unusual, elongated object seen at the top belongs to a category that is known among astronomers as "elephants trunks". They are formed when newborn massive stars appear in the dark molecular cloud and start to push the surrounding material away, creating an expanding bubble of hot gas. The walls of such a bubble are unstable, and while most of the walls continue to recede from the luminous young stars, dense tongues of material are sometimes left behind. These objects therefore always point towards one or more massive O and B stars. In this particular case seen here, the elephant's trunk points toward NGC 6231. Source: Laustsen, Madsen, West; "Exploring the Southern Sky".

To be continued

Created By
John Gleason
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