NGC7293 Helix Nebula; Aquarius
Astro-Physics 155 (155TCC) f/5.4 refractor(wide field view)
Mak Newt 250mm f/4 astrograph (central nebula view)
KAF-16803 FLI Proline (wide field view)
KAF-3200ME SBIG ST (central nebula view)
Total Exposure Time: 25 hours; H
:L:R:G:B 540:540:540:275:50:50:50. RGB used for star color and core.
September-October 2009; RDO, Moorook, AU (wide field view)
July-August 2006; Inkom, ID (central nebula view)
Comments: This FOV is much wider than is usual for imaging this planetary nebula, but this gives it a different view -- particularly of the outer shell. Narrower field of view. This image is a composite of a higher resolution core view and lower resolution wide view.
The Helix Nebula is one of the closest of all planetary nebulae: Lying at a distance of perhaps 450 light years, it is the only planetary nebula for which a parallax could be obtained by ground-based observations. Nevertheless, its distance is quite uncertain: The first determination by A. Van Maanen yielded about 85 light-years, Becvar (1961) has 590, L. Kohoutek (1962) 280, I.S. Shlovskii (1956) and P.A. Ianna & H.A. McAlister (1974) 160, the Sky Catalogue 2000.0 gives about 300 ly, and C.R. O'Dell (1963) obtains 450 light-years. It is also one of the apparently largest planetaries known: Its apparent size covers an area of 16 arc minutes diameter, more than half of that of the full moon; it halo extends even further to 28 arc minutes or almost the moon's apparent diameter. Although the nebula is quite bright, its light is spread over this large area so that it is not an easy object for visual observing (SEDS).
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