NGC 6902 / NGC 6902B / IC 4946 - Galaxy Group in Sagittarius
In the far south-eastern corner of Sagittarius, a constellation otherwise known for its spectacular highlights near the crowded Milky Way centre, lies the very rarely imaged galaxy NGC 6902 and a couple of its neighbours. Despite its beautiful and elegant appearance there is very little information about this galaxy to be found anywhere.
It contains a bright central ring and possibly also an elusive inner bar. The spiral arms are quite faint despite almost 17 hours of exposure, which is indicative of a rather weak population of O type stars. The arms also have a knotted appearance, perhaps due to the presence of brighter HII regions located within them.
The galaxy lies approximately 33 million light years away and was discovered by John Herschel.
A number of other galaxies can be seen scattered across the field of view, including the smaller face-on spiral NGC 6902B to the upper left. At the top of the frame lies edge-on galaxy IC 4649 with some traces of obscuring dust and a hint of a bar structure surrounding its core.
And far in the background countless distant galaxy groupings can be seen as small fuzzy yellowish dots throughout the image.
Date: 29th July, 5th, 6th, 7th, 8th and 9th August 2013
Exposure: LRGB: 645:152:122:93 mins, total 16 hours 52 mins @ -30C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand