October 11, 2013 – The Amazing Sky

A star cluster and nebulas highlight a glorious starfield in Cassiopeia.

I shot this three nights ago on a very clear autumn evening. The telescope field takes in the star cluster Messier 52 at upper left, a cluster of 200 stars about 5000 light years away. It is one of the best objects of its class for viewing in small telescopes. Charles Messier found it in 1774 as part of his quest to catalog objects that might be mistaken for comets.

The brightest area of nebulosity below M52 is the Bubble Nebula, aka NGC 7635, found in 1787 by William Herschel. It’s an area of star formation marked by a central bubble of gas (just visible on the scale of my photo) being blown by the winds from a hot central star. The Bubble can be seen in amateur telescopes but is a tough target to spot.

Above the Bubble is a small bright nebula, NGC 7538.

Below the Bubble lies a larger claw-like nebula known only as Sharpless 2-157, an object that shows up only in photos.

In all, it’s a complex and beautiful field, set in the constellation of Cassiopeia the Queen.

A footnote for the technically minded: This is a stack of 5 x 15 minute exposures with a filter-modified Canon 5D MkII at ISO 800 shooting through a TMB 92mm apo refractor at f/4.8, mounted on an Astro-Physics Mach 1 mount guided by a Santa Barbara SG-4 autoguider.