NGC 7635, The Bubble Nebula

OBSERVING REPORT

NGC 7635 - THE BUBBLE NEBULA in Cassiopeia

Date: August 15, 2012
Time: 07:51 UT   LOCAL TIME (UT-7hs.)
Telescope: 24" (61cm.) f/4
Observer: Leo Cavagnaro

Click on the image to enlarge

Finder chart 

How to find it,
About 1° 10' to the south-southwest of the star 4 Cassiopeiae (visual magnitude 5).
 

Stars in chart up to visual magnitude 6.0

NGC 7635 (Bubble Nebula).

This nebula is formed by gas being compressed by a strong stellar wind from “Wolf-Rayet” massive star BD+602522. NGC 7635, discovered by Friedrich Wilhelm Herschel in 1787, lies not too far from the well-known cluster, for the northern stargazers, Messier 52 (about 35 arc minutes to the southwest), in the constellation Cassiopeia. A pattern of five stars (linked with gray lines in the DSS image to the right), with visual magnitudes between 8.7 (the brighter one) and 10 (the fainter one), helps to identify the nebula in the field of view of the telescope. The nebula surrounds one of the stars of the pattern, the 8.7 visual magnitude BD +602522 that lies to the side within the nebulosity. I have indicated the star with the white arrow in the lower DSS image.

At 59x through a 24-inch telescope and an OIII filter, the nebula looks smooth in brightness. The outer parts look fainter than the central region near the star. At higher magnification (122x) and using a nebular filter (OIII), the structure of NGC 6735 is very interesting, showing bright nebulosity surrounding the star with a small region even brighter immediately to the west of the star BD +602522. Fainter nebulosity is visible, elongated northwest-southeast.

Close-up view of NGC 7635 and its brighter region. 

North is up.