Sh2-157 in Cepheus/Cassiopeia

Click on the image for a high res color version. MOUSE OVER for H-alpha only. Look also to the H-alpha only hires.

Sh2-157 is a large and faint nebula only 1° South-West of the Bubble Nebula (NGC 7635). This image frames both objects, with the Bubble Nebula on the lower-left corner. The main nebula resembles me a "Current Clamp", but it is universally nicknamed "The Claw". More objects are framed: the nebula encircling the bubble is Sh2-162, while the yellow small globular nebula is GN 23.15.3. The small isolated red nebula in the middle-left is Sh2-159. The open cluster on the top border is NGC 7510. The bright and small red nebula near the middle of Sh2-157 is LBN 537.
image is an 8 h Ha-RGB composition, with most of the exposure focused on H-alpha emission (5.5 h) and only a few RGB (2.5 h). Unfortunately only a single night of the new Moon weekend was clear; I would like to have collected at least the double of the exposure for a best rendition. Be sure to look not only to the color version but also to the black and white Ha only version.

Technical Data
Optics TEC 140
Focal Length
1011 mm
Focal Ratio f/7.2
Exposure Time Total 8 h, composed of Ha 5 h 30 min, RGB 50:40:60 min (single exp of 30 min for Ha, 10 min for RGB)
CCD SBIG STL-11000M @-35°C
Location Bazena (BS, Italian Alps) at 1800 m height
22 November 2014
Mount Gemini G-41
Tracking Lodestar on an 80mm f/5 refractor
Temperature and humidity T= 0 °C, RH= 85%
Sky brightness at zenith (with SQM-L) 21.1-21.4 mag/arcsec^2
Notes North at left. Veils in part of the exposures. Bad seeing in the RGB images due to low altitude on the horizon.

HTML Editing and Publishing by Lorenzo Comolli. Email me at
Back to Main Page