How to photograph the Cave Nebula (Sh2-155)
A faint hydrogen cloud with a dark opening like the mouth of a cave.
Photo byHewholooks(CC BY-SA 3.0)
When to shoot it from your location
About the Cave Nebula
The Cave Nebula is faint and needs a lot of exposure time. With a dual-band filter and several hours of data, the bright rim and the dark cave mouth stand out against the dust around it.
Gear and framing
The Cave Nebula spans about 50′ of sky. It frames best with:
- Small refractor (250-600mm)
You can see how other people have built their rigs on RigDesigner, including my Sony a6700 and 60mm refractor rig.
Filters
This target glows in hydrogen-alpha and oxygen-III light. A dual-band filter, or separate narrowband filters with a mono camera, lets that light through and blocks most light pollution and moonlight. It is a good choice for city skies and for nights with the Moon up.
Tips
- Plan for four hours or more across several nights.
Processing
Stack your light frames with darks and flats, then remove the background gradient before stretching. AstroBake does all of this for you. Point it at your folders of raw frames, then adjust the result with live sliders.