How to photograph the Great Hercules Cluster (M13)
A dense ball of several hundred thousand stars, bright in summer skies.
Photo byChuck Ayoub(CC0)
When to shoot it from your location
About the Great Hercules Cluster
M13 is the best-known globular cluster in the northern sky. It is bright enough to image in moonlight and short sessions, which makes it a good target when galaxies are washed out.
Gear and framing
The Great Hercules Cluster spans about 20′ of sky. It frames best with:
- Small refractor (250-600mm)
- Long focal length (800mm and up)
You can see how other people have built their rigs on RigDesigner, including my Sony a6700 and 60mm refractor rig.
Filters
This is a broadband target, which means its light is mostly starlight across the whole spectrum. Shoot it with no filter or a UV/IR cut filter. A broadband light pollution filter can help a little in the suburbs. Dual-band and narrowband filters block most of its light, so leave them off. Plan it for a moonless night at a dark site.
Tips
- Globulars are compact and bright, so they tolerate moonlight better than galaxies.
- Keep exposures short enough that the core does not saturate, and aim for round, tight stars.
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.