M13 — Hercules Cluster
Globular Cluster in Hercules
About
The brightest globular cluster in the northern sky, holding several hundred thousand stars about 24,000 light-years away. In 1974 a radio message was sent from Arecibo toward it, which will take about 25,000 years to arrive.
Imaging tips
- Only 20′ across, so it needs 1,210–2,020 mm on APS-C to fill a third to half of the frame. A short wide-field refractor records it small and needs heavy cropping.
- Dither between subs. One example stacked 130 one-minute subs (about 2 hours); from a city, stacks of 30-second subs work.
- The faint edge-on galaxy NGC 6207 sits nearby, about 28′ to the northeast, and only shows in a deeper stack. M13 is best placed in May and June.
Facts
- Size
- 20′
- Magnitude
- 5.8
- Coordinates
- RA 16h 41.7m, Dec +36° 28′
- Framing, APS-C
- 1210–2020 mm
- Framing, full frame
- 1860–3090 mm
- Best months
- May, Jun
- Peak altitude
- 77° from 50°N, 89° from 35°N