When to photograph M 22
M 22 is a globular cluster in Sagittarius, 13′ across at magnitude 6.2. Also listed as NGC 6656.
When to photograph it
From 45° N it never climbs above 30°. It peaks at 21° when it crosses the meridian, low enough that haze and light pollution soften it. It is possible with a clear southern horizon, but hard.
From 35° S the best months are June and July, with up to 9.2 hours of astronomical darkness above 30° in June. It reaches 79° at its highest.
Framing
Its long axis is 13′. It fills 35 to 80% of the short side of an APS-C sensor at about 1490 to 3410 mm, and of a full-frame sensor at about 2290 to 5240 mm.
Filters and the moon
Clusters are broadband targets, but bright ones tolerate some moonlight and light pollution. Short subs keep the brightest stars from clipping. The dark sky calendar shows which nights this month are moon-free where you are.
Plan it for tonight
Dates and times depend on your exact location. The imaging planner shows M 22's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- M 28 2.9° away
- M 25 4.9° away
- M 24 Sagittarius Star Cloud 7.0° away
- M 8 Lagoon Nebula 7.5° away
- M 21 7.5° away
- M 54 7.8° away
Gear that suits M 22
M 22 is 13′ along its long axis. These frame it on an APS-C sensor with room to crop.
- Celestron C8 OTA 2032 mm f/10: fills 48% of an APS-C frame's short side View at High Point Scientific
- Celestron EdgeHD 8 OTA 2032 mm f/10: fills 48% of an APS-C frame's short side View at High Point Scientific
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