When to photograph M 3
M 3 is a globular cluster in Canes Venatici, 16′ across at magnitude 6.4. Also listed as NGC 5272.
When to photograph it
From 45° N the best months are February to April, with up to 7.3 hours of astronomical darkness above 30° in March. It reaches 73° at its highest.
From 35° S it never climbs above 30°. It peaks at 27° when it crosses the meridian, low enough that haze and light pollution soften it. It is possible with a clear northern horizon, but hard.
Framing
Its long axis is 16′. It fills 35 to 80% of the short side of an APS-C sensor at about 1160 to 2650 mm, and of a full-frame sensor at about 1780 to 4070 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 3's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
Gear that suits M 3
M 3 is 16′ along its long axis. These frame it on an APS-C sensor with room to crop.
- Celestron C8 OTA 2032 mm f/10: fills 61% of an APS-C frame's short side View at High Point Scientific
- Celestron EdgeHD 8 OTA 2032 mm f/10: fills 61% of an APS-C frame's short side View at High Point Scientific
- Sky-Watcher Esprit 120ED 840 mm f/7: fills 25% of an APS-C frame's short side View at High Point Scientific
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