When to photograph M 4
M 4 is a globular cluster in Scorpius, 28′ across at magnitude 5.4. Also listed as NGC 6121.
When to photograph it
From 45° N it never climbs above 30°. It peaks at 18° 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 May and June, with up to 9.2 hours of astronomical darkness above 30° in May. It reaches 82° at its highest.
Framing
Its long axis is 28′. It fills 35 to 80% of the short side of an APS-C sensor at about 670 to 1520 mm, and of a full-frame sensor at about 1020 to 2340 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 4's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- IC 4604 Rho Ophiuchi region 3.1° away
- M 80 3.8° away
- IC 4592 Blue Horsehead Nebula 7.6° away
- M 19 8.7° away
- M 62 9.0° away
- M 107 13.6° away
Gear that suits M 4
M 4 is 28′ along its long axis. These frame it on an APS-C sensor with room to crop.
- Sky-Watcher Esprit 120ED 840 mm f/7: fills 44% of an APS-C frame's short side View at High Point Scientific
- Sky-Watcher Quattro 200P 800 mm f/4: fills 42% of an APS-C frame's short side View at High Point Scientific
- Sky-Watcher 130PDS 650 mm f/5: fills 34% of an APS-C frame's short side View at High Point Scientific
Retailer links are affiliate links. If you buy through one, the site may earn a commission at no extra cost to you. Details