When to photograph IC 4604 (Rho Ophiuchi region)
IC 4604, the Rho Ophiuchi region, is a nebula in Ophiuchus, 60′ x 25′ across at magnitude 5.1.
When to photograph it
From 45° N it never climbs above 30°. It peaks at 22° 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 9.0 hours of astronomical darkness above 30° in May. It reaches 78° at its highest.
Framing
Its long axis is 60′. It fills 35 to 80% of the short side of an APS-C sensor at about 310 to 720 mm, and of a full-frame sensor at about 480 to 1100 mm.
Filters and the moon
Reflection and dark nebulae are broadband targets. They need dark, moon-free nights and plenty of integration time. 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 IC 4604'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 IC 4604
IC 4604 is 60′ along its long axis. These frame it on an APS-C sensor with room to crop.
- Takahashi FSQ-85EDX 450 mm f/5.3: fills 50% of an APS-C frame's short side View at High Point Scientific
- William Optics Zenithstar 73 III 430 mm f/5.9: fills 48% of an APS-C frame's short side View at High Point Scientific
- Sky-Watcher Evostar 72ED 420 mm f/5.8: fills 47% 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