When to photograph C 9 (Cave Nebula)
C 9, the Cave Nebula, is an emission nebula in Cepheus, 50′ x 30′ across.
When to photograph it
From 45° N the best months are September to November, with up to 9.8 hours of astronomical darkness above 30° in October. It reaches 72° at its highest. It never sets from this latitude, so some imaging is possible all year.
From 35° S it never rises.
Framing
Its long axis is 50′. It fills 35 to 80% of the short side of an APS-C sensor at about 380 to 860 mm, and of a full-frame sensor at about 580 to 1320 mm.
Filters and the moon
It glows in H-alpha, and often OIII, so a dual-band filter on a color camera or narrowband filters on a mono camera cut light pollution and keep it workable with the moon up. 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 C 9's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- NGC 7635 Bubble Nebula 3.0° away
- M 52 3.3° away
- NGC 7380 Wizard Nebula 4.6° away
- NGC 7822 8.3° away
- NGC 7129 8.8° away
- IC 1396 Elephant's Trunk Nebula 11.0° away
Gear that suits C 9
C 9 is 50′ along its long axis. These frame it on an APS-C sensor with room to crop. It shines in H-alpha and OIII, so a dual-band filter on a color camera cuts through light pollution and moonlight.
- Sky-Watcher Esprit 100ED 550 mm f/5.5: fills 51% of an APS-C frame's short side View at High Point Scientific
- Askar FRA600 600 mm f/5.6: fills 56% of an APS-C frame's short side View at High Point Scientific
- William Optics GT81 IV 478 mm f/5.9: fills 45% of an APS-C frame's short side View at High Point Scientific
- Optolong L-Ultimate 3 nm 3 nm dual-band, Ha, OIII, for color cameras View at High Point Scientific
- Antlia ALP-T 5 nm 5 nm dual-band, Ha, OIII, for color cameras View at High Point Scientific
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