When to photograph NGC 4755 (Herschel's Jewel Box)
NGC 4755, the Herschel's Jewel Box, is an open cluster in Crux, 8′ across. Also listed as C 94.
When to photograph it
From 45° N it never rises.
From 35° S the best months are March to May, with up to 10.0 hours of astronomical darkness above 30° in April. It reaches 65° at its highest. It never sets from this latitude, so some imaging is possible all year.
Framing
Its long axis is 8′. It fills 35 to 80% of the short side of an APS-C sensor at about 2410 to 5500 mm, and of a full-frame sensor at about 3700 to 8460 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 NGC 4755's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- NGC 4609 Coalsack Cluster 3.0° away
- C 99 Coalsack Nebula 4.3° away
- NGC 3766 Pearl Cluster 9.4° away
- IC 2944 Running Chicken Nebula 9.6° away
- NGC 4833 10.5° away
- NGC 4945 11.0° away
Gear that suits NGC 4755
NGC 4755 is 7.8′ along its long axis. These frame it on an APS-C sensor with room to crop.
- Celestron C8 OTA 2032 mm f/10: fills 30% of an APS-C frame's short side View at High Point Scientific
- Celestron EdgeHD 8 OTA 2032 mm f/10: fills 30% of an APS-C frame's short side View at High Point Scientific
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