When to photograph M 103
M 103 is an open cluster in Cassiopeia, 5′ across at magnitude 7.4. Also listed as NGC 581.
When to photograph it
From 45° N the best months are October to December, with up to 11.0 hours of astronomical darkness above 30° in November. It reaches 74° at its highest. It never sets from this latitude, so some imaging is possible all year.
From 35° S it never rises.
Framing
At 5′ it is small. Even 4000 mm of focal length leaves it filling less than a third of an APS-C frame, so it suits long focal lengths, small pixels and good seeing.
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 103's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- NGC 663 1.7° away
- NGC 559 2.7° away
- NGC 457 Owl Cluster 2.9° away
- IC 63 Ghost of Cassiopeia 4.1° away
- IC 59 4.4° away
- NGC 896 6.4° away
Gear that suits M 103
M 103 is only 4.5′ across, so it stays small in any amateur telescope. The longest focal length gives it the most pixels.
- Celestron C8 OTA 2032 mm f/10: fills 17% of an APS-C frame's short side View at High Point Scientific
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