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Is the target worth it tonight? How high does it climb, how long to expose, do you need the filter?
Altitude above horizon NGC869 · Kempen (Niederrhein) · tonight
Very good: 84° high around 22:40. Ideal conditions.
How long to expose?
75 minutes
≈ 450 frames of 10 s · star cluster – needs less time
- 40 min – first usable result
- 75 min – recommended
- 150 min – really clean, little noise
Noise drops with the square root of total time: four times longer halves the noise. So doubling only gives 40 % less grain – but every minute helps.
Filter?
LP filter OFF
Star cluster: stars shine across the whole spectrum. A narrowband filter would only remove light and distort colours – leave it off.
Moon calendar Finding dark nights
Today: Waning crescent, 8 % illuminated – ideal for deep sky.
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Bars = moon illumination. The violet nights are dark enough for faint targets.