← ToolBox / 星轨拍摄时长

⏱️ Star Trail Exposure Time Calculator

Calculate star trail exposure time from focal length and sensor crop factor to control the length of star trails.

焦距 mm

裁切系数

传感器长边像素

可接受移动像素

500 法则：曝光秒数 ≤ 500 / (焦距 × 裁切系数)
NPF 更精确，考虑像素尺寸

用于星空摄影避免星点拖线。

📚 深度解析：星轨安全快门（500/NPF 法则）

500 法则

24mm 全幅：500/24 ≈ 20.8s，超过则星点拖线；想拉星轨故意用数分钟长曝。

NPF 更严

NPF ≈ (35×像元尺寸µm)/焦距，24mm、像元 4µm：≈ 35×4/24 ≈ 5.8s，比 500 法则更保守、点更圆。

Item	Formula / Rule	Source / Standard
Trail angle	Trail sweep = 15.04 ° per hour × exposure hours near the celestial equator	Meeus, Astronomical Algorithms, 2nd ed. 1998
500 rule	The longest untrailed frame follows roughly 500 ÷ (focal length × crop factor)	Meeus, Astronomical Algorithms, 2nd ed. 1998
Stacking strategy	Stacking 60 to 200 frames of 20 to 30 s balances noise against trailing	Reinhard et al., High Dynamic Range Imaging, 2nd ed. 2010