月球南極莫雷環型山不同取樣度效果比較 Comparing image scales on Lunar South Pole Moretus Crater
分類: 器材 Equipment, 觀測報告 Observations
2025-10-05
Lunar Moretus crater - Savio Fong, Galaxy Scientific Group Tai Mei Tuk observatory
月球莫雷環型山 - 方社長，攝於星河科研社大美督天文台
在9月14日一個視寧度頗理想的早上，試以直焦及加上2x巴羅鏡拍攝兩段月面南極大特寫影片，同時以最優化的參數後期處理，按理後者的每像素取樣度已超出理論上實效，同時要在曝光時間、增益及幀度等付出代價，但似乎仍有些許增益。奈奎斯特定理指出取樣度應是訊息的2倍，一般說法是二維影像要提升至3倍，但很明顯目前的每像素0.05"取樣度，已遠超視寧度、望遠鏡成像甚至其他如調焦誤差等的量度。所以理論歸理論，實踐仍是最佳方法。
On the morning of September 14th, under fairly good seeing, I captured two close‑up videos of the lunar south pole—one at prime focus and one with a 2× Barlow lens—then processed them with optimized settings. Although the latter setup exceeded the theoretical effective sampling rate and required compromises in exposure, gain, and frame rate, it still showed a slight improvement in details. According to the Nyquist theorem, sampling should be twice the signal frequency, or about three times for 2‑D imaging. Yet the current 0.05″ / pixel scale clearly surpasses the limits of seeing, optics, and focus accuracy. In the end, theory aside, practical testing still proves best.
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Right image
2025-09-14 04:31
Celestron EdgeHD14
SkyWatcher EQ8R Pro
ZWO ASI678MM
image scale 0.11"/pixel
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Left image
2025-09-14 05:08
same setup + Carl Zeiss Abbe Barlow 2x
image scale 0.05"/pixel
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