A radio determination of the time of the New Moon
A radio determination of the time of the New Moon
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DOI：
10.1093/mnras/stt2476
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发表时间：
2013-12
影响因子：
4.8
通讯作者：
Y. Hafez;L. Trojan;F. H. Albaqami;A. Almutairi;R. Davies;C. Dickinson;L. Piccirillo
中科院分区：
文献类型：
--
作者：
Y. Hafez;L. Trojan;F. H. Albaqami;A. Almutairi;R. Davies;C. Dickinson;L. Piccirillo
观测和探测新月日落对于基于农历的社区来说非常重要。传统上这是通过目视观察来进行的。我们提出了一种无线电方法，它可以使月球相对于太阳的可见度更高，从而使我们能够比目视观测更接近太阳的距离来检测月球。我们首先比较月球和太阳在可能的频率范围内的相对亮度，发现 5-100 GHz 的范围是合适的。下一个考虑因素是水蒸气和氧气引起的大气吸收/发射作为频率的函数。这一点尤其重要，因为相关观测都在地平线附近。我们表明~10 GHz 的频率对于该计划是最佳的。我们设计并建造了一台半高全宽分辨率为 0. 6 且旁瓣较低的望远镜，以展示这种方法的潜力。 2012年5月21日新月时，太阳/月亮亮温比为72.7±2.2，结合当天观测到的太阳黑子数量，与文献预测相符。月球在距离太阳约 2° 的地方很容易被探测到。我们在世界标准时间 16 小时 36 分钟的观测表明，月球距离太阳最近的时间是早 16 小时 25 分钟；这是2012年5月21日世界标准时间0时00分的日环食。
SightinganddetectionoftheNewMoonatsunsetisofimportancetocommunitiesbasedonthe lunar calendar. This is traditionally undertaken with visual observations. We propose a radio method which allows a higher visibility of the Moon relative to the Sun and consequently gives us the ability to detect the Moon much closer to the Sun than is the case of visual observation. We first compare the relative brightness of the Moon and the Sun over a range of possible frequencies and find the range 5‐100 GHz to be suitable. The next consideration is the atmospheric absorption/emission due to water vapour and oxygen as a function of frequency. This is particularly important since the relevant observations are near the horizon. We show that a frequency of ∼10 GHz is optimal for this programme. We have designed and constructed a telescope with a full width at half-maximum resolution of 0. 6 and low sidelobes to demonstrate the potential of this approach. At the time of the 2012 May 21 New Moon, the Sun/Moon brightness temperature ratio was 72.7 ± 2.2 in agreement with predictions from the literature when combined with the observed sunspot numbers for the day. The Moon would have been readily detectable at ∼2 ◦ from the Sun. Our observations at 16 h 36 min UTindicated that the Moon would have been at closest approach to the Sun 16 h 25 min earlier; this was the annular solar eclipse of 00 h 00 min UT on 2012 May 21.