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《天文学报》2017,(2)
云对天文观测具有重要影响,云量是衡量天文台址质量的重要指标.位于姚安天文观测站的红外云量仪,用于获取实时的全天高空间分辨率云图.结合空间碎片的实际观测,严格按照天文夜对累积1yr(2015-08-01—2016-07-31)的夜间云量数据进行统计和分析.姚安站的年平均夜间云量为4.42成,年天文可用夜为236个,其中测光夜98个,半测光夜44个,光谱夜94个.云量具有明显的两季特征:5月至10月间为雨季,云量显著增多,其中7月份观测条件最差;11月至次年4月为旱季,云量较少,每月的天文可用夜均在23个以上,其中1月份的测光夜最多,3月份的天文可用夜最多.结合云层对天文观测的威胁程度,统计不同云量的总时间和每月的云量分布情况,评估观测站的气象条件,为合理安排观测计划提供参考. 相似文献
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对高美古选址云量观测可靠性的讨论 总被引：1，自引：0，他引：1
通过对新月和满月和夜期间测光夜数和云量统计数的比较,高美古的天文测光夜数和可用夜数与丽江县的气象晴日数的比较,以及在同样的以观测时间高美古和丽江县云量观测值的比较,本文对高美古选址云量观测可靠性的有关方面进行了讨论。 相似文献
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通过对新月和满月夜期间测光夜数和云量统计数的比较, 高美古的天文测光夜数和可用夜数与丽江县的气象晴日数的比较, 以及在同样的观测时间高美古和丽江县云量观测值的比较, 本文对高美古选址云量观测可靠性的有关方面进行了讨论 相似文献
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根据１９９４年６月—１９９５年１２月期间在新疆天山南坡的奎先达坂进行的云量观测结果和邻近的巴仑台气象站的多年气候观测资料作统计分析，作者推断奎先达坂的天文可用小时数和天文夜数均可与目前世界上最优良的天文台址相比。 相似文献
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本文通过对ＮＯＡＡ－１０，１１两颗气象卫星１９８９年５月至１９９０年４月的云图资料，在作等经纬度投影处理和定标，定位订正的基础上，利用红外域值方法，对东经９９°—１０４°，北纬２３．５°—２８．５°云南区域内３１个天文台址侯选点的云量进行了统计和计算，得到几个云量最少的候选点。此外，我们还对卫星云图ＣＣ≤３的晴日晴夜和三十年地面气象观测资料中ＣＣ≤２的晴天数作了相关分析，发现它们之间具有很好的相关性。云图和地面资料综合分析表明：（１）永仁的俄尼刀博，姚安的老官山，元谋气象区的白露，祥云的大营后山，宾川的小鸡山，华坪的蘑菇山，宁蒗的他尔布子都是较理想的候选点。（２）俄尼刀博，老官山和白露可用夜（ＣＣ≤３）预计可超过２５０夜。因此应列为下一步选址的重点。 相似文献
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使用1994—2007年在1．56m反射望远镜CCD照相机拍摄的资料，测定了上海天文台余山工作站夜天亮度的变化。由于上海城市的发展，佘山工作站的夜天亮度在V波段从每平方角秒约19mag变到15．8mag，也就是说，夜天亮度自1994年以来变亮了约20倍。国际上优良台站的夜天亮度在V波段等于或暗于21．5mag。上述夜天亮度是优良台站的200多倍。现在在佘山工作站使用1．56m反射望远镜对暗于V=14mag的星做精确测光已经很困难了。 相似文献
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V. S. Shevchenko K. N. Grankin M. A. Ibragimov S. Yu. Melnikov S. D. Yakubov 《Astrophysics and Space Science》1993,202(1):121-136
Light curves of 78 Herbig Ae/Be stars were studied by digital analysis methods. Twenty-five thousand photoelectricUBVR observations of these stars were made by the authors in 1978–1990. A star was usually observed once a night. The stars were observed between 70 and 770 nights and on average each star was observed at more than 300 nights. The mean epoch for a star is 5 years. A morphologic classification of the light curves is suggested. The method of digital analysis are briefly described. To estimate the reliability of cyclic phenomena discovered in our study, a large number of them has been examined. 相似文献
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Jorma J. Riihimaa 《Earth, Moon, and Planets》1988,42(3):303-308
Dynamic spectra of Jovian noise storms at 20–30 MHz are compared with the scintillation indices of the overhead radio source Cas A at 45 MHz. Of six intense storms observed, four that displayed broadband lane patterns occurred on nights when the scintillation index of Cas A was unusually low, while two that did not display broadband lane structures occurred on nights when the scintillation index was high. It is evident that the scintillation boundary was located north of Oulu on the nights when the broadband lane patterns occurred and was therefore not involved in the lane-producing mechanism. 相似文献
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N.R. Thomson 《Planetary and Space Science》1976,24(5):447-454
Whistler-mode signals received at Wellington, New Zealand, from NLK in Seattle are typically doppler shifted ~0.1 Hz from the transmitter frequency, implying a changing phase path. At least during quiet times, this is shown to be primarily caused by (inward) drifts of the whistler duct rather than by changing electron density along the path. The mechanism is established by measuring the ratio of the changes in phase and group times for the path during the nights studied. On one of these nights, the drift is further confirmed by measurements on natural whistlers. 相似文献
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Josef Gochermann Walter F. Wargau Claus Tappert Theodor Schmidt-Kaler Robert S. Stobie Fred Marang Greg Roberts Francois G. van Wyk Peter Rucks 《Experimental Astronomy》1999,9(1):1-15
In order to decide whether the seeing conditions at SAAO/Sutherland justify the erection of a 3.5 m telescope and also to compare Sutherland with the Gamsberg/Namibia site, a seeing campaign covering 15 months has been carried out. For direct comparison with the results of the seeing campaign at Gamsberg twenty years before the same QUESTAR telescope was employed. The seeing is determined by the scattering of the star-trail exposed on a film in the focal plane of the telescope. The campaign commenced in February 1992. Up to May 1993, data for 204 nights, that is 47.3% of the total number of nights, were collected. Due to wind speeds above 30 km h-1, 25 out of the 204 nights were not considered in the final reduction. The useful 179 nights are evenly distributed over the campaign period. The median seeing value for the whole period is = 0.52. There are differences during the year: the best season gives = 0.42, the worst = 0.67. Each night was divided into three intervals, although data for each of the three intervals were not always available. Generally, there is an improvement in the seeing during the course of a night. The results are compared to the seeing values of Gamsberg/Namibia and ESO/La Silla. 相似文献
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C. O'Sullivan R. M. Redfern N. Ageorges H.-C. Holstenberg W. Hackenberg T. Ott S. Rabien R. Davies A. Eckart 《Experimental Astronomy》2000,10(1):147-156
In this article we investigate the short-term characteristics of the sodium layer and their implications for laser guide star systems. We report measurements of sodium density andcentroid-height variations on timescales of 100 ms upwards. Significant centroid-height variations on short timescales may necessitate frequent refocussing of the beam and wavefront sensor system.We present results from observations of the mesospheric sodium layer taken at the Max Planck observatory in Calar Alto, Spain in September 1997 and August 1998. We describe our experiment which uses the resonant optical backscatter of 589.2 nm laser light from the upper atmosphere as a measure of sodium abundance.Short-term variations are dominated by the formation of dense sporadic layers in the normal sodium layer. Measurements were made on 3 nights in 1997 and on 2 nights in 1998. Somewhat unexpectedly for a mid-latitude site, sporadic sodium layers were seen on 4 of these 5 nights. One of the sporadic layers was observed for its duration. The 2 km wide layer reached a maximum intensity of approximately two and a half times that of the background layer and could be distinguished from the background for over five hours. Centroid height variations of up to 400 m were observed on timescales of 1–2 min. In 1998 we were sensitive to variations of 5% or more in total sodium abundance on timescales of 100 ms upwards. We found no evidencefor variations of this level on these short timescales. 相似文献
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R.H. Wiens 《Planetary and Space Science》1974,22(7):1059-1065
Filter photometer data on OH intensities reveal a midnight maximum of the average ratio I(8?3)/I(5?0) in midwinter at Adi Ugri. This midnight maximum is a regular feature on those nights when the intensity also goes through a midnight maximum. An interpretation in terms of a dynamic model is presented. On nights of steadily decreasing OH intensity, the pre-midnight ratio variation is uncertain. 相似文献
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Six nights of BVR photometry and three nights of R photometry were collected over a month-long period shortly after the Cassini encounter with Hyperion on September 24 2005. Our observations were designed to help constrain the rotational state of the chaotically rotating satellite. Fourier analysis of our lightcurve data yields three possible periods: 10.2±0.2, 13.9±0.2, and 19.7±0.4 days. Our B-V and V-R colors agree well with previous ground-based and Voyager 2 measurements. 相似文献
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J. S. Mikhail B. B. Baghos M. Y. Tawadrous Y. E. Helali H. Awad KH. I. Khalil M. El-Saftawe M. Ibrahim 《Earth, Moon, and Planets》1995,70(1-3):143-149
Clear air atmospheric transparency of eight nights at Helwan Observatory site during autumn period of 1987 have been determined using the yellow filter GG5. The prevailing atmospheric transmission extends to 58%. A comparison with previous values obtained with the same filter and site during autumn period of 1963 shows a considerable decrease at the present years in the clear air transmission of the site of Helwan. This can be attributed to the aerosol pollution of the site caused mainly by the increase of the industrial centers at Helwan Zone. Clear air atmospheric transparency values at the beginning of winter season and at spring season are also given. 相似文献
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P. R. Vishwanath 《Journal of Astrophysics and Astronomy》1987,8(1):69-78
The Ooty data on VHE (> 600 GeV) γ-rays from the Crab pulsar have been used to look at possible emission on three different
timescales,viz. years, minutes and hours. When averaged over three years of observation, there is no significant time-averaged emission.
But interesting aspects are revealed when the data are subdivided into miniruns of one-minute duration. Minutes with moderate
γ-ray activity were isolated with a κ2 analysis. The summed phasogram of such minutes shows two strong peaks coinciding with the radio main pulse and the interpulse
respectively. The probability that these are due to chance is small. The phasogram has a bimodal distribution which indicates
some emission from the middle region between the two phases. In general, there is no significant emission on the timescale
of a few hours. However, the main pulse, as well as the bimodal distribution, were seen also in the total data of two nights
of simultaneous observation at two sites during 1984–1985. 相似文献
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Naosuke Sekiguchi 《Earth, Moon, and Planets》1980,23(1):99-107
The photometric observations of the lunar surface during lunar eclipses were carried out on four nights between 1972 to 1978, using the 91 cm reflector of the Dodaira Station of the Tokyo Astronomical Observatory. The photometry was performed in B-, V-, and R-colours, and arranged in accordance with the angular distance from the centre of the Earth's shadow. The results do not show any large systematic differences between the four nights, showing no support for Danjon's proposition. 相似文献