共查询到20条相似文献,搜索用时 375 毫秒
1.
2.
本文给出了用簿型CCD作为探测器的Coude高色散光谱系统的光路,机械调整装置,可用色散,一次可摄波段,光栅转角的计算,滤光片的选择。 从1987年11月起,对该系统进行了一年的试观测,获得了较好的结果,本文给出了从3900(?)—11000(?)的观测结果。观测结果表明可提高1.5—3个星等。 相似文献
3.
4.
5.
6.
本文讨论了光纤用于一米望远镜Coude摄谱仪中代替从第一面镜到Coude狭缝之间传光系统的损光情况并进行了比较。 相似文献
7.
8.
《天文学报》2014,(3)
在天文底片数字化工作中,利用高端商用扫描仪可能是一条简单而有效的途径.针对1988年云南天文台1m RCC(Ritchey Chretien Coude)望远镜拍摄的6张土星卫星天文底片,探讨了利用Epson公司10000XL商用扫描仪的底片数字化技术和数据处理方法.基于底片数字化图像和UCAC2(The Second US Naval Observatory CCD Astrograph Catalog)参考星表,重新测量土星卫星的位置.通过与IMCCE(Institut de Mecanique Celeste et de Calcul des Ephemerides)提供的土卫历表位置比较表明,土星卫星的定位结果在赤经和赤纬方向上的残差均值分别为0.056″和0.009″,在赤经和赤纬方向上残差的标准偏差分别为0.106″和0.089″. 相似文献
9.
一个巨型望远镜方案 总被引:4,自引:0,他引:4
提出一个有特色的巨型望远镜(FGT)方案.其主镜口径为30米,主焦比为1.2,由1095块圆环形子镜构成.采用地平式装置.光学系统包括Nasmyth系统、折轴(Coude)系统和一个大视场系统.提出一个由4个镜面组成的新的Nasmyth系统,在约10′的视场范围内像斑小于爱里斑,达到衍射极限.比传统的Nasmyth系统的衍射极限视场大得多.可在这样的大视场内同时作好几个小区域的衍射极限的观测.当由Nasmyth系统转换到折轴系统和大视场系统时,采用主动光学技术改变子镜的面形、倾斜和平移,产生一个新的主镜面形,使折轴系统和大视场系统都能得到很好的像质.大视场系统的视场直径25′,场曲轻微,并有可能校正大气色散.给出了子镜面形和位置的公差,并讨论了望远镜的装置和结构,方案中的特色和创新对未来大望远镜的研制有普遍意义. 相似文献
10.
介绍与LAMOST低色散多目标光纤光谱仪五种方案对应的CCD照相机,每个照相机都给出了结构示意图和像斑直径的RMS值,并从多方面分析了它们各自的优缺点,章末节给出了低色散光谱仪最后的光学设计方案。 相似文献
11.
L. S. Marochnik 《Astrophysics and Space Science》1983,89(1):61-75
The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R ⊙≈0.03, where ΔR=R c ?R ⊙,R c is the corotation distance from the galactic center andR ⊙ is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT 1≈4.6×109 yr,T 2?108 yr,T 3?106 yr detected by the radioactive decay of various nuclides. The timescaleT 1 (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT 2 is the presolar cloud lifetime in a spiral arm.T 3 is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found. 相似文献
12.
Yoshio Kubo 《Celestial Mechanics and Dynamical Astronomy》1982,26(1):97-112
Perturbations in the motion of the Moon are computed for the effect by the oblateness of the Earth and for the indirect effect of planets. Based on Delaunay's analytical solution of the main problem, the computations are performed by a method of Fourier series operation. The effect of the oblateness of the Earth is obtained to the second order, partly adopting an analytical evaluation. Both in longitude and latitude are found a few terms whose coefficient differs from the current lunar ephemeris based on Brown's theory by about 0.01. While, concerning the indirect effect of planets, several periodic terms in the current ephemeris seem to have errors reaching 0.05.As for the secular variations of
and due to the figure of the Earth and the indirect effect of planets, the newly-computed values agree within 1/cy with Brown's results reduced to the same values of the parameters. Further, the accelerations in the mean longitude,
and caused by the secular changes in the eccentricity of the Earth's orbite and in the obliquity of the ecliptic are obtained. The comparison with Brown shows an agreement within 0.3/cy2 for the former cause and 0.02/cy2 for the latter. An error is found in the argument of the principal term for the perturbations due to the ecliptic motion in the current ephemeris.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980. 相似文献
13.
E. L. Ruskol 《Earth, Moon, and Planets》1973,6(1-2):190-201
It is suggested that the overall early melting of the lunar surface is not necessary for the explanation of facts and that
the structure of highlands is more complicated than a solidified anorthositic ‘plot’. The early heating of the interior of
the Moon up to 1000K is really needed for the subsequent thermal history with the maximum melting 3.5 × 109 yr ago, to give the observed ages for mare basalts. This may be considered as an indication that the Moon during the accumulation
retained a portion of its gravitational energy converted into heat, which may occur only at rapid processes. A rapid (t < 103 yr) accretion of the Moon from the circumterrestrial swarm of small particles would give necessary temperature, but it is
not compatible with the characteristic time 108 yr of the replenishment of this swarm which is the same as the time-scale of the accumulation of the Earth. It is shown that
there were conditions in the circumterrestial swarm for the formation at a first stage of a few large protomoons. Their number
and position is evaluated from the simple formal laws of the growth of satellites in the vicinity of a planet. Such ‘systems’
of protomoons are compared with the observed multiple systems, and the conclusion is reached that there could have been not
more than 2–3 large protomoons with the Earth. The tidal evolution of protomoon orbits was short not only for the present
value of the tidal phase-lag but also for a considerably smaller value.
The coalescence of protomoons into a single Moon had to occur before the formation of the observed relief on the Moon. If
we accept the age 3.9 × 109 yr for the excavation of the Imbrium basin and ascribe the latter to the impact of an Earth satellite, this collision had
to be roughly at 30R, whereR is the radius of the Earth, because the Moon at that time had to be somewhere at this distance. Therefore, the protomoons
had to be orbiting inside 20–25R, and their coalescence had to occur more than 4.0x109 yr ago. The energy release at coalescence is equivalent to several hundred degrees and even 1000 K. The process is very rapid
(of the order of one hour). Therefore, the model is valid for the initial conditions of the Moon. 相似文献
14.
In this paper we first emphasize why it is important to know the successive zonal harmonics of the Sun's figure with high
accuracy: mainly fundamental astrometry, helioseismology, planetary motions and relativistic effects. Then we briefly comment
why the Sun appears oblate, going back to primitive definitions in order to underline some discrepancies in theories and to
emphasize again the relevant hypotheses. We propose a new theoretical approach entirely based on an expansion in terms of
Legendre's functions, including the differential rotation of the Sun at the surface. This permits linking the two first spherical
harmonic coefficients (J
2 and J
4) with the geometric parameters that can be measured on the Sun (equatorial and polar radii). We emphasize the difficulties
in inferring gravitational oblateness from visual measurements of the geometric oblateness, and more generally a dynamical
flattening. Results are given for different observed rotational laws. It is shown that the surface oblateness is surely upper
bounded by 11 milliarcsecond. As a consequence of the observed surface and sub-surface differential rotation laws, we deduce
a measure of the two first gravitational harmonics, the quadrupole and the octopole moment of the Sun: J
2=−(6.13±2.52)×10−7 if all observed data are taken into account, and respectively, J
2=−(6.84±3.75)×10−7 if only sunspot data are considered, and J
2=−(3.49±1.86)×10−7 in the case of helioseismic data alone. The value deduced from all available data for the octopole is: J
4=(2.8±2.1)×10−12. These values are compared to some others found in the literature.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005238718479 相似文献
15.
B. P. Kondratyev 《Solar System Research》2013,47(1):1-10
A two-component theoretical model of the physical libration of the Moon in longitude is constructed with account taken of the viscosity of the core. In the new version, a hydrodynamic problem of motion of a fluid filling a solid rotating shell is solved. It is found that surfaces of equal angular velocity are spherical, and a velocity field of the fluid core of the Moon is described by elementary functions. A distribution of the internal pressure in the core is found. An angular momentum exchange between the fluid core and solid mantle is described by a third-order differential equation with a right-hand side. The roots of a characteristic equation are studied and the stability of rotation is proved. A libration angle as a function of time is found using the derived solution of the differential equation. Limiting cases of infinitely large and infinitely small viscosity are considered and an effect of lag of a libration phase from a phase of action of an external moment of forces is ascertained. This makes it possible to estimate the viscosity and sizes of the lunar fluid core from data of observations. 相似文献
16.
M. V. Samokhin 《Astrophysics and Space Science》1979,62(1):159-183
In order to understand the reason of the existence of the electric field in the magnetosphere, and for the theoretical evaluation of its value, it is necessary to find the solution of the problem of determination of the magnetosphere boundary form in the frameworks of the continuum medium model which takes into account part of the magnetospheric plasma movement in supporting the magnetospheric boundary equilibrium. A number of problems for finding the distribution of the pressure, the density, the magnetic field and the electric field on the particular tangential discontinuity is considered in the case when the form of discontinuity is set (the direct problem) and a number of problems for finding the form of the discontinuity and the distribution of the above-mentioned physical quantities on the discontinuity is considered when the law of the change of the external pressure along the boundary is set (for example, with the help of the approximate Newton equation). The problem which is considered here, which deals with the calculation of the boundary form and with the calculation of the distribution of the corresponding physical quantities on the discontinuity of the 1st kind for the compressible fluid with the magnetic field with field lines which are perpendicular to the plane of the flow in question, concerns the last sort of problems. The comparison of the results of the calculation with the data in the equatorial cross-section of the magnetosphere demonstrates that the calculated form of the boundary, the value of the velocity of the return flow and the value of the electric field on the magnetopause, agree satisfactorily with the observational data. 相似文献
17.
18.
19.