DCMT枢轴误差的光电测定  

The Photoelectric Measurement of the DCMT Pivot Error

作　　者：朱紫[1] 李志刚[1] 

机构地区：[1]中国科学院陕西天文台

出　　处：《陕西天文台台刊》1994年第0期70-76,共7页Publications of The Shaanxi Astronomical Observatiory

摘　　要：枢轴误差是影响天体位置测量精度的重要因素．对于现代子午环的高精度天体测量而言，枢轴误差的精确测定是必不可少的．利用ＤＣＭＴ的自校准光源的像．并采用Ｖ形光栅的光电扫描直接测定ＤＣＭＴ枢轴误差在赤经和赤纬上的分量．通过几次测量结果的比较表明．该方法具有很高的测量精度与重复必．The pivot error is an important factor for the accuracy of the stellar position determination.It is necessary to measure the pivot error in order to reakuze the high precise astrometry for a mordern meridian circle. The method of measuring the DCMT (Danish-Chinese Meridian Telescope) pivot error and the resalts are giren in this paper.For the DCMT,the main tube of the telescope is not movagle, only the objective fixed on the mian box is rotatable[4,5]. The main optical axis of the telescope is therefore fixed in the space. A photoelectric micrometer with a V-shaped slit is mounted on the main box in the place of the focal plane of the telescope[5]. A pin hole used for the self-calibration light source is on the slit plate (Fig. 2). The image of the light source, reflected by the main paraboloidal mirror of the optical centre of the telescope in the micrometer coordinate can be directly calculated from the position of S4(eq. (2)). The S4 image will move circularly in the viewing field of micrometer when the telescope is rotating, The variation of the optical centre position can be calculated via the movement of the S4 image. Its irregular part deviated from a circle is the pivot error. The pivot irregularity of the DCMT, measured with the photoelectric micrometer, is given in Fig. 3. The unit for the position measurement is the sampling interval (1 samp ling interval=0' 77325). We define that the telescope position is '0' when it point to the nadir, and it is increasing while the telescope rotates clockwise. The pivot constants and errors in the directions of right ascension and declination are independently calculated by means of the least squares fit. The pivot constants obtained from 4 inaependent measurements are given in Table 1, where x0 and y0 is the position of the average centre of the povot. The results show a good stability of the DCMT pivot. The pivot corrections are shown in Table 2 and Fig. 4. The correction values are less than 0'.4 in both of right ascansion and declination.

关 键 词：水平子午环 光电测量 枢轴误差 

分 类 号：P124[天文地球—天体测量]