Csoeke-Poeckh A, Macqueen R M, Poland A I
Appl Opt. 1977 Apr 1;16(4):931-7. doi: 10.1364/AO.16.000931.
The stray radiance present in the field of view of the High Altitude Observatory's Skylab coronagraph has been measured from results obtained in orbit with two techniques. First, employing images of the lunar disk made near the time of solar eclipse, a comparison of the apparent contrasts recorded by the coronagraph of maria and highlands with those of previous studies, allows the determination of the magnitude of the stray radiance and its variation along a radius. Next, the azimuthal (position angle) variation was found through measurement of the change in the net radiance of a point in the coronal image, as the image (coronagraph) was rotated. From these measurements the stray radiance was found to be a maximum near the inner limit of the instrument field of view, variable in azimuth from 1.4 to 5.6 10(-9)B(O), where B(O) is the mean solar disk radiance. Further, the stray radiance was found to be a steep, decreasing function of distance along a radius, falling to a nearly uniform, azimuthally independent va ue of ~3.5 x 10(-10)B(O) in the outer field. In this latter region, the coronagraph stray radiance is well below a typical midtotality eclipse sky radiance of ~1.8 x 10(-9)B(O). Finally, the radiance of lunar maria and highlands (in units of 10(-10)B(O)) was determined to be 2.2 and 4.5, respectively, for the 30 June 1973 eclipse and 1.4 and 3.0, respectively, for the 24 December 1973 eclipse, in agreement with other observers.
利用两种技术在轨道上获得的结果，对高空天文台“天空实验室”日冕仪视场中的杂散辐射进行了测量。首先，利用日食期间拍摄的月球圆盘图像，将日冕仪记录的月海和高地的表观对比度与先前研究的结果进行比较，从而确定杂散辐射的大小及其沿半径的变化。其次，通过测量日冕图像中某一点的净辐射在图像（日冕仪）旋转时的变化，发现了方位角（位置角）的变化。通过这些测量发现，杂散辐射在仪器视场的内边缘附近最大，方位角变化范围为1.4至5.6×10⁻⁹B₀，其中B₀是太阳圆盘的平均辐射亮度。此外，还发现杂散辐射沿半径方向是距离的陡峭递减函数，在外场中降至约3.5×10⁻¹⁰B₀的几乎均匀、方位角无关的值。在后一个区域，日冕仪的杂散辐射远低于典型的全食中期日食天空辐射亮度约1.8×10⁻⁹B₀。最后，1973年6月30日日食时，月海和高地的辐射亮度（单位为10⁻¹⁰B₀）分别确定为2.2和4.5，1973年12月24日日食时分别为1.4和3.0，与其他观测者的结果一致。
