白天CCD观星可探测极限星等值分析
Analysis of the detectable stellar magnitude limit using CCD camera in daytime sky background
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摘要: 介绍了白天天空背景下，在大气层内用CCD探测恒星可探测极限星等值的计算方法。根据恒星和白天大气背景辐射的对比度，计算和分析了3°3°视场下，可探测星等极限值随观测高度、太阳天顶角、波段和恒星光谱类型的变化情况。结果表明：可探测星等极限值随观测高度和太阳天顶角的增加接近线性增加；对K和M类恒星，长波波段可探测星等极限值高。在25 km高度、3°3°视场、太阳视线20°以外，可探测星等极限值可达到6.3等。Abstract: The method to estimate the detectable stellar magnitude limit in daytime sky background is introduced. Based on the results of the contrast of star to sky background in daytime, the detectable stellar magnitude limits are computed and analyzed as functions of observing heights, solar zeniths angle, wavebands and stellar spectral types for 3°3° field of view. The results show that the detectable stellar magnitude limits linearly increase with observing height and solar zenith angle. A higher detectable stellar magnitude limit is obtained by using longer wavelength bands for stars of K and M types. For the case of 25 km observing altitude, the field of view of 3°3°, the maximum detectable stellar magnitude limit is 6.3 when the sun is out of 20° line of sight.
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Key words:
- detectable stellar magnitude limit /
- stellar /
- sky background /
- ccd /
- signal to noise ratio
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