光子计数测微器和视频CCD

Photon Counting Micrometer and Video CCD

介绍了低纬子午环上原设计的光子计数测微器的结构和观测方式，并针对目前仪器的具体状态，说明了为什么这一测微器不能采用，而用视频ＣＣＤ替代它，文中还叙述了采用视频ＣＣＤ的观测方式和有关参数的测定方法。

The structure and observational method of the photon counting slotted micrometer are proposed in this paper.The micrometer is made up of a piece of slotted plate and a photomultiplier.Three groups of slits are cutted on the plate:the first is of the shape of lambda in Greek character lambda used for meridian amimuth observation,including simultaneous observation of the stellar passing hour and zenith distance,and the observation of the optical axis change.The second is 16 horizontal slits used for the determination of the stellar zenith distance at the moment the star passes the prime vertical.The third is one vertical slit used for the determination of the time when a star passes the prime vertical.The slotted plate is driven by a stepper motor to scan the star image back and forth.The photon counting micrometer is replaced by a video CCD for regular trial observation and as a test for the equipment of one scientific CCD,because the micrometer transmission in the instrumental vertical angle transmission mechanism is dull,and the telescope is ont able to observe regularly since the optical axis changes greatly as the telescope points to different vertical distance and the first group of slits cannot scan the star image every time.Besides,this micrometer is considered to be used only to examine the instrumental precision.The video CCD is fixed in the course of observation,recording a picture every forty milliseconds,or one hundred pictures within four seconds,resulting in simultaneously after smoothing treatment the moment and stellar zenith distance when a star passes through the meridian or prime vertical. Thus only the limiting magnitude decreases from twelve designed before to seven,it does not influence the examination of instrumental observation precision and the judgement on whether the scientific CCD may be equipped.