Recoating of Reflection Reducing Film and the Exploitation for the Photographic Lenses

In order to prepare the solar observation during the solar maximum of the 22nd cycle, the reflection reducing flim was recoated for the eleven photographic lenses of the solar spectrograph at Yunnan Observatory in 1988. The status of exploitation is given for the spectrograph after the recoating. The transmissivity of these lenses is only 77%-84% before and 92%-98%after recoating, i.e. the t ransmissivi ty of the lenese is increased 14%-26%. The exposure time of the photograph of the spectrograph is only half of that before the recoating . Thses lenses have been used for about 8 years since they were recoated.