From: PO2::"czdiatom@LCAC1.LORAS.EDU" "Dave Czarnecki" 1-MAR-1995 10:28:39.46 To: Multiple recipients of list DIATOM-L CC: Subj: coverslips To comment on the choice of which number coverglass to use for making diatom mounts: If at all possible, it is wise to use a number 1 1/2 coverglass (i.e., thickness of 0.17 mm) unless your optical system dictates otherwise. In most cases, the design of the objective lens is based in part on the optical power of the coverglass which is actually a lens element itself. When oil immersion is used, the effect of coverglass thickness is not usually as critical. However, the higher the NA of dry objectives, the more critical the thickness becomes. Whatever objective is used, it would be wise to check the last inscription engraved on it. If it reads /0.17, you should use a No 1 1/2 coverglass; if it reads /0, then the lens has been constructed to use no coverglass, e.g., in microbiological observations, immersion objectives are designed to directly observe immersion-oiled, stained specimens without a coversglass at all; if it reads /-, then coverglass thickness is not critical; if it reads some other number than 0.17, the number corresponds to the thickness (in mm) of the coverglass to be used. ****************************************************************************** * David B. Czarnecki Tel: (319) 588-7231 * * Curator, FW ALGAE CULTURE COLLECTION Fax: (319) 588-7964 * * Department of Biology Fax: (319) 588-7292 * * Loras College E-mail: * * Dubuque, Iowa 52004-0178 U.S.A. czdiatom@lcac1.loras.edu * ******************************************************************************