Oneof the first things which the^owner of a lens, either of a telescope^or of a photographic camera, wants^to know, is how to clean it. Mere^dust can be removed with a camel's^hair brush, there being nowhere^found any opinions forbidding that.^But in the changes of an ordinary^climate a lens will get considerably^blurred with filmy accumulations,^even though it may never have been^touched by the hand or brought in^contact with grease in any form. Yet^satisfactory knowledge of how to^clean a lens seems to be always diffi^^cult to get. A practical photographer^once said that if a finger mark should^come upon a lens which he valued^very highly he would immediately^return it to its European manufac^^turers. Ho would not dare to touch^it himself.
Lenscleaning is simple and easy.^Popular Astronomy contains a paper^on this subjet^ by one of the first of^authorities, Mr. J. A. Brashear, one^of the leading telescope makers liv^^ing. Mr. Brashear disposes of the^common advice that on ^no account^should two glasses forming an ob^^jective be separated or taken apart^by an amateur.^ Any one may ven^^ture upon taking an objective apart^and cleaning it, provided he will only^do it carefully.
