ISBN: 9781153772563

Excerpt: ...and no scratches of any kind. In washing large objectives in water I generally use a ''tub'' and stand the lenses on their edge. When thoroughly washed the… More...

Excerpt: ...and no scratches of any kind. In washing large objectives in water I generally use a ''tub'' and stand the lenses on their edge. When thoroughly washed they are taken out and laid on a bundle of cheese cloth and several pieces of the same used to dry them. I think it best not to leave them to drain dry; better take up all moisture with the cloth, and vigorous rubbing will do no harm if the surfaces have no abrading material on them. I have yet to injure a glass cleaned in this way. This process may seem a rather long and tedious one, but it is not so in practice, and it pays. In some places objectives must be frequently cleaned, not only because they become covered with an adherent dust, but because that dust produces so much diffused light in the field as to ruin some kinds of telescope work. Mr. Hale of the Kenwood Observatory tells me he cannot do any good prominence photography unless his objective has a clean surface; indeed every observer of faint objects or delicate planetary markings knows full well the value of a dark field free from diffused light. The object-glass maker uses his best efforts to produce the most perfect polish on his lenses, aside from the accuracy of the curves, both for high light value and freedom from diffused light in the field, and if the surfaces are allowed to become covered with dust, his good work counts for little. If only the front surface needs cleaning, the method of cleaning with cheese cloth, soap and water, as described above, answers very well, but always throw away the first and, if necessary, the second cloth, then wipe dry with a third or fourth cloth; but if the surfaces all need cleaning I know of no better method than that of taking the objective out of its cell, always using abundance of soap and water, and keep in a good humor. Richard Threlfall, Books, History, On Laboratory Arts Books>History, General Books LLC<

ISBN: 9781153772563

Excerpt: ...and no scratches of any kind. In washing large objectives in water I generally use a ''tub'' and stand the lenses on their edge. When thoroughly washed the… More...

Excerpt: ...and no scratches of any kind. In washing large objectives in water I generally use a ''tub'' and stand the lenses on their edge. When thoroughly washed they are taken out and laid on a bundle of cheese cloth and several pieces of the same used to dry them. I think it best not to leave them to drain dry; better take up all moisture with the cloth, and vigorous rubbing will do no harm if the surfaces have no abrading material on them. I have yet to injure a glass cleaned in this way. This process may seem a rather long and tedious one, but it is not so in practice, and it pays. In some places objectives must be frequently cleaned, not only because they become covered with an adherent dust, but because that dust produces so much diffused light in the field as to ruin some kinds of telescope work. Mr. Hale of the Kenwood Observatory tells me he cannot do any good prominence photography unless his objective has a clean surface; indeed every observer of faint objects or delicate planetary markings knows full well the value of a dark field free from diffused light. The object-glass maker uses his best efforts to produce the most perfect polish on his lenses, aside from the accuracy of the curves, both for high light value and freedom from diffused light in the field, and if the surfaces are allowed to become covered with dust, his good work counts for little. If only the front surface needs cleaning, the method of cleaning with cheese cloth, soap and water, as described above, answers very well, but always throw away the first and, if necessary, the second cloth, then wipe dry with a third or fourth cloth; but if the surfaces all need cleaning I know of no better method than that of taking the objective out of its cell, always using abundance of soap and water, and keep in a good humor. Richard Threlfall, Books, History, On Laboratory Arts Books>History <

ISBN: 9781153772563

No Synopsis Available On Laboratory Arts, 9781153772563, Book, Textbook Books > Art > Art History and Criticism Paperback, General Books

ISBN: 9781153772563

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