Lacock Abbey

Feb 11/54

Dear L^d Rosse

Since I wrote last, ^<1> some additional remarks have occurred to me which may possibly be useful.

Your object is not so much to obtain a large image of the moon, but a perfect one, because however small it is it can subsequently be magnified to any size by photographic means, in a camera constructed for that special purpose. In order that the image sh^d be perfect it must be obtained with great rapidity which can be done in 2 principal ways, the first by augmenting the sensibility of the chemical preparation, a subject we have already discussed.

The 2^d way is of course, by augmenting the intensity of the lunar light, which is likely to be successful not only because a strong light acts more rapidly than a weak one of the same kind, but also because its rapidity of action increases in a higher ratio than the mere quantity of light. I would therefore propose to intercept by a glass lens the cone of light reflected from your large mirror, and thus cause it to form a small but intensely light image of the moon, from 6 to 10 times smaller in diameter than that which the mirror would form, if used alone. The rapidity of action would I think then be quite satisfactory, at best the experiment is easily tried –

Thanks for your letter of the 8^th. ^<2> I hope you will follow out so important an enquiry which I am convinced can be successfully done in some way or other.

I remain
Yours very truly

H. F. Talbot

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Notes:

1. See Doc. No: 06914.

2. Doc. No: 06915.