JOHN'S LODGE, NEAR AYLESBURY, 25-7-'59.
MY DEAR MISS MITCHELL: ...

We are much pleased to hear of your acquisition of an equatorial instrument under a revolving roof, for it is a true scientific luxury as well as an efficient implement.

The aperture of your object-glass is sufficient for doing much useful work, but, if I may hazard an opinion to you, do not attempt too much, for it is quality rather than quantity which is now desirable.

I would therefore leave the multiplication of objects to the larger order of telescopes, and to those who are given to sweep and ransack the heavens, of whom there is a goodly corps.

Now, for your purpose, I would recommend a batch of neat, but not over-close, binary systems, selected so as to have always one or the other on hand.
I, however, have been bestirring myself to put amateurs upon a more convenient and, I think, a better mode of examining double stars than by the wire micrometer, with its faults of illumination, fiddling, jumps, and dirty lamps.