Athenæum. May 4/ 51
Dear Sir
For the observations of Honolulu I refer you to the french newspaper Le National of April 23 – I am much obliged for a Copy of the Suggestions – Of the cities and places mentioned only one is accessible by railway, namely Warsaw, and it is therefore probably that most observers and amateurs will select it. I suppose the journey might be made conveniently in a week (the railway time tables give 3 ½ days – which theoretical time may be doubled in practice). You do not say that you are going Yourself. I think the Suggestions embrace rather too many points – I beg to observe that the experiment proposed in page 10 appears to me to be fallacious. I have no doubt that the title page will be easily read by the remaining light of the sky exclusive of any assistance from the light of the Corona. Now as to the point whether a photographic image can be obtained, without the necessity of having the telescope moved by clockwork or otherwise, which would be highly inconvenient except in a fixed Observatory what amount of displacement of the image would be tolerable on a Daguerreotype plate? Might we allow a displacement of 1/100 of an inch? I find by a rough mental calculation that the image of the Sun in Ld Rosse’s telescope moves 1/100 inch in about 1/5 of a second. Which length of time would be undoubtedly sufficient to obtain an image with that telescope, nor does it appear Doubtful that the experiment might be made to succeed with any good telescope. Red light affects the photographic plates so little that I fear the red mountains would not be portrayed at all.
I am afraid I shall not be able personally to take part in the observations – altho’ it is too soon to come to a decision about it, but I hope that a numerous assembly of zealous observer will distribute themselves along the line
Yours vy Truly
H. F. Talbot