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Frank

If this image was produced one wet afternoon around 1900, the first question ought to be how they managed to produce it.   I don't think a two lensed camera could have coped.  Perhaps they wiggled the head of their projector plate holder around between prints, but that doesn't explain the sudden large movement in the positions of Sirius and Procyon with respect to their close minor stars, which is obvious without the need for a ruler. They might have lampblacked real Sirius and Procyon out and scratched new ones in. Meanwhile, more work needed on the back of an envelope. DaveP