Lady Luck has sent an early Petzval (8292) to my door. This is a one of the first with a Braunschweig made Waterhouse Slot, but still with the difference in viewing and chemical focal lengths.
Claus Prochnow's book lets me identify this as model 4, which is a EFL 8 1/4" F.2.6 - quite a uniquely fast version. He also has a few remarks about adjusting for chemical focussing after visual focussing.
I reproduce the passage.
I have always assumed that the comments refer to movements of the tangential drive, but I could be mistaken! The main problem is the word "Thir." for which I have unable to find in translation or German dictionaries. The numbers given for the "movement" seem excessive, if they refer to the turns of the knob or even gear teeth.
I know I can always do a trial and error experiment and play with filters and test cards, but it would be nice if I could use other's knowledge of German or experience with this very first Petzval design.
Reply With Quote
Bookmarks