Friday, 25 August 2017

Improvements

When I made my prototype Tudor telescope I simply glued the 50 mm diameter objective lens to one end of the 2" diameter carboard mailing tube. I used silicone glue as I thought it would be easy to remove and did not penetrate the cardboard.  This was a wise thing to do in hindsight. Firstly I peeled off the glue and made a lens holder out of one of the plastic end stoppers that came with the cardboard tube. Because the lens had a fractionally smaller diameter than the mailing tube this worked very well, the blurred annulus disappeared. Next I looked into changing the mirror angle. I had tried to emulate a Newtonian reflector when I made my prototype and set the mirror at 40 to 45 degrees so that I could view the image just off a purpendicular direction to the telescope tube. Unfortunately the abberation was too great and resulted in blurred images. By setting the mirror to about 20 degrees I found I could get a much clearer image. Finally I cut three wooden dowels and used them to strengthen the overlap between the two card tubes and I filled in the gaps with draught excluder tape to cut out some of the stray light. In Tudor times this could have been done with horsehair, or wool, or rags and the lens holder could have been made from leather instead of plastic. I took the two photographs below of Ely cathedral whilst out on the Fens about five miles away from the cathedral. The field of view is very restricted but the image clarity is greatly improved and shows some fine detail. Would a Tudor telescope of this nature have been useful at spotting a Spanish armada on the high seas off the south coast of England? I think the answer is yes as despite the small field of view it would have enabled the watcher to see far off vessels on the horizon more clearly and in much greater detail so they could raise the alarm of a potential naval attack much earlier if required. 



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