Quote:
Originally Posted by Omaroo
Ian - both of yours are wonderful  I musy have missed mention of it before - but your refractor has adjustable ratios - f/5 to f/16? I notice the helical objective mount - so how do you change the f/length in relation to its diameter? Are you moving a flint & crown in relation to each other or something? |
Hi Chris,
The objective lens system is actually the optics from an ex NASA satellite tracking camera. "MOTS". There appear to be 6 or more elements contained within the 500mm long lens cell. In the centre of the cell is an adjustable iris diaphram just like a normal camera lens - just that this one is on steroids. The objective cell is 220mm diameter, 500mm long and weighs 26kg if I recall correctly. Mounting it was a significant exercise. I have attached some additional images that hopefully show how it works. The whole scope weighs more than my 407mm F4.5 Dob!!
While it was designed to deliver a 200mm diameter flat and orthoscopic photographic image, it is not much as a visual instrument and I don't use it. Great fun to build though
.
In order the images are:
Objective cell prior to mounting after I had fitted some mounting rings to firtinside a 250mm diameter tube.
Next 2 from the front showing iris partly closed and fully open.
F/Ratio Change Knob below focuser F5 - F16.
F/Ratio change drive gear.
Internal collimatable diaginal mirror.
Cheers,