Originally posted by ripit Would you know specifically what the spirotone is called (ie scope adapter, telescope converter etc)?
I went ahead and rounded up my knock-off Monocular/Telescope converters.
The Spirotone one is from the 60's - 70's and was not really designed well as the aperture lever on Pentax lenses scratch the inside because of clearance issues.
If you use the Spirotone on a mirror lens - which don't have an aperture lever - it's fine.
The Spirotone is called a "Telescoper", and has a 1/4-20" tripod hole - which is good
The Kenko one is just called a Telescope Adapter.
Notice how their design is very different in terms of diopter adjustment or not.
So many clones were produced, that they died off as an accessory.