Centra magnifying diopter

[Metfordman]

Does anyone know how to adjust the focus on a Centra 1.5x magnifying diopter? I can't find any instructions on the web. Many thanks.

[Tim S]

Turn the optik until the foresight is sharp and the foresight is visible. The option should be marked something like -4/+4 (or whatever the adjustment range is). The optik is at the front, where the whole unit screws into the rearsight.

[Metfordman]

Thanks but I can't find anything that turns other than the adjustable iris. There is the thread that goes into the main body of the sight then a double knurled section with the words CENTRA UK -3.5/+3.5, this seems solid with the rest of the diopter then there is the adjustable iris that seems to work ok. Do you know which bit moves to adjust the focus?

[Tim S]

The double knurled part marked Centra UK -3.5/+3.5 is the optik/dioptre/lens system. It should be a slightly smaller diameter than the main eyepiece. The -3.5/+3.5 is the adjustment range in dioptres: quite short sighted to quite long sighted. If you bought it used, and hasn't been focused for a while, the threads may be a bit gummed up.

[Metfordman]

Thanks Tim, So I should secure it tightly in the backsight then rotate the double knurled section to refocus? Sorry to keep coming back but it does all seem to be very reluctant to move.

[Tim S]

Don't mention it.

Yes you should be able to adjust the optik when it's screwed into the rearsight. Without dioptre markings (like the iris sizes) AND a good idea of your prescription, it would be nearly impossible to focus the lenses off the rearsight.

If the ring is stuck don't force it. You might try a little heat, like a hair dryer.

[Metfordman]

Many thanks, I will give that a try.

[Metfordman]

It worked! Gentle heat has released the ring and it now has the full range of movement. If you need any advice about muzzle loading Match Rifle shooting that is my speciality; not using magnifying diopters with them though. Thanks again.

[Tim S]

Glad to have helped.

Ah, I was thinking the Metford in your user name was a .303in reference, rather than his earlier work.

I live in Taunton where W E Metford was born, and walked past his family home not long ago.