Rear aperture with diopter correction.

[mbradley]

I am looking for feedback of experience with using a rear aperture that has internal diopter correction. Specifically:

1.) Are these ISSF legal? I assume they are, but the rules that disallow the attachment of lenses to the sight makes me wonder.

2.) My correction is -3.25 with a mild astigmatism. I realize that the internal diopter does not have an astigmatism component to it. At the same time, I can shoot in my contacts which also do not have the astigmatism correction. I am curious as to others experience with this.

3.) Any other recommendations or pluses and minus vs contacts and frames.

Thanks,

Mike

[KennyB]

Hi Mike,
magnifying diopters are NOT legal for ISSF.

I used one for ten years or so and only just managed to wean myself off it this year to become ISSF legal, with no loss of performance.
I spent several months doing testing with SCATT to see if there was any difference in aiming accuracy and (for me) there wasn't.

I originally only needed a small correction but, as I've aged, my eyes have now settled to a place where I'm lucky enough to be able to shoot without any correction.

Also, if you DO decide to get a diopter, test that it gives you the adjustment that you need before you hand over the cash. I found that I had to try (and reject) three before I found one that adjusted properly.

Regards,
Ken.

[mbradley]

Thanks Ken.

If I understand you correctly, the 1.5 magnification that comes with many of these is illegal, but the actual diopter correction is legal. Am I correct?

[Martin Catley]

As I understand it neither is legal for ISSF you cannot have the lense attatched to the sight you need glasses or contacts to be legal. I use a frame to attach the lense to the peep this is not legal for ISSF either.

[David Levene]

If I understand you correctly, the 1.5 magnification that comes with many of these is illegal, but the actual diopter correction is legal.

Apart from the fact that one is specific and the other isn't, what's the difference between them.

[mbradley]

David, the diopter correction changes the focal point to bring the picture in focus on the retina, while the magnification just makes it look bigger.

The Centra sight has the ability to take the magnification piece off of the sight. I assume that is to make it legal?

[Tim S]

The diopter focus relates to the lens. Remove the lens, and there isn't anything to focus, you just have the iris aperture and any filters/polarisers.

[KennyB]

As I understand it - having taken my old Gehmann unit apart to clean it once...

The variable focal length is achieved by varying the distance that two lenses are separated by.
A by product of this is that you also get a degree of magnification which again varies with the distance between the two lenses.

Removing the magnification piece is also removing the variable diopter as both lenses are in that unit - leaving you with a standard iris.

Regards,
Ken.