Quote: I too wear specs all the time (astigmatism)
Then a dioptre would be of no use to you unless your astigmatism is even and regular or, if it isn't, the dioptre had been created indivually for your shooting eye, and even then would only of use one way up i.e. portrait or landscape.
Perhaps I should have made it clear that my specs do correct, and very well, for my astigmatism, and I only needed the help of eyepiece correction when my accommodation decreased - to near zero! It's a bad thing this anno domini thing...