I had my eyes tested and my prescription (it turns out) includes correction for slight astigmatism. The optician never mentioned this at the time.
When the lens holder was returned with the lens fitted, I just collected it and went home. Only then did I realize that the lens was in backwards, so I just loosened the screw and flipped the lens over.
For three weeks now my shooting has been awful. I have centred and recentered the lens, tweaked this that and the other, with my adjustable iris and without but no improvement. My focus on the front sight is spot on, with the iris it brings the rear sight clearer and the target is improved but I began to notice that the black of the target had a ghost to the left, about half width again. If if moved my eye (not my head) ever so slightly to the right the ghost disappeared but I guess this was introducing parallax error plus it was uncomfortable. This got me into thinking about astigmatism and when I read my prescription, there it was +1.50/-0.25/10.
I remember reading something about the notch on the lens being there to indicate the correct rotation of the lens in the holder to achieve the correct axis for correction but I cannot find it online now. I am of a mind that I have rotated the lens when I reversed it (effectively increasing my astigmatism) but now I don't know where the notch should be. I have spoken with the optician and they have not got a clue, I tried to speak to the glazing department but they refused to give me any advice/info, all they did was ring the optician and give them a rollicking for giving me their number!
After my ramble, can the collective help, please?
Is there any standard/norm? I am guessing that the notch should be either 12/3/6/9 o'clock?
Thanks in advance.

Atb
Chris