Depends on scope & personal preference, with the mag on 10x I used 23 on my MTC, 20 on my Nikko Sniper & hawke SR 6 was about 30 IIRC. You have to try to find a happy medium, 8 will nearly always be blurred on 10x mag & I used to have 45 just blurred in my MTC, nikko was to clear to have 45 like that. If you drop down to say 8 mag it will be less likely to be blurred dependant on the scope.

HTH
Steve