Two things jump out at me. One is by your description of your arms getting tired. This says to me you are not using the glass the way you should. Everybody is right. Get something for a rest, get comfortable, get steady, glass in a pattern, and use your eyes a lot. The second thing is that you may be better suited with an 8x glass. I think far too many people assume that you will see more at distance with 10x than 8x. Maybe, but just as likely, maybe not. Magnification increase magnifies everything, including the tremors we transfer through our body and arms, ultimately to the glass. Hence image shake will be worse with 10x than 8x. A steady clear 8x will show you a lot more than the best 10x image that is jumping around with your pulse rate.