[size="1"]Truglo Tru-Lite Extreme Violet Sight Light
The Truglo above is the one I installed on my sight because I hunt out of a dark ground blind also. It does help in low light & cloudy days. There are others on the market you can check into. Search for "sight light" to see the options.
A light may help on the sunny days you described. I don't remember having that problem on a sunny day but then I haven't had any shot opportunities over 25-30 yards anyway.
I have since gone to the Hind Sight Cross Fire that has the same Truglo lite incorporated in the sight & after messing with it last night I really like it.
While practicing you might try a small flashlight shining on the fiber optics to see if it might help. Maybe someone can hold it there for you while you draw? Since the sight lights are a low intensity violet light, maybe a low intensity flashlight to test it out?
Thomas Jefferson, 1774 July. "The God who gave us life, gave us liberty at the same time."
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