Have you tried taking one out to the car and shining it up on the windshield during the day? Without any special windshield coatings you'll get a double-image,

Have you tried taking one out to the car and shining it up on the windshield during the day? Without any special windshield coatings you'll get a double-image, but at least you can get an idea of how visible and focused it would be under normal driving conditions.