[OzRob (Rob)]

Originally Posted by TheDecepticon

And when they are guiding, they "sing"! Awesome sound, I like it.
By the way, I'm 44 and can still hear it. Must be my Decepticon birth and upbringing!

Same with me. I can clearly hear it if I am doing some testing indoors but when I am using it properly I don't notice it but can hear it if I listen for it. I also notice the different in the sound when changing from sidereal to lunar tracking. When I first turn the mount on I listen for the hum as a check that everything is OK.