Concerning heat and scopes.......

So I'm outside looking at Mars. 10" dob. I was using a bino with either 20mm or 20mm barlowed eps, I don't remember. Anyway, I defocused until I had a somewhat large image of the primary, and for some reason I reached out and held my hand about 12" in front of the scope. I could see the outline of my hand, but I could also see heat radiating off of my hand like pluming smoke. When I took my hand away, the heat lingered and dissipated in about a second and a half. It looked like a transparent black and white thermal image. It got me wondering though....how much might my entire body heat be affecting the scope. I use the bottom lip of the dob to move it. The heat from my hand would go right into the front of the light path. How about when someone stands in front of the scope, not obstructing it, but just off to the side. The heat radiated might really be degrading the image. I couldn't believe I could see the heat radiating like that. Imagine what sun heated concrete, buildings, etc. can do to image quality. I've heard they can, now add a misplaced hand to the list. Anyway...just an equipment observation. Maybe it's not as bad as it looks.