Dob Tube Insulation

I'm building an 8" f6 dob and using a 10" aluminum tube. I heard that I should insulate the tube but I'm not sure why. Is it so the the tube does not dew up as quickly? If so, shouldn't the insulation be on the outside? Is it to help with tube currents? If so, shouldn't it be on the inside?

I'm using a tube 2" larger than the mirror and an open back mirror cell, so I don't expect tube current problems. Would I gain anything by cutting ventilation slots directly above the mirror to allow for a laminer air flow? Any thoughts would be appreciated.

Thanks
Dave Burtrum

The aluminum will cool beyond the air temperature and will get to dew point on nights when you would not see dew point. This causes dew on the inside and outside of the tube. This is why most recommend flocking or cork lining. Michael Zammit uses cork on the inside of his mirror box because it is made of aluminum.