Dome Ventilation

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The first winter for the dome presented some interesting issues.  One of which was the build up of moisture on the inside surface of the dome, which froze.  Some of this moisture was coming from the house, even with double doors weather stripped to minimize air leakage from the house to the control room/observatory.  To me, it was an indication higher than desirable humidity as a result of poor air circulation.  This could spell trouble for fragile electronics and other equipment in the dome.  After reading about using vent fans to expunge warm air from domes and roll-off roof observatories, I immediately concluded that the same arrangement could be installed to improve circulation and reduce moisture build-up.  I observed that the amount of moisture that was condensing (and freezing) increased further up the dome.  I reasoned that slightly warmer air was rising within the dome and carrying the moisture with it.  So I installed a 4 inch fan and flexible duct that vented the moisture-rich air out through the back soffit of the dome ( I didn't want to create a new hole in the dome itself).  Fresh air is drawn through a vent from the outside at floor level, as well as from the gap between the dome and base.  This arrangements has significantly reduced condensation, and could probably be further reduced with a more powerful venting fan, such as the ones used to exhaust moisture air from bathrooms.