I have not seen anyone declare a "best" OTA position for quickest and best cooling down (or warming up) of a newt. Knowing that warm air rises and cool air sinks, I would think keeping the tube horizontally (front end open and no wind present) would be best since warm air inside the tube can rise and exit out the top edge of the tube while cooler air will migrate into the tube to replace the warmer air that has escaped. This is of course, for newts that have no ventilation openings at the primary mirror end. But even with them, is a horizontal position the best? This also does not include fans for cooling.

Mr Q

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Meade DS-10 (10" newt)
10x50, 10x70 binos