Apr 232011

Time Machines do their best work at night.  If you’ve ever slept in a tent, you know that dew does, too.  Which is why dew is the enemy of every Astropotamus.  We use all sorts of things to get rid of it when it shows up.  Mostly hair dryers and big tubes on the end of our Time Machines.  Sometimes we use electric heaters like you have on your car’s rear window.  In the end, it’s all about physics.

Dew forms because objects radiate heat into the air.  The air contains moisture, which then condenses on the object because the surface temperature of the object becomes less than the dew point of the air.  And as we all know, the dew point is the temperature at which atmospheric moisture condenses.  So dew gets on all our stuff.

This is fine if you’re in a tent with a fly – generally the water condenses on the fly and the tent (and you) stay dry.  This is not so good on the optics of a Time Machine.  It really messes with the seeing.

One way to get rid of it is to hit the optics with a brief blast from a hair dryer.  The air warms up, which allows it to absorb more moisture, and the surface temperature of the optics rise above the dew point so the water evaporates and goes back into the warmed air.  This is temporary, as the dew process will repeat itself.  At least, until everything stabilizes or the sun comes up and warms up the air (and increases the dew point).

Another trick is to put a long extension tube on the front of the Time Machine.  This is sort of like cupping your hands around your mouth to make your voice travel farther and be louder.  You lose less noise to the sides, and focus more of it in front of you.  Similarly, on a Time Machine, the dew shield limits the amount of heat that is lost to the sides and only allows the heat to be lost out the end of the tube.  This slows down the heat loss and postpones the time at which the surface temperature of the front of the Time Machine reaches the dew point.

But it’s still a battle – eventually Mother Nature will win and you’ll have blurry optics.  This is especially bad for astroimaging, since blurry optics make for very blurry images.  So by combining dew shields with small electric resistance heaters, you can go all night (with a little power) without any dew, just like you drive down the road being able to see out your rear window.

So this is why, if you ever go to a gathering of Astropotamuses, you’ll see all their Time Machines wrapped up, heated up, and sitting with giant extension tubes on their front.  And it might also explain all those hair dryers…