Friday, March 21, 2014

Which Comes First? Dark Adaptation, or Hypothermia?

We had no Moon last night, so I tried to find M51, the Whirlpool Galaxy.  I have seen it before, and I could see just a faint smudge of it last night.  The problem is that it takes not just a dark sky, but your eyes need quite a bit of time in complete darkness to completely adapt.  This Wikipedia article on the subject says that "the brightest and the darkest light signal that the eye can sense are a factor of roughly 1,000,000,000 apart."  It also says that it can take twenty to thirty minutes to go from sunlight to complete darkness adaptation.  I remember from my Biology of Aging class, long ago, that how rapidly your eye can adjust from darkness to light gets worse as you age, and I would not be surprised if the other direction is also age-dependent.

Anyway, as much as I wanted for my eye to get completely dark adapted, the real question became: which will come first?  Dark adaptation, or hypothermia?  Maybe I'll try this again on a night that isn't below freezing.


  1. You could have sat in the house with a blindfold on...

  2. I guess a -15 sleeping bag is out of the question?
    James Bourke, author of "On the Border with Crook" described in that book what the cavalry men wore when on the march, and their clothing included multiple layers of furs. the Infantry, as well as the horses wore much less, as they were active in the cold. Somehow I don't think furs would be as acceptable nowadays, so you probably would have to make do with down or some synthetic fill.


  3. astrogoggles?

  4. Turn off all the lights in your front entry and living room.

    Take the scope out and set it up, pointing near your target.

    Then go inside to the front room (where it's very dark) and wait 30 minutes. At that point, your eyes should be almost fully dark-adapted.

    Go back out to the scope, wait five minutes, and you should be good to go.

  5. I forget his name, but the amateur astronomer credited with discovering the most comets uses oxygen to enhance his vision.