Any amateur astronomer (such as myself - ahem) would tell you that it's not
to reduce eyestrain, but to improve your eyes' dark-vision capabilities.
Even a small amount of light drastically impairs night vision. It takes your
eyes about 20 minutes to become fully dark adapted, and every glance at your
instruments will significantly diminish your ability to see on a dark
One item that this thread has overlooked is the British motorist's legendary
disdain for turning on his lights until it is pitch dark out.
From: David Riker <email@example.com>
To: Justin Cook <firstname.lastname@example.org>; email@example.com
Date: Tuesday, September 14, 1999 1:55 AM
Subject: Re: Mystery switch (at least to me)
>I would guess it is the same reason there are dimmers on them now, to
>eyestrain on a dark road at night. Not that spridget dash lights are all
>that bright to start with. Anybody know if maybe it was legislated?
>----- Original Message -----
>From: Justin Cook <firstname.lastname@example.org>
>Sent: Monday, September 13, 1999 12:45 PM
>Subject: Re: Mystery switch (at least to me)
>> I don't mean to beat this to death... but what good reason could there
>> be for turning off your dash lights while your headlights are on?