Mark,
I can't follow your math.
Assuming the inverse-square law for distance and holding Redding as a
constant, if Adin is 2X farther away from Redding than Bumpass (is from
Redding), the light dome at Adin should be 1/4, not 1/16th, that of
Bumpass. (All other things being equal.)
Now, comparing Adin's Redding light dome to Lava Bed's Klamath Falls
light dome needs an assumption about light output as a function of
population. If we assume this is linear, not quadratic, then these two
light domes should be comparable, because you have 4X greater
population traded off against 2X the distance.
Bob
--- Mark Wagner <mark.wagner@No-Spam> wrote:
> Shane Raney wrote:
>
> > Is anyone planning a Trip here for viewing? I'd love to go!
>
> Shane asked (on TAC at
> http://observers.org/tac.mailing.list/2008/Jan/0191.html ) if anyone
> is
> going to Lava Beds, after he saw the NPS night skies photo. I've
> included TAC-SAC in order to reach a wider base of knowledgeable
> people.
> I expect we'll see all sorts of responses.
>
> Shane, GSSP is close, being held 40 miles from Lava Beds National
> Monument, and 46 miles further from Klamath Falls.
>
> I found the photos interesting and a possible way to interpret what
> light pollution could be like at GSSP (Adin, CA). Here are some
> numbers
> to play with, for anyone who likes such things:
>
> Klamath Falls to Lava Beds = 43 miles.
> Klamath falls population = 20,000
> no intervening mountain range.
>
> Klamath Falls to Adin = 86 miles.
> Adin population = 500
> No intervening mountain range.
>
> Adin to Alturas = miles.
> Alturas population = 2,900
> Intervening mountain range.
>
> Adin to Redding = 87 miles.
> Redding population = 87,000
> Intervening mountain range.
>
> Adni to Susanville = 56 miles.
> Susanville population = 13,000
> Intervening mountain range.
>
> Adin to Reno = 131 miles.
> Reno population = 193,000
> Intervening mountain ranges.
>
> I assume at a certain distance from the source, a light dome will
> follow
> the inverse square law - so when one moves twice as far from the
> source, it should reduce brightness by 4x.
>
> Two cities are almost exactly the same distance from Adin. Redding
> and
> Klamath Falls are both just about 86 miles away. Klamath Falls' light
>
> dome (and others) is shown in the National Park Service photos here:
>
> http://www.nps.gov/labe/parknews/night-sky-maps-and-images.htm
>
> Other than Reno at 130+ miles away, Redding is by far the biggest
> population center. Let's place ourselves 43 miles from Redding to
> equal
> the distance in the photo Lava Beds is from Klamath Falls. Redding's
> population is more than 4x the size of Klamath Falls. I assume the
> light dome from Redding would be over 16x as bright as Klamath Falls'
>
> dome is from Lava Beds.
>
> To put this in perspective with a place we know, Bumpass Hell parking
>
> lot in Lassen Park is 47 miles from Redding. Can we threrefore
> assume
> Bumpass Hell's "Redding" light dome is about 16x that of Klamath
> Falls'
> light dome from Lava Beds, due to 4x the population (approx)? Should
> Redding from Adin be about 16x less bright than Bumpass Hell's
> Redding
> light dome at twice the distance?
>
> I used Google Earth and the ruler tool to measure all these
> distances.
> It is easy to measure and compare distances.
>
> I think this exercise might be most beneficial to imagers.
>
> I'm sure there are folks out there on the mailing list who are much
> better at this sort of thing than I am. Feedback would be
> interesting.
>
> Mark
> --
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>
--
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Received on Mon Jan 14 17:30:36 2008