How much impact does a full moon have on the Bortle's scale?

For examples sake, suppose one was visiting a region of the world where
the skies were a 1 on the Bortle's light pollution scale. Would a full
moon directly overhead pollute the sky enough to move it a whole unit
up the scale? Two units? Three etc...?

I live in light polluted New Orleans but recently traveled through an
area (about 35 miles SW) that was marked a 4.5 on a light pollution
map. Having a little time left on the kitchen pass, my two young sons
and I decided to try to find a little dark road leading away from the
highway; so we could get a little look around look around town.

We did and I tell you it was nice. But there was nearly a 1/2 moon up.
Can I expect it to be "considerably" better than I remember when I go
back when there's no moon?

In a couple of weeks (provided the skies are clear) I'll have first
hand knowledge. Just figured I'd ask anyway....

My experience is limited to my backyard and skies are so polluted, it
seems a full moon hardly has any impact on seeing (except right next to
it).

Clear skies! (and no Moon?)

Errol
pasnola.org

On Dec 2, 8:02 pm, "Starboard" wrote:

For examples sake, suppose one was visiting a region of the
world where the skies were a 1 on the Bortle's light pollution
scale. Would a full moon directly overhead pollute the sky
enough to move it a whole unit up the scale?

It doesn't work like that. I'm not wild about the Bortle classes, but
it goes something like this: A place that would be Bortle class 1 at
new Moon is Bortle class 8 at full Moon -- as is everywhere else
in the world except for Bortle class 9, which remains Bortle
class 9 at full Moon.

Half Moon is just about as bright as a typical darkish suburb,
meaning that the Milky Way is readily visible, but severely
washed out.

If you want to go looking for dark skies, do so either when the
Moon isn't up at all or when it's within 3-4 days of new.

- Tony Flanders

In article .com,
wrote:
On Dec 2, 8:02 pm, "Starboard" wrote:

For examples sake, suppose one was visiting a region of the
world where the skies were a 1 on the Bortle's light pollution
scale. Would a full moon directly overhead pollute the sky
enough to move it a whole unit up the scale?

It doesn't work like that. I'm not wild about the Bortle classes, but
it goes something like this: A place that would be Bortle class 1 at
new Moon is Bortle class 8 at full Moon -- as is everywhere else
in the world except for Bortle class 9, which remains Bortle
class 9 at full Moon.

Half Moon is just about as bright as a typical darkish suburb,
meaning that the Milky Way is readily visible, but severely
washed out.

If you want to go looking for dark skies, do so either when the
Moon isn't up at all or when it's within 3-4 days of new.

- Tony Flanders

....of course the Moon isn't up at night for very long when it's within
3-4 days of new..... :-)




--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Can I expect it to be "considerably"
better than I remember when I go back
when there's no moon?

I can't give you a numerical answer, but yes, it will be MUCH better if
you go out when there's no moon.
Marty

I can't give you a numerical answer, but yes, it will be MUCH better if
you go out when there's no moon.
Marty

Sorry to bore the group with a silly question. I know it was a shade
(I'm so sad) ridiculous. I was just wondering if anyone had been out
on a dark field and could say overall, a quarter moon degrades the sky
about this much or half moon that much, yadda yadda.... Like I said, I
pulled over on side the road in an area with cat 4-5 skies, and even
with a half moon, I was in awe. I'm very excited about the prospect of
going back when the conditions are better. My curiosity of how much
better it would have been had the partial moon not been there was
killing me so I had to ask.

I hope this spot works out because it's only a 30 minute ride in the
pickem' up truck @ 70mph. Once there, there is this 10 mile winding
road with sugarcane fields on both sides that reach back hundreds of
yards so I can dang near see the horizon on all sides. Not a single car
passed the entire two hours we were there. Some new roads in the area
with higher speed limits have made this old road obsolete.

The club I'm in has a dark observing site (complete with bunkhouse)
with cat 3 skies, but it's a couple/few hour drive. Shamefully, I've
never been. I'll make time soon.

Here on the home front, when the moon is up, it's just ANOTHER light
shining on me.

Errol

"Starboard" wrote:

I was just wondering if anyone had been out
on a dark field and could say overall, a quarter moon degrades the sky
about this much or half moon that much, yadda yadda....

Go to http://meghar.blogspot.com/ and scroll down to the posting
titled: "5 NOVEMBER, 2006 UT". You'll find a description of the full
moon's effect upon a relatively clean, rural sky -- a sky with a
limiting magnitude better than 6.5 on a "good", moonless night.

On that night I was able to see, with the unaided eye, all the stars
that make up the pattern of the "Little Dipper" -- translating to a
naked-eye limiting magnitude of about 5.0. That's right, the Little
Dipper that was recently discussed on saa -- the asterism that some
claimed to be unrecognizable due to too few visible stars even on a
moonless night . . . it was visible under the light of a full moon!

The blog entry provides additional details, pointing out various DSOs
that were visible or invisible with binoculars, etc.

The blog entry titled: "30 October 2006 UT" describes the sky under a
moon near its first quarter phase. My naked-eye limiting magnitude
was 5.9.

Moonlight along with atmospheric particulates is *much* worse than
moonlight alone. I suspect that many people have been blaming the
moon for effects that are actually caused by the combination of
moonlight *and* atmospheric particulates. What you really want is a
dark, clean sky.

P.S. Don't bother bookmarking the above linked blog. I've scheduled
it for deletion (and 'maybe' replacement) in the not too distant
future.

Willie R. Meghar

On or about 3 Dec 2006 10:51:54 -0800 did "Starboard"
dribble thusly:


I can't give you a numerical answer, but yes, it will be MUCH better if
you go out when there's no moon.
Marty

Sorry to bore the group with a silly question. I know it was a shade
(I'm so sad) ridiculous. I was just wondering if anyone had been out
on a dark field and could say overall, a quarter moon degrades the sky
about this much or half moon that much, yadda yadda.... Like I said, I
pulled over on side the road in an area with cat 4-5 skies, and even
with a half moon, I was in awe. I'm very excited about the prospect of
going back when the conditions are better. My curiosity of how much
better it would have been had the partial moon not been there was
killing me so I had to ask.

Well, my sky is mag 6.1 at the zenith according to darksky.org, and a
half moon doesn't prevent me from spotting 9 stars in the Pleiades
(which includes mag 5.79 Sterope I).

Though it might be my imagination, I thought I could spot (ever so
tenously) mag 6.43 Sterope II at the same time. It happened to be an
exceptionally clear night (i.e. high transparency). That's not the
only indication I have that the value given by darksky.org is too low.

I live in a rural area now (as north and west as you can get in NJ),
but used to live in central suburbia. The ZLM given by darksky.org
for that location is 3.3, while my own measurement showed it to be
4.5. Maybe I'm not using the same definition, however. All I did was
find the faintest star I could see continuously, and look up the name
and magnitude (16 Auriga, at mag 4.54).

Overall, however, keep in mind that the full moon is about ten times
brighter than the half moon. A full moon makes my sky as bad, if not
worse, than the suburban sky I used to suffer under. A half moon, at
one tenth the brightness, has a tolerably minor effect - Milky Way
still plainly visible with decent structure. But once it starts
getting gibbous, things move down hill quickly.
--
- Mike

Ignore the Python in me to send e-mail.