Which major star parties have Bortle Class 1 skies?

[a***@gmail.com]

I'm an easterner and have attended Stellafane which I would rate
Bortle class 3 to 4. The WSP which I would say 3 to 4. Cherry Springs
which I would call 2 to 3. I have not been to Spruce Knob but would
guess based on light pollution data it is probably class 2. Are there
any Class 1 sites in the east?

Looking out west, my view of the light pollution data suggests that
the TSP, Oregon star party and Nebraska star party are the best bets
for Bortle class 1 skies. Can anyone who's attended confirm?

Another consideration for me is the length of the star party. The
Oregon star party seems too short to bother going all the way out
there. Mt Kobou (sp?) in Canada is a longer star party but my look at
the light pollution data suggests it may only be Class 2.

Any star parties I'm missing that are at least 5 days or so to make it
worth my while? I'd really like to try Texas but hate the idea of it
being in June this year.

Alvan Clark

[j***@comcast.net]

Post by a***@gmail.com
I'm an easterner and have attended Stellafane which I would rate
Bortle class 3 to 4. The WSP which I would say 3 to 4. Cherry Springs
which I would call 2 to 3. I have not been to Spruce Knob but would
guess based on light pollution data it is probably class 2. Are there
any Class 1 sites in the east?

Alvan

The Oregon Star Party (elevation 5000 feet) is definitely Bortle
class 1 skies. Prineville ( population 8000) 40 miles to the west, is
difficult indeed to even see a light dome.. It is held in the Ochocho
National Forest in a very large clearing with 700+ attendance.
Although the "official" star party is Thursday-Friday-Saturday, many
people camp early and make it a 7-8 day affair. For instance, I came
on Monday and there were already 75 there.

see

http://www.oregonstarparty.org/

for more information.

Jim Jackson

Post by a***@gmail.com
Looking out west, my view of the light pollution data suggests that
the TSP, Oregon star party and Nebraska star party are the best bets
for Bortle class 1 skies. Can anyone who's attended confirm?
Another consideration for me is the length of the star party. The
Oregon star party seems too short to bother going all the way out
there. Mt Kobou (sp?) in Canada is a longer star party but my look at
the light pollution data suggests it may only be Class 2.
Any star parties I'm missing that are at least 5 days or so to make it
worth my while? I'd really like to try Texas but hate the idea of it
being in June this year.
Alvan Clark

[David Knisely]

Yes, the Nebraska Star Party frequently has Bortle Class 1 skies.
Zenith limiting magnitude figures are in the 7.0 to 8.1 range depending
on the night and the sensitivity of the observer. My eyes are not quite
as sensitive as they used to be, but this last summer at NSP, I reached
about magnitude 7.6 with my unaided eyes. Clear skies to you.
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[Margo Schulter]

Post by David Knisely
Yes, the Nebraska Star Party frequently has Bortle Class 1 skies.
Zenith limiting magnitude figures are in the 7.0 to 8.1 range depending
on the night and the sensitivity of the observer. My eyes are not quite
as sensitive as they used to be, but this last summer at NSP, I reached
about magnitude 7.6 with my unaided eyes. Clear skies to you.

Hi, there, David -- and also Alvan and Jim -- and thank you for an
opportunity to Google "Bortle Class" and learn about a very interesting
concept.

Here in Bortle Class 9 territory, the idea of seeing the Milky Way without
an optical aid seems idyllic -- not to mention NELM 7.6 and all the neat
zodiacal light and other effects explained on the Web pages.

Most appreciatively,

Margo Schulter
***@calweb.com
Lat. 38.566 Long. -121.430

[laura halliday]

Post by Margo Schulter

Post by David Knisely
Yes, the Nebraska Star Party frequently has Bortle Class 1 skies.
Zenith limiting magnitude figures are in the 7.0 to 8.1 range depending
on the night and the sensitivity of the observer. My eyes are not quite
as sensitive as they used to be, but this last summer at NSP, I reached
about magnitude 7.6 with my unaided eyes. Clear skies to you.

Hi, there, David -- and also Alvan and Jim -- and thank you for an
opportunity to Google "Bortle Class" and learn about a very interesting
concept.
Here in Bortle Class 9 territory, the idea of seeing the Milky Way without
an optical aid seems idyllic -- not to mention NELM 7.6 and all the neat
zodiacal light and other effects explained on the Web pages.

I have family who live in the B.C. interior, and they have,
depending on how good a night it is, Class 1 or Class 2 skies.
M33 is naked eye, the Milky Way is bright, and there are
so many stars you start to lose the constellations. At
53 degrees north Vega is circumpolar, and it's kinda neat
to see it down in the trees in January. You pay for it
with midnight twilight in June and July.

I'd have to classify Mount Kobau as Class 2 at best, since
the lights of Penticton, Oliver and Osoyoos are starting to
intrude. My usual February getaway on the Gulf of Nicoya
in Costa Rica is Class 2 as well, as long as you're not looking
toward the light dome from Puntarenas. Transparency can
be an issue there, with the monotonous dry season tropical
weather. There is something to be said for observing in
shorts and a t shirt at 0300. :-)

Good skies really are idyllic. And all too rare, alas.

Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

[Jim Jam Gee]

You must be one spoiled brat!

Post by laura halliday
I have family who live in the B.C. interior, and they have,
depending on how good a night it is, Class 1 or Class 2 skies.
M33 is naked eye, the Milky Way is bright, and there are
so many stars you start to lose the constellations. At
53 degrees north Vega is circumpolar, and it's kinda neat
to see it down in the trees in January. You pay for it
with midnight twilight in June and July.
I'd have to classify Mount Kobau as Class 2 at best, since
the lights of Penticton, Oliver and Osoyoos are starting to
intrude. My usual February getaway on the Gulf of Nicoya
in Costa Rica is Class 2 as well, as long as you're not looking
toward the light dome from Puntarenas. Transparency can
be an issue there, with the monotonous dry season tropical
weather. There is something to be said for observing in
shorts and a t shirt at 0300. :-)
Good skies really are idyllic. And all too rare, alas.
Laura Halliday VE7LDH "Non sequitur. Your ACKS are
Grid: CN89mg uncoordinated."
ICBM: 49 16.05 N 122 56.92 W - Nomad the Network Engineer

[City of Blood]

Post by a***@gmail.com
I'm an easterner and have attended Stellafane which I would rate
Bortle class 3 to 4. The WSP which I would say 3 to 4. Cherry Springs
which I would call 2 to 3. I have not been to Spruce Knob but would
guess based on light pollution data it is probably class 2. Are there
any Class 1 sites in the east?
Looking out west, my view of the light pollution data suggests that
the TSP, Oregon star party and Nebraska star party are the best bets
for Bortle class 1 skies. Can anyone who's attended confirm?
Another consideration for me is the length of the star party. The
Oregon star party seems too short to bother going all the way out
there. Mt Kobou (sp?) in Canada is a longer star party but my look at
the light pollution data suggests it may only be Class 2.
Any star parties I'm missing that are at least 5 days or so to make it
worth my while? I'd really like to try Texas but hate the idea of it
being in June this year.
Alvan Clark

Maybe you should explain to people what Bortle Class refers to,

just in case people think you are on drugs and too fucking smart
to communicate with the rest of reality?

[Greg Crinklaw]

Post by a***@gmail.com
Any star parties I'm missing that are at least 5 days or so to make it
worth my while? I'd really like to try Texas but hate the idea of it
being in June this year.

You should take the claims of Bortle 1 skies with a big grain of salt.
In my experience the difference between Bortle 1 and Bortle 2 is much
more about the current weather conditions than the level of light
pollution. In other words, there are not any places in the continental
US that are truly Bortle 1 except on a few exceptional nights.

Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[David Knisely]

The Bortle scale is rather inconsistent and uses some gages which are
not commonly possible to use, especially towards the faint end. For
example, the claim that in a Bortle 1 sky, "Even with direct vision, M33
is an obvious naked-eye object" is a little exagerative, as for many
people with fairly decent vision, their "dead-on" direct vision stops at
around mag. 4.5 to 5.0 even when fully dark adapted (M33 has a total
integrated magnitude of 5.8). I can easily see M33 with just slightly
*averted* vision from NSP, but if I look directly at the galaxy, it is
gone. Similarly, the use of a description of "color" in things like the
Zodiacal Light and the Milky Way again are questionable, as they are
often below the ability of many people to discern such colors at that
low light level.

For specifics, the Gegenschein, Zodiacal Band, and even some faint high
altitude airglow bands are visible from the site of the Nebraska Star
Party. Its Zenith Limiting magnitude does frequently fall into the
Bortle 1 classification (the record is 8.15 done by Dave Nash at NSP-2).
The Bortle description of the appearance of the Milky Way does match
what is seen at NSP (Milky Way allowing shadows to be cast), and people
have observed Einstein's Cross in a 30 inch from NSP, so you can push
your scope as far as possible on a good night from there. At the very
least, the common ratings for NSP skies are Bortle 1 and Bortle 2
depending on the weather conditions only.

Greg, I don't recall seeing you at the Nebraska Star Party. What year
did you attend?
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[Greg Crinklaw]

Post by David Knisely
Greg, I don't recall seeing you at the Nebraska Star Party. What year
did you attend?

When did I say I had? Although I have planned to go on several
occasions something always seems to come up.
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[David Knisely]

When did I say I had? Although I have planned to go on several occasions something always seems to come up.

Well, after the initial post (which specifically mentions the skies of

In my experience the difference between Bortle 1 and Bortle 2 is much more about the current weather conditions than the level of light pollution. In other words, there are not any places in the continental US that are truly Bortle 1 except on a few exceptional nights.

Thus, I would have assumed that, from your statement, you had
experienced the skies of the area around Merritt Reservoir where the
star party is held. Obviously, you have not. This might account for
your initial rather blanket declaration that "there are not any places
in the continental US that are truly Bortle 1". There are a number of
sites in the U.S. (mostly in the western half) where skies that fulfill
many if not most of the stated Bortle 1 characteristics do occur. A
number show such sky quality on a fairly frequent basis, although
perhaps not on every night. Regular attendance at some of the western
star parties is enough to show many amateurs that these sites do deliver
a Bortle 1 and/or Bortle 2 level of dark sky. I consider the site of
the Nebraska Star Party to be at least "potential" Bortle 1 (if not
actual), as long as the weather conditions are reasonably clear. Clear
skies to you.
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[Greg Crinklaw]

Post by David Knisely

Post by Greg Crinklaw
When did I say I had? Although I have planned to go on several
occasions something always seems to come up.

Well, after the initial post (which specifically mentions the skies of

Post by Greg Crinklaw
In my experience the difference between Bortle 1 and Bortle 2 is much
more about the current weather conditions than the level of light
pollution. In other words, there are not any places in the
continental US that are truly Bortle 1 except on a few exceptional
nights.

Thus, I would have assumed that, from your statement, you had
experienced the skies of the area around Merritt Reservoir where the
star party is held. Obviously, you have not. This might account for
your initial rather blanket declaration that "there are not any places
in the continental US that are truly Bortle 1".

I thought at first you were just being nice. I don't wish to argue with
you David. I believe what I said stands on its own. Your unfortunate
attempt to suggest that I don't know what I'm talking about because I
haven't been to one particular star party is really rather disrespectful
and does not merit further comment.

Post by David Knisely
There are a number of
sites in the U.S. (mostly in the western half) where skies that fulfill
many if not most of the stated Bortle 1 characteristics do occur.

Yeah, I know. I live in one. You'd think that in all the years we have
been conversing you'd have noticed that!

Post by David Knisely
A
number show such sky quality on a fairly frequent basis, although
perhaps not on every night. Regular attendance at some of the western
star parties is enough to show many amateurs that these sites do deliver
a Bortle 1 and/or Bortle 2 level of dark sky. I consider the site of
the Nebraska Star Party to be at least "potential" Bortle 1 (if not
actual), as long as the weather conditions are reasonably clear. Clear
skies to you.

In fact I pretty much said exactly what you said above. The key
sentence was the one you left out: "In my experience the difference
between Bortle 1 and Bortle 2 is much more about the current weather
conditions than the level of light pollution."

As you have pointed out the Bortle 1 class is inconsistent and poorly
defined. See my second post on the matter for a more long winded
explanation of what I meant. The short version is this: once the sky
reaches a certain level of darkness it isn't about darkness anymore,
it's about transparency. Surely we can agree on that? No hard feelings?

Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[David Knisely]

I thought at first you were just being nice. I don't wish to argue with you David. I believe what I said stands on its own. Your unfortunate attempt to suggest that I don't know what I'm talking about because I haven't been to one particular star party is really rather disrespectful and does not merit further comment.

I may have read too much into what you initially said. Your posting
alleging that there were no true Bortle 1 sites right after the initial
poster mentioned at least one where that does happen seemed to indicate
that you were dismissing the possiblity of Bortle 1 at NSP completely
without having been there (and I wanted to make certain that you had not
been there). This seemed a little unfair.

In fact I pretty much said exactly what you said above. The key sentence was the one you left out: "In my experience the difference between Bortle 1 and Bortle 2 is much more about the current weather conditions than the level of light pollution."

Well, I didn't really leave anything out as I quoted the paragraph
exactly and then commented about the portion of your statement which I
found inaccurate. The problem was the use of an absolute which seemed
to imply that there were *no* sites that produced the characteristics of
a Bortle 1 site except on very rare nights. If you had not said this in
the way you did, then I would probably have not objected to it.

I agree that the Bortle scale is not all that great (too many levels,
too little consistency on what characteristics or gages should be
applied, etc.), but in at least the limiting magnitude figures, it is at
least approximately valid. For me, however, I would probably use a bit
simpler set of levels to gage sky quality (use of averted vision assumed
for magnitudes fainter than 5.0:

SEVERE: only stars brighter than mag. 4.0 are visible with bright
skyglow over
most of the sky.
MODERATE: mag. 4.0 to 4.9 stars visible (variable skyglow depending on
direction of observation).
MILD: mag. 5.0 to 5.9 stars visible (some notable darker areas
visible).
DARK SKY: mag. 6.0 to 6.8 stars visible (dark, sometimes with a few light
domes along the horizon).
PRISTINE: mag. 6.9 and fainter stars *consistently* visible (little or no
light pollution in any direction).

There might be room to add in an "extreme" category, but I think
something like these levels would about cover things. Clear skies to you.
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[t***@yahoo.com]

Post by David Knisely
I may have read too much into what you initially said.

Yes, I think so. I read Greg's post and did *not* infer what you did.

I think that Greg's use of the word "truly" was unfortunate, and
misled you into
thinking he was saying something that he didn't intend. His primary
point was
simply that the difference between Bortle Class 1 and Class 2 is *not*
due
to light pollution, but rather to local variations in transparency. In
other words,
a Bortle Class 1 site is simply a Bortle Class 2 site on a good night.

That sounds right to me. Many other people have said or implied the
same.
Does anybody disagree?

On your other two points, David, I think it's possible to take some
action.
Your claims are:

1. The Bortle scale has too many levels.
2. The criteria within a scale are inconsistent.

The first point, I think, is partly a matter of taste and partly a
matter of
experience. It's very hard to criticize the Bortle scale on those
grounds
unless you've *habitually* observed at each of the levels, and
concluded,
in essence, "oh, the difference between level x and x+1 isn't really
important." And frankly, I don't think that *anybody* has ever
observed
consistently and habitually at all the different levels of light
pollution.
Why would they? Nobody goes out of his or her way to observe in
light pollution *worse* than what they've got at their own homes.

On the second point, I heartily agree. For instance, the business
about telescopes being invisible is just plain wrong. Yes, that
can easily happen in the eastern U.S., where people observe
in clearings in the forest, and you see the scopes with dark trees
in the background. But in the desert, the light of the Milky Way
is ample to highlight telescopes and people against the brightly
lit ground. Likewise, I'm quite sure that I'll never see M33
naked-eye no matter where I go.

But the fact is, it's very easy to criticize the Bortle Scale. But
when
you actually try to substitute a different one, you start to realize
just how much hard work went into it, and how hard it is to do
better. And since it is, for better or worse, widely used, I'd like
to propose that instead of throwing it away, we attempt to
preserve the categories but improve on the way they are
defined. That's something that I don't think any single person
can do, for the reasons I've stated above. But it does seem
possible as a collective enterprise. Among the entire internet
amateur-astro community, we have the knowledge and ability
to come up with a really consistent scale.

- Tony Flanders

[AM]

Post by t***@yahoo.com
On the second point, I heartily agree. For instance, the business
about telescopes being invisible is just plain wrong. Yes, that
can easily happen in the eastern U.S., where people observe
in clearings in the forest, and you see the scopes with dark trees
in the background.

Actually what I try and do is find a small spot/clearing
in a small hollow and setup in a little *dark spot*
With the rolling countryside of Virginia it is easy
to do. And these little hollows can get soo dark, no
you cant see your hand in front of your face, or the scope.
There are times when I will sacrifice a lot of horizon
do get a nice dark spot, but even in a light polluted area
this can mean seeing a mag fainter DSO's, and or more low
SB objects. And in light polluted areas, zenith can be all
that is worthwhile anyway.....

But I agree, I cant see how on an open plain, with full
Milky Way visable how scopes could be invisible.

[Greg Crinklaw]

Post by David Knisely
The Bortle scale is rather inconsistent and uses some gages which are
not commonly possible to use, especially towards the faint end.

Yeah, that's for sure. Another one that gets me is "your telescope,
companions, and vehicle are almost totally invisible." This brings up
what I believe to be the heart of the problem; the whole question of
what a "dark" sky really means. Eventually transparency dominates.
After all, the darkest sky is one where the sky is completely overcast!

To my way of thinking after the point where most light pollution has
been avoided the question is no longer one of darkness, but one of
transparency. Bortle also defines a class 1 sky thus: "The Scorpius and
Sagittarius region of the Milky Way casts obvious diffuse shadows on the
ground." But obviously this is at odds with the statement that
everything around you is almost totally invisible. In fact, in my
experience, a transparent sky away from lights is rather bright--so
bright that you can often see your surroundings fairly well.

It's too bad this scale wasn't created by someone who has common access
to dark and transparent skies. On that end it really suffers and sounds
more like the description of an imagined perfect sky rather than a real one.

Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[eddie]

David,

As I recall, M33 is a naked eye object..without using obverted
vision...at Cherry Springs. I'm sure that it must be the same at NSP
too:)

[David Knisely]

M33 may be naked eye for some people, but for others, it is simply an
averted or "near" averted vision object. A lot of people get so used to
using averted vision that they use it without thinking and report things
as being seen directly. A year or two ago, I did some checking on my
own dark adapted absolutely "dead-on" direct vision on faint stars of
known magnitude, and with some difficulty, I got to about 5.0 (more
typically, it is around 4.8 to 4.9). With averted vision, I have gone as
faint as magnitude 7.8., although from my local dark sky site, the
limiting magnitude (averted) is often in the 6.5 to 6.8 range. M33's
total integrated magnitude is about 5.8, but this is below my limit (and
is spread over an area of nearly a square degree). I can often see M33
with the unaided eye, but not directly, and from speaking to other
observers, this is apparently a fairly common situation for many people.
I don't have to look very far away from it to see it (even from my
regular dark sky site), but if I stare absolutely directly at it, it
vanishes, no matter how good the skies are. In any case, whether
something is visible with direct vision vs. averted vision is not
necessarily a good indicator of how good the skies are. Again, this is
a flaw in the Bortle scale, as *only* the visibility (averted or direct)
of the object should have been the indicator used. Clear skies to you.
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[eddie]

David & Tony,

Before I went to The Black Forest Star Party at Cherry Springs, I
never had seen M33 ever....

Naked eye to everyone at Cherry Springs...I never heard that anyone
didn't see it.

And my eyes are pretty darn nearsighted without my glasses and I'm 50
years old now just a few years older then when I was last at Cherry
Springs.

Believe it or not, my eyesight is very far from ideal and I'm not even
a light year close to Steve O'Meara.

I think you guys are selling yourselves short and possibly Cherry
Springs maybe darker than what others say?

Of course, I wish you the best:)

[palsing]

Alvan Clark wrote;

Another consideration for me is the length of the star party. The

Post by a***@gmail.com
Oregon star party seems too short to bother going all the way out
there.

**********

Although OSP is advertised as being only 3 days long, the fact of the
matter is that there are a LOT of people who get there early.

IIRC, the porta-potties are delivered by Tuesday at the latest, and
maybe even on Monday.

The last 2 times I attended, I got there on Tuesday and therefore had
5 full nights of observing, and at least 150-200 others did the same
thing.

Since OSP doesn't Officially start until Thursday, however, that means
the other amenities don't start until then, that is, you will have to
wait until then for the roach-coach that serves up Star Burgers all
night and the Latte Tent where you can get fancy coffee, etc.

I've observed all over the West, including TSP, Enchanted Skies in New
Mexico, Northern Arizona Star Party, from Sentinal, Az, from Mt.
Lassen and the Bristlecone Pines in California, and even from
Coonabarabran in Australia, and I must say that when it is good at
OSP, those skies are as dark as anywhere else in the world.

\Paul A

[David Knisely]

The Bortle Dark-sky scale:

http://www.skyandtelescope.com/resources/darksky/3304011.html?page=2&c=y
--
David W. Knisely ***@navix.net
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 14th Annual NEBRASKA STAR PARTY *
* July 15th-20th, 2007, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

[ike]

Post by David Knisely
http://www.skyandtelescope.com/resources/darksky/3304011.html?page=2&c=y

She just don't know what she's talkin about

[eddie]

Alvan et al....

I believe in giving credit where credit is due...

Mr. Bortle has done a lot of good work over the years and
no one else came up with a suitable scale...at least that I know of.

Having been at the 9,000 ft level (Visitors Center) of Mauna Kea, I
would have
to think that it is a 1 on the Bortle Scale.

From Cherry Springs (which can't be much worse than Mauna Kea) you can

see
M33 naked eye. The Milky Way appears at dusk and grows brighter as
twilight turns into night. Clouds, when they appear, look like dark
blobs because there is very little uplight.

Interestingly enough, Cherry Springs caught the eye of someone in the
Travel section of the New York Times last week:

http://travel.nytimes.com/2007/09/14/travel/escapes/14dark.html?ref=escapes

Better get up there and down to Spruce Knob if you have never been
because both sites are being eyed for Wind Farm development.

[A***@gmail.com]

Are there any Class 1 sites in the east?

As an observer in the northwestern U.S. I don't know; but as others
have mentioned a Bortle-Class 1 site is *very* unlikely to *always* be
a Class-1 site. Such ideal conditions can be *very* easily destroyed
by minor variations (which can and do occur) in sky conditions.

Looking out west, my view of the light pollution data suggests that
the TSP, Oregon star party and Nebraska star party are the best bets
for Bortle class 1 skies.

It's not very difficult to find starparties (and observing sites) west
of Nebraska that have low-number, Bortle-Class skies.

Another consideration for me is the length of the star party. The
Oregon star party seems too short to bother going all the way out
there. Mt Kobou (sp?) in Canada is a longer star party but my look at
the light pollution data suggests it may only be Class 2.

An aurora, smoke from distant (or near) wild fires, a night of
brighter than average natural sky-glow, etc. can each raise a site's
Bortle-Class a few notches. Even the observer's exposure to sunlight
on the previous day can have a noticeable effect on the eye's Bortle-
Class judgement.

As for starparty durations. It's not all that uncommon in the western
U.S. to allow observers to come earlier and stay later than the
official starparty dates. Check with the organizers of any interested
starparty.

Any star parties I'm missing that are at least 5 days or so to make it
worth my while? I'd really like to try Texas but hate the idea of it
being in June this year.

The Montana StarWatch can be good; but like many other starparties,
area fires (which resulted in the cancellation of the 2007 MT
StarWatch), etc. can easily make the sky much worse than one might
have anticipated. There are no gaurantees when it comes to *any*
site's sky darkness!!

As for the Bortle scale itself, I'm in agreement with most that has
been said about it here. It can be difficult to draw a line between
Class-1 and Class-2, Class-2 and Class-3, etc.

For the sky right outside my front and back doors, a "good" night
might be anywhere between Class-3 and Class-1. Zodiacal Light, by its
very nature, is more prominent on some nights than it is on others. I
saw and carefully recorded (sketched) the Gegenschein from by front
yard last year. Part of the Zodiacal Band was visible as a narrow
extension extending eastward from the large, faint Gegenschein. A
similar extension was not seen west of the Gegenschein. Yet, when I
record my naked-eye limiting magnitude it's nearly always within a
tenth of a magnitude of 6.5. Visual acuity has a very noticeable
effect on my own NELM -- and I'm over-due for an eye-exam and new
glasses . . .

On a personal level, I would rate a Class-3 to Class-1 night to be a
good night. Class-4 conditions can often be enough to deter me from
engaging in any deepsky work from my location.

Bill Greer
To sketch is to see.
http://cejour.blogspot.com
http://www.rangeweb.net/~sketcher

[Margo Schulter]

Post by A***@gmail.com
On a personal level, I would rate a Class-3 to Class-1 night to be a
good night. Class-4 conditions can often be enough to deter me from
engaging in any deepsky work from my location.

Hi, there, and thanks for a comment that illustrates an important point:
whatever scale we use to rate sky darkness and transparency, people's
customary environments and experiences are going to vary radically.
Getting urban light pollution in hand might somewhat reduce, but not
eliminate, these striking contrasts.

Thus to me, accustomed to Bortle Class 9 (around NELM 3.5), and guessing
whether I just might see NGC 253 with a broadband LPR filter, Class-4
conditions seem utopian -- the Milky Way "impressive" to the naked eye,
and NELM around 6.1-6.5. Give me that one night a week, preferably a
clear one when the Moon will be close to new or absent from the sky
during the relevant observation period, and I'll have no complaints!

However, this is also an opportunity to exercise a bit of imaginative
empathy, and try putting myself in the position of an expert observer
and sketcher for whom Class-4 conditions might mean fewer faint galaxies
or globulars, say, seen at all; and less detail teased out of visible
ones, even with prolonged observation. I ask myself, "How would you like
it if conditions got so bad that you could no longer see M22?" Would this
be like how it feels for an expert observer when conditions shift from
the Class 1-3 range to Class 4?

This discussion raises an interesting question: how utopian would it be
to set a goal of getting an urban area with about a million people
(for me, Sacramento, California, USA) to around Bortle Class 4 or 5?
Of course, if this happened, it would mean that _everyone_ could have
a reasonably nice view of the Milky Way, and also that present dark
sky sites might more often offer Bortle Class 1-3 conditions.

Is this thread maybe an invitation to solidarity between people observing
under different Bortle Class conditions: urban observers advocating for
pristine dark sky sites, and dark-sky observers advocating for better
urban conditions?

Most appreciatively,

Margo Schulter
***@calweb.com
Lat. 38.566 Long. -121.430

[shawn]

Margo Schulter wrote:

snip

Post by Margo Schulter
This discussion raises an interesting question: how utopian would it be
to set a goal of getting an urban area with about a million people
(for me, Sacramento, California, USA) to around Bortle Class 4 or 5?
Of course, if this happened, it would mean that _everyone_ could have
a reasonably nice view of the Milky Way, and also that present dark
sky sites might more often offer Bortle Class 1-3 conditions.
Is this thread maybe an invitation to solidarity between people observing
under different Bortle Class conditions: urban observers advocating for
pristine dark sky sites, and dark-sky observers advocating for better
urban conditions?

This is a job for IDA! (Or somebody who *can* make a difference.)
There are so many selfish reasons for people to decrease their light
pollution:
Lower electricity bills
Lower lighting installation and maintenance costs
Lower local pollution from power generation.
Lower taxes (thinking of excess illumination of streets and public
buildings)
Safer driving environment by eliminating glare with proper shielding of
street lights.
Security issues can, to a great extent, be addressed by motion sensing
fixtures and well engineered lighting design.

None of the above address less selfish but still very compelling
benefits of decreasing light pollution:
Decreased CO2 emissions
National energy independence (in the US anyway)
Terrorism funded by the rat bastards we buy oil from
Mountain top removal coal mining
Water contamination from coal bed methane extraction
etc.


All of these reasons seem compelling enough to make a dent in light
pollution. My cynical assumption is that the energy industry is
stifling reform, no data though.
Anyone know why we're still so thick?


Shawn
Under Class 11 Clouds at the moment (6 on a good night).

[Per Erik Jorde]

Yet, when I record my naked-eye limiting magnitude it's nearly
always within a tenth of a magnitude of 6.5.

Pardon changing subject, but I am interested in how to determine
naked-eye limiting magnitude. Should I choose stars near zenit?
Should I use direct vision or averted?

Although not a newbie (I started out in the early 70's and have been
active from the early 90's), I haven't paid much attention to estimate
sky quality or darkness this far. However, I don't think I have ever
seen the velvet black sky that some observers describe. My sky is
definitely _gray_, as compared to the dark silhouettes of the wood,
and I am growing curious about how my observing spot compares to other
amateurs'. I live on the countryside in a sparsely populated area in
southern Norway (local community of 1864), with two smaller towns
(population ~6000 each) some 30 - 40 km away. I have never actually
seen M33 naked eye (I'll make another try) or the zodiacal light, and
find the Bortle scale difficult to apply.

pej

[t***@yahoo.com]

Post by Per Erik Jorde
Pardon changing subject, but I am interested in how to determine
naked-eye limiting magnitude. Should I choose stars near zenit?
Should I use direct vision or averted?

By convention, naked-eye limiting magnitude is measured at the zenith
(unless stated otherwise), and uses averted vision. But NELM has very
little value as a way of comparing your skies to someone else's,
because there's a variation of at least one full magnitude, and maybe
more, in NELM estimates from different individuals under the same
skies.

Post by Per Erik Jorde
However, I don't think I have ever
seen the velvet black sky that some observers describe.

That's because no such thing exists. "Velvet black sky" is a term
usually employed by people who are used to severe light pollution. In
fact, skies devoid of artificial light pollution are quite bright.

Post by Per Erik Jorde
I live on the countryside in a sparsely populated area in
southern Norway (local community of 1864), with two smaller towns
(population ~6000 each) some 30 - 40 km away.

You might try to locate yourself on the Light Pollution Atlas at
http://www.lightpollution.it/worldatlas/pages/fig4.htm

Post by Per Erik Jorde
I have never actually seen M33 naked eye

It's worth a another try! I can see it at sites with obvious light
pollution. But it's mighty subtle.

Post by Per Erik Jorde
or the zodiacal light.

Well, there we run into one of the fundamental problems with the
Bortle Scale. The visibility of the zodiacal light depends heavily on
your latitude. It must be very hard indeed from Norway. Though it's
also worth pointing out that the zodiacal light is one of those things
that seems very difficult and exotic until the first time you've seen
and identified it. After that, it doesn't seem so hard after all.

Many of the Milky Way features cited by Bortle are also heavily
latitude-dependent. For instance, the bulge into Ophiuchus is a real
test of dark skies here at 42N, and must be extremely hard at 60N. But
the first time I saw it clearly, in southern Arizona, it seemed quite
bold and bright. And from the Southern Hemisphere, where it's nearly
overhead, it probably shines through fairly heavy light pollution.

[Greg Crinklaw]

Post by t***@yahoo.com

Post by Per Erik Jorde
Pardon changing subject, but I am interested in how to determine
naked-eye limiting magnitude. Should I choose stars near zenit?
Should I use direct vision or averted?

By convention, naked-eye limiting magnitude is measured at the zenith
(unless stated otherwise), and uses averted vision. But NELM has very
little value as a way of comparing your skies to someone else's,
because there's a variation of at least one full magnitude, and maybe
more, in NELM estimates from different individuals under the same
skies.

Quite true. But it is rather useful when a specific observer is
comparing different sites. The problem comes about because the results
of different observers vary greatly. It seems that everyone's eyes are
different in terms of sensitivity, acuity and perhaps even spectral
response. But it seems a valid way to compare skies as long as it is
the same observer and done in a consistent way.

Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[t***@yahoo.com]

NELM seems a valid way to compare skies as long as it is
the same observer and done in a consistent way.

Agreed -- with a couple of caveats.

First of all, I find that determining NELM to a high accuracy is very
tedious and time-consuming -- it takes me a minimum of a half hour,
and even then I wouldn't give it better than +-.2 mag reliability. So
in practice, I usually make do with a casual, non-numeric assessment.

Second, like Bill Greer, my NELM tops out in skies that are clearly
less than ideal, and simply doesn't get any better no matter how dark
or transparent the sky is. I've been to many places where I could see
some stars fainter than mag 6.5, but I've never been anywhere where
I've seen every mag-7.0 star that I've looked for.

So while I find NELM quite useful for a quick assessment of light-
polluted sites -- or for assessing transparency at a pretty-good site
-- I find it useless for distinguishing good skies from great skies.
For that purpose, I find the best criterion is the visibility of naked-
eye dark nebulae in the Milky Way. Unfortunately, there's no easy way
to make that quantitative!

[Greg Crinklaw]

Post by t***@yahoo.com
So while I find NELM quite useful for a quick assessment of light-
polluted sites -- or for assessing transparency at a pretty-good site
-- I find it useless for distinguishing good skies from great skies.
For that purpose, I find the best criterion is the visibility of naked-
eye dark nebulae in the Milky Way. Unfortunately, there's no easy way
to make that quantitative!

Yeah. It's basically the same problem that the Bortle scale runs into.
These things are good for determining your level of light pollution,
but begin to fail when the light pollution is dominated by differences
in transparency. Once the light pollution is basically gone, contrast
becomes the primary issue and contrast is a very difficult thing to
quantify.

Clear skies,
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

[A***@gmail.com]

Post by Per Erik Jorde
Pardon changing subject, but I am interested in how to determine
naked-eye limiting magnitude. Should I choose stars near zenit?
Should I use direct vision or averted?

There's more than one method. It's easy to find one or more star-
counting method via an Internet search; but I prefer to use stars of
known magnitude in the neighborhood of Polaris (Alpha Ursae Minoris).
Various books and magazines over the years have published variations
of this North Polar Sequence.

A weakness of the North Polar Sequence is the existance of gaps within
some of the magnitude ranges. An advantage is that one eventually
memorizes enough of the stars to dispense with the use of charts and
dim lights. Atmospheric extinction tables can be used to correct for
the altitude of the Polar Sequence. IIRC, the most recent edition of
Norton's Star Atlas and Reference Handbook has both north and south
polar sequences as well as an extinction table. My own NPR is based
on several such references. I've retained stars that most of the
charts have had in common (with the same magnitudes) and dropped
others that various sources have differed on. The extinction table
can be used to interpolate your zenith limiting magnitude from the non-
zenith location of the sequence of stars.

Averted vision is the usual mode of observation used when determining
one's Naked Eye Limiting Magnitude (NELM). Of course, one should also
allow sufficient time for one's eyes to dark adapt.

Post by Per Erik Jorde
Although not a newbie (I started out in the early 70's and have been
active from the early 90's), I haven't paid much attention to estimate
sky quality or darkness this far. However, I don't think I have ever
seen the velvet black sky that some observers describe. My sky is
definitely _gray_, as compared to the dark silhouettes of the wood,
and I am growing curious about how my observing spot compares to other
amateurs'. I live on the countryside in a sparsely populated area in
southern Norway (local community of 1864), with two smaller towns
(population ~6000 each) some 30 - 40 km away. I have never actually
seen M33 naked eye (I'll make another try) or the zodiacal light, and
find the Bortle scale difficult to apply.

The only times I've seen a "dark" sky have been when I've gone out
(from a brightly lit indoor environment) and looked at the sky without
allowing my eyes any time to dark adapt. Yet, some nights (from the
same location) have been *noticeably* darker or brighter than others
due to more or less natural sky glow. I suspect (but don't know for
certain) that the darkest skies, all other things being equal, may be
a bit closer to the equator -- further from the poles and their aurora-
induced glows.

The zodiacal light can be obnoxiously *bright* at times as seen from
my 45 degree latitude; but more often than not I don't make (deepsky)
observations near that "light source".

I've never seen M33 with direct vision -- at least not with the
unaided eye. It helps to pay careful attention to dark adaptation for
at least half an hour prior to attempting to see M33 with the unaided
eye -- *no* lights -- not even dim red ones! Of course, for some of
us M33 rises higher in the sky than it does for others. There are a
lot of variables when it comes to such things . . .

For your own NELM estimates, find a method you like and stick with
it. Eventually you'll get better and faster at it!

Bill Greer
To sketch is to see.