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SkyscraperJim
professor emeritus
Reged: 07/29/07
Posts: 537
Loc: Providence, RI
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Personally, I find the description of the different stages of the Bortle scale to be highly inaccurate (not the limiting magnitude, but what you can expect to see).
For example, our observatory is in a zone red, but close to the boundary with a zone orange. However, the description of zone green (a full 3 steps down the scale) is more accurate with what I can see from the site--particularly the fact that I can see the Milky Way bulge into Ophiuchus from the site. We definitely don't have mag 6.2 mag skies though, low 5's on a good night, so the limiting magnitude is accurate.
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Jim
TMB/APM 130/780 (#185) on G11
TMB/APM/Lomo 80/600
Tele Vue Pronto (#3533) on Half Hitch
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RonBurgundy
sage
Reged: 06/16/09
Posts: 252
Loc: Philadelphia
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Hey, Jim. Yes, I agree that the Bortle scale has some inaccuracies, as I have observed myself. If you think about it, it's got to be incredibly difficult to make a fully accurate scale. Since the skies regularly affect viewing, it makes it even more difficult (i.e. what should we define as the "average" sky?)... So, this is why my interest is sparked. From what I originally heard, the Louvar Scale will actually set a "reference sky" based on the average seeing/transparancy/etc. of small regions (less than 100 square km). It would also take into effect small towns, and also differentiate between individual regions in larger towns. It sounds rather accurate, and thus exciting (especially for finding a nearby space to observe for us apartment dwellers). That's why I'm so incredibly anxious to hear more information about this scale. I'll keep you all posted.
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Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
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mbares
member
Reged: 06/15/06
Posts: 32
Loc: Pilsen, Europe
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Bortle scale has nothing to do with color zones. You look at the sky and based on what you see you estimates what is appropriate Bortle class for that sky.
World LP atlas and color zones:
1) is outdated (IIRC it is based on data from years 1992-1993)
2) shows relative amount of artifical light pollution, NOT actual quality of the sky (there are other maps for that purpose)
3) its color coding was never intended to correspond with Bortle scale
Therefore it makes no sense to say that Bortle scale is highly inacurrate, because it doesn't correspond with colors of the LP atlas.
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Mike
10" truss dob just finished!, 8x42 & 7x50 binos, 70mm f/7 achro, 6" f/5 GSO eq newt
my sketching page - only in czech, but sketches don't need translation 
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Hrundi
Pooh-Bah
Reged: 02/06/08
Posts: 1230
Loc: Estonia
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The bortle scale is flawed in that it doesn't predict anything. Some conditions it claims are a sign for great skies can be easily matched in rather bad ones. Some descriptions for perfect skies don't match perfect sky experiences.
It's also entirely dependent on eyesight, the season, and as such, the position of various key objects in the sky.
In short, it's a scale that doesn't relay really anything I'd consider that useful.
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Coromandel
super member
Reged: 02/27/09
Posts: 146
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The Bortle scale is quite useful imo. Even if the descriptions aren't 100% accurate or suited to every single site on every single night.
For instance if somebody asks you what your observing site is like you can tell them it's "class 3" or whatever and they immediately have a reasonable idea of what to expect.
Sure the site may not EXACTLY fit the Bortle class 3 description but it will probably be near enough to distinguish it from a class 2 or class 4 and allow others to get an idea of what to expect.
It's not like there are any other better scales that I know of!  
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RonBurgundy
sage
Reged: 06/16/09
Posts: 252
Loc: Philadelphia
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I had a meeting with the professor today regarding the Louvar Scale. Unfortunately, he had an emergency of sorts and had to leave before we got down to business. On a brighter note, the man is a professional astrophysicist with an intense interest amateur observing. We put together an observing trip for the Leonids & Orionids next week as part of an upstart for a university astronomy club. Thus, I can be sure to have the final word on the Louvar Scale for all of you by the end of next week! Alas, victory!
Regards,
Kipp
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Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
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