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What's your home's Bortle/MPSAS number?

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42 replies to this topic

#26 mccambjd

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Posted 21 November 2020 - 12:25 AM

Bortle 7 here in the Delaware Valley.



#27 havasman

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Posted 21 November 2020 - 02:54 AM

Average SQM-L here over the last year is < 17   shocked.gif   so it's solar only from here.

 

The church behind me decided to "upgrade" their security lighting. The punch line is that nobody's there at night any more at all. Ever. But they're catholics and know when they're right. Like talking to a post.


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#28 kopite

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Posted 21 November 2020 - 03:18 AM

Bortle 6, SMQ 19.47 here in the Bay Area according to Clear Outside app.



#29 Marty0750

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Posted 21 November 2020 - 07:41 PM

The Bortle scale is biased to northern hemisphere in regard to the Milky Way. It indicates the zenith MW is not visible at B5 (=>19.4 mpsas). Yet we regulary see the Sagittarius MW at zenith visble with detail at B6. (~18.8 mpsas) We also have the Magellanic Clouds as an indicator. These are fainter and require less than B5.

 

I suggest the Bortle scale should include the south hemisphere visiblity indicators for the MW along side the northern one. We may only have on 15% of the world population but we have a brighter galaxy sections and more numerous stars. Oh, and we have less light pollution generally.

 

Martin


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#30 Tony Flanders

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Posted 22 November 2020 - 06:49 AM

The Bortle scale is biased to northern hemisphere in regard to the Milky Way.


The Bortle scale is biased toward mid-northern latitudes in many regards -- the visibility of M33 and the zodiacal light being two other examples. And this is just one of many known problems with the Bortle Scale in general. I don't really think they can be fixed, nor do I think it's worth trying. You just have to accept the scale together with its limitations.

The Bortle Scale has value as a kind of simplified lingua franca for casual mid-northern observers. But for serious observers, SQM readings and verbal summaries of what can be seen are much more useful.


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#31 wesastro

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Posted 22 November 2020 - 07:47 PM

I haven’t even tried to measure the Bortle or SQM at my home because I don’t have a place to setup, but my observing site 45 minutes away has a SQM-L of 20.8 to 20.95 depending on sky conditions and where I’m looking. I have a bright northern sky.



#32 ShaulaB

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Posted 22 November 2020 - 07:50 PM

Bottle sad to dreadful.

SQM 17

#33 viewer

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Posted 23 November 2020 - 09:34 AM

According to the Light Pollution Map I'm at SQM 18.0 and Bortle 8-9. Seems accurate. Glare can be minimized near the sea though, so it feels darker than it is smile.gif

 

If I put in an hour and a quarter of drive I get my best: SQM 21.6 and Bortle 4. Definitely worth the trip now and then!



#34 BrooksObs

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Posted 23 November 2020 - 11:45 AM

The Bortle scale is biased to northern hemisphere in regard to the Milky Way. It indicates the zenith MW is not visible at B5 (=>19.4 mpsas). Yet we regulary see the Sagittarius MW at zenith visble with detail at B6. (~18.8 mpsas) We also have the Magellanic Clouds as an indicator. These are fainter and require less than B5.

 

I suggest the Bortle scale should include the south hemisphere visiblity indicators for the MW along side the northern one. We may only have on 15% of the world population but we have a brighter galaxy sections and more numerous stars. Oh, and we have less light pollution generally.

 

Martin

 

Probably 90% of astronomy hobbyists live in the northern hemisphere. Likewise, I've spent 60 years observing from it myself under all manner of skies, only venturing south to Australia once. Further, I conferred with countless experienced northern observers over the years to get their impressions on object visibility in differing skies to compile the Bortle DSS. So...with those most likely to use it being northern hemisphere hobbyists it was only logical that it should be bias toward them.

 

There will never be a southern version as I'm never likely to spend decades in the south to evaluate different sky situations there in my time remaining. I would also anticipate that someone else compiling a scale of this nature is highly unlikely to mesh neatly with mine. So I'm afraid you are stuck with what you have.

 

BrooksObs


Edited by BrooksObs, 23 November 2020 - 11:45 AM.


#35 BrooksObs

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Posted 23 November 2020 - 01:58 PM

The Bortle scale is biased toward mid-northern latitudes in many regards -- the visibility of M33 and the zodiacal light being two other examples. And this is just one of many known problems with the Bortle Scale in general. I don't really think they can be fixed, nor do I think it's worth trying. You just have to accept the scale together with its limitations.

The Bortle Scale has value as a kind of simplified lingua franca for casual mid-northern observers. But for serious observers, SQM readings and verbal summaries of what can be seen are much more useful.

 

Tony, I'm not sure just what you regard to be "serious" observers, but in my observing work over the years I've dealt with countless truly serious hobbyists who are doing the sort of observing that actually has meaning to it, not casual weekend sky gazing. Very few among them employ SQMs in conjunction with their efforts, but most do uses the Bortle scale, particularly the comet observing people. You may champion SQMs but even after years of availability, only a small percentage of hobbyists of any sort actually are willing to expend the many dollars to obtain one and time to use them correctly.

 

BrooksObs 



#36 GeorgeLiv

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Posted 02 December 2020 - 02:45 AM

Not to open another can of worms...assuming clear nights, are you putting your average or best SQM or Bortle numbers here??

 

My best ever SQM occurred this September 2020, in a cool (0°C), clear, continental-polar air mass, 4km east of Vennachar, Ontario. I got 22.35 mag/arcsec2 for awhile before dawn.

 

The last few years I've been typically getting between 22.15 and 22.25 mag/arcsec2 near 2 to 4:00 am and when the summer milky-way isn't overhead. I was a bit pleased with the 22.35 number until I figured smoke from the recent California fires darkened my sky.


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#37 ScopeJunkie

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Posted 02 December 2020 - 03:02 AM

Personally, I listed numbers that are slightly above average.  Not a lot, but a little above average.  



#38 N_DD

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Posted 02 December 2020 - 08:19 AM

Estimated Bortle 7 at home (no garten/terrace, so never imaging/observing from there) or Bortle 5 in 1.5 h driving. In the corner of Europe where I live, there is no point in driving further, as the next big city will make things worse...



#39 George N

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Posted 02 December 2020 - 01:14 PM

According to the map/software linked to in this message below - (https://www.cloudyni...pollution-maps/) --

 

My Southern Tier NY (Binghamton, NY area) home is SQM=20.72 Bortle=4 --- but my own experience is more like 20.4 and Bortle=5 --- but friends living just a little more from 'town' are getting 21.0 - which is also a typical reading at Kopenik Observatory & Science Center - about 50 yards North of the PA line.

 

My central Adirondack Camp (Indian Lake, NY area) -- according to the map is SQM=21.94 and Bortle=2 --- but again my experience is more like SQM=21.75 Bortle=3 --- not to mention that a clear January night will feature -20F (before you add in wind chill) and snow up to my belt buckle -- with howling coyote packs and the occasional yowl from a lynx.....  ;)


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#40 Notoriousnick

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Posted 03 December 2020 - 05:49 AM

According to lightpollutionmap.info, I'm in a Bortle Class 4 zone with an MPSAS of 20.7.

 

I am however awaiting the arrival of an Unihedron SQM-L next week, so will be able to see how that instrument's reading compares with the one derived from the map whee.gif.



#41 Inkswitch

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Posted 03 December 2020 - 12:33 PM

My home is Bortle 4.  I have an SQM-L and the worst reading I have ever had is 20.8X, best reading is 21.2X.



#42 AstroFPV

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Posted 03 December 2020 - 03:32 PM

Tampa Fl area...  18.88 and Class 8....



#43 birger

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Posted 03 December 2020 - 04:29 PM

Bortle 5 or 6 I would say, based on the following:

 

- Limiting naked eye magnitude may reach up to 5.5 on good nights

- Milky Way visible through Cygnus, dark lanes visible

- M31 easiliy seen with averted vision with the naked eye

- M33 visible with averted vision in 8x40 binoculars

 

lightpollutionmap.info claims my house is at 21.03 MPSAS. I have my doubts, since I've never measured this myself.

 

My biggest problem is a streetlight right outside my balcony. If I go to an unlit road some 100 m from my house, the sky is even darker, perhaps reaching down to Bortle 4 on the very best night. I have previously lived in Bortle 7 areas, and the difference is quite remarkable. I could never see the Ring of Pisces from home, but now it's obvious.

 

This spring, I'm going to try to see the Zodiacal light. It should be visible, given that I have the sea to the west, but alas, I probably need to go to a (very) nearby hill.


Edited by birger, 03 December 2020 - 04:32 PM.



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