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

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42 replies to this topic

#1 ScopeJunkie

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Posted 01 November 2020 - 06:10 PM

I'm curious to find out what the average amateur astronomer's (on this forum) light pollution level at home is.  I'm guessing that most people are like me and the majority of the time they are observing/imaging from their home.

 

My Bortle number is 3.6

 

My MPSAS number is 21

 

Thanks! 



#2 Jim Waters

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Posted 01 November 2020 - 06:32 PM

My backyard is Bortle ~8.5 and about SQM 18.35.



#3 calypsob

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Posted 01 November 2020 - 06:34 PM

Bortle 5 - Mag 20.4 

 

But I dont really shoot from home. A good darksite is right down the road.  A 29 mile drive gets me to Mag 21.4 


Edited by calypsob, 01 November 2020 - 06:36 PM.

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#4 raylinds

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Posted 01 November 2020 - 06:41 PM

Bortle 5 Mag 19.89



#5 dswtan

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Posted 01 November 2020 - 06:55 PM

B4.5-5, M20-20.5.

 

I chose the site to balance commuting with astronomy -- so no immediate street lights, but close to civilization. I have darker sites a short or (better) long drive away, but home is good enough for my level of skill and interest. I could do with fewer trees and more horizons though!



#6 Grounddweller

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Posted 01 November 2020 - 07:00 PM

Backyard is Bortles 6

20 min drive down to a berm-protected beach area brings in a Bortles 4

Astronomy club dark site is about a Bortles 3.5

Humidity is the big challenge here on the coast.

 

Steve



#7 Ittaku

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Posted 01 November 2020 - 07:26 PM

Class 8. 18.7.



#8 John Carlini

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Posted 01 November 2020 - 07:30 PM

Being fairly rural and sparsely populated, I'm in a Bortle-2 area.


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#9 Chevy5759

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Posted 01 November 2020 - 07:40 PM

Bortle-4.5 at my home.



#10 Jim R

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Posted 01 November 2020 - 07:42 PM

8  and   18.6 from my home.



#11 emr7

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Posted 01 November 2020 - 07:56 PM

Bortle 6 and SQM 19.31

 

but drive 47 minutes to the desert to image at Bortle 2 and SQM 21.92



#12 Tony Flanders

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Posted 02 November 2020 - 05:53 AM



I'm curious to find out what the average amateur astronomer's (on this forum) light pollution level at home is.  I'm guessing that most people are like me and the majority of the time they are observing/imaging from their home.

 

My Bortle number is 3.6

 

My MPSAS number is 21

 

Thanks! 

You should state where you obtained that data; I doubt that it came from your own observations. If you're obtaining it from a map or database, different sources often give very different data -- and none of them are likely to be a good match for your actual conditions.

 

For what it's worth, this is the first time I have ever seen a Bortle Class specified to a tenth; I'm not sure what that's supposed to mean. Conversely, it makes no sense to me to specify magnitude per square arcsecond to an accuracy less than a tenth. If you're rounding off, 21 could mean anywhere from 20.51 to 21.49, and there's a vast difference between 20.51 and 21.49!

 

As for my own readings, I rarely or never observe from my city home, because of the streetlights and obstructions. But my local city park is Bortle 8, perhaps trending toward 9, and I usually get SQM readings there between 17.5 and 18.0 in the early evening, perhaps a bit better after midnight.

 

My country home is Bortle 4 by most criteria, though it matches John Bortle's description of Class 5 better with respect to the zodiacal light. SQM readings on nights of typical good transparency range from about 20.7 in the early evening when there's snow on the ground to 21.4 in the small hours of the morning when the trees are fully leafed out.


Edited by Tony Flanders, 02 November 2020 - 05:59 AM.

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#13 ScopeJunkie

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Posted 02 November 2020 - 07:53 PM

Well.....

 

 I can’t speak for anyone else, but my Bortle class number is based on the MPSAS number given by my Unihedron Sky quality meter (21).  The Bortle class number I stated (3.6), is an estimate based on the MPSAS reading.  My skies aren’t a 3 or a 4, but closer to a 4 than a 3.

 

it’s just a judgement call on the Bortle number, but the MPSAS number is pretty accurate.  Of course this is just a friendly comparison, not scientific research, so there’s nothing to get your knickers in a twist about.



#14 Tony Flanders

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Posted 03 November 2020 - 05:06 AM

I can’t speak for anyone else, but my Bortle class number is based on the MPSAS number given by my Unihedron Sky quality meter (21).  The Bortle class number I stated (3.6), is an estimate based on the MPSAS reading.  My skies aren’t a 3 or a 4, but closer to a 4 than a 3.


Ah, now at least I have some context. I was genuinely baffled where that tenth of a Bortle Class came from; I have never seen such a thing before.
 
However, my other comment stands. Quoting an SQM reading accurate only to one whole magnitude makes no sense. I don't even know it the reading is rounded to the nearest whole magnitude or truncated. So your actual readings might be anywhere from 20.50 to 21.99, which is the difference between purgatory and heaven.

Anyway, the fact that I have never seen anybody on Cloudy Nights post data derived in this way emphasizes how important it is to say how their sky quality data was derived.

Here's how I would have phrased the original post:

I'm curious to find out what the average amateur astronomer's (on this forum) light pollution level at home is. I'm guessing that most people are like me and the majority of the time they are observing/imaging from their home.
 

My Sky Quality Meter gives readings of 21.0, plus or minus 0.4.

 

According to the XYZZY source, that translates to a Bortle Class somewhere between 3 and 4.



#15 pstarr

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Posted 03 November 2020 - 12:13 PM

I'm a 5, near the edge of 4.5.



#16 Voyager 3

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Posted 03 November 2020 - 11:24 PM

Can't quite tell the bortle/SQM but the NELM at zenith is nearly 4 on a quite clear day but still a bit of high clouds.

#17 ScopeJunkie

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Posted 04 November 2020 - 03:42 PM

I understand what you’re saying Tony. I’m basically just asking for “educated guesses” on the numbers based on light pollution maps, NELM, or personal SQM readings.

What you’re stating is true, but the majority of us (including me) are amateurs and don’t have the equipment to provide truly accurate Bortle numbers for their home.

Thanks for the interest. That’s just one of the things I love about this hobby. You can dabble with the naked eye and a pair of binos or you can dive head first Into it (Astrophotography, Stellar Spectroscopy, Transit Photometry, etc).

It all depends on your level of interest, the amount of free time you have, and how much money you’re willing to spend.

#18 aa6ww

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Posted 04 November 2020 - 08:59 PM

My Signature is my answer. I prefer observing from Home more so lately since its comfortable and easy. My skies aren't great but I have thousands of objects to choose from my 60mm refractor to my C11.

 

 

...Ralph


Edited by aa6ww, 04 November 2020 - 09:02 PM.

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#19 Illinois

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Posted 05 November 2020 - 07:43 AM

My backyard is SQM 20.67 mag./arc sec Class 4. It’s far better than I grew up in around Chicago.  My land in Wisconsin is SQM 21.93 mag./arc sec Class 2



#20 rhetfield

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Posted 05 November 2020 - 04:32 PM

According to the light pollution map, I am bortle 7 and SQM 18.78.  In reality, more homes, mini malls and at least a couple car dealerships have been built within a mile of my location since the last time the map has been updated and I am certainly brighter than what the map says.



#21 river-z

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Posted 07 November 2020 - 11:36 AM

I love maps and data and traveling so I got pretty curious about this Bortle stuff once I got into this hobby last year.  I knew my home location was atrocious.  Here in LA it's Bortle 9 for sure.  When I got an SQM device I confirmed just how bad it is with a 17.4 measurement on clear night with no moon.  

 

Fortunately, there are some excellent, darker places to go here in CA.  For example, in the Sierra last summer I got a reading of 21.8 one night.  Next week, I'm planning on going out to the desert for the new moon and look forward to finding out how dark it is there.


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#22 jgraham

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Posted 08 November 2020 - 10:09 AM

Bortle 8 here.

 

Average lenses SQM 18.6.

 

It’s not the best, but it’s mine and I’m near my sweetie bear.

 

:)



#23 Arcticpaddler

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Posted 09 November 2020 - 12:02 PM

Bortle 3.  Very consistent over the past 25 years due to zero population growth and the vast majority of the region being undeveloped public lands.



#24 AstroFalcon

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Posted 10 November 2020 - 10:57 AM

I've recently moved back to Colorado, and here in the suburbs, I'm a Bortle 7. That being said, I'm an hour away from Bortle 4, and and hour and fifteen minutes away from Bortle 3 skies. 

 

Not ideal since I do a majority of my observing from my home, but I like that I have options that are easily accessible. 

 

Keith


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#25 GeoNole94

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Posted 13 November 2020 - 05:59 PM

Bortle zone 4 at the house, with zone 3 close nearby where I observe. Unfortunately, I live at sea level and we “enjoy” high humidity half of the year.


Edited by GeoNole94, 13 November 2020 - 06:01 PM.



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