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DaveS

What's your Bortle number?

  

69 members have voted

  1. 1. What's your Bortle number?

    • 1
      0
    • 2
      1
    • 3
      5
    • 4
      16
    • 5
      11
    • 6
      20
    • 7
      6
    • 8
      10
    • 9
      0


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I'd say a 5 for me. I can pick out the glow of the great nebula in Orion with my naked eye , and the rest (on both those charts) seems to fit quite well.

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Sorry, It was not my intention to put down the pole or anything, as you say it is good as a general rule and did not mean to put it down as a useless concept but one that has limitations, and therefore only useful -  to a point.  

OK, that's fair enough, and something I'd agree with.

After my last post I got to wondering. Just how dark could we get our city suburbs if we tried?

Not rigid Dark Sky Park levels, but just sensible things like not using un-needed light, such as architectural lighting, making sure that any outside lights were only *just* as powerful as needed, and directed to only light where it was wanted, also requireing shops an offices to turn off lights after business hours.

Not only would it provide a more pleasent environment for us (A small minority, I know), and wildlife that *needs* dark night, but would also save energy and (Here's the kicker) *money*.

I reccon Bortle 5 should be do-able this far out, or even 4 with a bit of a push. Further in to London it might well be brighter, but I don't see why 6 shouldn't be possible.

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post-23944-0-97015100-1390855805_thumb.j

Wow - I'd heard about the Defence Budget cuts and the govt's 'Future Force 2020' strategy, but I had no idea this was all that's left of 4 Para.... 

I hope thats a Kevlar Elf hat.

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I doubt there's bottle 1 skies in the uk anywhere is there ? Reading the criteria .

Scottish highlands ?

I reckon Lundy island 12 miles off North Devon would be a 1 or 2 bortle

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Bortle 3 on a good night, that'll be me.

 

Certainly very dark last night with the Winter Milky Way visible.

 

Different story when the neighbour's external insecurity lights go on.

Good point there. The summer Milky Way is a relatively 'easy' spot, being bright and well defined. Looking outwards away from the centre of the Galaxy the winter Milky Way is a rather more elusive target and needs dark skies to see well.

Until I moved into the country side I had no idea about 'the outward view' of the Milky Way. A lovely, wide river of stars flowing past Orion's left shoulder and down into Puppis. Altogether more ethereal than the bright galactic centre.

Blue3.jpg

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Normally a 4 I would think but definitely get into the 3s on a good night (usually when I am working)

I appreciate that I am more fortunate than many

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Good image, LaserJock.

Some of the grading systems around are crazy - Needless rates my area as Bortle 5! Granted, it may be so on some nights, but when the sky is clagged up with thin cloud or mist.

Going to treat myself to a Unihedron Sky meter soon....

Edited by Beulah

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I found an iOS app called Dark Sky Meter, which attempts to give an SQM reading.<br />

<br />

I tried last night under partly cloudy skies, aiming for a large clear area of sky. The reading was 18.44, which correlates reasonably well with my NELM of 4.5 (I do know that the relationship is not necessarily that rigid).<br />

<br />

Since then, I've been doing a fair bit of reading on Sky background, surface brightness and visibility of faint objects for my site. It does not make for happy reading and makes me more determined to get somewhere darker more regularly.<br />

<br />

I'll post separately on it later.<br />

<br />

Stu

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Good image, LaserJock.

Some of the grading systems around are crazy - Needless rates my area as Bortle 5! Granted, it may be so on some nights, but when the sky is clagged up with thin cloud or mist.

Going to treat myself to a Unihedron Sky meter soon....

I think simulators like Needless do a good job in trying to raise more awareness of light pollution but I've found the actual figures it gives to be way of the mark and quite often by as much as a full magnitude!

I think theres a lot to be said for Google Maps and a SQM meter. :)

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4 on a "good" clear night for us here, managed a 3 on VERY odd....... and cold... occasions.

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I reckon Lundy island 12 miles off North Devon would be a 1 or 2 bortle

Perhaps, I visited lundy As a nipper. Just reading the criteria I'd imagine you'd want to be a a long long way from any town or city to get no glow down to the horizon . I'm imagining bortle 1 as places with no built up areas for many many miles.

As mentioned , it's quite a rough guide though .

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Perhaps, I visited lundy As a nipper. Just reading the criteria I'd imagine you'd want to be a a long long way from any town or city to get no glow down to the horizon . I'm imagining bortle 1 as places with no built up areas for many many miles.

As mentioned , it's quite a rough guide though .

Yep completely agree with this.

If you think of the Bortle scale covering the complete globe rather than just the UK then Bortle 1's are probably somewhere like mid Atlantic, Bortle 2's 'true dark sites' like Namibia, Arizona deserts etc, Bortle 3 would probably cover the very best sites in Western Eurpoe + Uk so Scottish highlands, Norway maybe?? Thats just the way that I read the Bortle scale anyway so I'm gonna change my NELM 6.6 skies to a Bortle 4. :)

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Yep completely agree with this.

If you think of the Bortle scale covering the complete globe rather than just the UK then Bortle 1's are probably somewhere like mid Atlantic, Bortle 2's 'true dark sites' like Namibia, Arizona deserts etc, Bortle 3 would probably cover the very best sites in Western Eurpoe + Uk so Scottish highlands, Norway maybe?? Thats just the way that I read the Bortle scale anyway so I'm gonna change my NELM 6.6 skies to a Bortle 4. :)

Lol, psychologically an improvement at any rate mike ! Ha

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