What's your Bortle number?

[DaveS]

There was a time, even here, when on a good night I could see all the main stars of Ursa Minor, now it's only the main three.

[coulthamst]

8 with tendencies towards 9.

[jnb]

Probably a 4 based on visiibility of the milkyway and M33. It might get to 3 in the early hours when the councils now turn off some of the distant lights and it probably drops to 6 or worse if the neighbours leave their lights on (fortunately they don't very often)

[Qualia]

7/8 on the city roof top about 3 when I head out on the bus.

For those in a similar situation don't be down hearted! We know dark sites are the bee's knees for astronomy but if you have 8" of aperture or more you can do a lot.

• You don't need dark skies to view solar system objects such as the Moon, Sun, Jupiter or Saturn.
• You can view the entire Messier list, allbeit you will always get a better impression of them from a dark site. 
• You can feast your eyes on as many open clusters as your heart desires.
• You can split hundreds of double stars.

You also get the chance to use different techniques which will make you stronger when out at a dark site.

You need to up the power on wide-field eyepieces, which typically narrow your FOV and dim even more that distant DSO. We could moan about this and be all tragic but it actually helps train your eye to discover fainter objects. When you get out to a dark site, so long as you have a general idea of where the DSO is, you point in that direction, check your map and off you go; you can pick of Messier's wonders, for example, with relatively little problem. "Oh look, there's one, there's another, and another!" At an urban site, you know it's a very different game. You need a detailed map, you need to read it well, and there's no room for error when star-hopping. Discovering something like M 76 or M 74 in a dark setting may need little more than a gentle pat on the back. If you can do this in an urban setting, you've accomplished quite a significant feat in stargazing.

[Naemeth]

Between 8 and 9 . The site where the astro club meets is probably between 5 and 6 but is difficult to tell due to local glare.

[Chucknorris1975]

6.5-7

[LukeSkywatcher]

I just asked wiki. based on http://en.wikipedia.org/wiki/Bortle_scale it's probably 6.

According to this link,my location is a 4.

[wxsatuser]

Put 5 but may be at times it could be 4.

[SnakeyJ]

Hmm checking Wiki, I probably get up to 3 on a good night at home  - though that can be compromised occasionally by domestic security lights triggered by nocturnal cats/foxes, or even the misses visting the loo.    Probably a range of 4-3 is a good estimate!      I did quite well on the CRE's Orion poll last year, but  will have another go at NELM indication - this is always ruined by computer displays while imaging, so will have to when reasonably dark adapted.

[DaveS]

Well now....

I've been looking at Stelarium, and according to its LP scale I was getting a definate 7 on Saturday, possibly hitting 6, better than I'd thought. I haven't altered my vote, because I'm not sure that wasn't a fluke.

According to the LP guide again, when I gave up astronomy (Because of the LP  ) I was getting a solid 6 edging to 5 on a very good night, from the same location.

Depressing isn't it

[AlexB67]

Another handy tip is pick your targets close or near to zenith as well as you can  that are available in the observing time. I rarely waste my time with anything above 60 degrees from zenith where I am for DSOs, and usually higher up ( unless I want to see something and have no choice for the time of year where it can be seen I'll it a go) . If I look to my west and north it is waste of time looking into the city lower down above 45 degrees from zenith, but right above, east and south east it is that much better.  I can certainly see  more than a few of the brighter 7 stars in  Orion on a good night if I look hard enough naked eye after midnight, though when it comes to Ursa minor facing towards the bad side into the city, a more depressing story.

Bortle is all well and good I guess, but it is a kind of average and basic guide, if I had an SQM-L meter and pointed it in various directions I would get some very different results depending on orientation. if I looked from zenith going towards the north west I'd say Bortle 7 to 8 would not be a bad figure a lot of the time.  I'll pick  based on the better options I've got and try to make the most of it.

[Beulah]

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.

[rory]

heres a nice little chart for working out your *bortle scale*  . I originally put myself as a 6 but probably more a 7 after reading this.

http://www.bigskyastroclub.org/lp_bortle.html

[Mike73]

heres a nice little chart for working out your *bortle scale*  . I originally put myself as a 6 but probably more a 7 after reading this.

http://www.bigskyastroclub.org/lp_bortle.html

Yeah I think the Bortle scale is pretty open to how you want to interpret it really. If you go by the NELM's then even the darkest place in the UK which is Scotland and has a SQM 22.1 / NELM 6.6 is still only just Bortle 3!! 

Light pollution maps are ok to give a rough idea but a SQM meter is probably the best way of seeing how dark your site is but even they aren't perfectly accurate.

[Paul73]

Well now I know what Gegenschein is! I'm pretty sure that my garden is 5 going to 4 in the early hours. But I still can't see M33 or the Owl nebula even with the scope (M33 obviously).

Would a "faintest magnitude detected (corrected vision - averted vision)" be a better way of measuring it?

Paul

[recceranger]

4!

I live in an Army Married Quarter and the MOD can't afford the energy bills to illuminate the estate.

Happy days!

Cheers Mr Chancellor

[laser_jock99]

Somewhere between 2 & 3.

SQM readings vary on my site between 21.3 - 21.85 a lot depends on how much moisture there is in the air scattering light from distant sources.

A good test of a dark sky site's potential is how dark the undersides of the clouds are!

https://vimeo.com/58415246

https://vimeo.com/21948151

[DaveS]

If I went outside my front door the Bortle would be 9 for certain due to the street lighting, but the lamp posts are lower than the houses round here so my garden is shielded, the main local LP is from lit windows, giving a local Bortle as low as 7 or even 6.5 on a very good night, such as last Saturday. Just shows how locally variable the number can be. Need-Less says 8 or 9 around here.

Still not as dark as I remember in the past, when the Milky Way was faintly visible, as was M31 and M42 was easy, even from here.

[AlexB67]

Well now I know what Gegenschein is! I'm pretty sure that my garden is 5 going to 4 in the early hours. But I still can't see M33 or the Owl nebula even with the scope (M33 obviously).

Would a "faintest magnitude detected (corrected vision - averted vision)" be a better way of measuring it?

Paul

There is  no hard rule as far as I am aware. The whole NELM and Bortle is a bit wishy washy IMHO, and only useful as a rough indicator not using tricks such as averted vision.

Some wil look through a small peep hole and point to the faintest possible star they can see that way and say NELM is x, but that is more akin to the same thing an SQM-L meter where you focus on a small area to give you a localised measurement. Others will look up at an area of sky and conclude it is y. 

Ultimately SQM readings in  mag / arc sec^2 is a more robust and meaningful concept to use to quantify visibility of objects IMO, as Mike already pointed out.

[davefrance]

if it ever stops raining I will check again in real time but checking Stellarium by the warmth of our wood burner I reckon very conservatively a 3.   Don't hold your breath for an update

[DaveS]

Any clag at all in the air can have a disastrous effect in any light polluted area, as it doesn't just dim the stars but heavily back-scatters the LP compounding the effect.

[DaveS]

There is  no hard rule as far as I am aware. The whole NELM and Bortle is a bit wishy washy IMHO, and only useful as a rough indicator not using tricks such as averted vision.

Some wil look through a small peep hole and point to the faintest possible star they can see that way and say NELM is x, but that is more akin to the same thing an SQM-L meter where you focus on a small area to give you a localised measurement. Others will look up at an area of sky and conclude it is y. 

Ultimately SQM readings in  mag / arc sec^2 is a more robust and meaningful concept to use to quantify visibility of objects IMO, as Mike already pointed out.

To be fair, I think the Bortle scale was only ever intended as a rough rule of thumb, rather than a precise measurement. And it will depend on such things as age and tiredness.

I just use the unaided Mk1 eyeball to judge the local quality, which is what my poll was after.

[rory]

id love just a single night sat up a mountain in that Atacama desert .  it would be mind blowing I bet !  

[Superdavo]

Probably about 6.5 for me.

David

[AlexB67]

To be fair, I think the Bortle scale was only ever intended as a rough rule of thumb, rather than a precise measurement. And it will depend on such things as age and tiredness.

I just use the unaided Mk1 eyeball to judge the local quality, which is what my poll was after.

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.