BORTLE 5

[DAVE AMENDALL]

Hi, Is Bortle 5 classed as moderate light pollution or worse?.............Dave

[vlaiv]

Not sure how to answer that. Scale has 9 steps and that is smack in the middle of it

But then again, if you consider difference between Bortle 9 and Bortle 5 and on the other hand Bortle 5 and Bortle 1 - perceived difference / enjoyment improvement is much greater on 5-1 side.

[Waddensky]

The darkness is about the same as a first quarter Moon illuminating a dark sky. It's far from great, but if you're used to Bortle 9 for example it makes a huge difference, of course. If you're driving to a Bortle 5 spot for a night of stargazing, I'd suggest to drive a little further 😉.

[ScouseSpaceCadet]

As an example, I live in Bortle 8. 5.5 miles outside of a large city centre but, still within the city boundary. Multiple sources of local light pollution, i.e. street lights, neighbours' windows and security lighting. Plus surrounding sky glow from one million people squashed together.

If i had an astronomer friend or relative living in Bortle 5, I'd be happy observing in their yard, but I wouldn't travel a significant distance just to observe at Bortle 5, or usually book a holiday with observing time in any more than Bortle 4 (rural/semi rural)

Bortle 5 is moderate light pollution, usually encountered in a less densely populated suburban area on the fringes of a town or urban conurbation.

 

 

[TerryMcK]

https://en.wikipedia.org/wiki/Bortle_scale

[Ken82]

I think the bortle scales are often outdated. Unless you evaluate the LP yourself it’s a difficult one. 
 

Where I live is supposed to be bortle 5/6 but numerous new build houses have gone up within a few miles in recent years yet the bortle scale hasn’t changed. 

[DAVE AMENDALL]

Thanks for the input which must be pretty accurate. My views of deep sky objects from so called Bortle 5  my back garden are quite good except for galaxy spiral arms which prove elusive. Three miles down the road Whatton and Orston rural villages show dramatic improvement. Probably Bortle 4 there...Dave

[fifeskies]

posted this before but its a handy quick reference

 

[Guest]

I am technically in Bortle 5 on the edge of Bortle 4 but have a well lit dual carriageway within 100 yards west and very few houses then fields then the sea eastward. I can literally see a LP gradient above my head.

Suffice to say I rarely do anything visual to the west of zenith and enjoy what feels like Bortle 3 at 45 degrees to east. 

 

[John]

4 hours ago, DAVE AMENDALL said:

Thanks for the input which must be pretty accurate. My views of deep sky objects from so called Bortle 5  my back garden are quite good except for galaxy spiral arms which prove elusive. Three miles down the road Whatton and Orston rural villages show dramatic improvement. Probably Bortle 4 there...Dave

Sounds similar to my skies, which are listed by "Clear Outside" as Bortle 5.

I get a few nights when it's closer to 4 but it depends which direction you look in !

 

[Waddensky]

23 hours ago, Ken82 said:

Where I live is supposed to be bortle 5/6 but numerous new build houses have gone up within a few miles in recent years yet the bortle scale hasn’t changed. 

It depends on the source of the light pollution data. Some sites take actual (recent) SQM readings into account, but most sites use the sky brightness map generated in 2015 from VIIRS satellite measurements.

[Sky-searcher]

The Bortle scale is very good, but there are so many different local factors that make the difference within that. I’m in a Bortle class 4 area. The front of our bungalow has an old type street light across the road, due to the light pollution from the lamp, some less bright objects are not visible. At the rear it’s light shaded & with dark adaptation, the Milky Way is quite easily seen. After 1am the street lights turn off leaving it at something around Bortle 2. The skies are then amazing! I am lucky to live on an island in the Irish Sea, but still under fret of more street lamps, security lights etc from an every expanding town. Think people should eat more carrots, then there wouldn’t be the need for street lights 😂

[maw lod qan]

The image above is wonderful to use as a comparison!

I have to admit seeing it tells me I'm close to a 4-5, than a 3-4.

[DAVE AMENDALL]

Excellent Reference chart. Thanks for sharing  Bortle  6 7 8 and 9  look pretty grim. There is still the moon and planets though...Dave