What's the point - Bortle?

[Waddensky]

To compare observing spots, primarily. I don't use the Bortle scale myself (I use SQM values and readings), but I noticed that it gives observers an idea of how much darker a spot will be compared to other spots they're familiar with. It's easier to compare Bortle values than SQM values. 

Average reading in my garden is 21.05 mag/arcsec2 (Bortle 4 I believe). My favourite nearby spot reads 21.41 (Bortle 3).

[JOC]

57 minutes ago, Waddensky said:

Average reading in my garden is 21.05 mag/arcsec2 (Bortle 4 I believe). My favourite nearby spot reads 21.41 (Bortle 3).

Is there a way of easily taking a SQM reading - do mobile phones do it - is there an app for that?  They seem to be quite ubiquitous these days 😄

[josefk]

Hi @JOC there is indeed an app to take SQM readings. I'm not sure how absolutely accurate it can be but as a relative record i find it useful. I use an app called "Dark Sky Meter" on an iPhone and take several readings per night and average them for my observing log. Its definitely sensitive to moon phase and atmospheric moisture (sky glow) so its reading something...

[JTEC]

The skies where I live in Surrey can vary from a (very rare and marginal) 4.5 to a pretty bad 6.  So, I think the Bortle Scale has to be viewed as a somewhat useful but very broad brush indicator.  Some of the criteria do seem rather arbitrary and situation dependent - the detectability of the Zodiacal Light, for example - and some of the visual tests seem substantially dependent on the characteristics of the observer. Dark Sky maps have some limitations as well because most show light shining upwards and not the appearance of the sky when viewed from the ground with light domes from adjacent towns, etc - though it’s perhaps reasonable to assume that there’s a useful correlation. A simpler way of finding darker skies is to identify population centres and where people live and get as far away from them as possible. Applying this in the UK will take you to places where you usually can’t observe anyway because it will be raining. 🤣

[DaveS]

1 hour ago, JOC said:

Is there a way of easily taking a SQM reading - do mobile phones do it - is there an app for that?  They seem to be quite ubiquitous these days 😄

 

1 hour ago, josefk said:

Hi @JOC there is indeed an app to take SQM readings. I'm not sure how absolutely accurate it can be but as a relative record i find it useful. I use an app called "Dark Sky Meter" on an iPhone and take several readings per night and average them for my observing log. Its definitely sensitive to moon phase and atmospheric moisture (sky glow) so its reading something...

The smartphone app is, I think Apple specific as Android 'phones have so many different cameras that it's impossible to quantify them between brands.

FLO have several Sky Quality meters on their site.

https://www.firstlightoptics.com/unihedron-sky-quality-meters.html

 

[JOC]

16 minutes ago, DaveS said:

FLO have several Sky Quality meters on their site.

https://www.firstlightoptics.com/unihedron-sky-quality-meters.html

Nice, but given the cost I think I'm happy living in ignorance LOL!

[JOC]

Seriously, I guess in terms of what's the point of the Bortle scale is that once you have a measurement at a location and a scale of anything you can pictorially represent it esp. on a map.  No different to height contours, bicycle or telescope ownership numbers, numbers of potholes, where an eclipse will be seen, what the weather is like etc. on a map.  Give the numbers colours (esp. lighter to darker colours as appropriate to the scale) and you have an effective tool for communication of the problem to other influencers (i.e. planners or people with projects) who might not otherwise easily and quickly grasp A) the problem and B ) it's magnitude.  OK, exchanging the information may not help with a solution, but at least quantifying things at least helps with the explanation of a problem and they say a picture paints a thousand words.  Well that is one good reason for having a scale at least 🙂

[Naughty Neal]

SQM is typically 19.3 from my back garden viewing position, 10 mins drive I could be in SQM 20.25 places.

 Typically though I'm not a traveller so tend to stick to my back garden as my kit isn't G&G.

Edited February 27 by Naughty Neal

[MonsterMagnet]

18 hours ago, DirkSteele said:

Nothing puts me off as I live in central London so short of perhaps Tokyo or Beijing I live in the worst place in the world to pursue astronomy. Buy I do it anyway.

What the Bortle scale does for me is provide a quick check on what I can expect when I travel and as such whether it is worth packing a scope. Though saying that, I almost always a take a scope anyway.

Certainly, when I finally leave the big smog for a more rural location, the Bortle scale will help me eliminate a few places as if I make the move I want some significant incremental gain on sky darkness.

This is pretty much the same for me.  Central London location but I like to use the scale and maps to get an idea of what it's going to be like when I take my scope on holiday (or even just the Seestar if it's likely to be mostly cloudy).

MM

[Sunshine]

5 hours ago, Steve Ward said:

Well as it's somebody's name I think that's rather petty and schoolyard-like , how would you like folk to start referring to something related to you as Jabba or Neddie rather than your real name ...  😄

  It wasn’t an attack on Mr. Bortle, I’m sure hes a fine fellow, he’ll be ok.

I do like the sound of “Neddie” call me Neddie!

Edited February 27 by Sunshine

[alacant]

18 hours ago, mikeDnight said:

What's the point of the Bortle scale?

People seem obsessed with it. I image. To me, it's useless. Where I live, I can see the milky way. But if there's a moon, haze or I've been looking at my 'phone, I can't. I don't need a number to associate with these observations.
But... Is it a 'good' night if I can see the milky way? No idea until I've assessed the seeing. If it's poor, no amount of Bortle is going to change it.
Cheers and clear skies.

Edited February 27 by alacant

[Backyardscope]

I was in Bortle 8, but now in Bortle 3-4 

[JOC]

I must admit cloud probably trumps Bortle any night of the year in the UK!

[mikeDnight]

15 minutes ago, Backyardscope said:

I was in Bortle 8, but now in Bortle 3-4 

Is that called gloating? 😂

[josefk]

for the purpose of quantifying sky quality for your own observing notes - not identifying a site to travel to obviously - you can also use Ursa Minor.

This was a tip for Auto League observing notes where sky quality is a "required" metric. The sky quality you log is the first numeral.

It doesn't add anything you don't know on the night instinctively but adds another "data point" into your log...

Edited February 27 by josefk

[JOC]

6 minutes ago, josefk said:

for the purpose of quantifying sky quality for your own observing notes - not identifying a site to travel to obviously - you can also use Ursa Minor.

This was a tip for Auto League observing notes where sky quality is a "required" metric. The sky quality you log is the first numeral.

It doesn't add anything you don't know on the night instinctively but adds another "data point" into your log...

Next time I'm out on a starry night I'll check, but given that I know it's up there and can use it to find polaris I suspect I can see quite a lot it it's stars.

[MalcolmP]

1 hour ago, JOC said:

Nice, but given the cost I think I'm happy living in ignorance LOL!

Yes! Totally agree.

However if you have a camera and are curious about all the fuss/expenditure on SQMs (like I was) there is a clever piece of free software called ASTAP that can measure it with two quick snaps  More info on request   

Has anyone mentioned that there is, or was, an app for iOS can do similar

[DaveS]

12 minutes ago, josefk said:

for the purpose of quantifying sky quality for your own observing notes - not identifying a site to travel to obviously - you can also use Ursa Minor.

This was a tip for Auto League observing notes where sky quality is a "required" metric. The sky quality you log is the first numeral.

It doesn't add anything you don't know on the night instinctively but adds another "data point" into your log...

My eyes have deteriorated in recent years due to developing cataracts, so stars aren't as pinpoint sharp as they used to be, having a slight blur around them. Even so, on a good night I would go to 7 on that scale easily.

[DaveS]

I remember, I remember,.... many years ago, living in Acton (West London, about 8 miles from the centre) when I could see all the main stars of Umi.... *sigh*. And I gave up astronomy due to the light pollution...

[MalcolmP]

Ursa minor used to be my goto measure until I got a camera and started stacking

1. shoot yourself
2 Quit looking thro the bedroom window and get outside
,,,
5 Be delighted and rush back indoors to you computer and report on sgl
6 Start a business offering hosting
7 Advertise your domain for sale to a monied person on sgl , , oh hang on, I may have got something a bit wrong there ! 

[MalcolmP]

What's the use ? =
better than Bortle5 gives bragging rights and street cred on sgl
reporting worse than B6,  you're just looking for sympathy and a shoulder to cry on.
 

[JTEC]

Has anyone layered rainfall and other meteo metrics onto a map of UK Bortle data?  

[TerryD]

I use light pollution maps to locate parks and campgrounds with darker skies than my Bortle 6 back yard.  I'm retired and will be moving to Virginia later this year and I'm using the scale to determine areas I want to look for houses.  So yes, the Bortle scale is very beneficial to me. 

[jjohnson3803]

3 hours ago, josefk said:

This was a tip for Auto League observing notes where sky quality is a "required" metric. The sky quality you log is the first numeral.

It doesn't add anything you don't know on the night instinctively but adds another "data point" into your log...

This I like.  My home is almost always a 3, very rarely a 4.

If people dislike Bortle, there's a at least one LP map with color coded MPAS values.  (I'm in a grey zone on that, unfortunately.)

 

[Mircea]

17 hours ago, Sunshine said:

Did I ever mention how much I hate the word "bortle" sounds so ridiculous, out of rebellion I invented Nortle, close enough to bortle and at least for me it sounds better.

Bortle is the name of a person who tried to help a bit amateur astronomers. I respect that and I'm grateful to him for that.

Mircea