Light Pollution Atlas update

[JoeBlow]

Just noticed Light Pollution Atlas (link below) recently updated, now providing a 2023 map. Sadly it shows significant increase in LP between 2022 and 2023, in the Sydney region at least. This appears to confirm my own visual observations. I suspect the widespread conversion to LED street lamps played a big part in contributing to that.

https://djlorenz.github.io/astronomy/lp/overlay/dark.html

[kvmx]

Good find, I use the site every now and then and never would've thought to check if there was a more current dataset. :thumbsup:
Edit: It appears Melbourne is getting brighter too... :sadeyes:

[OzEclipse]

Over the past 6 years, Young Hilltops council has been installing LED lights. If you are in a high density area, these broad spectrum lights can be bad news. In Young, the council has progressively installed LED cutoff down lights and this has resulted in a corresponding decrease from a peak of 39 nW/sq cm to the current value of 31.5 in the Young town centre which is a relatively light polluted Bortle 4 (2015 World Atlas value).

Meanwhile, my property, 30km out of Young has seen no increase since 2012. I do see great variation in transparency throughout the year but have not noted any visible increase in light pollution in the 4.5 years I've lived here. While skies are always dark and has an average Bortle 2 rating by the 2015 World Atlas, my own visual estimates of Bortle value for my skies vary from Bortle 3/4 when pollen, dust, or smoke fill the air, to Bortle 1 on nights of highest transparency. I can see small light domes around my horizon from Young, Cowra, and the Galong mine. There is a broad very faint glow along the east horizon from the Sydney-Newcastle-Wollongong strip about 250km away.

My quick assessment method is to look for the outer arm of the LMC. LMC ~ 7 deg across. If I can see it naked eye, I know the transparency is excellent. A more rigorous assessment of Bortle rating necessitates estimation of limiting magnitude which is always lower for an older observer like me compared to a younger wide eyed observer.

Cheers

Joe

[Nikolas]

Nice but it doesn't give the actual Bortle Scale

[EpickCrom]

Hi JoeBlow

I love that site, interesting (depressing) comparing how LP has been going up over the years. As I suspected, my backyard has become brighter over the past year :(

Thanks for the heads up on the update!

[OzEclipse]

If you switch to the 2015 world atlas channel, it give a Bortle Estimate.

As I mentioned, Bortle rating is a mix of LP and transparency and varies a lot. Any atlas or survey value is just one point at one time.

When I was in WA in 2023, I noted that the dark skies during my visit were not low Bortle skies and I attributed it to poor transparency from lots of dust suspended in the air.

cheers

Joe

PS: Seems like you can only commennt on this thread if your name is Joe or Ni(c)k. :lol::rofl::lol:

[Nikolas]

Thanks Nick er Joe :)

[JoeBlow]

That's great to hear about Young Hilltop council. When done right LEDs can reduce LP. But doesn't appear to be the case in Sydney at least.

[JoeBlow]

Bortle is a subjective scale, based on visual observations made by indivdiual persons on a given night. Although it is still a useful tool off course. However the Bortle Scale often does not align with these satellite light pollution maps which only measure one specific variable.

[JoeBlow]

My dark sky site was once very comfortably inside a grey zone, now it's very close to the border with the blue zone. This is consistent with the increased brightness of light pollution domes I can see on the horizon. For example, Sydney is about 150 km North of my site. Until a few years ago, Sydney was seen just as a defuse glow along the horizon. Now it makes a small, but distinct, dome above the horizon. Although small, the darkness of the sky in that direction is clearly compromised and affects observations towards the horizon.

[JoeBlow]

Because Joe and Nicks make the best astronomers :lol:

[OzEclipse]

Urban development has expanded mainly eastwards from Young. The plot I showed is for the centre of Young. If you lived 10km east of Young for 10 years or more, you would have seen a fair increase. I do not live in that direction from Young so no increase for me.

[kvmx]

We're all definitely leaders in the field! :lol::lol:

[Startrek]

Thanks , yes I use the Atlas too.
It’s not just LED street lights but population growth and population density ( infrastructure in general) that’s causing LP to increase at alarming rates every couple of years. If you live in Rural or semi rural areas or towns , try imaging towards the centre of Sydney’s Light Dome it will test your patience for the hobby , not to mention neighbours who leave their backyard flood lights on until after midnight.
Your camera sensor will tell you how severe LP is in your location
In Sydney I’m imaging under B8 , using a luminance filter during new moon , a 30 sec sub is virtually a white out , off the Richter scale whereas down south at my Dome under B3, I can shoot 2 min luminance subs and the Histogram is well within range. Same camera 2600MM , same Gain and offset , but with a bigger light bucket 10” f5 Carbon Newt.
Sydney B8 and South Coast Rural B3 are simply chalk and cheese.
Those who live in B1 to B4 are truly blessed in this wonderful hobby of ours.
I haven’t observed in Sydney for years , my 12” Dob has been down at my B3 rural home since 2018.

Martin

[JoeBlow]

Development is certainly another major factor. Sydney for example is rapidly expanding. But the maps also show an increase in LP even in areas with no significant development. Looking around the world, some regions show increase and others decrease in LP, some significantly. Others have remained the same. I wonder if the time and conditions of when the satellite measurements were taken influence the results too?



Same here, for the past year I have left my 10" at my family's rural property 30 min outside of Goulburn. It will likely stay there long term.