Sky Quality/Bortle Quesstions

[Shasta55 (Chris)]

Hi all,

this may sound dumb to a lot of you, but anyway.... I have an observing spot not far from my house. It's just off a stretch of road with no street lights in Coodanup WA overlooking the Harvey River Estuary. There are trees behind which do a good job of blocking some of the skyglow from Mandurah & Perth to the north. On the light pollution map it's Bortle 4 with SQM 20.99. But seems better to me - more like 21.5 - 21.7 ish. Observing SE - SW seems good to me. Is this a thing or am I imagining it?

I've included a couple of shots of the Aurora Oz a month back to indicate. They were done with a hand held Android phone - a bit fuzzy.



Chris

[JA]

Hi

If you're using light pollution map info for your SQM readings, then the data you are probably using is from their World Atlas 2015 dataset, yes? If so then it's entirely possible that the light pollution readings have changed over the years, although one would think it unlikely that they'd reduce. The only real way to know is with your own SQM reading, and BTW remember that the SQM readings given are at Zenith, not anywhere down near the horizon or near any light domes, unless of course they're huge.

Best
JA

[Drac0 (Mark)]

You're not imagining it. If you can point towards darker skies, away from the source of major light pollution, you can reduce the overall effect it has. Yes, there will still be some effect, but imaging away rather than over or even towards the zenith can reduce the apparent bortle rating of the area in general.


Cheers,
Mark

[Shasta55 (Chris)]

Originally Posted by Drac0

You're not imagining it. If you can point towards darker skies, away from the source of major light pollution, you can reduce the overall effect it has.

Cheers,
Mark

Thanks for the input. I have a few good spots with SQM 21.76 - 21.88 but they are 30 - 35km further down the estuary. The one I described is just 5km so it's easy to just grab and go when conditions are right.



Chris.

[AussieTrooper (Ben)]

Jeez. Am already jealous of those numbers. I recently moved from a 19.23 to a 19.15 suburb. The difference is very noticable. Gut feel though is that the growth at the new place has been faster than at the old, so the gap is larger than this.
It's at the point where even with 50mm binoculars, I cannot see M42 without averted vision, even when it has good altitude.
As mentioned, there is a differnence when aiming away from whatever the main source of light pollution it.

[EpickCrom (Joe)]

Hi Chris, it seems like you have a nice dark spot there in Mandurah

Awesome that you managed to see Aurora Australia!

[Shasta55 (Chris)]

Originally Posted by AussieTrooper

Jeez. Am already jealous of those numbers. I recently moved from a 19.23 to a 19.15 suburb.

Yes I'm lucky to have good spots within a short drive. My house is in the city centre and is 19.90.

Originally Posted by EpickCrom

Hi Chris, it seems like you have a nice dark spot there in Mandurah

Awesome that you managed to see Aurora Australia!

Yes it was a nice surprise. My granddaughter texted me to come see.
We are pretty much hemmed in by the Alcoa, Boddington Gold & Worsley Alumina sites all down the escarpment. They shine as brightly as the very centre of Perth. Thank the Good Lord for the Peel/Harvey Estuary and the coast!!