Chris did you use that global light pollution map to zoom right down to your street to get the 2017 data on your location. It displays in the traditional lp colours and you can get other info as well. Unless you live on the fringes of Sydney, you are likely into yellow or orange range. Check here:
https://www.lightpollutionmap.info/#...ers=B0TFFFFFFT
You can drag the map around to your area, expand or contract as required. Perhaps you have check this already. The problem with sodium lights is the sky glow contribution, however they can be pretty effectively filtered out by a good light pollution filter. The new STC Multispectrum filter seems to be pretty good,
https://www.cyclopsoptics.com/filter...pectra-filter/
Check out the spectrum bandpass chart by scrolling down. BTW HKD converts to $264 AUD, but there are other lower cost filters.