San Jose light pollution + seeing northern lights from the city!

[Julien Lecomte]

Hi everyone!

Here is a 2D spectrum of my local light pollution in San Jose:

And here is a colorized version of the same 2D spectrum:

And the corresponding spectral profile:

Note that this spectral profile is calibrated in wavelength, but it is currently NOT calibrated in intensity, which explains why there is no graduation in the Y axis. I am still working out some issues there.

We can see a number of emission lines caused by mercury vapor and low pressure sodium lamps. But most importantly, we can clearly see the disastrous effect of LED lighting. I warned city officials about that 15 years ago when I participated in a study prior to the rollout of LED streetlights throughout the city of San Jose. In hindsight, I now realize that the "study", which was conducted by paid consultants, was just a pacifier, so that city officials could claim that they had listened to residents' concerns (yeah, right...) I recently contacted my council member (district 7) via email to obtain more information regarding the streetlight program, and more specifically whether or not streetlights are dimmed after midnight (as was promised back then) and what kind of budget savings those new streetlights have brought to the city. I received no response. They completely ignored my email... Surprised? I'm not!

What's next? I would like to measure the transmission of common light pollution rejection filters to find out which ones would work best on some average broadband target (the halo of a face-on spiral galaxy will be used as a reference) Several of you have already reached out to me (Jeff Crilly, Francesco Meschia, and Rich Klein) and I am planning to organize a session within the next couple of weeks. If you own a broadband light pollution rejection filter, I'd like to test it. Feel free to contact me privately.

If you are interested in the results from the first batch of filter measurements, check out this video: https://www.youtube.com/watch?v=KW-6qUbf6zs

Now, I mentioned seeing northern lights from the city in the subject line. That was to get your attention, but there is some truth to it... If you look VERY CLOSELY at the spectra I included above (and if you know precisely where to look), you can actually see emission lines caused by neutral atomic oxygen (OI), in the green and the red part of the spectrum. These emission lines are caused by airglow, which is the same phenomenon that creates the beautiful northern lights we can see from higher latitudes. Isn't it astonishing?! I suspect those lines would get stronger when the solar activity is higher.

More on this soon, in video format. If you are not yet a subscriber, go ahead and "smash" that subscribe button :p (sorry, I couldn't resist) -> https://www.youtube.com/@darkskygeek

Thanks,

- Julien

[Peter Santangeli]

Outstanding work!

Not sure if you have access to one, but I'm happy to loan you my IDAS LPS-P2 if you are still doing analysis.

pete

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[Hy Murveit]

Julien,

I'm going back to your clickbait!

According to this, the OI lines are at 558nm and 630nm.

It looks like your tickmarks are spaced at 31 Angstrom.

So, I tried to place the lines on your chart accordingly.

You said "look very closely" but these arrows are pointing at or very near some big emission lines, so I suspect I have it wrong.

Are the emissions near the arrows the result of LEDs or the airglow?

Hy

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[Julien Lecomte]

Thanks, Pete. Jeff (Crilly) already has me covered with that specific filter.

- Julien

On Sun, May 14, 2023 at 11:31 AM Peter Santangeli <pe...@santangeli.net> wrote:

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