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A scientific survey suggestion

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#1 Eddgie

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Posted 17 March 2020 - 12:11 AM

With the great decline in traffic in some cities due to covid19, it would be interesting to see if the drop in tailpipe emissions improves transparency and reduces light pollution readings.  I believe tail pipe emissions and car headlight and taillight emissions are huge contributors to the problem.

 

In cities like SF or other areas where traffic is hugely reduced due to social distancing, it would be an interesting time to get a baseline of SQL readings to see if (and how much) the decline during this period of extreme limit vehicular use. If areas go under lock down it would be very interesting to see if There is any impact.

 

If you have an SQL meter is recording site near you and you notice a very large decrease in road traffic it would be interesting to see if readings change.


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#2 Sleep Deprived

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Posted 17 March 2020 - 12:20 AM

One of Seattle's local TV stations picked up a story about watching the planets in the morning, since we shouldn't be going out and rubbing elbows at the coffee shops for a while:

 

https://komonews.com...g-entertainment

 

This is not a local story, but it applies to anywhere that the Covid19 is preventing people from living their (social) life as they normally would.  Fewer people on the road, fewer emissions, fewer headlights, etc, may make for a better skygazing experience.  Hopefully, some of the people who 'try' this end up getting hooked!


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#3 MikiSJ

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Posted 17 March 2020 - 02:24 AM

During the day of 9/11 and the next two(?) days there was no air traffic and the atmospheric scientists took the opportunity to do some good research. I did't follow the research but the current reduction in auto/truck traffic might be an opportunity for some serendipitous atmospheric research - an not just for astronomy.


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#4 PrairieAstronomer

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Posted 17 March 2020 - 02:26 AM

My observations, admittedly local to Southern California and also positively affected by a lot of recent rain, is that the mid-level and upper-level air is much clearer than it has been in several years. I would estimate that road and freeway traffic volume is 1/3 or less of normal.

 

The sky is noticeably darker right up to the Moon’s disk and some nights Archenar is very bright and unmistakable low in the southern sky, just a few degrees high at culmination. My backyard is usually ~16 to 18.2 mag/arcsec**2 on clear nights, depending strongly on local humidity (marine layer), which strongly scatters the very prevalent light pollution. I measured 18.9 the last clear night and the number of faint stars not normally visible certainly helped confirm it.

 

Interesting historical note: I’ve read that Eudoxus made such careful measurements of the brightnesses of the same stars both in ancient Egypt and Ancient Greece (Rhodes), hence as a function of zenith angle (airmass) at culmination, that atmospheric extinction coefficients can be inferred. Wow!

 

It will be interesting if there is a measurable dip in CO2 or other aerosols.

https://www.co2.earth/daily-co2


Edited by PrairieAstronomer, 17 March 2020 - 05:07 AM.

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#5 Migwan

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Posted 17 March 2020 - 06:36 AM

This is empirical only, but I noticed long ago that it appears noticeably darker at 03:00 than at Midnight when in the outskirts of small cities and towns here in central Michigan.   If out in the country five or six miles, that difference seems to disappear.  I've always thought this was due to there being less traffic and interested to see if this is so.   jd



#6 bogg

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Posted 17 March 2020 - 09:54 AM

Over Italy the pollution decreased significantly after quarantines were issued

#7 PrairieAstronomer

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Posted 17 March 2020 - 11:57 PM

This is largely because of two factors:

 

- Homes, businesses, car lots, etc. may actually shut off their lights late at night. There are also fewer headlights.

- Water vapor has largely settled out as dew or very low ground-lying fog, leaving the atmosphere drier than in the evening hours.

 

This is empirical only, but I noticed long ago that it appears noticeably darker at 03:00 than at Midnight when in the outskirts of small cities and towns here in central Michigan.   If out in the country five or six miles, that difference seems to disappear.  I've always thought this was due to there being less traffic and interested to see if this is so.   jd



#8 Migwan

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Posted 18 March 2020 - 01:29 AM

This is largely because of two factors:

 

- Homes, businesses, car lots, etc. may actually shut off their lights late at night. There are also fewer headlights.

- Water vapor has largely settled out as dew or very low ground-lying fog, leaving the atmosphere drier than in the evening hours.

Worked nights in and around same towns/cities for years.   Never noticed any businesses or car lots shutting the lights down.   As far as humidity, around here relative humidity rises as temps drop and that continues well past 03:00.   So I kinda doubt its due to a change of humidity. 

 

Home lighting (maybe even indoor lighting) and headlights seems more likely. 

 

jd



#9 Eddgie

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Posted 25 March 2020 - 09:36 AM

After a five week trip I finally returned home.

 

Yesterday (March 25th) was a clear, bright, and dry day in Austin Tx. Rather than the kind of smokey blue that is typical of my spring skies, the sky had a decent light blue color to it that did not whiten substantially towards the horizons.  

 

Now it is typical that about this time of year, we start seeing deteriorating sky conditions due to the agricultural burning that is performed across the border in Mexico every year, so I beat that. The sky looked very good, and in line with my post on the topic, I wondered if this could be do to the dramatic decrease in vehicle traffic, which I theorize to be the greatest factor in light pollution other than the lights themselves due to the particulate matter in the atmosphere reflecting and absorbing light from the ground.

 

As my post suggested, I would take a baseline SQM-L reading and at 10:PM I did so.  My measurement was 18.52 to 18.62 taken over several parts of the sky down to about 30 degrees away from zenith.  This is considerably better than my average night where SQL readings can be in the 17s. This was close to Bortle 6 conditions, so noticeably darker than is typical for my location.

 

I did a nice two hour session and the sky was pretty cluttered with galaxies (though I am using an image intensified eyepiece) and I would say it was the best galaxy observing I have had from my back yard since I started using image intensifiers (which is to say the best ever from my back yard).

 

Now of course the evaluation is anecdotal at this point and it could have just been a fluke weather thing but the sky quality really did seem to be much better than I get on a typical spring night.  This is why I wanted to do this though, and I will continue to do SQM measurements as a baseline until the ag burning makes that impractical.

 

The car traffic is maybe 50% of normal.   The city went on Lockdown last night at midnight, and I expect that the traffic will be lighter today and since the day is forcast to be similar to yesterday (high in the 90s) I will be interested in seeing if there is any change, but I think I need 10 to 20 nights readings at this lowered activity to really be anything close to reliable.

 

Have fun out there.



#10 Jon Isaacs

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Posted 25 March 2020 - 03:35 PM

I took some SQM-L readings a couple of days ago. 18.6 mpsas near the zenith. That's very typical for my backyard. It does get darker but not much. 

 

Of course the prevailing winds are It on the west and to the west about 4 miles is the Pacific Ocean so airborne particle contamination is not a problem.

 

Jon



#11 Tony Flanders

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Posted 26 March 2020 - 06:36 AM

At my country home near the NY/MA border, my SQM readings on March 21 (with lockdown almost complete) were about 0.1 magnitude darker than they had been at the same time of night one week earlier. But that's well within the normal range of variation.

 

The transparency was also quite good, which may or may not have been related to reduced car and/or airplane exhaust. Probably not, given that the transparency this morning doesn't look so hot. In this particular location, light from automobile headlights is a non-issue. The nearest interstate highway is 10 miles away, and it doesn't have a lot of traffic even at the worst of times.



#12 iwannabswiss

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Posted 26 March 2020 - 06:09 PM

NASA and ESA released some images that show the impact or change from reduced emissions over China.  CNN created images using the Sentinel-5P satellite data processed by Descartes Labs showing it's impact around the U.S.



#13 bunyon

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Posted 27 March 2020 - 09:01 AM

It would be nice for some positive to come out of all this.

 

Alas, I have natural limitations to transparency that prevent me testing this. Since working from home, I've had one night of clear skies and then there was significant haze and poor seeing. We may get a clear night next week. Ugh.



#14 Tony Flanders

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Posted 30 March 2020 - 06:16 AM

Three nights ago, at 11:40 p.m. at my country home, I got SQM=21.32+-.01, SQM-L=21.55+-.01

 

That's about as dark as I've ever recorded, and all my other comparably dark readings were taken when there were leaves on the trees, which makes it significantly darker. So I'd have to say that this is almost certainly attributable to the lockdown, one way or another. There has also been a striking lack of contrails.


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