29 replies to this topic

[jjbroomco]

I recently read a post here on CN from 2023 about an overall increase in night sky brightness due to the near-peak solar maximum. At first I thought it was my imagination when I noticed my “dark” sites from 2021 seemed brighter in 2024, but now it makes sense, as others have reported it too.

I havent been able to find certain dark-sky objects this year in my 10x50 binoculars. Examples are open clusters NGC 7160 and NGC 7235, and dark nebulae like LG3 or Barnard 171. Even though the transparency forecasts and actual conditions were ideal (plus no clouds or moon), I couldn’t see as much as I had hoped.

I realize there are a lot of variables at play like dark adaptation and possibly thin layers of wildfire smoke. But I’m wondering how much of this is inability to spot deep sky objects is due to airglow.

Has anyone here put off deep sky observing or traveling to dark sites because of the increased airglow caused by solar plasma & winds in 2023-2024? Should I wait until 2030 to do my deep sky observing? (Half joking here…) There doesn’t seem to be any talk about it online.

Edited by jjbroomco, 30 October 2024 - 05:29 PM.

[timelapser]

I guess a specific question would be: has anyone been taking regular SQM zenith sky brightness readings over most of a solar cycle, at the same site?  And to deal with variable transparency etc, what were the best readings 5 or so years ago (solar minimum) vs this year?

[jjbroomco]

That’s a good objective way to test it. I personally have a SQM meter but haven’t taken yearly readings at the same site for comparison. Just not enough opportunities to observe because of work, family, etc.

[AstroFam]

I'm glad to see this post as my teen son and I have had the same wonderment.  We live near Florissant, Colorado under Bortle 3ish sky.  As members of the Colorado Springs Astronomical Society, we also use the club site near Gardner, Colorado which is more like Bortle 2ish sky.  For a few years we've been doing Astronomical League observing programs and have always recorded our SQM numbers for every observing session.  We consistently find slightly brighter skies at both sites.  I'm seeing between 0.2 and 0.3 lower SQM readings plus or minus a little. This is confirmed by at least one other club member with an SQM.  Our deep hope is that solar maximum accounts for almost all of this light increase but we'll just have to see what the numbers show the next couple of years.

Edited by AstroFam, 30 October 2024 - 08:58 PM.

[BrushPilot]

Where I live this isn't a question, it is reality. I've done astronomy through four solar maximums and the airglow is like having a medium sized city to the North East. I should be Bortle 1 due to lack of human caused light pollution but I'm lucky to get 2 under current conditions. If the sky is transparent and I'm well dark adapted I can make out the edge of the Milky Way, but only just. The Aurora can be pretty but it can also destroy any DSO observing.

There is always something trying to ruin an otherwise perfect night – I wonder if there is any real estate openings on Mauna Kea or Teneriffe?

[jjbroomco]

I'm glad to see this post as my teen son and I have had the same wonderment. We live near Florissant, Colorado under Bortle 3ish sky. As members of the Colorado Springs Astronomical Society, we also use the club site near Gardner, Colorado which is more like Bortle 2ish sky. For a few years we've been doing Astronomical League observing programs and have always recorded our SQM numbers for every observing session. We consistently find slightly brighter skies at both sites. I'm seeing between 0.2 and 0.3 lower SQM readings plus or minus a little. This is confirmed by at least one other club member with an SQM. Our deep hope is that solar maximum accounts for almost all of this light increase but we'll just have to see what the numbers show the next couple of years.

Hey, it’s good to hear from a fellow Coloradan. I’m up in Broomfield. The Florissant area is beautiful. Thanks for sharing your experiences with the increased brightness. About a month ago, I went to Agate Fossil Beds in Nebraska, which is supposed to be a dark area away from major cities. But the area was so bright that I didn’t need a flashlight to see where I was going. There was a huge light dome to the south, could have been Cheyenne. I couldn’t spot many of the deep sky clusters I needed for the AL Binocular Deep Sky program. I also may have to put the Dark Nebula program off for a few years. Or switch to images instead of visual observations. Cool that you are doing these programs with your son.

[jjbroomco]

Where I live this isn't a question, it is reality. I've done astronomy through four solar maximums and the airglow is like having a medium sized city to the North East. I should be Bortle 1 due to lack of human caused light pollution but I'm lucky to get 2 under current conditions. If the sky is transparent and I'm well dark adapted I can make out the edge of the Milky Way, but only just. The Aurora can be pretty but it can also destroy any DSO observing.
There is always something trying to ruin an otherwise perfect night – I wonder if there is any real estate openings on Mauna Kea or Teneriffe?

Thanks for sharing your experiences with the same phenomenon. I also couldn’t make out any detail in the Milky Way at my “dark” site (SQM reading was 21.4). I could see the Great Rift but that was it. I like the idea of Mauna Kea. One can only hope…

[triplemon]

Oh, absolutely. The high solar activity does make the skies here in Oregon measurably brighter.
I was the last two months in two locations for multiple nights in central oregon that should be on the dark end of Bortle 2. No cities or even a tiny settlement anywhere near, 6000' elevation.

In both locations I had at least one completely smoke free night with very good transparency and I did still measure 21.6 mags at best. Visually it was also not as inky dark as I remember. I have seen multiples times 21.85 mags or higher there before. I guess when I'm getting higher numbers again in two or three years it will be pretty obvious.

Edited by triplemon, 01 November 2024 - 06:00 PM.

[Astro-Master]

I guess a specific question would be: has anyone been taking regular SQM zenith sky brightness readings over most of a solar cycle, at the same site?  And to deal with variable transparency etc, what were the best readings 5 or so years ago (solar minimum) vs this year?

Five years ago, in July of 2019 I visited a Bortle 1 mountain with an elevation of 9,000 feet.  The Milky Way was blazing overhead casting my shadow on the ground, the Cygnus star cloud was resolved into a myriad of 8th magnitude stars, the SQM, not a SQML was reading 21.95 MPSAS even with the Milky Way blazing overhead.

 

There was, no distant light domes visible anywhere, it was the best sky I've seen in over 45 years, so it was the perfect place to test the sky to see how much it has changed over the last 5 years with the solar max doing its thing.

 

In June of 2024 near new Moon, I returned to the same mountain, but the magic was gone, the Milky Way seamed not even a quarter as bright as before, there was still no light domes to be seen, the SQM's best reading was 21.72 MPSAS at 1.30 am, so it was only the solar max to blame for the difference.

Edited by Astro-Master, 01 November 2024 - 06:20 PM.

[jjbroomco]

Five years ago, in July of 2019 I visited a Bortle 1 mountain with an elevation of 9,000 feet. The Milky Way was blazing overhead casting my shadow on the ground, the Cygnus star cloud was resolved into a myriad of 8th magnitude stars, the SQM, not a SQML was reading 21.95 MPSAS even with the Milky Way blazing overhead.

There was, no distant light domes visible anywhere, it was the best sky I've seen in over 45 years, so it was the perfect place to test the sky to see how much it has changed over the last 5 years with the solar max doing its thing.

In June of 2024 near new Moon, I returned to the same mountain, but the magic was gone, the Milky Way seamed not even a quarter as bright as before, there was still no light domes to be seen, the SQM's best reading was 21.72 MPSAS at 1.30 am, so it was only the solar max to blame for the difference.

Thanks for your post. Hopefully in another five years or so, we’ll be able to see the Milky Way in all its glory again. In the mean time, I guess I’ll switch to some “star” projects…variable stars, double stars, solar neighborhood, asterisms, etc.

[WillR]

I had no idea this was a thing. I had just posted on another topic that my skies seemed noticeably brighter than a few years ago. This could account for at least some of it.

[rgk901]

I have no hard evidence but the 2 or 3 different dark sky spots from which I could clearly see the milky way have brightened up to the point of barely perceiving our galaxy.

Noticed this brightening over many trips past couple years or so...and actually looked it up on space weather site

[Keith Rivich]

I have 25 years experience at our dark site outside Leakey, Tx. Just a few years ago SQML's would be in the 21.5 to 21.8. The last two years we have been lucky to hit 21.0 to 21.3. Nothing in the area has changed light pollution wise. San Antonio (100 miles east) has grown a bit but most of that has been on the east and north side of the city. 

 

As stated above we will see in a few years if solar sky glow is to blame. 

[N-1]

My impression is the same, the sky between the stars, even from a world-class dark sky site, does not appear as dark to me at present. Airglow responds well to filtering, though, so it's definitely not as bad as other types of light 'contamination'.

[Redbetter]

I guess a specific question would be: has anyone been taking regular SQM zenith sky brightness readings over most of a solar cycle, at the same site?  And to deal with variable transparency etc, what were the best readings 5 or so years ago (solar minimum) vs this year?

Yes, I have at several sites, and the sky has become much brighter at all of them.   Typical difference has been about 0.35 mag brighter at dark sites and sometimes about 0.5+ mag brighter without obvious aurora activity at the time.  I haven't put it all into a spreadsheet yet for more careful comparison, but the difference has been obvious in the readings as well as visually.  Too often I get readings brighter than 21.0 mpsas now at sites that were hitting 21.5+ mpsas often enough 3 or 4 years ago.  The zodiacal band has become very difficult to trace even when well placed high in the sky, while in solar minimum I could trace it even at a ~Bortle 4 site (which was a solid Bortle 3 on good nights when the band was more apparent.)  

[DenverGreg]

There is historical SQM-LE data archived at https://globeatnight.org/gan-mn/.

 

I would expect this dataset to be able to demonstrate the effect of airglow related to the solar cycle.

[BrushPilot]

There is historical SQM-LE data archived at https://globeatnight.org/gan-mn/.

 

I would expect this dataset to be able to demonstrate the effect of airglow related to the solar cycle.

Thanks for the link – it's too bad the data set for the Utah dark sky site only covers 2017-18 as that is close to solar minimum at a dark sky site at mid latitude. It would be perfect to get their readings now.

Even more perfect, a dataset from a dark sky site at the equator and then every 10 degrees progressing north. It would be interesting to see if the glow increase is linear or some other gradation.

The magnetic pole is heading for Russia but is still on the Canadian side of the north pole so even though I'm only at 57 north, the glow can be terrible and even on fairly good nights, you can see big glow starting in the NE like a middle sized city 60 miles away.

 

On a Star Trekkian note – even when I'm grousing about the air glow, I like to see that our magnetic 'shields' are up and running.

Edited by BrushPilot, 11 November 2024 - 07:02 PM.

[timelapser]

There is historical SQM-LE data archived at https://globeatnight.org/gan-mn/.

 

I would expect this dataset to be able to demonstrate the effect of airglow related to the solar cycle.

Thanks a lot for that, Greg.  Looking at the data, the darkest site with the longest stretch of data I noticed is the Elsterland Observatory, south of Berlin.  Lorenz's sky brightness map shows it at 21.5 mpsas, so not pristine but not too bad for central Europe.

 

Here's a plot of the sky brightness there for January and February 2017-2024 (excluding 2022 which only had 11 days data those months):

I plot the darkest reading each night.  The green lines show times of full moon, when the sky goes up to 19 or 20 mpsas.

 

Coming off the previous solar maximum around 2014 the darkest nights are getting darker until solar minimum around 2020.  Then they generally get brighter approaching the next maximum this year.  One excception is really dark skies in February of this year - I'm not sure what's going on there.

 

Light pollution should only get worse, so it does look like we can see the effect of the solar cycle on airglow.    The range of darkest skies from solar max to min is very roughly 0.5 mpsas, so roughly comparable to the measurements folks posted above.

 

There are lots of caveats - eg the data doesn't specify weather conditions and I haven't filtered out nights with auroral activity.  Also it should definitely be easier to see this effect at a truly dark site.

Edited by timelapser, 20 November 2024 - 05:38 PM.

[Special Ed]

My SQM-L records here confirm what others have reported.  My skies are roughly 0.2-0.4 brighter than they were during solar minimum.  I've been keeping records at my observatory for over ten years.

[mrflibbles]

I had suspected, but thought it was in my head. This is really interesting.

 

I realize this is a old thread but the info is quite good, so I'm reviving it on purpose. Just because this is information others can benefit from.

[12BH7]

Yup, to my north east is nothing but wilderness for hundreds of miles. Yet the sky is milky looking out there. That used to be my primary viewing location. Now, it's just another patch of sky.

[rgk901]

milky is exactly it... even adding magnification doesn't darken the sjy like previously...in all directions not just towards the ligh dome.

the good news? it can only get better!

[Jon Isaacs]

I have frequent SQM and SQM-L measurements from our place in the high desert east of San Diego.  

 

The skies have certainly been brighter the last two years.  Last October and November were the worst, 20.80 - 20.90 mpsas after the end of astronomical dusk.  

 

These last couple of months, the skies have been getting darker again, 21.2 mpsas on the SQM is pretty normal April 29th, the skies overhead measured 21.33 mpsas on the SQM and 21.42 mpsas on the SQM-L.  

 

 

Jon

[triplemon]

There is hope.

[ABQJeff]

Add one more who has seen a couple tenths change in SQM-L readings at my dark site (21.9s now read 21.8s, sometimes 21.7s).

But as to whether I don’t observe DSOs due to this, heck no. I still observe.

Maybe it is because I only have an 11” and am still relatively new and am only doing NGC and IC objects down to those listed for instance in Herschel II 400, Roger Clark’s 611, Illustrated 650 DSO guide, etc. (basically Mag 14 fuzzy DSOs or brighter). I can still see everything on my lists.

Perhaps if I was trying to do Arp or Hickson galaxy groups at limits of even 20”+ Dobs my observing would be more impacted by solar activity.