I shared this in a post over at CloudyNights and thought it would be good to document this here, in my blog. We are slowly losing the battle over the darkness of our skies and with the emphasis on building here along the Wasatch Front, I do not see that war being won. Our best effort is to try to educate and perhaps mitigate however slightly, the impact of LP on our skies.
I also believe more and more people in the hobby are not visual observers like me, but are imagers. Thus the sky may not matter to them as much. Are our skies getting lighter? Data and experience show they are.
Of my dark sites, one in the Unita Mountains has stayed basically the same but it is a two and a half to three hour remote drive and is only available from June through October. However, even there I am starting to see a slight decline. Of late I can go into late October as we aren't getting the snow we used it until later in the season it seems. Of my sites within 1 1/2 hours of my home there is an impact from all the building going on. I'll share SQM L data since 2014. Elizabeth Ridge measurements are done in late July to early August during my annual visit there (I camp over for 2-3 days). Cedar Mountain is listed here for September Readings as I usually go there in the later spring, summer and into the fall. Forest Road 006 is my main site and these measurements are from October of the year listed. Readings are at zenith and to the south as the southern sky is usually the darkest for me at these sites.
Year Site Reading SQM L
2015 Elizabeth Ridge UT 21.9
2015 Forest Road 006 West Desert, UT 21.84
2015 Cedar Mnt Wilderness West Desert UT 21.85
2015 Conger Springs Western Utah 21.94
2016 Elizabeth Ridge, UT 21.89
2016 Forest Road 006, West Desert UT 21.84
2016 Cedar Mnt Wilderness West Desert UT 21.86
2016 Conger Springs Western Utah 21.95
2017 Elizabeth Ridge UT 21.89
2017 Forest Road 006 West Desert UT 21.89
2017 Cedar Mnt Wilderness West Desert UT 21.85
2018 Elizabeth Ridge UT 21.91
2018 Forest Road 006 West Desert UT 21.83
2018 Cedar Mnt Wilderness West Desert UT 21.82
2018 Conger Springs Western UT 21.94
2019 Elizabeth Ridge UT 21.91
2019 Forest Road 006 West Desert UT 21.81
2019 Cedar Mnt Wilderness West Desert UT 21.80
2020 Elizabeth Ridge UT 21.91
2020 Forest Road 006 West Desert UT 21.79
2020 Cedar Mnt Wildernness W.D. UT 21.78
2021 Elizabeth Ridge UT 21.9
2021 FR 006 WD UT 21.75
2021 Cedar Mnt Wilderness WD UT 21.77
2022 Elizabeth Ridge UT 21.88
2022 FR006 WD UT 21.73
2022 Cedar Mnt Wildnerness WD UT 21.74
2023 Elizabeth Ridge UT 21.89
2023 FR006 WD UT 21.7
2023 Cedar Mnt Wilderness WD UT 21.73
2024 Elizabeth Ridge UT 21.87
2024 FR006 WD UT 21.72
2024 Cedar Mnt Wilderness WD UT 21.69
2024 Conger Springs Western UT 21.9
Elizabeth Ridge has held pretty constant though I must say the light domes in the far distance from Salt Lake area are increasing in height slowly, even from there. I'd say we are up to the 10% to 14% range on the horizon if I am looking southwest toward that region. This is the only site that east, north and south are the best. Even there I am seeing a reduction in darkness.
Forest Road 006 which is my main observing site is really starting to be impacted by all the growth in the south/west Salt Lake Valley and in the Utah County area, especially as Saratoga Springs and Eagle Mountain continue their growth. I've seen a decline of over .14 in 10 years of keeping SQM L readings at this site.
Cedar Mnt Wilderness which I enjoy as there are wild horses out there and other animals and such, is really getting impacted as the Tooele valley and southern Davis County and the western part of Salt Lake County continues to grow and grow rapidly.
Now, having said that, the skies are still plenty dark. The SQM only tells part of the story. I have nights that are those nights and for that I am grateful for where I live. However, I think over the next 10 years I'll see Elizabeth Ridge drop down into the 216 to 21.7 and Forest Road 006 and Cedar Wilderness will go from the lower 21.7 to the lower 21.5's.
Again, SQM L readings are only part of the decline. More noticeable to me is the increase of the light domes. I mentioned the increase at Elizabeth Ridge. At Forest Road 006 the Salt Lake/Utah County light dome has increased from about 10% above the horizon in 2014 to now it is about 20% if I am looking east. I very rarely observing looking east, waiting for those objects to transition to a better portion of the sky later in the night. At the Cedar Mountain Wilderness it is perhaps a little worse. There in 2014 I would say the light dome to the east was about 10% also but is now approaching 25% or so because Salt Lake is directly east of that location. Forest Road 006 is more southerly from the Salt Lake/Utah County dome which impacts view to the Northeast and east.
Also, IF I want to observe on Forest Road 006 on a Friday, I need to be out there by 3:00 p.m. to get my site. That is the greatest impact. People have discovered the site and ATV on it. From 2005 to 2018 I could go out almost any day and only have 1 or 2 people disperse camping about a half mile to a mile away. It is far more on the weekend. I now go there during the week as there is still nobody out there then. It is the same with Cedar Wilderness. More people in the area so more have discovered that. It is why I am taking day driving trips out to the West Desert to find new locations and yes, I am being selfish and not sharing them unless it is with a local amateur whom I know.
I have always and continue to observe in the southeastern, southern and western skies at Forest Road and Cedar Mnt Wilderness, as these are the darkest, especially south and west and of course approaching zenith.
Conger Springs is a different beast. It is very remote, harsh and very, very dark. Probably the darkest site I've been to. During the day you may get an occasional fossil hunter out here (there are some good fossils out there) but they are friendly and leave you alone. You can rock hound by the springs. I usually set up well before the springs. You can see the Salt Lake light dome to the northeast faintly, and the Las Vegas light dome far to the south (I assume it is Las Vegas but is is a dome and it is south of the location but no impact). Hot hot in the summer during the day, cold at night even in the summer and really cold in the winter. Thanks for the post, as you have made me put Conger Springs back on my places to observe and I may plan a late spring trip out there. BTW if anyone goes there, during the day you can hike up to Conger Mountain which has marvelous views all around. I like it better than Great Basin Natl Park because it is so remote and there are no lights out there. No facilities but I can manage that.
So to answer the original question, no my skies are not getting darker. They are dark, but not as dark as they once were and there are more people out using the areas I use to observe. I've played with the idea of looking for a piece of remote remote land I can put a trailer on or build a small cabin and observatory and go and observe from. Maybe, maybe not. We'll see. I still enjoy loading up, the drive out, setting up and enjoying my time out under the stars. However, the days for the western US being great for observing are slowly degrading and over the next 100 years they will be come probably more like the central and then eastern US than they are now. I won't be here so I'll enjoy what I have.
This is the road out to Conger Springs and is near where one location on the road where I will pull off and setup and observe and camp. Wonderful dark skies.
