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Cherry Springs SQM

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#1 IVM

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Posted 18 November 2013 - 01:47 PM

I believe I got my SQM-L two years ago and in Cherry Springs (a state park in Pennsylvania) 21.7 mag/sq arcsec overhead (away from Milky Way) was the norm. In the last six months or so I am measuring 21.5 if not worse. I blamed a variety of conditions that were specific to this or that night but now I am afraid that it may be a real, consistent change in the light pollution in the area. I haven't had a really outstanding viewing from Cherry Springs during this time (I am usually going visually for details in galaxies) but I cannot say the views have been systematically worse than before. And I don't know how accurate the Sky Quality Meter is in this sense - I know it is consistent to a few hundredths and I always average out the variation within those bounds by taking multiple measurements from the same point in the sky. But long-term consistency, such as year over year, may be a different matter. So it is not inconceivable that the difference (21.7 to 21.5) was due to some kind of drift in the device or perhaps to some damage that it sustained in transport. Can anyone please comment?

P.S. Since the time I bought my SQM Cherry Springs has been pretty much my only observing site. There is one other site from where I made a few measurements, but that site has a huge brightness gradient over the sky, and for that reason alone I would not expect those measurements to resolve the question if something went wrong with the SQM-L. Whether I could or not, I did not as a matter of fact notice any systematic brightening at that other site.

#2 knightware

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Posted 18 November 2013 - 03:06 PM

That is really discouraging. I would recommend that you compare readings taken by someone else with a Sky Quality Meter taken at the same time and place if at all possible. I don't think it has to be at Cherry Springs, but that would be optimal. I tend to get readings within about .02 mag/sq arcsec of other SQMs present when I observe.

If your meter has lost calibration for some reason, I believe Unihedron will re-calibrate it for you. They are always quite responsive with me.

#3 Tony Flanders

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Posted 18 November 2013 - 03:16 PM

How many readings are you talking about?

My guess is that it's a combination of three things. First of all, bad luck -- you just happen to have hit Cherry Springs on a succession of nights with poor transparency, which tends to increase skyglow.

Second, at any site in the Northeast, skyglow tends to increase fairly dramatically when the leaves fall from the trees.

It is also known that light pollution at Cherry Springs has increased due to fracking. That's presumably both because of flaring and the added light of truck headlights and industrial infrastructure.

Dirt on the front window would obviously change the SQM-L's sensitivity. I doubt the change is due to drift in the optics or electronics.

#4 IVM

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Posted 18 November 2013 - 04:53 PM

Thank you, Phyllis and Tony, for this advice and information.

I tend to go there two times a month and make at least one (averaged) measurement on each night... so ten measurements in the last 6 months and three dozen in the last two years may be the number.

#5 Dave Mitsky

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Posted 18 November 2013 - 06:41 PM

Have you seen the videos on the decrease in the darkness of the skies at CSSP that Gary Honis has posted on YouTube?

http://www.youtube.c...h?v=fXaieJrH3tA

http://www.youtube.c...h?v=wBpP3uxJ3OY

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#6 IVM

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Posted 18 November 2013 - 07:53 PM

I had not - thank you, Dave. The average SQM readings in the last two years at the end of the second video (21.36 and 21.54 mpsas) seem brighter than what I remember measuring with my SQM-L in those two years. I need to pull out my measurements from my records, but it seems brighter by 0.1-0.3 mpsas. Is there a known systematic difference between SQM and SQM-L (the later lensed model of Sky Quality Meter) measurements? Also, were the measurements in this video made overhead? In Cherry Springs, the sky can be brighter by 0.2 mpsas at least if you go (with the SQM-L) to 30 degrees from the horizon in some directions. My measurements were made at the zenith or within 20 degrees of it if the Milky Way was there.

The diagram and table at the end of the second video is excellent work and now I really feel I need to compile my SQM data in a comparably precise form.

#7 darknesss

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Posted 18 November 2013 - 08:24 PM

Second, at any site in the Northeast, skyglow tends to increase fairly dramatically when the leaves fall from the trees.

Everybody should plant pine trees, everywhere.

#8 George N

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Posted 18 November 2013 - 10:22 PM

Back at CSSP 2013 the park manager said that IDAS is considering re-evaluating the park's 'gold' status. It might be dropped to a 'silver' level by IDAS. His concern was the long-term impact from the lights associated with the gas industry infrastructure (equipment yards, and lighted facilities, not drilling).

However, I've found that humidity and transparency have an impact on SQM readings. My own readings at CSSP over the last 4 years have run from 21.4 to 21.7, with most nights being 21.6. I've had the exact same levels and variability at my Adirondack camp (but thanks to the mountains, I don't have CS's good horizon views, except looking south down the lake).

#9 IVM

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Posted 18 November 2013 - 11:00 PM

Interesting info, George. Is the park status with IDAS based strictly on factual darkness or on such soft matter as future concerns and preservation success?

Well, I went through my notes and it turns out that I made far fewer measurements than I thought and even fewer of them were made overhead and therefore directly comparable:

mid-May 2012 through mid-May 2013: 13 nights, clear to mostly clear, transparency decent to above average, average 21.71 mpsas
mid-May 2013 through October 2013: 6 nights, clear or mostly clear, transparency decent to above average, average 21.56 mpsas

P.S. This could still be a regrettably protracted effect of summer humidity this year. I certainly hope so.

#10 GlennLeDrew

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Posted 19 November 2013 - 06:43 AM

Natural airglow probably does vary with solar activity. In any event, it is a variable quantity on time scales short and longer, with a range of perhaps 0.5 magnitude at any one site.

#11 Seanem44

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Posted 19 November 2013 - 11:25 AM

This is very discouraging.

#12 mountain monk

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Posted 19 November 2013 - 06:27 PM

Dave,

Thanks for those youtube videos--they are as compelling as anything I have seen on this issue.

Dark skies.

Jack

#13 George N

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Posted 19 November 2013 - 11:57 PM

Interesting info, George. Is the park status with IDAS based strictly on factual darkness or on such soft matter as future concerns and preservation success?

....


The IDAS status depends on both current darkness level, commitment to keeping the park dark by the owners (state of PA for CS), and commitment of the locals to dark sky preservation at the park. If you search around on the web you can find copies of both CS's original submission to IDAS and their official designation statement. It's been a long time since I found them and I've lost the links.

For example, in CS case the state has taken action to limit gas drilling in the immediate area, and one of the two nearby towns, Galeton, has changed out all of its streetlights to full-cutoff, specifically to help preserve dark sky at CS. The gas industry has agreed to not flare on moon-dark weekends, but they must keep the towers lit. None of that is of much problem right now since there is little or no drilling in Potter County because of the low price of natural gas.

On the other hand, PA has yet to enact anti-LP regulations for the oil & gas industry, although regs similar to those currently in Texas are under consideration.

It is my understanding that the IDAS has (or is trying to get) a grant to pay for full-time sky brightness monitors for all of its dark sky parks, with CS being probably the first to get one.

#14 Nightfly

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Posted 20 November 2013 - 05:53 AM

I've been monitoring my site in eastern Maine since 2007 and there has been a consistent degradation of overall darkness starting in 2010 with conditions poor by comparison during the last year or so. I do not believe it is related to increase in LP, but overall airglow with the increase in solar activity. The average in 2007/2008 was 21.7 with a current average of 21.5 when there is no Milky Way is overhead in the spring and fall.

This change has been consistent even on the best of nights where a .2 change is noted in the range of dark nights. In 2008 I noted a range of 21.6-21.8 on the very best nights and now I am seeing a 21.4-21.6 on the very best nights. I have confirmed this visually as well. The skies just don't look "quite right" compared to my recollection of five years ago. I would imagine this would only be noticeable under good dark skies to begin with. Cherry Springs qualifies.

#15 IVM

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Posted 20 November 2013 - 11:56 AM

I appreciate these responses and information. It will really be nice if it is just the solar activity.

#16 Dave Mitsky

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Posted 21 November 2013 - 05:01 PM

I can't speak to the question of solar activity but there's little doubt that the skies of Cherry Springs have brightened as a result of fracking in adjoining counties.

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#17 IVM

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Posted 22 November 2013 - 10:00 AM

In 2010 I saw a light dome in the east (ESE? probably 30 degrees high but comparable in brightness to zodiacal light - or so it seemed to me). And once, probably around that time, I saw a vertical or near vertical streak of light in the east (straight E?) - very narrow, perhaps 10 degrees high. The light dome was presumably development area illumination or flaring, and the streak (as I learned from the videos you linked) was tower illumination. And around that time (winter 2009-2010) it was difficult to get a room in local motels and there were plenty of trucks on the road, including at night and on occasion actually standing at night in the large (usually closed) parking area on the other side of the road from the Astronomy Field. They kept their lights off though when standing; it was not a bigger problem than the night traffic to the camping ground is in season. All that disappeared by the end of 2010 if I remember. One must assume that there is some residual impact on sky brightness generally, but at least all obviously bothersome aspects of the drilling development in my observation did not last longer than about 10 months in 2010. Just thought I would mention what I remember in this connection.

#18 George N

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Posted 22 November 2013 - 09:41 PM

In 2010 I saw a light dome in the east (ESE? probably 30 degrees high but comparable in brightness to zodiacal light - or so it seemed to me). And once, probably around that time, I saw a vertical or near vertical streak of light in the east (straight E?) - very narrow, perhaps 10 degrees high. The light dome was presumably development area illumination or flaring, and the streak (as I learned from the videos you linked) was tower illumination. And around that time (winter 2009-2010) it was difficult to get a room in local motels and there were plenty of trucks on the road, including at night and on occasion actually standing at night in the large (usually closed) parking area on the other side of the road from the Astronomy Field. They kept their lights off though when standing; it was not a bigger problem than the night traffic to the camping ground is in season. All that disappeared by the end of 2010 if I remember. One must assume that there is some residual impact on sky brightness generally, but at least all obviously bothersome aspects of the drilling development in my observation did not last longer than about 10 months in 2010. Just thought I would mention what I remember in this connection.


At the 2013 Cherry Springs Star Party the park ranger noted that while drilling in Potter Co is currently nil (thanks to the fall in natural gas prices), his LP concern is not so much from drilling activity, but rather from the "long-term increase in industrial infrastructure" resulting from the gas development. He pointed to increases in population in the area (the 'gas jobs' people) and lighted gas related facilities, pumping stations, etc. I have noted the recent (2013? or 2012?) construction of a large gas industry equipment storage yard along Rt 6, just to the east of Galeton. This looks like a large parking lot (bigger than a Wal-Mart super store) filled with trucks, various equipment, piles of gas pipeline, etc. It has "parking lot" type lighting that seems much brighter than Wal-Mart would use.

The ranger (also a leader at the IDSA) noted that PA has no Light Pollution control regulations for gas & oil industry. He mentioned efforts to get PA to institute such regs, aimed not so much at drilling, but at the related infrastructure and pipelines. He noted that the state of Texas has effective anti-LP regs for the industry, and he is hoping that PA adopts something similar.






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