Sky Quality Meter (SQM) readings

[ausastronomer (John Bambury)]

Originally Posted by BPO

Hi guys.

The highest ever reading by my SQM-LE was 22.02 in December 2009. (It's been in storage since then). This was on a moonless night at my very dark permanent observatory site, where there is essentially no light pollution.

Hi,

Where is your observatory located? I am not asking for the street address and number BTW, close enough is good

Cheers,
John B

[BPO]

Originally Posted by ausastronomer

Hi,

Where is your observatory located? I am not asking for the street address and number BTW, close enough is good

Cheers,
John B

Hi John.

It's called Benmore Peak observatory, in the South Island of New Zealand. The site's almost 2,000m ASL, and there's nothing much of anything to speak of for quite some distance in any direction.

[mithrandir (Andrew)]

Originally Posted by BPO

Hi guys.

The highest ever reading by my SQM-LE was 22.02 in December 2009. (It's been in storage since then). This was on a moonless night at my very dark permanent observatory site, where there is essentially no light pollution.

The SQM-LE is powered from a permanent supply: it has no battery.

However, anything much above 22 would be fairly suspect, and, as has already been mentioned in this thread, even the manufacturer states that readings significantly above 22 are likely to be inaccurate.

FYI, Darren says the readings reported on MyDarkSky must be in UTC, so you might want to fix the time on that reading.

Eric, I haven't seem Snake Valley readings appear yet.

Andrew

[ausastronomer (John Bambury)]

Originally Posted by BPO

Hi John.

It's called Benmore Peak observatory, in the South Island of New Zealand. The site's almost 2,000m ASL, and there's nothing much of anything to speak of for quite some distance in any direction.

Well, having a wife who is a New Zealander (we all make mistakes) and having done 30+ trips to NZ in the past 10 years I know how dark it can get in some parts of the South Island of NZ, particularly towards the West Coast. I have never been to Benmore but from memory it is about 100km east of Wanaka? I know how dark it gets South West of Te Anau in Fiordland National Park around Doubtful Sound and Dusky Sound; and further North on the West Coast of the South Island around Westland National Park (Franz Joseph Glacier and Fox Glacier). Allowing for the fact the units can have a 10% (.1 mag) error I would think your reading is accurate as it would be a genuine 21.9 to 21.95 (allowing for unit tolerances). I would think this is about as high a genuine reading as anyone is going to get. This area is certainly as dark and provides as good a sky conditions as anywhere on the planet I have been to. Most importantly, transparency is always very good (when the clouds part) as airborne particulate is usually low. Some places in OZ are just as dark, but dust particulate often knocks the sky conditions back a notch. Unfortunately I don't own any "toy" telescopes to take with me when i go to NZ, so I am stuck with my 16 x 60 binos. I think your reading is right. Some of the high readings from places I know aren't nearly as dark as your area, I take with a grain of salt.

Cheers,
John B

[BPO]

Originally Posted by ausastronomer

I have never been to Benmore but from memory it is about 100km east of Wanaka?

Hi John.

My site is 80km ENE of Wanaka, in the Mackenzie Basin high country. The climate is quite arid by NZ standards, far more so than that of the west coast. Precipitation in the area is around 200-300 mm per year. It is drier at my site, which is 1,500m above the surrounding terrain.

http://www.observatory.org.nz/about.html

http://www.observatory.org.nz/temp/pan1.jpg (4.16 MB)

http://www.observatory.org.nz/temp/pan2.jpg (1.80 MB)

http://www.observatory.org.nz/temp/Pan_max.jpg (5.22 MB)

[erick (Eric)]

Anthony said I could share his email:-

"The SQM has a method for not showing a display if the battery is too low, but there is a possibility that a fluctuating battery voltage, or dying
battery will present different voltages during the measurement cycle.
Generally this has not been a problem. Another way to check the battery
voltage is to get the unit temperature by pressing once, then again and
holding the pushbutton. If the temperature shown is bad, then the battery is probably on the verge of its life.

Also, we have found that not all batteries have the same terminal dimensions, and this could cause a loose or poor connection. This can be
corrected by lightly squeezing the flower shaped connector on the SQM
battery lead with pliers then re-attaching the battery.

Also, Alkaline batteries do not do well in very cold conditions.

The unit does not have a fixed high value because of the nature of the
sensor. In some cases a dark room might yield 24, or just time out.

Oddly, there are places where cloud cover results in darker skies because of the great distance from light pollution. Such places are the desert, the ocean, and the hilltop at Cherry Springs PA. In these cases, not even the light from the sky reaches the meter, and an apparently abnormal reading is obtained.

I hope that helps to answer your questions.

Best regards,

Anthony Tekatch
Unihedron"

[ArcturusMDS (Darren)]

Erick,

I also emailed Anthony and got the same response.

We're trying to do some testing with a dozen or so devices we have. So far we not had a problem, maybe we've not got a battery bad enough just yet. we'll keep testing in various conditions and let you know what we find. we do also regularly calibrate the devices against each other and have yet to find any device inaccurate. we'll keep testing for now.

[ausastronomer (John Bambury)]

Guys,

Please allow my single digit IQ brain to analyse this logically. I indicated earlier that 22.0 was the theoretical maximum and I felt 21.9 was the "practical" maximum because of skyglow and starlight. I did forget to adjust this for the fact there are bugger all stars visible in the Northern hemisphere to create starlite glow I did neglect to allow for the tolerance error of the unit which is stated at + or -10%, or .1 mag. Lets also assume some units could be a "touch" out of calibration, or have a slightly greater tolerance error, so lets allow a tolerance of .2 mag. This takes the practical maximum to 22.1.

Attached is a PDF file extracted from the Unihedron database on their website of all readings > 22.1. There are 8 of them. What I find truly amazing is that the highest 5 readings come from 4 different dark sites in CONUS. ONE OF THE MOST LIGHT POLLUTED CONTINENTS ON THE PLANET. It would be a tie between North eastern CONUS and Western Europe as to which area is the most light polluted area on the planet. Here is a link to the world light pollution map

http://www.lightpollution.it/downloa...idotto0p25.gif

The top 2 readings come from Potter County Pennsylvania which just so happens to be smack bang right in the middle of that really big patch of light pollution in the middle of North East CONUS. I have no doubt the skies there are reasonable (they hold a Star Party there), but darker than anywhere else in the world where people have taken readings from over the past 5 or more years? It's also worth noting that these eight readings >22.1 are all taken in 2005, 2006 and 2007 which in all likelihood would indicate they were taken with one of the older units.

I note the highest reading from Australia is 22.07 from outside Mullawa in WA, which is about 100km West of Geraldton and 500km North of Perth. I have no doubt it's right. There are 3 men and a dog per 1,000 square km out there. But not close to the equal of several readings in CONUS? I note the highest reading from New Zealand is 22.02 from Benmore Peak Observatory. Again I have no doubt it's correct as indicated in one of my earlier posts. But again not close to the equal of several readings in CONUS? I suggest some of you revisit that light pollution map.

You guys believe and think what you wish, that's your choice. But, if you don't believe me, please email Anthony and ask him to include that 23.45 reading of Andrew Murrell's taken at about 11:45pm on 12/10/2007 at Coonababran NSW

Cheers,
John B

[ArcturusMDS (Darren)]

John,

I didn't say I don't believe you. The fact that i'm looking into the issue and testing the units we have suggests I'm open to the fact you could be right.

[ausastronomer (John Bambury)]

Originally Posted by ArcturusMDS

John,

I didn't say I don't believe you. The fact that i'm looking into the issue and testing the units we have suggests I'm open to the fact you could be right.

Hi Darren,

I think looking at the Unihedron Database in all likelihood the problem could be isolated to the older type units. You may not find any issues with the newer units. I think it significant those 8 readings I mentioned would have all been taken with the older units, which is what Andrew and I have. I have repeated the high 22's readings on at least 4 different occasions (not counting Andrew's 23.45) from skies I know aren't 22+ skies, only to find the reading drops by at almost 1 mag when I put a fresh battery in.

Cheers,
John B

[ArcturusMDS (Darren)]

Originally Posted by ausastronomer

Hi Darren,

I think looking at the Unihedron Database in all likelihood the problem could be isolated to the older type units. You may not find any issues with the newer units. I think it significant those 8 readings I mentioned would have all been taken with the older units, which is what Andrew and I have. I have repeated the high 22's readings on at least 4 different occasions (not counting Andrew's 23.45) from skies I know aren't 22+ skies, only to find the reading drops by at almost 1 mag when I put a fresh battery in.

Cheers,
John B

Currently in our Database I think we have 3 reading over 22. The Benmore Park 22.01 reading and a reading of 23.1 in a very dark region of Scotland but with full cloud. The interesting one is the reading of 22.72 in Galloway Forest Park which is designated a dark sky park. The reading is quite a bit higher than other readings taken in the same area. The reading was taken with an SQM-L. My contact in Galloway Forest Park is investigating.

Those light pollution maps do make things look terrible here and in many places the light pollution is terrible. But it's not all bad, there are regions with little or no light pollution at all. Just not as big as your regions.

[BPO]

Perhaps I should add that the 22.02 reading was not the "best" or "worst" from my site...it was basically the only proper one I took, aside from a few tests, before putting the meter back in storage, where it's remained ever since.

[timokarhula (Timo)]

Originally Posted by ausastronomer

I note the highest reading from Australia is 22.07 from outside Mullawa in WA, which is about 100km West of Geraldton and 500km North of Perth. I have no doubt it's right. There are 3 men and a dog per 1,000 square km out there. But not close to the equal of several readings in CONUS? I note the highest reading from New Zealand is 22.02 from Benmore Peak Observatory. Again I have no doubt it's correct as indicated in one of my earlier posts. But again not close to the equal of several readings in CONUS? I suggest some of you revisit that light pollution map.

Cheers,
John B

Hi all,

It was me who submitted the SQM-L 22.07 reading from outside Mullewa, W.A. I visited a remote farm together with Finnish amateur astronomers in December 2009 to do some really dark DeepSky-observations. They had also a SQM which showed 22.09 as best. In a series of three readings I got 22.01, 22.02 and 22.07. That was when I pointed to a relatively "blank" region of the sky, not the Milky Way or the zodiacal light. From here we observed the Light bridge between LMC and the Milky way. See my thread

http://www.iceinspace.com.au/forum/s...ad.php?t=68088

From my regular observing site here in Sweden, the SQM-L has shown 21.48 at most and my naked eye limiting magnitude was 7.4. My Australian site is way darker than that!

/Timo Karhula

[erick (Eric)]

"Pony Club" - Mangrove Mountain. 11:30pm last night - 21.1

[ArcturusMDS (Darren)]

Erick, Add Pony Club to the mydarksky website if you can.

Are you guys still enjoying long dark nights at the moment? Were still stuck in Astronomical Twilight here. Although I did get my first glimps of the milkyway this summer a few nights ago.

[erick (Eric)]

Done Darren, I was going to get to it soon.

[ngcles]

Hi All,

Unusually good night out at my "nearly dark but reasonably convenient" site in the southern highlands (nr Bargo). There is a significant difference between Saturday and Sunday nights (this was a Sunday) I think.

Tonight at 1am I recorded 21.38, 21.38, 21.40 (I take three readings and average -- so 21.39) with my SQM-L pointed at zenith (nr Grus, Microscopium) and 5 degC. This equates to a ZLM of 6.33 (rounded).

This is the best reading I've had there in a couple of years. On Sundays there there is considerably fewer lights on in Sydney (like sports grounds, car-parks etc) and I think this makes a substantial difference. I saw 4 Vesta very easily -- direct vision at mag 5.7 and 40 deg elevation in Capricornus earlier at about 11pm. Could also see with direct vision nearby 27 Capricorni at mag 6.26 when closer to Zenith with no difficulty. The light-dome from Sydney in the northeast was somewhat lower than normal and less bright and the Wollongong light-dome was hardly worth speaking of.


Best,

Les D

[ArcturusMDS (Darren)]

Originally Posted by erick

Done Darren, I was going to get to it soon.

Thanks Erick. It's good to see new Data entered. It's very quiet over here at the moment. Hopefully is should pick up again in 3 or 4 weeks.

[ArcturusMDS (Darren)]

Originally Posted by ngcles

Hi All,

Unusually good night out at my "nearly dark but reasonably convenient" site in the southern highlands (nr Bargo). There is a significant difference between Saturday and Sunday nights (this was a Sunday) I think.

Tonight at 1am I recorded 21.38, 21.38, 21.40 (I take three readings and average -- so 21.39) with my SQM-L pointed at zenith (nr Grus, Microscopium) and 5 degC. This equates to a ZLM of 6.33 (rounded).

This is the best reading I've had there in a couple of years. On Sundays there there is considerably fewer lights on in Sydney (like sports grounds, car-parks etc) and I think this makes a substantial difference. I saw 4 Vesta very easily -- direct vision at mag 5.7 and 40 deg elevation in Capricornus earlier at about 11pm. Could also see with direct vision nearby 27 Capricorni at mag 6.26 when closer to Zenith with no difficulty. The light-dome from Sydney in the northeast was somewhat lower than normal and less bright and the Wollongong light-dome was hardly worth speaking of.


Best,

Les D

Any chance you could register on the website and add your results?

I'm guessing the dark nights are getting shorter down under now as the nights are getting longer here. A few more reading from your guys would be nice before the window closes.

We've been stuck with Astronomical Twilight for a couple of months but things are moving again now.

[erick (Eric)]

Tuesday 22 May, 2012, around midnight, about 1 deg C

Yerrinbool NSW - 20.85