Sky Quality Meter (SQM) Measurements in Jackson Hole area, Wyoming,
 and Teton Valley, Idaho (Yellowstone & GTNP areas & other locales) (Mountain Time Zone)
Jackson (Hole) Astronomy Club
Beginning April 26, 2005, general elevation for JH is 6,300' (MSL).
  Meters don't  have an equivalence to limiting or stellar magnitudes, so readings are relative only to others on the same scale (MPSAS) and our meters A& B apparently don't read exactly the same, even when placed side by side & readings taken simultaneously.  However, manufacturer advises that a difference of + or - .1 is within design tolerance., regardless of temps -40 to +40F.
 For quick reference however  sky readings of  16  or less are poor;  17 is  good;  20 is very good;  21 - superior; 22 is max.
Seeing is objective and should be G, VG, or E.  All readings should be made with no moon and a min. of  "G" seeing conditions.  See key below.  Color code is for quick area ID. (Users are encouraged to take units out of Jackson on vacation to other cities: Salt Lake, Boise, Denver, Cheyenne, Casper, Sheridan, Phoenix, Boston, Cody, Great Falls, Seattle, etc.; and to places near observatories such as Mauna Kea, Mt. Hamilton, Lowell, Kahului, San Diego, Taos, Marfa, Cerro Tololo, etc., to get readings that so far no one has recorded.)


   Reader Guidelines for instrument operation and needed information.   link info.

SQM Readings, 2008, for the Jackson Hole Airport

Key
Readers:  WF=Walt Farmer, AN=Arlo Niederer, JF=John Farmer, BB=Bill Braman, MS=Mike Silverman, (Ed Henze, Eleanor Onyon, Loretta Scott - Gp1)
GPS: if available / Readings: in degrees.minutes.seconds. First reading is N latitude, 2nd is W longitude.
We have two meters:  MA = Meter 1, MB = Meter 2.  Both are version Mark 2. MC = Meter 3.
Seeing:          G - Minor star fluttering, minor breeze or warm air rising              VG - Reasonably steady
                       E - Superior, very steady seeing, no wind or warm air rising
Color coded areas for quicker reference:
Jackson/Wilson    Grand Teton NP/Moran   Yellowstone NP        NW WY     SW WY       E  WY     Driggs/Victor, ID      Other      Out of WY
Scroll right for complete matrix.
Date Loc UTC / MDT
Temp (F)		 SQM reading
(MPSAS)		 Reader Description of location, ambient light, GPS, etc.
All W readings are negative (-)		 Zenith description Seeing
20050426 aaa 0600 / 0000 / 21 MA = 21.52
MB = 21.62		 WF N. Jackson, 505 Ponderosa Dr., deck,  .5 mile from airport lights,     43* 35.87' N  x  -110* 44.70' W Tail star in Big Dipper E
20050427 aab 0600 / 0000 / 21 MA = 21.45
MB = 21.50		 WF Same as above Tail star in Big Dipper E
20060728 baa 0545 / 2345 MC = 21.61 AN 43.34.41 x 110.44.59
Backyard (Grand Cosmic) Observatory in Bar B Bar		 ? ?
20060728 bab 0555 / 2355 MC = 21.53  AN 43.34.32 x 110.44.38, Bar B Bar Entrance ? ?
20060728 bac 0559 / 2359 MC = 21.60 AN 43.34.28 x 110.43.52, Gros Ventre Jct. ? ?
20060728 bad 0605 / 0005 MC = 21.48 AN 43.35.27 x 110.42.21, Kelly Rd. Turnout ? ?
20060728 bae 0613 / 0013 MC = 21.58 AN 43.37.14 x 110.40.10, GV Campground Ent. ? ?
20060728 baf 0620 / 0020 MC = 21.57 AN 43.37.33 x 110.37.24, Kelly , WY ? ?
20060728 bag 0626 / 0026 MC = 21.55 AN 43.38.31 x 110.37.21, Slide Lake Jct. ? ?
20060728 bah 0630 / 0030 MC = 21.52 AN 43.39.16 x 110.37.24, Teton Science School Jct. ? ?
20060728 bai 0637 / 0037 MC = 21.45 AN 43.40.26 x 110.38.14, Antelope Flats. ? ?
20060728 baj 0642 / 0042 MC = 21.46 AN 43.39.55 x 110.39.49, Mormon Row ? ?
20060728 bak 0649 / 0049 MC = 21.42 AN 43.39.54 x 110.41.37, 191-Antelope Flats ? ?
20060728 bal 0703 / 0103 MC = 20.96 AN 43.36.11 x 100.43.54, JH Airport Park. Lot ? ?
20060728 bam 0714 / 0114 MC = 21.46 AN 43.32.48 x 110.44.20, 191 Park Sign South ? ?
20060728 ban 0719 / 0119 MC = 21.48 AN 43.31.43 x 110.44.20, Fish Hatchery Turnout ? ?
20060728 bao 0723 / 0123 MC = 20.92 AN 43.31.11 x 110.44.46, NMWArt Jct. ? ?
20060728 bap 0727 / 0127 MC = 20.02 AN 43.30.24 x 110.45.20, Flat Creek Motel ? ?
20060728 baq 0730 / 0130  MC = 20.75 AN 43.29.28 x 110.45.40, N. Jackson Welcome Sign ? ?
20060728 bar 0737 / 0137 MC = 20.66 AN 43.28.47 x 110.44.33, E. end of Broadway ? ?
20060728 bas 0743 / 0143 MC = 18.67 AN 43.28.47 x 110.45.39, Jackson Town Square ? ?
20060728 bat 0748 / 0148 MC = 20.11 AN 43.28.22 x 110.45.37, Phil Baux Park ballfield ? ?
20060728 bau 0753 / 0153 MC = 19.98 AN 43.28.41 x 110.46.13, 89-22 Jct. ? ?
20060728 bav 0802 / 0202 MC = 19.67 AN 43.28.20 x 110.47.19, Albertson's ? ?
20060728 baw 0810 / 0210 MC = 19.93 AN 43.27.29 x 110.48.60, JHHSchool ? ?
20060728 bax 0814 / 0214 MC = 19.24 AN 43.27.32 x 110.47.38, Smiths ? ?
20060728 bay 0820 / 0220 MC = 21.13 AN 43.26.70 x 110.47.10, River Rock Lodge ? ?
20060728 baz 0825 / 0225 MC = 21.36 AN 43.24.54 x 110.46.22, 89-S. Park Lp. Jct. ? ?
20060729 caa 0515 / 2315 MC = 21.56 AN 43.52.54 x 110.27.51, Mel Tucker's home, Pacific Crk. ? ?
20060729 cab 0537 / 2337 MC = 21.58 AN 43.52.12 x 110.30.40, Pacific C reek Dugway  ? ?
20060729 cac 0543 / 2343 MC = 21.47 AN 43.51.16. x 110.31.10, Pacific Creek Jct. ? ?
20060729 cad 0549 / 2349 MC = 19.64 AN 43.50.35 x 110.30.39, Moran park entrance  ? ?
20060729 cae 0557 / 2357  MC = 21.41 AN 43.48.40 x 110.31.35, Marker 187 turnout  ? ?
20060729 caf 0604 / 0004 MC = 21.45 AN 43.47.15 x 100.32.21, Moose Head Ranch & 89  ? ?
20060729 cag 0610 / 0010 MC = 21.42 AN 43.46.24 x 100.33.19, Cunningham Cabin  ? ?
20060729 cah 0619 / 0019 MC = 21.41 AN 43.45.00 x 110.37.37, Snake River Overlook  ? ?
20060729 cai 0630 / 0030 MC = 21.48 AN 43.43.40 x 110.39.35, Teton Point Overlook ? ?
20060729 caj 0635 / 0035 MC = 21.53 AN 43.41.28 x 110.40.19, Glacier Vierw Overlook  ? ?
20060729 cak 0644 / 0044 MC = 21.41 AN 43.38.10 x 110.43.00, Albright Turnout  ? ?
20060729  cal 0031 / 1931  MC = 20.47 AN 43.35.21 x 110.49.36, Four Seasons Peak patio, Teton Village ? ?
20060730 cam 0606 / 0006  MC = 18.41 AN 43.35.15 x 110.49.36, JH Tram, TV  ? ?
20060730 can 0611 / 0011 MC = 21.41 AN 43.34.57 x 110.49.56, JH Mtn. Resort Condos  ? ?
20060730 cao 0618 / 0018  MC = 21.40 AN 43.35.90 x 110.49.90, TV entrance  ? ?
20060730 cap 0653 / 0053  MC = 21.39 AN 43.38.00 x 110.43.00, Albright Turnout  ? ?
20060723 daa 0400/2200 ?-21.32 JFBB 43.50.94x110.34.04, Signal Mtn. summit Vega E
20070723 dab 0553/2353 ? - 19.52 JFBB 43.55.79x110.38.40, Leeks Marina, parking lot lighting nearby Cygnus E
200710113 faa 0230/2030 ? - 20.06 Gp1 43.28.672x110.46.281, N. end of EGVButte Cygnus E
20071014 fab  0215/2015 ? - 21.34 Gp1 43.37.9000x110.42.952, Albright Turnout in GTNP Cygnus E
20061022 fac 0545/2345 ? - 20.66 Gp1 43.28.550x110.45.060, Jackson alley Cygnus  E
20061022 fad 0300/2100 ? - 21.40 Gp1 43.38.550x110.37.347, Jct. of Kelly and GV Rd. Cygnus E
20070724 dac 0613/0013 ?-20.83 JFBB 43.54.19x110.38.68, Colter Bay, marina lighting nearby Cygnus G
20070724 dad 0630/0030 ?-19.73 JFBB 43.52.64x110.34.56, Jackson Lake Lodge, parking lot by pool w/nearby lights Cygnus E
20070724 dae 0645/0045 ?-21.96 JFBB 43.50.75x110.36.04, Chapel of the Sacred Heart Cygnus E
20070724 daf 0655/0055 ?-19.44 JFBB 43.50.63x110.36.66, Signal Mtn. parking lot Cygnus ?
20070724 dag 0713/0113 ?-22.06 JFBB 43.50.47x110.30.44, Moran school Cygnus g
20070714 eaa 0515/2315 ?-21.86 MS 43.52.77x110.27.66, 14780 Braman Rd., Moran, WY Vega E
20070715 eab 0530//2330 ?-22.12 MS Same as above ? ?
20070716 eac 0555/2355 ?-21.92 MS Same as above ? ?
20070717 ead 0544/2344 ?-21.58 MS Same Cygnus E

Here is a description from the manufacturer Unihedron, regarding their means of measurement:
Magnitudes are a measurement of an objects brightness, for example a star that is 6th magnitude is brighter than a star that is 11th magnitude.  The term arcsecond comes from an arc being divided up into seconds. There are 360 degrees in an circle, and each degree is divided into 60 minutes, and each minute is divided into 60 seconds. A square arc second has an angular area of one second by one second.
STYLE="text-align: left; color: rgb(204, 204, 204);">   The term  magnitudes per square arc second  (MPSAS) means that the brightness in magnitudes is spread out over an square arcsecond of the sky. If the SQM provides a reading of 20.00, that would be like saying that a light of a 20th magnitude star brightness was spread over one square arcsecond of the sky.
Quite often astronomers will refer to a sky being a "6th magnitude sky", in that case you can see 6th magnitude stars and nothing dimmer like 11th magnitude stars. The term "6th magnitude skies" is very subjective to a persons ability to see in the night, for example I might say "6th magnitude skies" but a young child with better night vision might say "7th magnitude skies". Nobody has performed the task of defining a relationship between the two methods of sky brightness  (x magnitude skies and magnitudes per square arcsecond) -- probably because one is subjective and the other is objective and a wide variety of people would have to be polled.  The "magnitudes per square arcsecond" numbers are commonly used in astronomy to measure sky brightness, below is a link to such a comparison. See the third table in section 10 for a good chart showing how these numbers in magnitudes per square arcsecond relate to natural situations:  www.stjarnhimlen.se/comp/radfaq.html
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