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HOW WE MEASURE NIGHT SKY BRIGHTNESS Chaco Sky Survey Data Acquisition Protocol Four sites will be chosen for the survey. They may be the visitor's center, campground, water tank and Pueblo Del Arroyo. Each site will be documented by GPS measurements, and reference Horizon pictures during the day. The tripod will be aligned with the North Star. Rebar stakes or surface markings will be installed to ensure repeatable site set up. Measurements are to be taken when the sun and moon are more than 18 degrees below the horizon, and no clouds are in the sky. Days and times shall be random, but well documented. Data shall be collected during each new moon window. Horizon images shall be taken every 15 deg. covering the full 360 degrees. A zenith image will be taken with north up. Twelve images will be taken at 45 degrees altitude at every 30 degrees, zenith up, starting at north. The horizon content shall be minimal but contained in all horizon shots. Both north images will be duplicated after making the 360 degree rotation. Exposure time will be 90 seconds. All images will be dark frame subtracted. The CCD chip will be cooled to minus 30 degrees centigrade. Data will be initially stored and archived in SBIG compressed format. A separate directory will be created for each data run named by date and location (4-9-01V). Files will be named A through X for horizon measurements, (A=0 deg., B=15 deg., X=345 deg., etc.), Z for zenith, and 45N, 45S, 45E, and 45W for 45 deg. measurements, respectively. Repeated measurements will be double lettered (AA, 45NN, etc.). Data Collection Procedure Set up the survey equipment per the picture in the computer box. Make sure the battery voltage is over 12 volts. Set the camera focus and tripod indicator on "A" pointing north. Set battery mode switch to operate. Green light should come on. Turn on inverter. Its green light should come on. Turn on CCD camera at camera computer. It's orange light should come on. Turn on laptop computer. It should start to boot up. After boot up press the space bar once. At the DOS prompt enter "cd ccd36". At the next prompt enter "ccdops". The software should come up and automatically connect to the CCD camera. Set the cameras cooler to -30. Create a new directory using the date followed by a "W" if at the water tank, or an "E" if at the E line road, etc. This is where the data will be stored. The telescope setup comment field should already be set. After the camera has been at -30 +/- 0.5 degrees for about five minutes begin taking data per the SOW provided by the NPS. There should be a total of 39 images taken and stored. To shut down, set the camera's temperature control to off or inactive. Wait until the temperature regulation is down to 0%. Next shutdown camera control and exit the program. At the DOS prompt turn off the computer. Next turn off the camera computer. Then turn off the inverter, and return the mode switch to its center off position. Unplug all cables in any order and pack up. Note: Do not connect or disconnect any cables while any part of the system is powered up. This could result in equipment or personal injury. You can view some of the raw data, compiled into a 360 degree panorama, by clicking here. Click "BACK" on your browser to return to this page. 'Light domes' from unshielded lighting over metropolitan areas are clear and obvious. Warning: this is a large file. 290k.