Final Report: Dark-Sky Measurements at Organ Pipe National Monument

Casper, Dennis; Esquerdo, Gilbert

The goal of this project is to find a simple method for measuring night-sky brightness to an accuracy of 10% or better. Sky brightness measurements are needed for any long-term assessment program of the effects of light pollution on night-sky quality. The National Parks and Conservation Association (NPCA) stated that "The National Park Service must be proactive and lead by example to aggressively reduce sources of light pollution within the national parks." We have modified the Night-sky Brightness Monitoring Protocol previously developed at Organ Pipe Cactus National Monument (ORPI) in order to make it quicker and easier to execute. This technique uses a small telescope to do aperture photometry and is now simplified to where one person can accomplish the data collection in three hours. In an effort to further streamline data collection we have explored using wide-field CCD imaging in parallel with the modification of the current protocol. Full-sky data collection has been conducted four times at ORPI, at Kitt Peak National Observatory, at Saguaro National Park East and West, and at Vega-Bray Observatory. Additional data collection has been done at Chiricahua National Monument (CHIR), Jarnac Observatory, and Tumamoc Hill Observatory. Along with the measurement experiments, important information has been gleaned about the relationship between atmospheric conditions and night-sky brightness. It has become clear that otherwise photometric (cloud-free) skies vary greatly (up to one magnitude per square arcsecond) in night-sky brightness, depending on the amount of particulates and moisture in the atmosphere above the observing site.