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Author (down) Benn, C.R.; Ellison, S.L.
Title La Palma night-sky brightness Type Report
Year 1998 Publication La Palma Technical Reports Abbreviated Journal
Volume Issue 115 Pages
Keywords Skyglow; solar cycle; airglow; zodiacal light; light pollution; observatories; *Light
Abstract The brightness of the moonless night sky above La Palma was measured on 427 CCD images taken with the Isaac Newton and Jacobus Kapteyn Telescopes on 63 nights during 1987 – 1996. The median sky brightness at high elevation, high galactic latitude and high ecliptic latitude, at sunspot minimum, is B = 22.7, V = 21.9, R = 21.0, similar to that at other dark sites. The main contributions to sky brightness are airglow and zodiacal light. The sky is brighter at low ecliptic latitude (by 0.4 mag); at solar maximum (by 0.4 mag); and at high airmass (0.25 mag brighter at airmass 1.5). Light pollution (line + continuum) contributes < 0.03 mag in U, approximately 0.02 mag in B, approximately 0.10 mag in V, approximately and 0.10 mag in R at the zenith.
Address Isaac Newton Group, Apartado 321, 38780 Santa Cruz de La Palma, Spain
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Notes Lots of useful theory on the various contributions to natural sky background level and expected surface brightnesses Approved no
Call Number IDA @ john @ Serial 1101
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Author (down) Arnott, J. T.
Title Growth Response of White and Englemann Spruce Seedlings to Extended Photoperiod Using Three Light Intensities Type Report
Year 1982 Publication Technical Report: Pacific Forestry Centre Abbreviated Journal
Volume Issue Pages
Keywords Plants
Abstract Four seedlots of white spruce (Picea glauca (Moench) Voss) and three of Engelmann spruce (Picea engelmannii Parry), covering a range of 10 degrees of latitude and a range of altitudes, were sown in BC/ CFS Styroblocks and grown in a heated greenhouse and an unheated shadehouse, using incandescent light to provide a 19-h photoperiod. Four intensities of lighting were used: 0, 100,200, and 400 Ix. A second experiment with the same seedlots was conducted in growth rooms that were programmed to evaluate the effect of low night temperature on seedling shoot growth when the photoperiod was extended to 19 h, using a light intensity of 200 Ix.

Shoot length of white and Engelmann spruce seedlings grown under an extended daylength of 100 Ix were significantly taller than the control (0 Ix). There were no significant differences in shoot length or weight among the three intensities of light used to extend the photoperiod for all seedlots except the southern latitude-low elevation population of Engelmann spruce. The more northern populations of white spruce and the high altitude populations of Engelmann spruce did not require light intensities higher than 100 Ix to maintain apical growth. Low night temperature (7°C) did produce significantly smaller seedlings than the warm night (1SoC) regime. However, terminal resting buds of seedlings grown under the cool night regime did not form any sooner than on those seedlings grown under warm nights.
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Call Number IDA @ intern @ Serial 2372
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