The world at night offers a wealth of stimuli and opportunities as a resource for Optics education, at all age levels and from any (formal, non formal or informal) perspective.
The starry sky and the urban nightscape provide a unique combination of pointlike sources with extremely different emission spectra and brightness levels on a generally darker, locally homogeneous background. This fact, combined with the particular characteristics of the human visual system under mesopic and scotopic conditions, provides a perfect setting for experiencing first-hand different optical phenomena of increasing levels of complexity: from the eye's point spread function to the luminance contrast threshold for source detection, from basic diffraction patterns to the intricate irradiance fluctuations due to atmospheric turbulence.
Looking at the nightscape is also a perfect occasion to raise awareness on the increasing levels of light pollution associated to the misuse of public and private artificial light at nigh, to promote a sustainable use of lighting, and to take part in worldwide citizen science campaigns.
Last but not least, night sky observing activities can be planned and developed following a very flexible schedule, allowing individual students to carry them out from home and sharing the results in the classroom as well as organizing social events and night star parties with the active implication of families and groups of the local community.
Some related works:
Salvador Bará, The sky within your eyes (Eye aberrations and visual Astronomy), Sky and Telescope, 126 (2), 68-71 (August, 2013). (Full text)
Salva Bará, Naked-eye Astronomy: Optics of the starry night skies, Proc. SPIE 9289, 12th Education and Training in Optics and Photonics Conference, 92892S (July 17, 2014); http://dx.doi.org/10.1117/12.2070764 (Full text)
Salvador Bará, Marisol Robles, Isabel Tejelo, Ramón I. Marzoa, and Héctor González, Green Laser Pointers for Visual Astronomy: How Much Power Is Enough?, Optometry and Vision Science 87 (2), 140-144 (2010). (Abstract)
Salvador Bará y Alejandro Suárez, El "láser verde" en Astronomía, AstronomíA, Núm. 114 Diciembre 2008, pp. 76-83 (Equipo Sirius, ed). (Full text)