1. Atmospheric Distortion Troubles for seers

2. Seeing The term Astronomers use to indicate how good or bad the view is of the sky More of a problem for visible light observers –Particulates –Scattered light –Atmospheric Absorption –Twinkle

3. Particulates, etc Why the sky is blue! Windblown dust Ice crystals in clouds Smog Problems: –Color change –Scattering  dependent Cure: high altitudes

4. Scattered Surface Light Light pollution Hg/Na lamps Cure –Shades –Go where it’s dark (mountain tops) –Low pressure Na preferable: easy to filter –Turn off unneeded lights!

5. Atmospheric Absorption

6. Different molecules absorb different wavelengths

7. Twinkle Pretty but annoying Caused by winds, inhomogeneities, “heat” waves Improved by adaptive optics –Product of 1980’s Cold War technology –Uses segmented mirrors

8. Adaptive Optics Guide star laser bounces off Na in the upper atmosphere Beam reflected back to chip which then deforms to sharpen image See next slide

10. Finally, a plug “Celebrate the exceptional sunny days and starry nights at Yucca Valley’s annual Starry Nights Festival at the Hi-Desert Nature Museum and the Yucca Valley Community Center.” Check website for date, usually end of Sept.