On Sunday September 27th West Coast lunar observers will be treated to a rare event. Starting at 6:45pm the Moon will rise already eclipsed by Earth’s shadow. The moon is also at its closest approach to the Earth in its orbit as well (known as a Super Moon by the public) and it is the first full moon after the Autumnal Equinox making it a Harvest Moon.
For best viewing it is recommended that you find a location high enough to allow an unobstructed view of the horizon. The moon will rise already in eclipse and as the sky fades from twilight to full darkness viewers will be able to observe a condition known as a “blood moon”. This is caused by the sun’s light being refracted by the upper atmosphere and directed to the moons surface.
The atmosphere filters out all color but red giving the moon a red shade. The intensity and brightness of the color is affected by upper air particulates and can be much more dramatic in effect when recent volcanic or fire soot is circulating in the atmosphere.
Each of the lunar events described occur regularly. The Harvest moon happens each year after the Autumnal Equinox, the moon reaches close approach every 27.3 days in its orbit, and there are two lunar eclipses each year. What makes this event rare is that all three happen at the same time Sunday night. The next event does not take place until 2033, so if you have a chance to get out there and look up!