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Blood Moon: longest eclipse in a century
(versión en ingles)

ESA Space Science Image of the week

CESAR team witnessed and recorded, on 27th July 2018, the longer lunar eclipse in a century, from its location at ESAC (European Space Astronomy Center). A moon eclipse happens when the moon passes into Earth's shadow. Unlike with solar eclipses, you need no special equipment to observe lunar eclipses. You can safely view the eclipse directly with the naked eye.

The eclipse started in ESAC at 21:30 local time, with the Moon just on the horizon already in full umbra. The eclipse progressed for 1h42min in umbra until 23:13 CEST. At 00:19 the Moon left completely the umbra, and at 01:28 the eclipse ended.


The eclipse as seen from ESAC (images Manuel Castillo). Canon EOS550D (1sec exposure, ISO1600). Telescope CG8 20 cm aperture.


Eclipse timelapse.


Steady context cameras with Moon and Mars rising. Left: with Solar Helios dome in front (images Konstantin Karchev). Right: with ESAC D-building (courtesy of Cedric Pereira)


But the Moon does not go fully black during eclipse. It turns deep red because some of the sunlight passing Earth's atmosphere is refracted around our planet's limb and hits the moon's surface. Earth's air also scatters more shorter-wavelength light (in colors such as green or blue); what's left is the longer-wavelength, redder end of the spectrum. It is the same phenomena responsible for sunrises and sunsets: actually the Moon's blood color comes from all the sunrises and sunsets taking place at the same time around the world along the terminator line (day-night boundary).

What is an eclipse? (ESA infography)


For the event, the CESAR team set up several cameras and telescopes:

- 1 newtonian telescope CG8 20 cm aperture with a Canon EOS550D camera

- the white visible Solar dome telescope (9cm aperture) was modified into a Moon catcher, with a new color camera QHY-IIC, and a the solar filter removed.

- Canon XF200 pro-camera for livestream

- Fixed DSLR cameras for context images

The event was streamed live in a experimental set-up. You can re-watch the event in our youtube channel.

The event was twitted by ESA comms and ESAC-Spain comms (thanks Arantxa Alonso, Beatriz Arias and Emmet Fletcher @ ESAC, Emily Baldwin @ ESTEC). CESAR worked on several news around the event :


The observing team at CESAR's Solar dome Helios, ESAC


The ESAC astronomy club organized an event with 50+ people attendance (a sample timelapse from Wouter van Reeven is found here). 

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