Guide to observe the Total Lunar Eclipse on July 27, 2018

EDIT – Discover the lunar eclipse captured by the Stellina telescope on 07/27/2018 in Martigues, France:

Guide to observe the Total Lunar Eclipse on July 27, 2018

Eclipses are considered as the most fascinating natural phenomena we can observe to the naked eye. On the July 27th 2018, around 9:30 pm (Paris time), the moon will pass accross the Earth’s shadow for about 1 hour and 43 minutes. It makes it the longest total lunar eclipse of the 21st century!

When and how observe it? Why does the moon shift its color to orange-red during an eclipse ? How to photograph it ?
Find out in this article all the information that will help you to better understand this rare phenomenon occuring in the night between July 27th and July 28th in France and Europe.

Total Lunar Eclipse september 28 2015, Credit: Guillaume D.

What is a lunar eclipse?

In Astronomy, we can observe two types of eclipses:

• A solar eclipse: it occurs when the Sun, the Moon and the Earth are perfectly aligned according to this order. The sun is then more or less covered by the lunar disk. Solar eclipses can be divided into 4 other types, in respect to the alignement of these three bodies: total eclipse, annular eclipse, partial and hybrid. The most astonishing eclipse as we imagine is obviously the total eclipse, when the moon covers entirely the solar disk. Actually, the Earth-Moon distance is 400 times shorter than the Earth-Sun distance but the diameter of the Moon is also 400 times shorter than the sun’s diameter. Thus, the apparent size (apparent diameter) of the Moon is similar or even identical to the apparent size of the Sun as seen from an observer on the ground.
• A lunar eclipse: it happens when the Moon is not this time located in front of the Earth but behind it. The Moon is then eclipsed by the Earth’s shadow. In contrast to a solar eclipse, an eclipse of the Moon can be easily observed and is harmless for our eyes.

Eclipses, whether they are solar or lunar, occurs at a specific moment of the day. If we look at the Earth-Moon-Sun configuration, we notice that a lunar eclipse will only be visible during the night whereas a solar eclipse can only be spotted at daylight.

Moreover, a lunar eclipse can only happen at a full moon phase because it is when the Sun, the Earth and the Moon are closest to an alignement. However there are not always perfectly aligned otherwise there will be a lunar eclipse every full moon, every month. At least, two is the minimum number of lunar eclipses estimated to occur each year. The total eclipses are the rarest and they do not occur every year.

Position of the Sun, the Earth and the Moon during a total lunar eclipse

Different kinds of Lunar eclipses

Although total eclipses are the most impressive to observe, they are relatively rare. The moon never crosses the shadow of the Earth in the same identical way. In respect to the part of the umbra or penumbra where the moon is shading, we differentiate 3 types of eclipses:

1. Penumbral lunar eclipses: the moon stays only in the penumbral part of the Earth. These eclipses do not pretend to be entirely interesting since it is difficult to notice a strong difference of brightness in comparison of a traditionnal full moon.
2. Partial lunar eclipses: a part of the moon is fading in the Earth’s shadow. Visually, this phenomenon produces a side of the moon totally black whereas the other side is still illuminated direcly by the sun. Such an eclipse could be considered as moon phase changing within hours. Except that during an eclipse, the moon is perfectly full.
   

   Partial lunar eclipse before totality, september 28 2015

3. Total lunar eclipses: the whole disk of the moon dives in the Earth’s shadow or ‘umbra’. The moon is not completely black but reflect an intense and peculiar orange color, visible to the naked eye. The brightness of the Moon is so low that stars at the background are even visible! You can find an explanation of why the moon has this color below.

The total lunar eclipse of July 27th, step by step

A total eclipse is not instantaneous. In other words, in order the whole surface of the Moon to cross the Earth’s shadow, there must be a series of phases in which the Umbra shades progressively the Moon until it reaches the lowest brightness. These phases or steps are actually corresponding to the 3 types of lunar eclipses already mentionned: the Moon first goes into the penumbral (penumbral eclipse) than shades slowly in the Earth’s shadow (partial eclipse) and finally becomes entirely hidden in the Umbral (total eclipse).

Below are listed the different steps of the total lunar eclipse of July 27th 2018, given in Paris time zone:

The full moon will rise at the East horizon around 9:30 pm. However, the eclipse will have already started two hours prior but the totality phase will begin at the same time the moon will rise.

• 9:30 pm: Beginning of the total lunar eclipse. The moon appears orange and is very dim. On a normal day, the rising moon is also orange because the atmosphere scatters the colors to keep only the orange one. But here, the moon will also be orange because of the total eclipse.
• 10:21 pm: Maximum of the total eclipse. It is at this moment that the Moon reaches its minimum brightness in the sky and its strongest coppery hue.
• 11:13 pm: End of the total eclipse. Beginning of the partial eclipse. The Moon loses its coppery color in order to become gradually white. The Moon is still in the shadow of the Earth but recovers its usual brightness and color.
• 12:20 pm: End of the partial eclipse. Beginning of the penumbral eclipse. The moon looks like a typical full moon. A photo can help you better notice a possible darker part on the moon.
• 1:30 am (July 28th, 2018): End of the penumbral eclipse and end of the lunar eclipse. The moon becomes nothing but a simple full moon.

Why is the Moon orange during a total eclipse ?

During an eclipse, we saw that the shadow of our planet is projected onto the surface of the Moon. This shadow would be completely black if the Earth did not have any atmosphere. In fact, the edge of the Earth is marked out by our atmosphere. The light coming from the Sun is absorbed by a thick atmospheric layer composed of particules of air, water and more. Because these particles scatter blue light, they aborb this color from the sunlight to let the others escaping as a filter. The result is that if you remove the blue color, you get a rather orange hue.

Blue and purple strips caused by ozone atmospheric scattering. Credit: Guillaume D.

The Moon gets this tint more or less accentuated according to the thickness and the density of the atmosphere at the moment of the eclipse. Moreover, as the atmopheric layers don’t have the same composition, it is even possible to see other grading colors right before or right after the totality. The image above shows blue and purple strips on one side of the moon caused by the light aborption taking place in the ozone layer.

How to observe and capture the total eclipse ?

A total lunar eclipse can be observed without any protection, since it is simply a full moon plunged into the shadow of the Earth. Consequently, there is no risk to harm our eyes, unlike solar eclipses which require the use of suitable filters.

Thus, a lunar eclipse can be observed with the naked eye, as well as with a pair of binoculars, a refractor or a telescope. There is not a method of observation better than others. For example, looking at the total eclipse with our own eyes lets us see the stars in the background sky as the moon is getting into the shadow. Of course, you will also be able to see the orange color of the moon. In another way, a telescope allows you to admire in detail the surface of the moon entirely tinged with shades of orange and red.

In order to photograph the lunar eclipse, three methods can be adopted according to the equipment you have:

• If you have a wide angle camera (no zoom), you will not be able to get a close-up view of the moon. However, you will have the opportunity to capture the landscape surrounding the moon: starry sky and landscapes in the foreground. A tripod is highly recommended to stabilize your camera in order to take long exposure pictures.
• If you have a camera with a zoom lens (200mm, 300mm … etc), you can get amazing close-up views of the moon. You will also need a tripod. The most important thing is to manually choose a short exposure time to avoid having motion blur caused by the motion of the moon and the Earth.
  Typically, an exposure time of less than 2 seconds with a zoom lens of 300 mm should be a good showcase.
• If you have a telescope –reflector or refractor– you can try to photograph the eclipse by sticking your phone’s camera to the eyepiece. This is a technique used by amateur astronomers who want to try astrophotography, but don’t have the appropriate equipment yet. Be careful not to move the telescope while shooting! For the next eclipses, the Stellina telescope will be an ideal solution to capture these moments, thanks to its integrated sensor and automated mode.

You are now ready to attend the total lunar eclipse of July 27th! Feel free to share with us your most beautiful pictures of this event. They might be selected to appear in a special dedicated article on our website.

Guillaume Doyen, blogger at Vaonis.com