Betelgeuse: the story of a mysterious Star

Betelgeuse could have remained just a star among stars. On December 8th 2019, though, an unusual decrease in brightness surprised astronomers worldwide. A decrease in intensity such as this had not been measured for 25 years. Ordinary classified as the tenth brightest star in our skies, Alpha Orionis has currently dropped to the nineteenth place! Is this peculiar occurance a premonitory sign of an upcoming supernova event? Let’s recap the story of the well-known star.

Sky-map of the Orion Constellation. Source: Stellarium.

The star of the stars?

Prior to the December 2019’s dimming event, Betelgeuse has been one of the most studied stars of our sky. For more than a century, astronomers have been fascinated by it and it has been compared to the rest of the stellar population in our galaxy.

Astronomer John Herschel was the first to witness the changing behavior of this star in 1836. The alternating, changing phases of brightness were later verified during the 20th century, and Betelgeuse became part of the semi-regular variable stars category: a type of star that displayed noticeable periodic intensity changes and whose cycle and amplitude vary in time. A property we will explain later in the article.

This red super-giant was not originally famous for its variable properties, which are very well-known in stellar astronomy, but for its angular diameter. Although Betelgeuse is at a distance of more than 400 light-years, its radius is about 1000 times larger than the Sun’s, which levels it up to the largest star visible in the starry sky! A superlative that was kept until 1997 when a larger angular diameter value was measured on the R Doradus star.

Image of Betelgeuse taken by ALMA. The star is here compared to the size of the Solar System. Credit:
ALMA (ESO/NAOJ/NRAO)/E. O’Gorman/P. Kervella

A star with a large angular diameter is very interesting if we want to observe details on its surface. Whereas the majority of the stars can be considered as infinitely small dots which are impossible to view with our telescopes, Betelgeuse has an angular diameter large enough to be noticeable with optical instruments!

Moreover, Betelgeuse was the first star (other than the Sun) to get an experimental estimation of its linear diameter, carried out with the recently-invented interferometric method. To do so, physicists Albert Abraham Michelson and Francis Gladheim used the Mount Wilson observatory telescope in 1921 and ended up with an angular diameter of 0.047”.

By combining light from several telescopes to increase angular resolution in the sky, this instrumental method is now being used by the most advanced astronomical observatories of the world, such as the VLTI (Chile) and CHARA (USA).

The popularity of Alpha Orionis does not rely only on this pioneer study. Betelgeuse was once again at the forefront in 1995 when the Hubble Space Telescope unveiled the very first direct image of the surface of a star.

View of the surface of Betelgeuse as captured by the Hubble Space Telescope (1995). Credit : A. Dupree (CfA), R. Gilliland (STScI), FOC, HST, NASA

In recent years, a handful of images using more developed instruments and techniques were captured. In 2017, the Atacama Large Millimeter/Submillimeter Array (ALMA) provided what is still the sharpest image of Betelgeuse ever.

A strange dimming behavior

The way Betelgeuse is getting dimmer doesn’t align either with the observations that have been gathered for the past 25 years or with the most recent theoretical models. Until now, astronomers have noticed that these brightness variations between magnitudes 0.0 and +1.3 could come from two coupled phenomena:

  • The first one would have a ~400-day-cycle and would be caused by the pulsation of the star’s atmosphere.
  • The second, whose period is much longer – a bit more than 5 years – would be the result of the motion of huge convective cells on the surface of Betelgeuse. The latter theory is likely to be tested within few months, in response to the great interest shown by worldwide observatories towards the recent changing state of Betelgeuse.
Evolution of brightness of Beltegeuse as of February, 10th 2020. Source: @Betelbot

Is Betelgeuse about to explode?

The cataclysmic phenomena of Supernovae is without a doubt fascinating for mankind due to its rarity and of the spectacular show it provides. Indeed, the most massive stars of our Galaxies like Betelgeuse should end the life releasing part of their matter in the form of luminous energy. A star with such bright intensity could be visible in a daytime sky for several weeks. The 1504 supernova from French astronomer Charles Messier’s catalog (M1) would be a historic example of a supernova humans were able to witness. The Crab Nebula was born from it.

Infrared image of Betelgeuse photographed by an adaptive optics system at the VLT. It shows giant structure of circumstellar gaz around the photosphere (2009). Credit:
ESO and P. Kervella

Nevertheless, today’s astronomers are not entirely convinced that a simple and progressive dimming in brightness will result in an immediate explosion of Betelgeuse. Observing light variations coming from the surface only does not necessarily contain all the information of the change that could occur inside the stellar core. Betelgeuse will very likely end up in a supernova. Even if it is currently getting dimmer, astronomers still struggle to equate this change as an indicator that could inform exactly when this explosion may occur.

Certainly no hypothesis is entirely off the mark, and professional astronomers as well as amateurs should be ready at anytime. Betelgeuse has not unveiled all its secrets yet, and could still surprise us as it has in the past. So, observe this red super-giant while it is still possible!

Photographing Betelgeuse with the STELLINA smart telescope

Betelgeuse is so bright in the sky that you can observe it in many ways: with the naked eye, using a pair of binoculars or a telescope… In order to give STELLINA‘s users the possibility of monitoring the variations in the red supergiants’ brightness, the Vaonis team added the star to its catalog of objects in its February 2020 software update (MAJ Stellinapp 1.17). Users are now invited to follow the evolution of the star over the weeks or months, in the hope of witnessing an exceptional supernova.

Betelgeuse STELLINA
Betelgeuse captured by the STELLINA smart telescope in February 2020


After several years spent looking for the perfect stand (tripod) for our space travel companion, we are pleased to announce our new partnership!
What company was the worlds’ best to create a tripod reflecting the aesthetics and quality of STELLINA as well as the ethical values of Vaonis? Our mission and high standards led us to meet the world’s most respected tripod manufacturer: Gitzo.

In September 2019, Vaonis teamed up with the Gitzo brand to equip all of its STELLINA observation stations. Renowned for its excellence, this historical brand is considered the world’s best tripod manufacturer. All Gitzo products are made with high quality materials and assembled by hand in Italy, north of Venice. Combining its French origins with Italian design, Gitzo offers state-of-the-art camera stands using innovative materials such as lightweight, high-strength aluminum alloys to ensure stability and efficiency.

When design meets excellence

A tripod inspired by the Systematic range

Despite their vast range, the specific needs of astronomical instruments required working to design a unique model in the world entirely dedicated to STELLINA. After many echanges and a meeting with Gitzo’s R&D team, the GT3520S-VS model, inspired by the Systematic range, was born.

Systematic is Gitzo’s top range of tripods, perfect for professional photographers using long lenses and heavy equipment. Systematic tripods are the strongest and most stable tripods, they are also modular and can be quickly set up in different configurations both as photography or videography supports. Made with 100% Carbon fibre eXact tubes and innovative design they represent all Gitzo’s high quality and performance. Systematic accessories can be used to adapt to any situation or environment.

Design of a made-to-measure tripod

With its extraordinary stability and perfect aesthetics, this tailored tripod perfectly illustrates the collaboration between 2 brands and their search for perfection.

The first necessity was to reduce the length of the tripod’s legs to increase its stability.

Subsequently, the team’s work focused on tailor-made finishing of aluminum parts injected at low pressure. This injection technique significantly increases the mechanical quality of the part, preventing the appearance of air bubbles that could weaken it. This piece was then treated specifically to get closer to the visual identity of STELLINA.

The next step focused on the bubble level.  If it was too close to STELLINA, visibility in a dark environment could be poor. We decided to create a custom level plate apart so that the bubble level is easily visible during installation.

Finally, the screw tightening locking levers were carefully studied to make their use simple and easy while guaranteeing the overall rigidity of the tripod.

After many prototypes and exchanges between teams of engineers and designers, STELLINA’s ideal partner was created.


STELLINA’s tripod zoom-in

The Gitzo Series 3 Systematic Tripod is a powerful, 3-section, professional carbon fibre tripod designed to safely hold longer lenses and heavy cameras. It is the perfect combination of minimal weight, durability, and uncompromising stability. The tripod weighs only 1.93kg and secures an impressive payload of 25kg. It reaches from as low as 9cm up to 130cm and folds down to 61cm. A highly reliable, versatile solution that’s easy to take anywhere, this model features Gitzo’s Carbon eXact tubes with G-Lock Ultra twist-locks that solidly connect the leg sections and protect them from dust and dirt damage. New, ultra-stable, removable feet make this support even more secure. With a top leg diameter of 32.9mm, this Series 3 model is the perfect choice for exacting professionals who want to travel light but require the adequate levels of stability for professional equipment.


Carbone eXact
The new Carbon fibre eXact tubes are revolutionary and even stiffer to maximize rigidity and image stability. Carbon eXact optimizes the fibre composition for each tube size.

Removable Feet
This functionality allows you to easily replace used feet and to put other attachments such as spikes.

G-Lock locking system
Gitzo entirely redesigned its G-Lock system. G-Lock Ultra offers new ergonomic and resistance performances. It brings a smoother use and efficiently protects the tripod from dust.


Spring-Summer 2019: Astronomical events not to be missed!

For astronomy lovers, the end of winter means the beginning of a new Milky Way season. However, stargazers will need to wait mid-spring to meet the suitable conditions for Milky Way observation. Here is our selection of the best moments you should not miss, from objects to catch through your binoculars or telescopes, to major astronomy events.


A Galactic triplet – March 2019

Leo Triplet. Credit: Philippe Durville

Observing several galaxies within a same field-of-view is not usual. You must already know the famous M81 M82 couple, visible in the winter sky. But, have you ever heard of this 3-spiral-galaxy-composed cluster – M65, M66 and NGC 3628 ? It is called the Leo Triplet, located in the constellation owning the same name. This 3-in-1 target always provides curiosity to observers whatever their skill level. Although they are distant 35 million light-years away from us, these galaxies reveal a lot more details in photography. A fascinating object not to forget!


The Sombrero Galaxy – April 2019

Sombrero Galaxy. Credit: NASA, ESO , NAOJ, Giovanni Paglioli – Processing: R. Colombari

Between the Virgo and the Corvus constellations, a deep sky object is hiding away: in contrast to the majority of face-on galaxies we can usually observe, M104 can only be seen from the side. Using a small-diameter telescope, this strange orientation enables us to focus on its dust line which make up its galactic plane. Located at a distance of 29 million light-years, this 8th-magnitude diffuse galaxy reminds the shape of Mexican hat. Can you see the sombrero too?


The Beehive stellar Cluster – April 2019

M44. Credit: Bob Franke

The Beehive Cluster (M44), also known as Praesepe is a stellar group within the Cancer constellation, composed of relatively young stars whose age is estimated to 600 million years. As a comparison, our Sun is much older, about 4.5 billion years. This wide and bright open star cluster covers a region of the sky which could contain 3 full moons, and shines with a 3.7 magnitude. Easily detectable to the naked eye as a scattered spot, a telescope will unveil its beauty. Notice that an image helps to make out the different colors of the stars, from blue to orange.


The Pinwheel Galaxy – May 2019

M101 galaxy

Located in one of the most popular constellations, Ursa Major, the Pinwheel Galaxy (or M101) is a face-on spiral galaxy. Evolving at 20 million light-years away, this aggregate is made of about one billion of a billion of stars and is about twice as wide as our Milky Way. Featuring a poor brightness, it is recommended to capture it with a telescope in order to identify its spiral arms and internal structures clearly.


The Great Globular Cluster in Hercules – June 2019

M13. Credit: Adam Block, Mt. Lemmon SkyCenter, U. Arizona

M13 is the most brilliant globular cluster we can observe from the Northern hemisphere. A refractor or reflector telescope will emphasize the natural beauty of this target! Containing more than 100 000 suns, its density is so high that it remains difficult to resolve its individual stars to the naked eye. Hercules cluster is part of the unavoidable summer targets to observe and photograph.


The Ring Nebula – July 2019

M57. Credit: H. Bond et al., Hubble Heritage Team (STScI /AURA), NASA

Despite its small angular size and low brightness – 8.8 magnitude – M57 is a planetary nebula which can surprise your mind with its sharp and contrasted edges, both in visual astronomy and astrophotography.  Resulting of a dying star’s explosion, planetary nebulae emit light in a peculiar way: by spectral lines – or colored lines. The highest throughput line is found in the green and is associated to a specific chemical element: Oxygen III. This Oxygen line fits almost perfectly to the highest sensitivity color of the human eye. Therefore planetary nebulae are always spectacular to observe in a telescope, compared to galaxies.


Total Solar Eclipse – July 2nd 2019 (South America)

This image shows the totally eclipsed Sun during the eclipse of 9 March 2016. Credit: ESO/P. Horálek/Solar Wind Sherpas project

Total solar eclipses will forever remain the most popular astronomical phenomenon all over the world. On July 2nd, only observers based over the Pacific Ocean, Chile or Argentina will be able to enjoy it. To join the event, we invite you to follow the adventures of Astroguigeek, editor for Vaonis, during his trip to Chile in partnership with the European Southern Observatory (ESO).


On the Moon Again – July 12/19 2019

On the Moon Again international event

For the 50th anniversary of the first men on the Moon, an international celebration event was launched by French scientists. On the Moon Again event invites telescopes owners to install their instruments on a corner of a street or in a public park to give the opportunity to anyone to look at the beauty of the Moon.

The mission of this event without borders is the occasion to celebrate the date of 12 July 1969, when 600 millions people around the world followed the most extraordinary moment in space exploration. So, will you be part of this event? More details here.


The Eagle Nebula – August 2019

M16. Credit: MPG/ESO (main image); NASA/ESA/STScI (Hubble); VLT/ISAAC/AIP/ESO (near-infrared)

Summer is the best time to enjoy the Milky Way, and more particularly its bright galactic bulge. In this region, a dozen of objects can be easily visible with a simple binoculars. Among them is the magnificent Eagle Nebula (M16), in Serpens constellation. In its core, a region of interest can be found, called the “Pillars of Creation” originating from a famous Hubble’s picture. This accumulation of hot and dense gas fall down by themselves because of gravity. The energy released is then used in the formation of sun-like stars.
With a small telescope, the Eagle nebula still reveals about twenty stars.


The Summer Triangle – August 2019

Although this geometric shape is an unofficial constellation, it serves as a useful indicator if you are looking for the position of the Milky Way in summer nights. Once you recognize the 3 stars forming it – Deneb in Cygnus constellation, Altair in Eagle constellation and the giant blue Vega in Lyra – this triangle informs you that our galactic arm is passing by Deneb and cutting the fictive line Altair-Vega.


The Perseids Meteor Shower – August 13 2019

Night of the Perseids. Credit: Petr Horálek

This year, the activity peak of the Perseids meteor shower (one of the most popular stargazing annual event) will take place on the night of August 12 to 13. The moon will shine strongly – 94% illuminated – but the brightness of the meteors will be high enough so that their burning phase in the atmosphere will not be compromised by natural light pollution.


Stellina honored with a Red Dot Design Award

The Stellina smart telescope receives the highest award from Red Dot Design, the most prestigious product design competition in the world.

Stellina Red Dot Design Award Best of the Best 2019

Vaonis is thrilled to announce that its revolutionary Stellina telescope won the Red Dot Design Award, “Best of the Best” in the Photography & Equipment category, on March 25, 2019. This is the 4th design prize awarded to Stellina, after the Observeur du Design (2018) and the Janus de l’Industrie (2017 and 2018). By winning this prestigious award, Stellina will gain further international recognition. The product, whose design is widely acclaimed by both professionals and the amateur public, also received the CES Innovation Award in the same category in January 2018, which recognizes the best technological innovations.

The Red Dot Design Award, a world-renowned distinction

The Red Dot Design Award is an international design competition for product and communication design, whose origins date back to 1955 in Germany. Receiving more than 6,000 applications every year through 48 categories of products, it is the most prestigious design competition in the world. The jury comprises some 40 international experts who test, discuss and evaluate the quality of each product on the basis of criteria such as the degree of innovation, aesthetics, functionality, ergonomics, durability or symbolic and emotional content. Award-winning products are presented at an annual ceremony and then exhibited at the Red Dot Design Museum located in Essen (Germany), and at the Red Dot Museums in Singapore and Taipei.

The Best of the Best honor is awarded for ground-breaking design and is the top prize in the Red Dot Award Product Design competition. This prize is reserved for the best products in a category. Last year, only 1,1% of all entries (69 products over 6000+) received this honor.

Behind the design: the story of Stellina’s inspiration

The design of this new generation telescope, whose idea emerged in 2013, is the result of a collaboration with Ova Design, an industrial design agency specialized in the study of usability and user experience. Based in Paris, the company has been rewarded for several of its achievements with prizes such as L’Observeur de Design, the Janus de l’Industrie or CES Innovation Awards. In 2014, Cyril Dupuy had already imagined Stellina in the monoblock form that we now know. The creator of the next-gen telescope asked Ova Design to help refine a few details of the design. The design team quickly identified the product vision desired by Cyril Dupuy, as well as its requirements and constraints. Through their research and hard work together, they have made Stellina one of the most innovative and aesthetic products in its category.

« We wanted to break with conventional telescopes. Stellina is a new generation of telescope, and as such we wanted a unique form factor. When closed, it has a refined and simple shape, which comes to life automatically as soon as the optics arm opens to position itself in the direction of the stars to be observed. We wanted to create a surprise when Stellina unfolds. The object wakes up and comes to life, the connected object becomes a companion to help its users live a new viewing experience.

Voluntarily there are few buttons on the product (only one in fact) a way to show the ultra-simple and guided use. The identity of the object makes it accessible to everyone, it does not have an over technological appearance (like conventional telescopes), it is a robotic object but it is not scary.

We also wanted to add the notion of autonomy and simplicity of use. Both can be found in the very sleek form and in the overall user experience. And above all, we wanted a little mystery in this new technological object, its monolithic shape attracts attention when closed, as does the blue ring that acts as the button.

To sum up, it was in robotics that we found inspiration combined with high precision technology and the elegance of a unique silhouette. »

Benjamin Sabourin & Nicolas Marquis
Co-founders of Ova Design


Demo at the Champ du Feu (Alsace)

Demonstration of Stellina at the Champ du feu on Saturday 25 May, 2019

Demonstration Stargazing Champ du feu Miguel GONCALVES

Credit: Miguel GONCALVES

Come meet us at the Champ du Feu, near Strasbourg and only 1 hour drive from the German border, for a demonstration of Stellina. We will welcome you in one of the best French stargazing spots to answer your questions and let you test the smart telescope live: observation of deep sky objects, live improvement of images (stacking), multi-viewer mode …
We advise you to download the Stellina app before your visit.

Where: Champ du feu, Vieux Prés car park (48°24’09.4″N 7°16’04.5″E)
When: Saturday 25 May, time to be confirmed

Join us by confirming your visit and the number of attendees at

This demonstration is subject to favorable weather conditions (visit Météociel). Its confirmation or cancellation will be notified by email 2 days before the event.

We are looking forward to introducing you the next generation telescope on which we have been working for 3 years!

Vivatech France

VivaTech (Paris)

Meet Vaonis and the smart telescope Stellina at Vivatech Paris


Vivatech 2019


Vaonis was selected from hundreds of entries to showcase its Stellina innovation at the 2019 edition of VivaTech. Come meet the team and their game-changing smart telescope, the perfect hybrid between the telescope and the camera, in the Discovery Zone, the beating heart of the Hall of Tech.

When : Thursday 16 to Saturday 18 May, 2019
Where : Parc des Expositions Porte de Versailles (Paris)
Area : Hall Discovery

Vivatech, an international tech show in Paris

VivaTech is the world’s rendezvous for startups and leaders to celebrate innovation. This international event, dedicated to the growth of startups, digital transformation and innovation, will take place 16-18 May 2019 at Porte de Versailles, Paris. Having attracted more than 100,000 visitors in 2018, the show reiterates the event for a fourth edition and will bring again together will bring together startups, business leaders and executives, investors, academics, students and media from around the globe. For 3 days, Viva Technology will brighten up to the rhythm of tech, where speakers will present the major trends in the field of technology and innovation, from blockchain to AI, GreenTech or the challenges of Connected healthcare and genetic modification. Among these topics, the theme of the New space race (space conquest) will also be highlighted, an odyssey of space that Vaonis has already begun!

Among the topics this year:

– Tech For Good
– Women in Tech
– United Tech of Europe

VivaTech figures

• 4th annual edition
• 100 000 visitors in 2018
• 2 days reserved to professionals, 1 day open to the general public
• 1 500 startups showcased
• 1 900 journalists
• 125 countries represented
• 180 talks and conferences, 450 speakers, 5 stages


Meeting, interview & demo

Forbes 30 under 30

Forbes 30 Under 30

The founder of Vaonis in the 30 Under 30 Entrepreneurs list of Forbes magazine


Forbes 30 under 30


Cyril Dupuy, who imagined Stellina and ceated the company Vaonis in 2016, was selected in March 2019 by the French edition of Forbes magazine to appear in its annual list of « 30 Under 30 ».

The Forbes France “30 Under 30” list rewards 30 young people under 30, entrepreneurs, athletes, creators, engineers who have emerged or are emerging in their field. A jury of experts – composed of Dominique Busso, CEO of Forbes France, Frédéric Jousset, founder of Webhelp, Taïg Khris, founder of OnOff, Chantal Baudron, head of a management consulting firm, and Stéphanie Hospital, founder of the OneRagtime investment fund – has scrupulously studied the various applications according to specific evaluation criteria. Each assigned one score per candidate, and the total score then selected our 30 winners for the 2019 edition of the “30 Under 30“. This is how the CEO of Vaonis was selected within the French laureates.

In the paper version of the magazine, we can read the portrait of the founder and the start-up:

« Vaonis is a start-up that wants the world to observe the stars simply, to take a little height on our world and to be aware of the present and future issues. Stellina is a first step: it is a hybrid between a telescope and a camera that lets anyone, child or adult, to discover the universe around us. Designed by a team of French astronomy and new technology enthusiasts, Stellina is the world’s first all-in-one smart telescope to photograph stars.

Catchline: The universe at your fingertips »



Where is STELLINA made?

If the parts that make up our products are bought in France, Europe or Asia, all of our STELLINA observation stations are assembled entirely by hand in Montpellier, not far from the offices of Vaonis, at APF34.


Production line APF 34

Production line


From the start, at the creation of the company in 2016 Cyril Dupuy, the founder, wanted all the elements to be locally produced.
Working with local actors allows for reactivity and fluid communication as well as establishing relationships and trust between partners; this results in the manufacturing of good quality products for the customers. After searching for a trusted partner for several months, the choice naturally fell on the company APF 34.

APF Entreprises 34

Founded in 1971, APF 34 is a company based in the South of France, specialized in electrical wiring and electromechanical assembly. Equipped with a real industrial know-how, its mission is the professional and sustainable integration of people with disabilities.

Under the care and support of the Association of People with Disabilities (APF in French), a French non-governmental organization, it enables disabled workers to take up paid employment under appropriate conditions by adapting workstations or adapted professional activities.

Packaging of STELLINA by APF 34

Packaging of STELLINA at APF34

Day to day, hand in hand

Human aspects play a key role in the choices of Vaonis’ collaborations, whether for internal employees or service providers. With APF 34, this aspect was favorable from the start.

Only 6 km separate Vaonis from the factory’s premises, allowing ease in frequent visits to the technician and production lines. They are responsible for assembling more than 300 parts together, from the optical tube to the sensor block, the external frame, electronics and wiring.

Quality before quantity

After a pilot production and a first batch produced in 2018, the pace will now go crescendo. A second phase of manufacturing will be launched at the beginning of the year, followed by a second next summer, with a progressive ramp up of the production capacity.

Going against the strategy of “mass production and large scale economics”, this deliberate choice was made in order to be able to control every stage of the production chain and make STELLINA a reliable device in every respect.

Eclipse de lune juillet 2018 vignette

Guide for the Total Lunar Eclipse of January 21, 2019

Guide to observe the Total Lunar Eclipse on January 21, 2019

Eclipses are considered as the most fascinating natural phenomena we can observe to the naked eye. On January 21, 2019, around 5:12 am UTC, the moon will pass across the Earth’s shadow for about 1 hour and 2 minutes, a bit shorter than the previous total lunar eclipse that happened on July 27, 2018 but still exceptional! This total lunar eclipse will be the last one visible until May 2022!

When and how to 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 occurring on January, 21st 2019 before dawn.


Lunar eclipse 2018

Lunar eclipse phases captured by the Stellina telescope (July 2018 , South of France)

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 alignment 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 alignment. 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, but it is difficult to notice a strong difference of brightness in comparison of a traditional full moon.

    Partial lunar eclipse before totality, September 28 2015. Credit: Guillaume D.

  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 direly 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.
  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 27, hour by hour

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 mentioned: the Moon first goes into the penumbra (penumbral eclipse) than shades slowly in the Earth’s shadow (partial eclipse) and finally becomes entirely hidden in the Umbra (total eclipse).

Below are listed the different steps of the total lunar eclipse of January 21th 2019, given in Universal Time Coordinate (UTC):

  • 2:36 am UTCBeginning of the penumbral eclipse. The Earth’s penumbra reaches the surface of the Moon. A this time, the eclipse only starts faintly and gently because the brightness of our satellite is almost imperceptible to the naked eye. A picture could possibly make you notice the behavior of a darker zone onto the moon.
  • 3:33 am UTCBeginning of the partial eclipse. The Moon enters into the umbra cone of our planet. From this step, the eclipse starts to be an interesting target to human eyes. A part of the moon gets darker and larger, until the full moon is tinted of orange-red.
  • 4:41 am UTC: Beginning of the total lunar eclipse. The moon is fading out and appears orange. On regular basis, the moonlight disables us to observer the dimmest stars of the sky. However, from 4:41 am and thanks to this eclipse, you will be able to do a bit of stargazing without the bright light of a full moon making you blind. A magical moment whose countdown is set to a hour.
  • 5:12 am UTC: 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.
  • 5:43 am UTC: 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.
  • 6:50 am UTC: End of the partial eclipse. Beginning of the penumbral eclipse. The moon looks like a typical full moon.
  • 7:48 am UTC: End of the penumbral eclipse. This is the official end of the total lunar eclipse. Keep in mind that depending on your location, the end of the eclipse might not be visible because of the moonset.


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 particles of air, water and more. Because these particles scatter blue light, they absorb 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 atmospheric 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 absorption 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.

Moonset eclipse by Fred Espenak

  • 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 January 21! 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, content editor at


Astronomy: the most beautiful targets of winter

With long full nights, winter remains the best period of the year to enjoy the starry sky and discover its rich objects. The night falls usually around 6:00 pm, which is a perfect timing for week and weekend stargazing. In the winter, you do not have to wait several hours as in summer time.

However, once your telescope is out and set up, what can you observe? If the Milky Way’s visibility is not suitable for winter observing, a large number of extraordinary targets can be admired using relatively modest instruments: bright galaxies and nebulae, huge clusters and interesting comets! Here is our selection of objects that could feed your astronomical hunger in winter.

The Great Orion Nebula – M42

A traditional target is obviously the splendid pink-colored nebula M42. Its strong brightness and its huge stretch make it easily visible in the sky, even to the naked eye. A simple pair of binoculars will reveal its internal structures. Orion is the brightest nebula of the Northern hemisphere, located in the constellation of the same name whose visibility starts around mid-October and ends at the beginning of March. The intense colors of the dust and gas clouds are not discernible to the naked eye but can be exposed using a telescope equipped with an image sensor, such as Stellina.

Horse Head and Flame Nebulae

Horse Head nebula

The Horse Head nebula (in black and red) and the Flame nebula (in yellow) are both located in the Orion constellation, very close from M42.

Still in the Orion constellation, the dark nebula IC 434 features a particular shape, similar to the profile of a horse, hence its name. This object is even more gorgeous when it is captured: we can then see pink tint clouds in the background which increase the contrast of the Horse Head which absorbes light. This original deep sky object is narrowly associated with another brighter nebula, called the Flame nebula. It becomes interesting to frame both of these nebulae into a single image.

Pleaides Star Cluster – M45

Pleaides star cluster

The Pleaides star cluster (M45) is composed of a merging of stars and interstellar clouds at the foreground. Image: AstroGuigeek

Let us travel from Orion to Taurus constellation and look at this great and luminous open star cluster, intensively tinted with blue. Often mistaken for the Ursa Minor constellation, the Pleiades star cluster is easily accessible to the naked eye. It is composed of a large group of 3 000 young stars among which seven of them can be observed with binoculars. Dust clouds give the impression that the Pleaides is a nebula, but the dust has actually nothing to do with the cluster itself: they are only dusty material in the foreground. Once more, a telescope fitted with a camera reveals the true blue color of M45 star cluster.

Andromeda Galaxy – M31

Andromeda galaxy

The Andromeda galaxy is certainly the most popular astronomical object. Do not forget to observe it at the beginning of winter each year.

With an angular size about 6 times the diameter of a full moon, Andromeda is a spiral galaxy close to the Milky Way, making it one of the rarest galaxies visible to the naked eye – the Large and Small Magellanic clouds are brighter but are only visible from the southern hemisphere sky. The beginning of winter is the most suitable period for admiring this masterpiece, whether with binoculars or telescopes. Andromeda lies within the constellation of the same name. Its angular diameter is so large that a telescope with too much magnification will not be able to observe the entire disc of the Andromeda galaxy. A telescope with a focal length between 400 and 800 mm is an excellent choice, particularly when it is combined with a photographic sensor. Despite being located just 2.5 million light-years from us, Andromeda shows a high density stellar population and hides a lot of interesting structures like its spiral arms which can be resolved with most amateur telescopes.

The Beehive cluster – M44

Beehive cluster

The Beehive cluster captured by Bob Franke.

Praesepe is a modest but amazing open star cluster which can be found inside the constellation of Cancer. Very bright, it is composed of more than 1 000 stars spreading over an angular distance of 3 full moons. With binoculars or telescopes, the Beehive cluster reveals shining stars whose differences in color temperatures are readily apparent. An image illustrates this.

Comet 46P/Wirtanen: the surprise of the year?

During the past few years, the Northern hemisphere has not often been visited by bright comets. You might remember the comet Hale-Bopp which enlightened the sky with a maximum magnitude of -1. This year, we will not be as lucky as in 1997, but comet Wirtanen is expected to reach magnitude 3 or 4 around December 16, 2018 when it is at its closest distance to the Earth, namely 12 million kilometers. In other words, it will likely be accessible to the naked eye and to binoculars.
Discovered in 1948, this comet belongs to the category of periodic comets, meaning that it orbits the sun every 5.4 years. Wirtanen was initially the comet on which the ESA’s Rosetta Mission set its route to deploy its Philae lander.
For more stories on comets, we invite you to read our previous article on the most impressive comets of the history.

Wirtanen is therefore an object to which you should pay attention, all December 2018 long!