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.


Where is Stellina made?

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

At the creation of the company in 2016, locally made products were already a will of the founder, Cyril Dupuy. Working with a local actor is synonymous with more reactivity and fluidity in communication, allow to establish a relationship of trust between partners, and ensure the manufacturing of good quality products for customers. That’s why after several months of searching for a trusted partner, 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 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 felt instantly.

Only 6 km separate Vaonis from the factory’s premises, allowing frequent visits to the technicians and the production line. 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 is launched at the beginning of the year, will follow a second this summer, with a progressive ramp up of the production capacity.

Going against the strategy of “mass production and large scale economies”, this well-considered choice is explained by the desire to control every stage of the production chain and make Stellina a reliable telescope 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

Great Orion nebula

The Great Orion nebula, birthplace of stars. Image taken using the Stellina telescope.

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!


Comets which made history…

Like solar and lunar eclipses or even meteor showers, comets are considered as the most tremendous astronomical phenomena. Since Antiquity, comets were already part of our culture since they were represented in paintings or engravings in religion or arts. Their origin was not as well understood as today.

Among some of the 6339 comets discovered until now, few deserve to be mentioned on account of the overwhelming shining tails left after them and their scientific interest. Find below our selection of the comets which helped in building the history of astronomy, or more generally humanity’s.

Comet Lovejoy C/2014 Q2 . Credit: Michael Jaeger

Comets, meteors and asteroids: what difference?

Comets are small icy bodies whose size ranges from hundreds of meters up to dozens of kilometers large. Comets would have been formed during the earliest stage of life of our solar system and are since then orbiting the Sun. When they travel too close from our burning star, their icy nucleus warms up, and due to sublimation, produces a dusty tail that can spread itself until hundreds of millions kilometers wide. Actually, it is this white or blue tail which makes comets visible from Earth, because of sunlight reflection. More rarely, a comet’s tail can be seen with an unaided eye for several months.

Meteors are dust originating mainly from comets. If the Earth crosses remnants of a comet’s tail – which happens with Perseids, Geminids, Leonids… – particles composing it are starting to fall off the Earth, because of the gravitational force. The extremely high initial velocity of these particles participates in increasing the friction with molecules located in the upper layers of Earth’s atmosphere. Friction is causing the meteoroids to break apart with high temperature, a phenomenon in which an intense and short stray of light is released, called meteor or shooting star.

Asteroids are totally different from meteors but pretty similar to comets. The difference is that they are not made of ice, but rocks. Consequently they do not feature any tails and are not as easily visible as comets, requiring astronomicals instruments to be observed.

Comet OUMUAMUA – 2017

This artist’s impression shows the first interstellar object discovered in the Solar System, Oumuamua. Credit: ESO

This strange looking planetary object whose discovery was made a year from now is still feeding controversial debates between astronomers. Initially admitted as a comet, then modified as an asteroid, the scientific community does not exclude its comet-like properties. In any cases, OUMUAMUA is the first ever interstellar body to be found in our solar system, and potentially the first comet coming from another star! More details about OUMUAMUA in our article >>.


Great Comet of 1811 (C/1811 F1)

Drawing of the great comet of 1811, by Mary Evans

Discovered in March 1811 by a French amateur astronomer, comet C/1811 F1 was considered as one of the brightest comets ever observed in the 19th century, reaching a magnitude of 0 and visible to the naked eye for almost 9 months with a coma of 25° maximum angular distance.

Halley’s Comet (1P/Halley)

Image of Halley’s comet nucleus as seen from Giotto space probe. Credit: MPAE

This comet is beyond the shadow of a doubt the most popular celestial object after the Sun, the Moon and the planets. However, do you know why this comet has become so famous?
Its first testimony was written in -240 BC, inside the Chinese book “Shiji”. Few century later, in 1705, and after several appearances of the same comet, the astronomer Edmond Halley was the first to prove the periodic trajectory of the comet. Thus, 1P/Halley became the first ever discovered periodic comet, with a frequency ranging between 74 and 79 years.

During its latest visible appearence in 1989, Halley’s comet was also the first one ever approached by space probes: the Soviets probes Vega 1 and 2 which flew over the nucleus at less than 9 000 kilometers, followed by the European probe Giotto which crossed it under a 600 kilometers radius!

To observe it, you will need to be patient: its next appareance is expected in 2061.

Comet Hale-Bopp (C/1995 O1) – 1997

Comet Hale-Bopp over the col of Val Paroloa (Italy). Credit: A. Dimai, (Col Druscie Obs.), AAC

Hale-Bopp is one the furthest comets ever captured by amateur astronomers. Indeed, it was located beyond Jupiter’s orbit, at 7.15 Astronomical Units when it was discovered on July, 23 1995. With a spectacular brightness, it can be considered as one of the most viewed comets of Human’s history since it holds the record of the longest visibility period to the naked eye: a total of 18 months spread out around its intensity peak of april 1997.
If its nucleus’s diameter of 40 km was determined by the Hubble space telescope, its rotating period of 11.4 hours had been estimated with the help of the French Pic du Midi Observatory!

Comet Mc Naught (C/2006 P1) – 2007

The long and impressive tail of Comet Mc Naught, after sunset over Paranal Observatory (Chile), January, 19th 2007. Credit: ESO/H.H.Heyer

Mc Naught is ultimately the most impressive comet of the 21st century thanks to its giant icy and dusty tail stretching around 35 degrees in the sky which helped a rich amount of sunlight to be reflected onto it. Its magnitude eventually reached -5.5 during its activity peak between January 12th and 14th 2007, or in other words brighter than any other stars and planets! A mindblowing display that only the Southern Hemisphere amateur astronomers got the chance to observe.


Comet Hyakutake (C/1996 B2) – 1994

Comet Hyakutake captured from Pic du Midi Observatory (France), March 23rd 1996. Credit: Francois Colas

In a world where gigantic state-of-the-art telescopes monitor the sky every nights, it is still possible that astronomy lovers discover themselves comets while observing. This was the case of the Japanese Yuji Hyakutake on January, 30th 1996, who discovered comet C/1996 B2 with his simple 25×150 binocular!
Hyakutake is the first comet whose tail has been crossed by a space probe (Ulysses), although it was a pure coincidence!

Comet Churyumov-Gerasimenko (67P)

Unique view of Comet 67P taken by Rosetta probe, from a distance of 86 kilometers, March 25th 2015. Credit: ESA/Rosetta/NAVCAM

Comet “Tchury” does not owe its popularity to its very modest properties and brightness but to the space exploration mission dedicated to it: Rosetta. This European probe launched in 2004 traveled alone for about 10 years within the solar system in order to reach its promised target and orbit around it: a never achieved mission. Rosetta did not rely on this success and launched its hidden baby lander “Philae” which touched down the comet’s surface on November, 12th 2014. Philae studied the composition and the chemical properties of the comet few days on. This mission had an ambition rarely reached by any space missions until now.


Comet Shoemaker-Levy – 1994

Remnant of the collision of comet Shoemaker-Levy with Jupiter, in July 1994 as seen from Earth-orbiting space telescope Hubble. Credit: H. Hammel (MIT), WFPC2, HST, NASA

In 1994, space and ground-based telescopes witnessed a rare planetary catastrophe: comet Schoemaker-Levy which had broke apart in 21 pieces two years ago collided with the gas giant Jupiter. Predicted by celestial mechanics calculations, this event of exceptional beauty had been waited for a while by worldwide astronomers,  a rare occasion to study the properties of the comet and its collision with Jupiter. The scars caused by the impact of the fragments of Schoemaker-Levy onto the surface of Jupiter remained visible for several months.

Capteur astrophoto

Why use a high resolution sensor in Astrophotography?

In astrophotography, the camera’s sensor is a key element which needs special attention when choosing your equipment. This rectangular component is about the size of a fingernail and can contain several million pixels made for converting photons coming from the stars into an image. Compared to the human eye, a sensor is able to detect far fainter objects and can see their actual colors. On the market, reams of sensors are used, all of them having their own dedicated application: webcam, smartphone sensor, DSLR sensor… For instance, the Stellina smart telescope is fitted with a 6.4 MP sensor covering deep sky and lunar imaging. Why is it necessary to choose a high resolution sensor for astrophotography like the one Stellina contains?

A resolution to fit with your devices’ screens

The most widespread sensors have fairly bad resolutions, ranging from 0.3 to 1.3 Megapixels. Such sensors are made for devices where image quality is not a big factor: webcam, front camera of smartphones or tablets.

For a picture to be pinpoint sharp on a Full HD screen, its definition should be at least 1920 x 1080 pixels, or around 2.07 MP. Breaking this rule, the quality of a 1.3 MP resolution image displayed on a Full HD screen will be extremely low since the celestial objects will be pixelated. A zoom in will damage even more the quality, which is not imaginable given that nowadays, FHD is the minimum resolution required.

The IMX 178 Sony sensor of the Stellina telescope was chosen specifically to display good-looking stills on an Ipad or even on an Ipad Pro without losing quality! With a 6.4 MP resolution, equivalent to 3086 x 2076 pixels, the sensor is able to capture photos of galaxies, nebulae, star clusters and our natural satellite: the Moon. Such a comfortable number of pixels guarantees an optimized experience for viewing your own images on most of your devices, smartphones, tablets as well as TV.

Sharper details and the ability to crop

Owning a high resolution sensor allows you to increase dramatically the overall details of the celestial object you captured. If the sensor you are using has higher resolution than a Full HD display, a crop on that picture yields simultaneously a close-up view and an identical degree of sharpness. The example below simulates the evolution of the image quality according to four different sensor resolutions applied to an image of the North America nebula – NGC 7000.

A high-performance sensor

Stellina contains a sensor specifically designed for astronomy, enabling a sensitivity in the near-infrared part of the electromagnetic spectrum, added to the common visible domain. Indeed, many deep sky targets like the Lagoon Nebula, Orion Nebula, the Soul Nebula, the Heart Nebula emit a large amount of infrared light. Stellina’s extended sensitivity increases the light collected by the sensor, raising the intensity of the signal while reducing digital noise. Another interesting feature of the sensor: its light pollution or CLS filter (City Light Suppression). This optical filter installed just in front of the sensor often makes urban space enthusiasts happier since it eliminates the typical coloration of the sky caused by artificial lighting: a must-have tool, especially nowadays, when the environment has never been so light-polluted by human activities, degrading the natural darkness of the night sky.

> Read our article listing the impacts of light pollution on astronomy and on our environment. 

Light pollution Dubai

Why do the stars disappear ?

“Turn off the lights, light on the stars !” is the purpose of the french national movement “The Day of the Night” aiming to raise awareness of the impacts of the light pollution among the general public. The surge of artificial light is indeed being questionable on our health, wild life but also on astronomical observation.

More than 400 activities are scheduled to take place within the french territory, during the night from the 13th to the 14th October 2018.

Light pollution is made of all kind of disturbing light sources whose origin comes from human activity (street lights, commercial signs, advertisement…etc). Currently, 99 % of the European and American population is living under light polluted skies. In the same way as the sound disturbance or the pollution as a whole, it produces reams of discomfort, especially as far as night-time observing is concerned. A recent scientific study has proved that more than a third of the global population can not see the milky way anymore.

What are the effects of light pollution on astronomy?

The light throughput generated by a city or a town does not spread itself exactly where it is meant to. An excessive amount of that light is projected towards the sky, forming a huge diffusive orange or blue halo depending on the primary type of light source used within the area. Whether inside these urban areas or in suburbs, the adjective “dark sky” seems to be obsolete, on grounds of this blurred veil disabling any contrasted view of the stars. Consequently, it becomes pretty hard to spot the stars and the constellations since the cities’ glow are decreasing the luminosity threshold –  called magnitude – our eyes are capable of reaching.

In a totally light-pollution-free sky, 6.5 is the limit magnitude our eyes can detect without help of any sorts of optical instruments. In other words, theoretically 2 500 stars of our sky would be accessible to the naked eye. In most of the cities, though, the magnitude over the one stars are being hidden because of light pollution drops down to 4.0 or 3.0. In these harsh conditions, only 300 or 200 stars are visible except in the heavy populated urban areas like Paris, London, New York, Hong Kong where around 30 stars and less are still shining.

Light pollution before after

Comparison of a heavy polluted sky (left) and a starry sky right after a blackout occurred (right). Images by Todd Carlson. Source : IDA

Keen amateur astronomers are the main victims of the rise of light pollution. Even today, professional astronomers observing through state-of-the-art telescopes are concerned by the over use of lighting, like in Chile.

How can we prevent light pollution from getting worse?

The main cause of visual disturbance can be explained by a high amount of useless lighting. Advertisement panels, empty parking slots, front store… typically are the types of lights mentioned as unnecessary.

An improvement in terms of light distribution and orientation could permit decreasing unwanted light glow over the towns, as long as a middle-ground to insure the security of customers and pedestrians is found.

Received idea: Shifting from orange sodium vapor lamps to LEDs does not mean to decrease light pollution. LEDs emit white light which affects a wider range of the visible light spectrum. Plus, they have usually an emission peak located in the blue which unfortunately fits with the main color of our night deep sky objects.

Light pollution in the US

Current situation of light pollution in North America. Source : Science Advances

For years, a couple of associations advocating the protection of the sky have born such as the ANPCEN in France or the International Dark Sky Assocation (IDA) at a global scale. With the support of local authorities, they could end up adopting a law dealing with regulation of the french public lighting : since the 1st July 2018, front stores and advertisement signs must be turned off from 1:00 am to 6:00 am. This measure should avoid wasting 1000 GWh per year which represents a money saving of about 100 millions euros, or even the consumption of electricity of 370 000 households for a year.

France is in a good way of ecological awareness, whereas 30% of the overall lighting in the United States are estimated to be useless and wasted, raising the money-loss to 3.3 B$ per year.


Stellina refractor telescope
Blog, Products

Reflector vs. Refractor telescopes

What is a telescope? This question could seem trivial but behind this universal word, we find two main types of instruments to observe the tremendous objects of our starry sky. The reflector telescopes are composed of mirrors whereas the refractor telescopes are only made of lenses. They are a lot of differences between both of these categories, in terms of performances, durability and especially optical quality.

Reflector telescopes

Principle of a reflectorReflector telescope

The newton telescopes are the most widespread reflectors in the market because of their easy building process and their low cost. The light coming from a star goes inside the optical tube and is first reflected on the primary mirror, located at the extremity. This primary mirror is the master piece of the reflector. It has to collect and make the light beams converging towards the eyepiece holder, the element where we put our eyes. Here, it is necessary to find a way to make the light beams going out of the tube. Therefore, a secondary mirror is installed next to the front aperture of the telescope, enabling beams to be deviated on the side of the telescope, and so, to observe an image.

The asset of a reflector is its primary mirror’s very large size. The bigger the mirror is, the brighter the objects appear in the eyepiece. However, a big mirror could quickly emphasize the optical aberrations of the telescope.

Optical quality of reflectors

Theoretically, getting a perfect round dot of a star requires having a newtonian reflector made with a hyperbolic primary mirror. In fact, such a mirror is relatively expensive and telescopes manufacturers choose rather a parabolic mirror instead, far simpler to build. However, a parabolic mirror is facing a defect: the coma aberration which deforms and elongates the star around the fields of view.

More often, the low-cost manufacturers do not use nor a hyperbolic neither a parabolic mirror but a spherical mirror. With such a geometry, you will never manage to focus perfectly the image of a star with your reflector, because of spherical aberration ; a delicate situation considering that astronomy requires to observe and photograph faint and diffuse celestial objects.

Reflectors in practice

Reflector telescopes are mainly open telescopes, meaning that the mirrors are exposed to the air, humidity and dust. This is why they require to be manipulated with precision and attention. For example, a mirror frequently exposed to this harsh environment could be less reflective within years, or put it in a different way, its ability to reflect light decreases. To this point, the cleaning of the mirror is highly recommended, paying extreme attention to the fragile optical parts while dismounting the telescope.

A key element not to be forgotten with a newtonian-like telescope is the necessity to collimate it. The collimation is a process which consists on adjusting the perfect alignment of the primary and secondary mirrors of the telescope. This should be ideally carried out each time you observe or start an astrophotography session.

Finally, reflector telescopes are first choice instruments when you want to collect the most light as possible. But the side effects are that you will need to know in details the optical system and should not be shy when you will have to modify or clean the mirrors, as mentioned above.

Pros & Cons



  • Large mirror = better light collecting capacity
  • No chromatic aberrations (colored fringes around stars)
  • Relatively low cost
  • Optical quality often disappointing
  • Collimation and mirrors cleaning processes
  • Open tube = high vulnerability to dust, humidity..etc
  • Bulky and heavy

Refractor TelescopesRefractor telescope

The principle of keplerian telescope is very similar to a monocular. The light goes through the front lens, key element making the light beams

converging to the eyepiece holder, where we install an eyepiece or a camera.
Because of their compactness and ligthness, refractor telescopes do not collect as much light as reflector but have a more stable optical quality and do not need any adjustement from the user/observer.

Optical Quality of the reflectors

They have the specificity to let us observing the starry sky with an amazing sharpness and contrast. These features are really appreciated in astronomical observation and astrophotography.
Nonetheless, keep attention on what type of refractor you choose. The cheapest are made of a single lens which undergoes the light dispersion. Consequently, a star will not be a single color point anymore but surrounded by colored rings. This is what we call chromatic aberrration.

Today, there are different manners to get rid of this optical defect such as adding a second lens to obtain a Doublet telescope.

Stellina : a refractor inspired by astrophotographersStellina

Most of amateur astrophotographers prefer a telescope whose durability, compactness and simplicity to use are better than the amount of light collected. Therefore they choose refractor telescopes rather than reflectors.

Vaonis has responded to this demand and built a refractor telescope from scratch, helped by one of the most reknown metrology laboratory in France : AiryLab.

The optical design is a Lanthane ED Doublet, permitting to decrease drastically chromatic aberration. A special treatment on the lenses has been applied in order to select only the wavelength of interest and reject all ultraviolet and infrared lights.

All these optimizations brought into this telescope are just contained in a small, transportable and entirely automated refractor. Refractors are thus a reliable choice for stargazers who want a dependable, pratical and easy-to-use astronomical instrument.

Pros & Cons



  • Impressive contrast and sharpness
  • Light and transportable
  • Closed tube = protection against humidity and dust
  • Maintenance and cleaning almost nonexistent
  • Small diameter = less light collected
  • Chromatic aberrations
  • Higher price
Milky Way by Astroguigeek

Guide for Milky Way Photography

Photographing the milky way

Is there something more beautiful than observing the Milky Way in the summer nights? On the same occasion, why not immortalizing this moment by capturing it? As a matter of fact, it has never been as simple and as fast as today to capture the stars. If you think that only expensive or professional material will allow you to capture amazing pictures of the night sky, don’t believe it. With the technological development, the Milky Way can now be photographed with standard consumer cameras and even our smartphones!

How to capture the Milky Way in 2018? Welcome in this 3.0 tutorial, updated and accessible to everybody.

Milky Way France Astroguigeek

The Milky Way taken from the Pic du Midi (France). 15 seconds at ISO 3200, 18 mm, f/1.8. Credit: AstroGuigeek Photographie

Mandatory Equipment

Before getting in depth, it is still useful to know what you will need to take pictures of the starry sky. Few equipment are actually required:

  • A camera equipped with a Manual Mode called mode “M”: nowadays, most of the camera embed this feature and our smartphones too. Look for the “Pro Mode” or the Manual Mode inside the camera app on your device.
  • A standard lens: for DLSR or mirrorless cameras, a 18-55 mm kit lens is enough to photograph the Milky Way.
  • A tripod or camera mount: The tripod is absolutely necessary to make your camera steady and avoid the vibrations caused by motion. Not to forget that small tripods or smartphone tripod adapters can also be purchased.

A short journey in our Galaxy

The galaxy in which the Earth, the Sun and other 250 billion stars are evolving in is called the Milky Way. In addition to this very high numbers, it is made of other components such as molecular clouds and interstellar dusts, giving this multicolored and milky structures in the night sky.

Theoretically, all the stars that our eyes can see are belonging to our galaxy. It will be correct therefore to consider that the whole sky is the Milky Way. Nonetheless, we call Milky Way the strip-shaped structure in which are concentrated most of the stars, interstellar clouds and nebulae.

Because we are located inside our own galaxy, we cannot see its global shape, for which we know that is a spiral. However, we can actually admire a tremendous slice view of the Milky Way. In the night sky we do see this long bright strip displaying shining and dark regions. The Milky Way is even far brighter when our eyesight is pointing towards the galactic center rather than towards the outskirts.

Milky Way France Astroguigeek

The Milky Way as seen from cities outskirts. 45 seconds at ISO 3200. 18 mm, f/1.8. Tracking mount to compensate Earth’s rotating motion

The Milky Way is easily visible with the naked eye from countryside or any other remote areas, far away from towns and cities. Its low brightness makes it hard for our eyes to see the whole picture. Indeed, our eyes can only observe a maximum of 6 000 stars, which is a very small part of our galaxy. Today, sensors from our DSLR or mirrorless or smartphones cameras manage to photograph stunning results and can multiply our eyes capabilities. Besides, they can capture the true colors of the Milky Way whereas our eyes cannot!

How to capture the Milky Way?

Obviously, digital cameras are not able to shoot the Milky Way instantly like a daylight scene helped by sunlight. Stars and clouds of gas are emitting a very few amount of light. To counter this darkness, it is necessary to take a picture lasting several seconds at least.
In the meanwhile, the sensor will record all the light emitted by the stars and will add it up to make the stars more visible and so the Milky Way.

Before getting into the typical camera settings you will need, ensure that you have full access to the camera settings through the manual mode (“M” Mode). This feature enables to set manually every parameter of the picture. Below are the different settings we will modify:

Focal Length ou Zoom

It is important to choose the widest field of view as possible and not to use a zoom. Adjust your lens (for digital cameras) to its smallest focal length value (24 mm, 18 mm, 14 mm or lower). The wider the field of view will be, the more visible the Milky Way will be.

Aperture or F/D ratio

One the most fundamental settings is the lens aperture. This number gives indication about the size of the front lens used. In photography, the aperture is expressed by the “F/D” ratio. Of course, this value is not fixed and can be modified. Here, we want to collect as much light as possible. The lower the aperture is (F/3.5, F/2.8 or F/1.8 …), the more light is passing through the lens. Consequently, the ideal is to let your lens wide open.

Exposure Time

As mentioned above, the longest exposure time your camera can handle should be chosen. Today’s digital cameras can for example go up to 30 seconds whereas smartphones can vary from 2 up to 32 or even 60 seconds exposure. The longer the shutter speed is, the more the sensor will collect light.

Tip: Be careful about the exposure time you choose. There is a limit beyond which the stars get shaped like elongated points, because of the Earth’s rotation about its axis. As we are standing on the Earth, this is not our planet which is moving with respect to us but the sky which rotates with respect to the Earth. While photographing, this rotating motion is noticeable from 20 seconds with a 18 mm standard lens. In order to know what time lapse is the limit before getting star trails, there are some non-intuitive mathematical formulas which work efficiently. However the best way is to check, once you picture is taken, that the stars are not drifting and are round. If not, simply reduce the exposure time from 30 to 20 seconds for example. Stop the process once you found a good middle-ground between have a exposure time long enough and not having star trails.

ISO sensitivity

ISO is what will enable you to bring a gain in brightness on your pictures.  For instance, changing ISO 400 to ISO 1600 will permit to capture fainter details contained in the Milky Way. Do not forget that increasing ISO does not have only advantages. Higher ISO means higher noise, this analog defect produced by the sensor electronics. The image will seem to be less sharp and grainy.
The average value to get enough sensitivity without losing too much quality is around ISO 1600 or ISO 3200.

To summarize the previous paragraphs, here are universal settings which should work in most of the cases for your camera:
– Focal length: 18 mm
– Aperture: F/3.5
– Exposure time: 20 seconds
– ISO Sensitivity: ISO 1600


Once all the parameters for your image have been correctly selected, one last step still remains to be done: adjusting the focus to avoid blurred stars. It can happen that you do not have the option of manually adjusting your focus on your camera or smartphone. In this case, you should look for a preset “Infinity focus” if available in your camera’s settings.
For classical cameras featuring a focus ring on the lens, it is much easier to find the infinity focus for the stars. Here is the 10-step process:

  1. Install the camera on a tripod or a stand
  2. Choose the focal length of your lens and all the other parameters mentioned above
  3. Activate the Live view mode of your camera (referred to on the screen)
  4. The screen should appear black, that’s normal. However, your camera should be sensitive enough to capture at least one star. Choose a very bright star from the sky (Vega, Altair or Deneb in summer, or Betelgeuse, Sirius or Capella in winter).
  5. Center this star on the screen.
  6. Activate the digital zoom of the Live View (“Magnifying Glass” button) x5 or x10
  7. The star appears magnified on the screen. If you can not see anything even after centering the star, turn the focus ring in one direction and then the other until you see a bright spot on the screen.
  8. To sharpen the focus, turn the focus ring in either direction.
  9. The focus is correct when the bright star has the smallest possible size on the screen (a few pixels)
  10. Disable the Live View and do not touch your lens (zoom) before taking the picture.

Taking the picture

Up to this point, you should have selected the correct parameters of your picture and you have finally found the infinite focus. Congratulations! Now, you just have to press the shutter button of your camera. Using the 5 or 10 seconds timer is a good option to avoid vibration while the camera is taking the picture.
If you are not satisfied of the outcome you get or if you want to improve your Milky Way pictures, find more advice and tips below.


Observation conditions

Leave the city

In order get the most light as possible from the Milky Way, it is strongly recommended to drive out of the cities or urban areas where the lights are making your eyes and your camera blind. An entry level camera under a dark sky from the countryside will be more performing than a top-of-the-range camera used in an urban sky.

Avoid the Moonlight

Artificial lights are not the only source of light pollution for astrophotography. The moon is also a real thread for the starry sky because it creates a bright diffuse light in the entire sky. The best conditions for Milky Way photography are between the new moon and the first or last quarter. Otherwise, you should check the moon phases with a dedicated app or website before getting outside and start your shooting session.

Schedule your night

It is also important to have an idea of the current position of the Milky Way in your sky. It is actually not oriented in the same way throughout the year. The best period in the Northern hemisphere is to observe it during summer nights whereas in the Southern hemisphere, it is the opposite.
A quick check on online skymaps or special applications allows you to see the elevation and the elevation of the Milky Way at your current position and time. We can mention apps like: Google Sky Map, Sky Safari, Stellarium Mobile…
Another popular freeware is Stellarium, available on every platform, Windows, Linux and Mac OS.

Image Processing and RAW files

To improve your picture of the Milky Way with an editing software, there is nothing more essential than the format of the picture you selected before capturing it. The high quality “RAW” format (.cr2 , .nef or .dng) enables you to get an uncompressed image while JPEG files will loose more information about the pixels.
Go into your camera settings to enable this RAW pictures option or RAW + JPEG. Then, capture your pictures and import them in your editing software. You can play with the contrast, noise reduction, white colors and more parameters.

Edited Milky Way picture

Photo of the Milky Way before (left) and after processing (right). RAW image of 15 seconds exposure, ISO 3200, 18 mm and f/3.5

Milky Way Stellina

Can we photograph the Milky Way with the Stellina telescope?

Stellina has a 400 mm focal length versus 20 mm focal length for standard wide angle lens for cameras. In other words, its strong magnification will not let you photographing the whole Milky Way. However you, with such a zoom, you will be able to get closer shots of deep sky objects contained inside the Milky Way like nebulae, star clusters, double stars… More details concerning this telescope here.