Stellina refractor telescope
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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
Blog, Products

Why a Telescope does not need an Eyepiece

Without telescopes, astronomy would not be as popular as today: observing celestial objects through these instruments is a way of being aware of the immensity and the beauty our starry sky features. Astronomical observation enables us to experience directly the marvelous pictures of galaxies, nebulae, star clusters that we see on the Internet or in astronomy books.

But, have you ever looked at the Andromeda Galaxy through the eyepiece of a telescope? Were you surprised to see only a blurred spot, diffuse and without any colors?
It’s a shame, you are told that this object is identical to the Hubble’s picture you found on the Internet!

Today, it is obvious that astronomical observation should be redesigned, modernized and enhanced. Professional astronomers were moreover the first ones to observe the sky using digital images displayed on their computer screens. In a similar way, the French start-up Vaonis offers an original feature which updates stargazing: “photobservation,” which consists of observing objects of our sky with an eyepiece-free telescope equipped with a very high definition camera, sending color images of the object you are looking at in real time to your smartphone or tablet!

If you are among those who are not convinced that the future of astronomical observation is in the replacement of telescope eyepieces by high-performance cameras transferring data directly to our connected devices, you should keep reading this article. It might change your point of view.

Observation through an eyepiece: the biggest disappointment of astronomy!

Contrary to the expectations of most people, looking through a telescope’s eyepiece does not mean observing images as sharp, as bright and as colorful as the ones we often see on Internet or in scientific magazines.

The overall image quality does not depend solely on the optical quality of the telescope, but rather on the capabilities of our eyes. Although our eyes are extremely powerful tools that no camera could match, when night falls, that is no longer the case!

The weaknesses of the human eye in astronomy: anatomy reminder

First of all, our eyes require a minimum amount of time to adjust to darkness. Between 10 and 15 minutes are needed in order to detect the slight contrast of a nebula or galaxy through a telescope or even of the Milky Way observed by the naked eye.
Obviously, our eye sensitivity is limited and does not permit us to observe objects of the starry sky at their best.

Composition of human eye

The human eye contains two kinds of photodetectors which are spread out on the surface of the retina: cones and rods. These photo-receivers are responsible for our sight and our ability to detect different colors. Cones are sensitive to colors and are divided into 3 types: red, green and blue. They are constantly used for our daylight vision, but when the luminosity plummets, the rods take their place. Rods are far more numerous than the cones but are insensitive to color!

On one hand, it is thanks to the rods that we have night vision at all, and on the other hand, it is because of them that our night vision is only in shades of black and white!

As a consequence, we will never be able to observing the colors of galaxies and nebulae without a huge amount of light to make their shapes and borders stand out. This applies both to telescope eyepiece observation and to naked eye observation.

The drawbacks of classical observation: one observer at a time

Even without taking into account the physical limits of our eyes, telescope observation has not always been as simple as one might think. Here is a list of difficulties encountered when observing through the eyepiece of a telescope:

  • Lonely observation because only one person at a time can observe through the instrument
  • The eye should not touch the eyepiece in order to keep the telescope stable
  • The focus is different for every observer, and the telescope shakes while adjusting it
  • The observation position is often uncomfortable: you must bend, crouch or even climb up to reach the eyepiece!

A screen: observing + photographing = “photobserving”

Orion nebula visual observing vs photographyImage comparison between of the Orion Nebula as seen with the eye through the eyepiece of a telescope (left, simulation) and an image obtained with a telescope with an embedded camera like Stellina (right)

In the end, eyepiece observation is not the best way to appreciate the beauties of the universe. In addition to being uncomfortable, traditional observation is limited by the capacity of our eyes to differentiate among the low luminosity stars and other celestial objects.

The primary purpose of astronomical observation is to observe objects of the sky with the highest quality possible. Since modifying the human eye remains impossible, the typical solution for improvement is to purchase bigger telescopes, which leads to spending more money. Even with larger telescopes, the result sill does not match our expectations.

Given this frustrating limiting factor of our eyes, a question can arises: since nowadays we have technology powerful enough to exceed the performance of our eyes at the night, wouldn’t it make more sense to remove the eyepiece and instead embed a CCD sensor?

Observing the colors of the Universe, at last!

Indeed, not only does a photo sensor reveal the true colors of nebulae and galaxies but also enables us to detect objects which were totally invisible through a telescope eyepiece!

The list of accessible sky objects thus becomes richer and the satisfaction of these images is even greater, because they reveal much more detail.

Real-time images on your smartphone

No need to adjust your night vision and to try to guess which astronomical object you are looking at. The captured photograph is directly shown on your tablet’s or smartphone’s screen, through WiFi.

Importantly, a Stellina telescope does not simply display an instantaneous grayish view of an object;  rather, it uses the process of live-Stacking, which consists basically of taking a series of pictures and superimposing them one by one. This technical process derives from practices by professional astronomers, and enables Stellina to make the celestial body stand out while the clock is ticking, by light amplification. The longer you keep the telescope pointed at an object, the brighter and the more visible it will be.

The mobile app provided with Stellina performs the entire image processing and automatically chooses the suitable image processing for each object. This permits you to avoid the complicated and unintuitive field of astronomical image processing.

A screen for sharing your experience and having a collective observation

Using the screen of a smartphone to replace the telescope eyepiece is especially appreciated when you wish to move freely about your telescope without having to come back and forth to it every minute. With this system, it is now possible to invite family or friends to observe your images simultaneously keeping your seat on your patio or even in your living room!
Your tablet serves as a support to look at your pictures and also as an interactive link to share your experience on every social network.

Sharing your astrophotographical work will never be as simple and effective as with Stellina. Stellina allows each of us to SHARE OUR UNIVERSE!

Why a telescopes does not need an eyeiece

New future for astronomy

Thanks to an eyepiece-free telescope, you will never need to fuss with focusing the telescope, changing the eyepiece, etc. The telescope will be ready to use within a few seconds.

A telescope like Stellina can help you observe the beauty of our universe at it’s best, and even make your first steps in advanced astronomy: collaborative astronomy. Asteroid occultations with 3D rendering, variable stars monitoring, exoplanet transits wich were previously limited to professional astronomers will now all be accessible to everyone.

Select the Universe which suits you the best with a new generation telescope: Stellina.

Certification télescope

2018.03: Certifications

Certifications Tests CEM télescopeBuying a telescope is good thing, buying a telescope which is certified is better! In March, our poor Stellina has gone through several days of torture in order to guarantee you a good functioning and a total safety of use. We passed several required certifications for the European and American markets: electrostatic discharges and electro-magnetic waves have tried to knock down our dear telescope but Stellina stayed steady as a rock. The device held up to 16 000 volts without flinching when the standard only requires 4000… A great achievement that rewards three years of intense development.

Three years designing, prototyping and testing the 272 parts that compose Stellina. Each element, from the small screw to the lens, had specifications requiring the best quality and stability in order to create a telescope as design as powerful. After selecting each component, we assembled the pieces to verify that they all worked in harmony. This step took longer than expected but we are now at the end of the optimization step. The engineering team is gathering all its energy to build a Stellina that will keep its promises of being a telescope letting you observe the universe in all ease and simplicity.

After passing first the certifications for the European and American markets, we won’t change anything about Stellina anymore! The production is currently in progress to deliver you this telescope that you are all waiting for!

About CEM tests

CEM qualification requires particular attention for safe equipment or specific operating conditions. An electromagnetic environment is the component of natural sources (solar radiation, electrical charges in the atmosphere – storm…) and artificial sources like radiofrequency wave emitters or interfering phenomena related to any electrical equipment running.
In sectors where electromagnetic constraints may be important and/or where safe equipment is concerned, the requirements set by specifications are generally very important. After an electromagnetic qualification, it can be determined whether or not the equipment is compatible with its electromagnetic environment. We are talking about electromagnetic compatibility qualification tests.

Source: Emitech


2018.03: Stellina’s release date

The date of launch has been confirmed. Stellina will be available from March 31, 2018 in France and in the rest of EU. It will be followed few months later by the North American markets.

The product will be shipped to the customers who placed a preorder in 2017 and to distributors across Europe. It will also be available for purchase on our website. Stay tuned!


2017.12: New pictures

New pictures taken with Stellina are now available! Many of you were very excited to see more pictures. You can see now the pictures of Orion nebula, the moon, the Double cluster and a new version of the galaxies M81 & M82. More pictures are coming in January and will be updated in the Products page.

Note: the banner image at the top of the page was not taken with Stellina.


2017.09: Improvement of optics

Depuis notre dernier email en juin annonçant le début de l’industrialisation, beaucoup de choses se sont passées tant au niveau interne (agrandissement de l’équipe, retombées médias, récompenses…) qu’au niveau du produit. En effet, après discussion avec nos fournisseurs, nous avons fait le choix d’apporter des améliorations à l’instrument :

Choix des matériaux
Les supports internes, auparavant fixés à la coque en plastique, sont désormais remplacés par une structure en aluminium, assurant la liaison du trépied à l’optique. Ceci assure à Stellina une rigidité digne des meilleures montures du commerce et amoindrit considérablement la sensibilité au vent de l’instrument.

Qualité optique
Deuxième point important, un nouveau cap a été franchi en termes de qualité optique. Reposant auparavant sur un simple doublet achromatique, nous avons décidé de le remplacer par un doublet ED à diffraction limitée afin d’améliorer la qualité des images (suppression du chromatisme, meilleur piqué d’image…).

Ces choix ont eu un impact sur le planning de l’industrialisation car elle implique des tests de qualité supplémentaires. De ce fait, la livraison des premiers télescopes est attendue le 1er trimestre 2018.

Notre engagement sur la qualité et notre mission de vous fournir la meilleure expérience utilisateur possible sont les raisons pour lesquelles nous avons décidé d’allouer du temps supplémentaire à ces modifications.