As any student of telescope history will know, France has a long and distinguished tradition of optical innovation that now extends into the twenty-first century. In a recent review of the eVscope (AN, August 2020), I described how Marseille-based company Unistellar used a successful 2017 Kickstarter crowdfunding campaign to turn their ‘Enhanced Vision’ telescope concept into a commercial product. The eVscope is a self-aligning computerised telescope capable of displaying near-realtime colour images of galaxies and nebulae via its built-in electronic ‘eyepiece’, or on the screen of a controlling smart device via Wi-Fi.
The eVscope was conceived in 2015, but the following year saw the founding of a competing French company called Vaonis, by Cyril Dupuy, a start-up entrepreneur with a background in optics and aerospace. Vaonis were also working on their own fully automated, self-aligning telescope system, again using a smartphone or tablet to both control the instrument and view its output on-screen. Vaonis’ product eventually came to be marketed as the Stellina ST80 observation station, the instrument reviewed here.
Vaonis’ idea of what the all-singing, all-dancing personal robotic telescope should look like and how it should perform is quite a departure from Unistellar’s eVscope. Stellina is, first and foremost, an astrophotographic instrument, primarily for deep-sky objects. It’s targeted at first-time users wishing to capture detailed images of nebulae and galaxies with the absolute minimum of effort, either to view on a smart device or – if you like to dabble in image editing – save in a variety of formats to a USB memory stick for subsequent processing on a desktop computer. More on this later.
The optical heart of Stellina is an 80mm ED doublet lens of 400mm focal length, hence it’s an f/5 system. While this may not seem a particularly ‘fast’ optic in conventional photographic terms, it is par for the course for refractors intended for astrophotography of extended objects like nebulae and galaxies. Remember that this is a doublet objective lens, albeit one made using high-index, low-dispersion lanthanum glass that reduces chromatic aberration for improved colour fidelity. Stellina is also self-focusing at the start of an observing session, so you never have any excuse for a blurry picture.
Stellina isn’t intended to be used visually, so an electronic detector lies at the focus of the objective lens. Vaonis chose a colour Sony IMX178 CMOS sensor delivering a field of view of almost 1.25 degrees across the diagonal, which is similar in extent to the Pleiades star cluster, for example. Given that most of us have the misfortune of living under some form of urban light pollution, Stellina incorporates a CLS (City Light Suppression) filter. Furthermore, the instrument has built-in humidity and temperature sensors, so if Stellina senses that the night air may be falling below the dew point, it activates a built-in lens heater!
Vaonis markets Stellina as a complete ‘observation station’ incorporating all the elements needed for astrophotography. This means that it must have a way of aligning itself by the stars and, once a desired target is selected on your smartphone or tablet using the dedicated Stellinapp (more on this later), precisely tracking that object for long periods of time – up to an hour or more, if necessary. Self-alignment and tracking is accomplished by an embedded computer and a motorised alt-azimuth mount. Stellina is also cable-free and self-contained, powered by a rechargeable battery pack and operated via Wi-Fi.
Stellina arrives at your door in a single shipping carton measuring 90 × 58 × 31 centimetres. Once opened, you’ll find the instrument’s day-to-day storage case, which is a glossy black box 62 × 46 × 19 centimetres in size, emblazoned with the words ’Stellina: share your universe’ and sporting a carrying handle on the top. There’s another 15 × 15 × 29 centimetre box for the Gitzo GT3520S-VS1 tripod. The tripod box also contains a bubble-level plate, a few Allen keys for making tripod adjustments, a rechargeable PowerCore Li-ion battery pack for Stellina rated at 10,000mAh/36Wh, and some USB adaptor cables. A tripod adaptor with a bubble-level plate on top connects to the base of Stellina via a standard 3/8-inch photo thread.
The supplied Gitzo tripod is very stubby indeed compared to those that come with conventional telescope mounts. With its two-stage carbon-fibre legs fully extended, the top plate is just 37 centimetres above ground level! The very low operating height of Stellina does mean that you occasionally have to give some advance thought as to where you should place the instrument, particularly when your target may lie close to the horizon – you won’t see over the fence! For operating in the country or a secure park this isn’t much of a problem as you often have more choice in your sight lines. Stellina’s built-in dew heater is certainly needed for long grass.
Nestling inside its foam-lined storage box, Stellina is shipped with a dust jacket made of a stretchy black Lycra material of a type used for the shrouds covering the open framework of truss-tube Dobsonians. When closed for storage, Stellina’s case measures 47 × 39 × 12 centimetres and tips the scales at 11 kilograms. Given that the instrument has a curvaceous design of smooth white plastic, I do question Vaonis’ wisdom of using such a slippery material for a dust cover – if one is not careful then Stellina could slip through your hands!
With Stellina safely attached to the supplied Gitzo tripod, the entire instrument stands just 86 centimetres tall. It’s certainly an eye-catching and tactile conversation piece – almost sculptural – when sitting in the corner of a room. I joked with my youngest daughter that it was a new domestic robot, because when switched off there is nothing outwardly to suggest it’s an optical device. (The instrument is unsettlingly reminiscent of EVE and some of the service robots in the 2008 Disney/Pixar movie WALL-E; one almost expects Stellina to suddenly announce itself in a thin, reedy voice.)
As I touched upon earlier, at the heart of Stellina is an 80mm, f/5 ED doublet lens utilising lanthanum glass for superior colour correction. Instead of an eyepiece, a colour Sony IMX178 CMOS sensor with a matrix of 3,096 × 2,080 pixels lies at the focus of the 400mm focal-length objective. The IMX178 has 2.4-micron (0.0024mm) pixels, hence the sensor’s overall dimensions are 7.4mm × 5.0mm, which gives Stellina a true field of one degree by 0.7 degree, or almost 1.25 degrees across the diagonal. Furthermore, the small pixels give the instrument a resolution of around 1.25 arcseconds per pixel, which means Stellina achieves optimal image sampling for typical two- to four-arcsecond FWHM seeing.
On paper, then, Stellina’s specification suggests that it can deliver images at the theoretical resolving power of its 80mm-aperture objective under normal atmospheric conditions. In addition to the built-in CLS light-pollution filter and dew heater, it clearly indicates that a lot of thought went into the design from a team well versed in astro-imaging. Furthermore, since Stellina uses an altazimuth mount, the engineers at Vaonis incorporated a de-rotation system to prevent those stars near the edge of the field forming short arcs instead of points as the field orientation changes throughout the duration of the exposure, operating in precisely the same way as professional astronomical research telescopes.
On one side of the instrument there is a battery compartment with a cover that pops open and lifts out at the bottom where a tab holds it in place. The tab has a small aperture at the end, large enough to accept a cable should you wish to power Stellina from a mains transformer supply, but most times you will use the supplied rechargeable 10,000mAh battery pack, or one of your own with maximum dimensions of 13 × 8 × 4 centimetres.
You will find three USB ports inside the battery compartment, the lowest being a USB-C port used for power input. According to the Vaonis specification, Stellina’s minimum power requirement is 2.4A at 5V. The specifications state that a 10,000mAh battery should give you five hours of operation. In my tests, two-and-ahalf hours of operating time was the most I could achieve with the supplied 10,000mAh battery pack, but the pack on the review model that I was sent was evidently well used, so maybe it wasn’t working near full capacity.
The other two ports in the battery compartment are USB-A sockets for connecting memory sticks for saving your images in JPEG, FITS or TIFF formats, the last being stored in 16-bit format without compression for higher quality (think RAW format on a DSLR camera). To give you some idea of the storage you’ll need, the file sizes generated by Stellina are up to 4–5MB for JPEGs, 12MB for FITS, and up to 36MB for TIFFs in full resolution.
As soon as a power source is connected to the USB-C port, Stellina’s power button on the opposite side to the battery compartment glows blue. Pressing the power button for a couple of seconds starts the initialisation process and the instrument creates a Wi-Fi hotspot. Up to ten smart devices can be connected to Stellina simultaneously, but only one is designated the administrator – the other nine can look on and see the pictures.
Before you can start capturing images with Stellina, you need a compatible Android smartphone/tablet, or an iPhone/iPad, onto which you must download the free Stellinapp from either the Google Play Store or Apple’s App Store. The minimum Android requirement is version 4.4, or iOS 10 for Apple devices. Vaonis releases regular software updates, some of which are updates for Stellina itself, so the first time I launched the app I wasn’t surprised that it also patched the instrument’s firmware, all without any issues. Another thing that you can do on first launching Stellinapp is to create a user profile where you can save your observation history, favourite targets and app settings.
The app’s user interface changes depending on whether you are in the Control, Catalogue, Capture, or User Profile tab. It’s intuitive to use and largely self-explanatory after a few minutes’ use. Control is where you wake Stellina, or engage sleep or park mode. Catalogue is where you select targets from a current list of about 200 objects compiled from Messier, NGC and IC deep-sky objects, asterisms, prominent double stars, the Moon and planets, or you can manually enter coordinates. Capture is the section of the app where you frame your compositions and start stacking sets of ten-second exposures (called frames in Stellinapp) to form long-exposure images, zoom and pan around them, apply simple processing before saving, and share or export your photos.
As explained earlier, Stellina has a built-in CLS filter, so rather than travel out to my usual dark-sky site, I chose to use the instrument in my suburban back garden on the edge of a mid-sized market town, typifying the environment in which Stellina would be used. The town recently made the switch to LED street lighting and three such lanterns lay within 50 metres of the test site, and I had placed the instrument in the shade of the nearest light.
Once connection to Stellina’s Wi-Fi network is established in Stellinapp, which is about a minute after booting, and after you have logged in (it’s not compulsory), you need to initialise the instrument. The first time that you see the central section of Stellina’s casing quietly rotate out of its parked position and the objective lens slowly point up to the stars is quite magical! Stellina then uses GPS geolocation to model what’s above you and then presents a catalogue of objects currently visible using a traffic-light system: green is good to observe, amber is too low or too near the zenith, and red is below your horizon.
Once you’ve selected the object that you wish to observe, Stellina performs a star-zone search and a star-pattern analysis – essentially a plate-solving exercise to determine precisely where it is pointed and how far it has to move to acquire your target. Next, the instrument performs an autofocus to get the sharpest imagery, before engaging tracking activation. After some rather mesmerising graphics reminiscent of particles disappearing at the event horizon of a black hole, the Capture tab opens and you see your target slowly appear before your eyes as each subsequent 10-second-long frame is live stacked with the previous one.
Faint emission nebulae and galaxies can take an hour or more (the Catalogue tab tells you roughly how long you need to stack frames) to build on screen, but bright planetary nebulae such as the Dumbbell Nebula (Messier 27) look great after 10 minutes, or 60 frames. You can replay a whole stack of frames from the beginning, or pan around and zoom in and out of the image on your smartphone/tablet using two-finger pinch and spread gestures, even as it is stacking. On occasion, the app crashed on my Android phone, but once I relaunched Stellinapp I could always resume from where I left off and nothing was lost.
For all its technical wizardry, Stellina is remarkably easy to use and certainly does what it says on the tin, delivering rewarding images of a wide range of deep-sky objects – many of which would be challenging to capture using conventional astrophotographic techniques. The only downside for Stellina is the usual one – its price of €3,999 (about £3,550 according to the exchange rate at the time of writing), which many of the astrophotographic cognoscenti will regard as excessive.
However, not everyone has the time or inclination to ascend the steep learning curve of getting familiar with astro-imaging hardware and software, so there is a definite market for Stellina and products like it. Furthermore, you may be interested to know that Stellina observation stations are assembled by hand by a workforce based in Montpellier, not far from the offices of Vaonis. And in these troubled times, it is always nice to know that we are using products that support and benefit the communities in which we live, which has a different value altogether.
At a glance
Size: 47 × 39 × 12cm
Autonomy: 5 hours with a 10,000mAh portable battery
Focal length: 400mm
Focal ratio: f/5
Field of view: 1° × 0.7°
Objective type: ED doublet with lanthanum glass
Filter: CLS light-pollution, built-in
Image sensor: colour 1/1.8-inch CMOS Sony IMX178
Sensor matrix: 3,096 × 2,080 pixels
Pixel size: 2.4μm (0.0024mm)
Resolution: 1.24 arcseconds
Field de-rotation: built-in
Dew heater: built-in
Magnification: Equivalent to 50× and up to 100× with digital zoom
Alignment: Automatic initialisation with star-field recognition
File formats: JPEG, TIFF or FITS (16-bit raw images)