Available from: 365astronomy.com
I have to confess to a keen interest in all forms of electronically assisted astronomy, or EAA as it’s commonly known. EAA encompasses a broad range of technologies, but inhabits the middle ground between visual astronomy and astrophotography. It’s partly responsible for restoring the ‘wow’ factor to deep-sky observing for my family and friends, many of whom have a peripheral interest in astronomy.
Traditionally, EAA practitioners replaced their eyepieces with sensitive video cameras connected to portable monitors. These days, however, most EAA is performed with a dedicated astronomical camera linked to a small, battery-powered, single-board computer connected wirelessly to a smartphone or tablet.
When I reviewed Unistellar’s eVscope last year (see Astronomy Now, August 2020), it was immediately apparent that this was an instrument that represented a substantial evolutionary leap in EAA. But the eVscope still possessed an eyepiece, albeit a high-quality miniature OLED screen masquerading as one. With the release of the eQuinox, are we finally freed from the paradigm that a telescope requires an eyepiece at all?
What is the eQuinox?
The eVscope eQuinox, to give it its official title, has a very similar specification to Unistellar’s debut product. Just like in the eVscope ‘Classic’, the optical heart of the eQuinox is an 11-centimetre diameter, 45-centimetre focal length (f/4) parabolic mirror. At its focus lies an extremely sensitive, low-noise, 1.2-megapixel colour Sony IMX224 CMOS sensor delivering a maximum field of three-quarters of a degree, as measured across the sensor’s diagonal. The eQuinox’s 55 × 14.5 centimetre diameter optical tube is permanently attached to an L-shaped, single-arm, computerised altazimuth mount. The wholly self-contained drive base houses a dual-axis drive, and an internal rechargeable lithium-ion battery pack powers the entire system.
Also contained within the eQuinox’s mount is a Linux-powered single-board computer that provides the instrument with sophisticated onthe-fly image-processing capabilities, celestial object tracking and wireless connectivity to the Unistellar app on your smartphone or tablet. The last is used for controlling the instrument and as a display for the object under scrutiny. Up to ten smart devices can connect wirelessly to a single eQuinox, which is wonderful for outreach work or public viewing sessions. Nine devices can connect as ‘ Watchers’, but only one device is deemed the ‘Operator’.
Other than the original eVscope having an electronic eyepiece that the eQuinox lacks, there is no other hardware or software difference between the two. The 64GB storage capacity of the eQuinox versus the 12GB of the eVscope merely reflects the size of the relatively inexpensive micro SD card used in each, while the 12-hour battery life of the eQuinox versus the eVscope’s 10 hours is solely because of the extra power drain of the latter’s electronic eyepiece. However, the eQuinox’s extra storage capacity will permit night-long data-gathering activities for exoplanet transit observations and the like, which were previously impossible.
The eQuinox arrives pre-assembled on its computerised altazimuth mount with a separate tripod, a box of accessories containing a charger with interchangeable plugs (EU, USA and UK) and a small toolkit, plus both quick-start and technical guides. Assembly is simplicity itself: all you need to do is open, extend and clamp the tripod legs to the required height, level the tripod head using its built-in bubble, then slide the mount into position and secure it by two thumbwheels. The rigid tripod is highly versatile; it can limbo down to just 17 centimetres above the ground with the legs fully splayed, while at full height on its three hand-locked sections it reaches 123 centimetres. Fully assembled, the eQuinox tips the scales at a modest nine kilograms.
Up to ten smart devices can connect wirelessly to a single eQuinox, which is wonderful for outreach work or public viewing sessions
The overall impression given by the eQuinox is one of stylish minimalism with a high build quality and exterior finish. The mount, tripod and lower tube section are matte black, while the optical tube’s front is charcoal grey (the original eVscope had a silver accent to the tube). There is no computerised hand controller or keypad – recall that your smartphone or tablet fulfils that role – and a single, lozenge-shaped power button resides in the fork arm. Pressing the button for a couple of seconds boots the eQuinox, the periphery of the power button transitioning from purple to red in less than ten seconds to show that it is ready.
One soon gets used to interpreting the instrument’s power button glowing different colours and pulsing a varied number of times according to the eQuinox’s current mode of operation. The underside of the fork arm sports a USB-C port for charging the internal battery (you can still use the eQuinox while it’s charging from the mains adaptor, but be mindful of power-cord wrap). There is also a regular USB-A port that is only used to recharge your smartphone – it’s not a means of connecting to the eQuinox for data transfer via a cable.
The Unistellar app
Once booted, the eVscope eQuinox generates a unique yet passwordless Wi-Fi hotspot that you must connect your smartphone or tablet to before launching the Unistellar app. I found that I could communicate with and command the eQuinox from up to ten metres away, but for responsiveness and reliability, closer is always better. It was fun to position the instrument outside on the garden patio and drive it from indoors while comfortably seated on the sofa, something that will doubtless appeal to those who don’t like outdoor observing in the cold!
At the time of writing, the current versions of the Unistellar app are v1.3.0 for iOS and v1.3.1 for Android. The app also automatically updates the telescope’s onboard computer firmware when required. I used the apps on an iPhone 6S (iOS 14.7) and an Android 7 phone without any apparent difference in functionality, though the Android version seemed to be the most stable of the two. Even when the iPhone app occasionally crashed, it would automatically reconnect to the eQuinox and no data were ever lost. This suggests that the eQuinox’s Linux-powered computer handles much of the instrument’s functionality, which likely accounts for some of the eQuinox’s flawless operation throughout many nights of subsequent testing.
The home screen of the Unistellar app opens with the Live-View stream from the eQuinox, which by default sets automatic limits on gain (analogous to the ISO setting on a digital camera) and exposure time (from zero to four seconds, calibrated in milliseconds). In the app settings you can disengage auto settings and use manual sliders to, say, view distant terrestrial objects once you’ve located them with the onscreen joystick.
Observing the Moon or a bright planet like Mars or Jupiter requires deft manual adjustment of gain and exposure. The eQuinox can slew at variable speeds of up to a maximum of four degrees per second about both axes, yet even at its fastest slew, the eQuinox is very unlikely to wake the neighbours at night, and at tracking speeds it is as quiet as a whisper.
Automatic alignment and navigation
The eQuinox has a built-in digital compass and three-axis accelerometer to help it navigate. Still, as long as its camera can detect stars, it will orient and align itself using a highly accurate system that Unistellar calls ‘Autonomous Field Detection’ (AFD). It doesn’t matter where the eQuinox is pointing when you start; just invoke AFD by pressing a button on the app’s home screen. The eQuinox’s on-board computer then pattern matches its view of the sky with an internal database of 20 million navigation stars in mere seconds, precisely determines where it’s pointed and then engages tracking. AFD, better known as plate solving, is spectacularly fast: you can switch the power on your eQuinox, align and be tracking the stars in under a minute.
Once your eQuinox is aligned and tracking, you can select the app’s ‘Explore’ tab and search for a target by name from a database of more than 5,200 objects, search by category, see what’s in the constellation you’re currently pointing to, or manually enter equatorial (J2000.0 epoch) or alt-azimuth coordinates. Also, under the ‘Science’ tab, you can participate in citizen science programmes run in partnership with the SETI Institute. These include asteroid occultations, exoplanet transits, planetary defence (a grand umbrella term for near-Earth asteroid observations in order to determine their orbits better) and cometary activity, to name but four. Indeed, every Unistellar product owner can join the growing network of eVscope users worldwide. A thriving online Unistellar community uses a dedicated Slack channel too.
It was fun to position the instrument outside on the garden patio and drive it from indoors while comfortably seated on the sofa
Introduced with the original eVscope, Enhanced Vision (EV) is also one of the showcase features of the eQuinox. Having selected, located and begun tracking a faint target such as a nebula, galaxy or asteroid, then touching the EV icon commands the eQuinox to continually superimpose subsequent images (‘stacking’ in astro-imaging parlance) to improve image quality. Each image is typically of four seconds’ duration, but over a few minutes hundreds of combined pictures quickly lead to images replete with fine detail, colour and texture that mesmerisingly grow in quality as you watch.
The eQuinox’s on-board computer automatically aligns each image with the next, removes the effects of image rotation (recall that it uses an altazimuth mount, so the object’s orientation changes as it moves across the sky) and does a superb job of removing the gradients associated with light pollution. The superimposition of hundreds of images of the same scene ensures that random electronic noise generated by the camera fades into the background. To further improve picture quality, you also have the option to create dark frames that effectively remove the ‘hot’ or ‘sticky’ coloured pixels.
Focusing and collimating
The eQuinox’s dust cap incorporates an indispensable aid to precise focusing called a Bahtinov mask. With it installed over the mouth of the tube, select and Go-To a bright star and you’ll see its diffraction pattern modified into an X-shape with a central spike. Gently turn the focusing wheel on the instrument’s base clockwise or anticlockwise until the spike meets the intersection of the X and results in perfect focus for the eQuinox, and it holds that focus very well between sessions, even when regularly moved.
Collimation is also adjusted from the rear of the instrument using the tools and clear instructions supplied. The review instrument required the merest tweak to deliver perfect performance, and did not need subsequent adjustment.
Pluto’s opposition date of 17 July 2021 coincided with a clear night for testing the eQuinox, so it was an obvious target. To make the challenge somewhat harder, the magnitude +14.3 dwarf planet lay amid the southerly stars of Sagittarius, crossing the meridian at an altitude of just 14.75 degrees above the southern horizon of my favourite rural observing site.
Deep nautical twilight lessened Pluto’s contrast against the sky, but viewing it through the dust, summer haze and a denser atmospheric window close to the horizon resulted in around 1.5 magnitudes of dimming. So at the time of observation, Pluto’s apparent visual magnitude approached +16. Consulting my detailed finder charts for confirmation, I was impressed that the dwarf planet appeared onscreen in the app after just 24 seconds of Enhanced Vision.
An excellent example of a small and detailed deep-sky object is the Ring Nebula (Messier 57) in the constellation of Lyra. Having waited impatiently for moonset from my favourite rural test site, I used the eQuinox to image the Ring just before 2am BST on 17 July when it lay high in the south-west. Despite the handicap of deep nautical twilight, the instrument readily revealed field stars of visual magnitude +17.8 (referenced against the Gaia catalogue), so Unistellar’s stated eighteenth-magnitude stellar limit is entirely feasible under dark skies.
In an image saved after just three minutes of EV, the zoomed-in view of M57 brimmed with structure and colour, which is impressive for an object just 60 × 85 arcseconds in size. The turquoise-green interior transitioned to red on the periphery, with clear changes in texture around the elliptically shaped annulus. Furthermore, the magnitude +15.6 central star was easily recorded, together with its sixteenth-magnitude companion plus two others on the southwestern extremity of the Ring. As a final treat, the eQuinox detected the soft glow of fifteenth-magnitude spiral galaxy IC 1296 just four arcminutes away to the north-west.
When one considers that the new eVscope eQuinox has an identical hardware specification to the phased out eVscope ‘Classic’, it does feel that Unistellar could have dropped the price to keep it competitive – after all, the eQuinox lacks the highcontrast colour OLED (organic LED) screen, eyepiece and associated electronics of its predecessor, so manufacturing costs are presumably lower.
I would also have liked to see a larger or higherresolution sensor in the eQuinox –a Sony IMX385 or IMX178, for example – but I concede that some sort of integral coma corrector would then be required. As such, the eQuinox feels more like an incremental upgrade. However, there’s no denying that the super-resolution algorithms and improved image-processing methods heralded by the Unistellar v1.3 app continue to push the performance envelope of the eVscope family, and one can only guess at the exciting features yet to be implemented.
At a glance
Aperture: 110mm (measured) parabolic mirror
Focal length: 450mm (measured)
Field of view: 0.61 × 0.46 degrees (measured)
Resolving power: 1.7 arcseconds
Saved image size (EV mode): 2,560 × 1,920 pixels without overlay; 2,240 × 2,240 pixels with overlay
Saved image size (Live-View): 1,280 × 960 pixels
Optical magnification: 50×
Digital magnification: up to 400×
Limiting magnitude: <+16 in medium quality sky in under a minute, up to +18 in excellent conditions in a few minutes
Imaging sensor: 1.2MP colour Sony IMX224LQR CMOS
Battery life: 12 hours
Data storage: 64Gb
Weight: 9kg including tripod
Price: £2,599 plus shipping (Unistellar backpack: £335)
Available from: 365astronomy.com
Ade Ashford has travelled the globe writing about astronomy and telescopes, serving on the staff of astronomy magazines on both sides of the Atlantic.