Unistellar eVscope Information (4.5" Newton)

Introduction | Look | Basic Data | Attempt at a Field of View Comparison with the Atik Infinity Camera | Photo Attempts | Visited Sky Objects | First Conclusions | Links | Appendix: Selected Questions from the Unistellar FAQ

On this page I provide some information about my (hopefully) forthcoming 4,5" Newton telescope Unistellar eVscope 114 mm/450 mm (f/4) (I took part in a Kickstarter campaign in mid-November 2017). The delivery is promised for November 2018, but it might also, as was the case with other Kickstarter projects, take a lot longer. And up to that date I will have to wait, until I can report any personal experiences on this page. But before that I can tell you already a few things about the telescope and its background.

 

Introduction

In November 2017, when reading the "Adventure Astronomy" newsletter , I learned about the Unistellar eVscope for the first time. For a few weeks already, a Kickstarter campaign was running on this new kind of telescope (it ended up with more than 2100 supporters and more than $ 2 million in cash by November 24, 2017), and I also supported this project. Regrettably, I was already far too late to get hold of one of the two cheap offers. The delivery of the telescope, which can be assigned to "electronically augmented astronomy" (EAA), is scheduled for November 2018.

Experienced Kickstarter supporters, however, rather expect one or more years more to delivery... Therefore, I decided to also buy a similar solution (which may be more flexible, but may also be much more cumbersome to install and operate) in order to get already an idea of ​​the possibilities of the eVscope. But note that this solution is still much simpler than "true" astro photography. It is an Atik Infinity Color camera (it has a similar Sony CCD chip as the eVscope, but the chip size is larger) that I will put on my Sky-Watcher Star Discovery mount with my 4" Heritage 100P and my 6" Explorer 150PDS Newton tube (except for the camera a "pure" Sky-Watcher solution...).

What is the eVscope?

First of all, the eVscope is a 4.5" Newtonian telescope (aperture 114mm, focal length 450mm, aperture ratio f/4) on an Alt-AZ GoTo mount. Its special feature is, however, that it is designed to produce images of celestial objects that are reminiscent of photos taken with large or space telescopes (of course, in a lower resolution, but at least, it can...) and that can even show colors. The telescope is announced as working simply and more or less fully automatically. The graphic below (similar to the one from the Kickstarter campaign) illustrates the main features of the eVscope:

    
  • Enhanced Vision Technology
    for incredible views of the night
  • Autonomous Field Detection
    easy pinpointing and learning
  • Campaign Mode
    feel the thrills of scientific discovery
  • Connected
    smartphone controllable and social media sharing
  • Portable and Autonomous
    carry it and use it anywhere

To be able to produce such images, the telescope uses a highly sensitive CCD sensor. The images it produces are processed in the built-in computer using complex algorithms, especially, images are superimposed with ever new images (this is called "image stacking") that are recorded continually to reduce the noise. Also, the field rotation that arises in Alt-AZ mounts over time is eliminated by the software. The processed image is displayed in "real time" on an OLED display, which is viewed through an eyepiece (i.e., a kind of electronic viewfinder), so that a similar observation experience as in normal visual observation is achieved. As you can see in the schematics below, this design does not need a secondary mirror - the sensor resides at its place. This kind of astronomy is called "electronically augmented astronomy (EAA)", because an electronically amplified and software-processed image is viewed.

Figure: Schematics of the Unistellar eVscope (source: Unistellar)

In addition, the image can be wirelessly transferred to smartphones and computers, so that you need photograph the image in the viewfinder.

The alignment of the telescope is fully automatic, which I appreciate very much, because the 2-star alignment procedure of my Sky-Watcher Star Discovery AZ GoTo mount is sometimes a bit tedious (or I can not find matching stars ...). Last but not least, the telescope is easy to transport (7 kg with tripod) and delivers acceptable results even under a light-polluted sky (which applies to astro photography in general, as I learned from a hobby astronomer who took photos with a DSLR...).

I am less interested in is the campaign mode, which is mainly pushed forward by a member of the founder team who works at the SETI Institute. But other supporters seem to be very interested in it.

Further details and technical data can be found at Basic Data for Unistellar eVscope.

Brief History of the eVscope

The basic idea of ​​the eVscope was developed by Arnaud Malvache, in exchange with Laurent Marfisi???, because both were disappointed of the possibilities of traditional telescopes. Malvache's idea was to use a "low-light sensor to progressively intensify the light we see through the eyepiece of a telescope." This must have happened in 2014...

Between January 2015 and November 2016, the image processing algorithms were developed, and a first prototype was built in the laboratory. During this time, also a business plan and a design concept emerged. In any case, after three years of development work, Unistellar had built a working prototype and presented it at astronomy events and computer exhibitions in Europe and the USA from early summer 2017 on. Meanwhile, there are also pictures available of what the final product will look like. Whether this design study is also functional, I do not know. The product is to be manufactured in Asia - from parts that originate from Europe and Asia.

In October 2017, Unistellar launched a Kickstarter campaign that ended on November 24, with 2144 supporters and over 2.2 million $ capital. I participated in this campaign on 11.11.2017 ($ 1499) as supporter no. 1834.

The delivery of the finished telescope is scheduled for November 2018, but hardly anyone dares to believe this. Therefore, I bought a used Atik Infinity Colour camera to understand the basic principles before the telescope will arrive and also to be able to practice a bit with it...

Who is Behind the eVscope?

The eVscope is being developed by four French scientists, each contributing his specific knowledge to the project. The eVscope was conceived by Arnaud Malvache, who specializes in image processing. Laurent Marfisi seems to have made the eVscope into a "product," Antonin Borot developed the optical architecture of the eVscope, and Franck Marchis, who works at the SETI institute, extends the eVscope towards scientific applications (e.g. SETI campaigns).

Photos: Arnaud Malvache (CTO, left), Laurent Marfisi (CEO, second left), Antonin Borot (Chief of Optical Engineering, second right) and Franck Marchis (Chief Scientific Officer, right) (Source: Unistellar)

Questions to the Founders (from Unistellar Website)

What was your initial motivation for creating Unistellar?

Classical telescopes are great for viewing the four main planets - Mars, Venus, Jupiter, and Saturn - but even expensive, high-end devices don't allow us to see much beyond that, and totally miss the truly awe-inspiring colors and details of many deep-space objects. While astronomy remains hugely popular as a hobby, most people quickly grow disappointed at what they see through their telescopes and wind up moving them into the basement, where they gather dust. This was the problem we wanted to solve. Our first goal was to make observational astronomy far more fun, exciting, and easy to do. As scientists, we also wanted to foster a strong, growing interest in astronomical research and citizen science, and we believed that the way to do that was by transforming the telescope into a far more powerful and user-friendly device.

How does the eVscope "enhance" an image? For example, you mentioned that it collects light over time…what does that mean?

Most astronomical objects are too faint to be seen by the human eye, even with a telescope. This is the case because our eyes simply cannot accumulate light the way a sensor does. Our idea was to use state-of-the-art, low-light sensor technology and proprietary algorithms to accumulate light and re-project it real time into the telescope’s eyepiece. In a matter of seconds, this allows observers to see colors and details of nebulae, galaxies, and comets that that normally cannot be seen, even in larger, traditional telescopes.

 

Look

Look - Media

The following photos are taken from the "Press Material" page of the Unistellar Website and demonstrate the prototype (or design proposal) "in action." I am, however, not sure, whether this prototype is really working (the working prototype looks more "engineer-like")... The photos below are screenshots that I cropped and in part post-processed.

    
     
 

Source: Unistellar (Media - Press material)

Unboxing

In preparation

Preparation and Look (at Home)

In preparation

 

Basic Data for Unistellar eVscope

Hardware

Electronics

Smarts

Sensor Data

*) Diagonal: 6.09 mm (type 1/3, Quad VGA mode) or 5.59 mm (type 1/3.2, HD720p mode)

 

Attempt at a Field of View Comparison with the Atik Infinity Camera

Since I bought an Atik Infinity camera in "anticipation" of or in preparation for the eVscope, which is promised to be delivered starting in November 2018, I am, of course, curious finding out, whether both solutions provide a similar image quality and field of view (or how I can achieve this).

First of all, the sensors differ in that the IMX224 is a CMOS sensor, and the ICX825 used in the Atik Infinity is a traditional CCD sensor. Secondly, they differ in their size: The diagonal of the ICX825 is almost twice as large (11 mm) as that of the IMX224 in the eVscope (5.5 or 6.1 mm, depending on the type of application). Both sensors have similar pixel counts (1392 x 1040 versus 1305 x 977). Accordingly, the (square) pixels of the ICX825 are about three times as large as those of the IMX224 (6.45 μm vs. 3.75 μm edge length).

What all this means in practice, I will probably find out only in the course of time ...

Field of View ...

In its FAQ, Unistellar states a field of view of ~30' (about 0.5°, about the size of the diameters of sun and moon) for the eVscope, moreover they state that a pixel corresponds to a viewing angle of about 1.7".

When I multiply 1.7" by 1305 pixels (sensor size is 1305 x 977 pixels) and divide the result by 60 (to get from seconds to minutes), I arrive at about 37' (or 0,62°), which is considerably more than the stated 30'. Since Unistellar does not mention how many cells of the sensor are actively used, I recalculated this for 1280 pixels and got 36.3' (or 0.6°). Further below, I use an approximation formula for slightly more precise results.

Basically, I found two approaches to calculating the field of view:

Field of View from the Focal Length of the Telescope and the Sensor Size

For the field of view of a camera at a telescope, Oden lists the following (approximative) formula:

When I use 1280 pixels, because I do not know the details and I need only a rough estimation anyway, I arrive at an edge length of 4.8 mm given a pixel site of 3,75 µm; the eVscope has a focal length of 450 mm. If I insert both values into the formula, I arrive at:

This value should be a little more precise than the one that I calculated from the field of view for one pixel (1.7") (because the value 1.7" is a little "imprecise").

Field of View from the Magnification and the Type of Eyepiece

The eVscope magnifies 50 x, 100 x, and 150 x, whatever this may mean in the context of a telescope without an eyepiece... Considering the focal length of 450 mm of the telescope, eyepiece that provide the respective magnifications would have focal lengths of 9 mm, 4.5 mm and 3 mm (magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece).

In a next step, one would have to calculate, which true visual angle, that is, which field of view, this corresponds to. The result depends, however, on the eyepiece that is being used (or assumed as being used...), because, depending on the type of eyepiece, the apparent field of view can differ (the true field of view is derived by dividing the apparent field of view by the magnification). For cheap Kellner eyepieces, the apparent field of view is 40°, for Plössl eyepieces it is 50-52°, and for wide angle eyepieces it nay range between 60° and 110°. So, which type of eyepiece should I select? Since Plössl eyepieces are in common use, I will select them for my calculations, and also a field of view of 50° to make the calculations easier.

Thus, for Plössl eyepieces, I arrive at the following true field of view values for the different magnifications:

And the same for Kellner eyepieces (40°):

For a 9 mm Plössl eyepiece, I thus get twice the field of view in comparison to what Unistellar states for the eVscope. Perhaps, the statement refers to a magnification of 100 x, in that case it would fit. However, I suspect that only a magnification of 50 x magnification is "native" to the telescope and that the higher magnifications are calculated. This is also suggested by the calculations based on the sensor data.

I do not know why I can achieve much larger visual fields using this method than for the case that the sensor is the basis for the calculation. Presumably, this is because the sensors occupy a much smaller area than is illuminated by eyepieces...

Atik Infinity

Atik provides the following formula (it is an adapted version of the formula provided by Oden and used above) for calculating the arc (in seconds) per pixel of the Atik Infinity camera:

For arriving at the edge length of the sensor, the pixel size has to be multiplied by the respective number of pixels for that edge (I arrive at 9 mm). When I insert into this formula the data for a telescope with a focal length of 450 mm (e.g. a f/4 Newtonian tube with an aperture of 114 mm), as it is used for the eVscope, I arrive at a field of view of 1.14° (68.6'), which is fairly similar to what I get for a 9 mm Plössl eyepiece. A telescope with a focal length of 500 mm (e.g. a f/4.38 Newtonian tube with an aperture of 114 mm) arrives at more or less identical values as a 9 mm Plössl eyepiece, that is, at a field of view of about one degree.

Of course, other focal lengths of the telescope would lead to different values for the field of view. Identical fields of view for both sensors would be obtained if the focal lengths of the telescopes used have the same ratio as the horizontal edge lengths of the sensors:

A telescope with an actual or shortened / extended focal length of about 750 to 900 mm would therefore have a similar field of view as the eVscope. Differences arise from the different aperture ratios and light gathering powers of the telescopes used, as well as the differences in the photosensitivity and the noise behavior of the two sensors. The sensor in the eVscope has only one third of the area of the Atik Infinity sensor. At similar pixel counts, the pixels are just about one-third the size, which means that they only receive 1/3 of the light, making them about 1.5 f-stops less sensitive than in the Atik Infinity sensor. On the other hand, the eVscope has an aperture ratio of f/4, and that is crucial for the exposure time. It still remains to be clarified, what the consequences of all these differences are...

Conclusion

Overall, a lot of information has still have to be clarified (e.g., the actual number of pixels; on which basis the given magnification values are based; differences in the noise behavior and in the sensitivity of the sensors; ...), before a satisfactory answer can be presented here.

 

Photo Attempts

Photos Published by Unistellar

I will start with photos that Unistellar has published on various Web presences. They are copyrighted by Unistellar and shown here according to the "fair use" principle in order to demonstrate what is possible with this telescope. Note that the photos do not show the correct size relations between the different deep sky objects.

Note: I do hope that Unistellar will in the future publish a photo gallery of deep sky objects that can also be used by other Websites in order to promote the product and the idea behind it.

   

M 42/43, 15.11.2017, Pourrières near Marseilles, France, Twitter

 

Ditto, enlarged, Twitter

 

M 42/43, 7.1.2017, Las Vegas desert, USA, Twitter

   

M 42/43, 23.9.2017, Herzberger Teleskoptreffen (HTT), Jeßnigk, Germany, Twitter

 

M 42/43, 23.9.2017?, Brandenburg?, Germany, Twitter

 

Ditto as above, a little enlarged, Twitter

   

M 17 (Omega/Swan Nebula), 14.7.2017, Baronnies Provencales, France, Twitter

 

Ditto, smaller (same image), Twitter

 

M 16?, date and location unknown

   

M 27 (Dumbbell Nebula), 29.9.2017, Sundance, UT, USA, Twitter

 

Ditto, enlarged, Twitter

 

M 27 (Dumbbell Nebula), 23.9.2017, San Francisco, USA, Twitter

     

M 27 (Dumbbell Nebula), date and location unknown

 

M 27 (Dumbbell Nebula), date and location unknown

 

 

   

M 57 (Ring Nebula), 10.7.2017, Marseille, France, Twitter

 

Ditto (enlarged), 10.7.2017, Twitter

 

M 57 (Ring Nebula), 14.8.2017, San Francisco, USA, Twitter

   

M 57 (Ring Nebula), 15.9.2017, Central Park, New York, USA, Twitter

 

M 57 (Ring Nebula), date and location unknown

 

M 57 (Ring Nebula), date and location unknown

   

M 81 (Bode Galaxy), 19.5.2017, location unknown, Twitter

 

M 82 (Cigar Galaxy in the Bode Galaxies), 19.5.2017, location unknown, Twitter

 

Ditto, enlarged, 19.5.2017, Twitter

   

M 51 (Whirlpool Galaxy), 10.7.2017, Plateau de Calerne, France, Twitter

 

M51 (Whirlpool Galaxy), 5.5.2017, location unknown, Twitter

 

M 51 (Whirlpool Galaxy), date and location unknown

   

NGC 891, 15.11.2017, Pourrières near Marseilles, France, Twitter

 

NGC 891, date and location unknown

 

NGC 6946 (Fireworks Galaxy) with newly discovered supernova, 15.5.2017, location unknown, Twitter

     

M 11 (Wild Duck Cluster), 9.9.2017, SETI Institute parking, Twitter

 

M 11 (Wild Duck Cluster), 15.9.2017, Central Park, New York, USA, Twitter

   
   

M 13 (Hercules Cluster), 15.9.2017, Central Park, New York, USA, Twitter

 

M 13 (Hercules Cluster), probably the same photo, date and location unknown

 

M 13 (Hercules Cluster), 14.8.2017, San Francisco, USA, Twitter

           

Moon, date and location unknown

 

Saturn, date and location unknown

   

Photos taken from various Unistellar Web presences (e.g.: Unistellar Website, eVscope Kickstarter campaign and others)

My Own Photos

With Atik Infinity

Above, I write that in "preparation" for the eVscope, I bought an Atik Infinity camera in the color version in order to get with it and with my existing equipment a taste of the possibilities of the eVscope. So far, I had, "thanks" to the weather, only few opportunities for testing this equipment. After all, I have already learned that, at the Heritage 100P telescope, the camera only comes into focus with a Barlow lens or a focal extender. In my 5th attempt I was able to also test the camera at my Explorer 150PDS (6", f5/750) tube, and in my sixth attempt briefly at the Skymax-127 (with a focal reducer).

My first photos are still far from presentable, but I do it anyway, and you can already recognize that similar image impressions as with the eVscope should be possible, although theses are not achieved with the same ease...

My Own Photos - Atik Infinity
 
eVscope Photos published by Unistellar
         

M 15 - Atik Infinity

 

M 13 (Hercules Cluster) - eVscope

 

M 13 (Hercules Cluster) - eVscope

   

M 27 (Dumbbell Nebula) - Atik Infinity

 

M 27 (Dumbbell Nebula) - eVscope

 

M 27 (Dumbbell Nebula) - eVscope

   

M 57 (Ring Nebula) - Atik Infinity

 

M 57 (Ring Nebula) - eVscope

 

M 57 (Ring Nebula) - eVscope

     

The same image enlarged to 200% and turned upside down

 

M 57 (Ring Nebula) - eVscope, for comparison purposes repeated

   

eVscope photos taken from various Unistellar Web presences (e.g.: Unistellar Website, eVscope Kickstarter campaign and others)

With eVscope

In preparation

 

Visited Sky Objects

So far, I have visited (and documented...) the following sky objects with the Unistellar eVscope:

 

First Conclusions

In preparation

 

Links

 

Appendix: Selected Questions from the Unistellar FAQ

I selected the following questions from the FAQ of the eVscope Kickstarter campaign (only the ones that interest me most...) and answered them using the answers provided there and a bit of my own knowledge. In any case, I highly recommend reading the original FAQ.

Note: I may add further questions in due course...

Question: Can I adapt a DSLR (or system) camera to the eVscope?

The CCD sensor is a fundamental ingredient of the eVscope, and the telescope is matched optimally to its size (therefore, a 4.5" Newton reflector was chosen). According to Unistellar, this design provides the best combination of resolution and sensitivity. It therefore does make little or no sense to replace the sensor with another one (i.e. with the one in the DSLR). For a DSLR you would probably chose a bigger telescope as the one used in the eVscope. Here, a small telescope was chosen for the reasons listed above, and also to keep size and weight low in order to create a portable telescope.

One might hold a camera to the eyepiece (as did the founders sometimes during their demos), but it is easier and leads to better quality if you receive the images with your smartphone or computer (raw data).

Question: Can we switch to a different eyepiece ?

The eVscope's eyepiece is not a "normal" eyepiece that receives an image that is created by the telescope with purely optical means. The image is received by a CCD sensor and is processed by software. The result is sent to a small OLED "screen" that is viewed with the eVscope's eyepiece (that is, in reality we have something like an electronic viewfinder in a digital camera). It therefore does not make any sense to replace the eyepiece, which is optimally adapted to its purpose. The different magnifications of the telescope (50 x, 100 x, 150 x) are created purely digitally.

Question: Why don’t you offer a larger telescope with a bigger primary mirror?

On the one hand, because telescope and sensor are a perfect match (see the questions above), and, on the other hand, because atmospheric turbulence limits the resolution, so that a diameter of less than 200 mm is optimal for most sites. Additionally, a 4.5" telescope can be carried around.

Question: Why don’t you offer a magnification of 225 x?

For Newtonian telescopes (reflectors), it is not recommended to go beyond a factor of 1.5 with respect to the diameter of the primary mirror in mm (114.3 x 1.5 = about 170 x). A magnification of 225 x corresponds to a factor of 2 x, which is often used in advertisements, but applicable only to refractors and, for example, Maksutov-Cassegrain telescopes.

Question: What is the field of view and the pixel scale of the eVscope?

The field of view is ~30 arcmin (about the diameter of the moon or sun), the pixel scale is 1.7 arcsec.

Question: What is the resolution of the images it captures?

The Sony IMX224LQR image sensor has a raw image size of 1305 x 977 pixels and a typical frame rate of 60 fps. I also found out that it has square pixels of 3.75 µm x 3.75 µm.

Note: When I multiply 1.7" by 1305 pixels and divide the result through 60 (seconds -> minutes), I get about 37' (or 0,62°), that is, a little more than 30' as given in the previous answer (36.3' or 0.6° for 1280 pixels). A somewhat more precise formula, which is still an approximation, leads to 36,7' or 0,61° for 1280 pixels.

Question: Can I use the telescope in cities, how sensitive is the eVscope to light pollution?

Most of the Unistellar demos were done in highly light-polluted areas. The image quality will not be as good if light pollution is high, since the fainter objects will tend to disappear below the light pollution threshold, but you will still see colors and details on many of the brighter nebulae, galaxies, asteroids etc. Unistellar states that staying away from street lights (that is, by going behind a building or trees) is sufficient to enjoy objects like, for example, M 27 (Dumbbell Nebula), M 57 (Ring Nebula), or M 51 (Whirlpool Galaxy).

Question: Is the eVscope good for planets?

The eVscope is not designed to provide stunning images of Venus, Mars, Jupiter and Saturn, particularly, because of its relatively low magnification (or short focal length). A Maksutov-Cassegrain telescope like my Skymax-102 or Skymax-127 is much better suited to this task. You can, however, see the planets and distinguish some of their structures (ring of Saturn, satellites, phase of venus) with it. Using the eVscope, you can also see the fainter planets like Pluto, Uranus and Neptune, which are difficult to pinpoint and see with a classical telescope.

Question: The observations are in real time, right? But you seem to combine multiple frames to get a better image quality - how do you this?

Yes, you see an image made by collecting photons in real-time. You see what is happening at the moment in the dark sky. If a plane, shooting star, or something else passes while you observe, you will see its trace in the eyepiece.

The eVscope also combines frames, which are recorded continually, to improve the image quality (that is, to remove noise etc.). It uses a fast image stacking algorithm and a variable exposure time to provide an "on-the-go while-it-stacks" live user experience. The algorithms are capable of compensating small movements of the field, the rotation of the field of view (which is a characteristic of Alt-AZ GoTo mounts), as well as correcting for light pollution. Thus, the stacking produces a neat image in the eyepiece.

Question: What will be the alignment procedure?

The eVscope will offer an automated alignment procedure. Simply connect with your app, and click "Autoalign." The telescope will learn its location and pointing direction by acquiring data (GPS positioning, stars in the field of view). In good sky conditions (no or a few clouds), the auto-alignment will take a few minutes.

Another mode will allow users to assist the telescope to point in specific the areas where the sky is clear, so that they can align it even though the sky is partially cloudy.

Question: Can the battery be replaced?

The telescope, its electronics, and sensors are powered with a rechargeable internal battery that can be replaced in case of malfunction or permanent damage.

Question: Collimation

According to Unistellar, collimation proved to be extremely robust on the prototype. Unistellar therefore expects that collimation will be done at the manufacturing plant once and then last for many years to come. However, a small key will be provided to adjust collimation by acting on small headless screws (hidden by caps), should that happen to be necessary.

 

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19.01.2018