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- FIELD TEST: THE NOH CT-20 ALT-AZ MOUNT
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- SharpStar Askar ACL200 200-mm f/4 astrographic telephoto lens
- A review of the Unistellar EVscope
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A review of the Unistellar EVscope
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A review of the Unistellar EVscope
Well here is another product that has received a lot of hype and press, but without divulging much useful information about the telescope itself. Well needless to say, the hype worked on me….and I took delivery of my (used) Unistellar EVscope today.
Why did I buy, and why should you?
I’ve been in the hobby since I was 13 years old. Over the years I’ve had everything from homebuilt 6F8 newts, to 11” SCTs to Questars and Televues, and you know what? - M13 and all the rest look exactly the same today as they did 40 years ago - so something had to change. I thought about getting into astrophotography as a way of perhaps looking at this differently, but there is a considerable investment in equipment, a steep learning curve, and generally you need to be attendant at your telescope when imaging.
So the EVscope checked several boxes for me.
· GOTO – check
· Self-aligning – check
· Portable – check
· Astrophotography for idiots – check (albeit on a limited basis)
· Ability for scope to operate remotely (ie: me indoors) - check
So what follows is a brief description, first impressions and first-light performance.
What is it?
The EVscope is essentially a Newtonian based camera in as much as the parabolic 4.5” F4 primary mirror focuses its image directly onto a Sony IMX224 sensor located in the position that would normally be occupied by the diagonal in a Newtonian or secondary in a Cassegrain.
The Sony IMX224 is a color sensor with a resolution of 1.2 Million pixels (1305 x 977).
The OTA is carried on a single fork arm ALT-AZ Goto mount with an integral lithium ion battery supposedly good for up to 10 hours. Also packed in there is a lot of computing power as evidenced by the scope’s ability to;
1. Recognize any star field you point it at and derive its internal map from that. (Plate solving)
2. Offer full GOTO and tracking capability.
3. View in both live view (no enhancement) or enhanced vision (EV) which takes frames every 4 seconds and stacks them internally in real time to provide an enhanced vision rendering of the target.
4. Cancel out field rotation that you get with any non-equatorial mounted telescope.
5. Sets up its own wireless network so it can access your phone or tablet to:
a. Get current GPS coordinates and time
b. Send real time pictures to your device (and 8 others)
c. Your phone or tablet runs the Unistellar app which is a free download from Google Play or the Apple store.
The eyepiece is not really an eyepiece in the sense that we’re all familiar with, but a ‘window’ looking at a Hi-res OLED display. You see on this display (and on your phone or tablet) whatever the main Sony chip sees. The sensor image is roughly the equivalent of 50X optical magnification. There is no facility to be able to change magnifications, although can zoom digitally on your device.
However, it is the EV mode that makes this scope different. While it is true that astrophotography has been around for decades, and no one thing that the EVscope does is groundbreaking – the EVscope accomplishes this without all the gear, wires, setup and steep learning curve necessary to get results with a more traditional setup.
It is this ability to capture and stack 15 images per minute with the commensurate increase in brightness and detail of the target that allows the EVscope to make some of its extravagant claims. I have an 8” SCT (which mathematically has 3X the light gathering power) and I can tell you that, with the possible exception of M42, the lowly 4.5” mirror on the EVscope reveals a lot more detail, brightness and color of the Messier and NGC objects when in EV mode – the magic of light stacking vs. raw aperture.
The EVscope arrived packed in the usual double cardboard box. Well protected. Once you get the outer wrapper off, you will be met with the following promise.
Opening the inner box reveals the following
a) EVscope in parked position
c) Accessory box for the AC adapter
d) Quick start manual and user manual
The scope and tripod together weigh approx. 20lbs. I wondered what the EVscope would be made of. The answer is aluminum for the OTA tube and plastic cladding for the lower end cell and mount cladding. The fork arm/base /rear cell have aluminum skeletons but in truth is, I was a bit disappointed.
With this scope commanding almost $3000USD, you’d like to think you could get away from the ETX black plastic syndrome, but the scope does have some heft to it, hinting perhaps at a substantial aluminum frame beneath the cladding.
The tripod is basically a heavy-duty camera tripod and the feet are tipped with squishy rubber pads which seem to allow a lot of ‘wiggle’.
Several times I would get the message that the ‘EV mode was dropped due to vibration’. It was a breezy night. I wonder if the squishy feet were allowing too much movement?
The tripod design allows the angle of the legs to be altered from a narrow footprint to almost horizontal in 3 steps. There are 3 ledges that the leg stop can butt against. Just pull out the detent to allow the stop to clear the lower ledge and butt against the next. It is not spring loaded so be sure to re-seat it.
The interface between the mount base and tripod head could also be more rigid. There are only 2 hold-down screws around the periphery, and this allows some movement between the scope and the tripod head. 3 screws would eliminate this issue, and indeed, there is a raised boss in the casting identical to the other two locations that has not been drilled/tapped. This would be an easily fixed oversight.
There is also some unwanted lateral play in the AZ axis. This could be contributing to the vibration warnings I sometimes get. I am currently working with Unistellar to address this issue and will advise the outcome.
Looking down the tube you will see the primary mirror at the bottom, and the ‘secondary cage’ forming the cross at the top of the tube where the Sony sensor is mounted.
Interestingly, the tube is double walled.. Whether this is to help with thermal stability, or to hide the wiring going up to the sensor – who knows? The inside of the OTA is painted a satin black which does a poor job of reducing stray light. A flat black paint, or even better, a textured flat black would help the cause.
The overall length of the OTA is a bit longer than a 4.5”F4 system would normally dictate. This is because the secondary light reflections that occur in a Newtonian or Cassegrain design that eat up some focal length are missing in the EVscope. It’s straight from the mirror to the sensor with nothing in between, so the OTA is as long as the mirror focal length plus whatever is needed at either end to house the optics and sensor.
Underneath the mount arm, there are two ports. The small one (USB-C) is the charging port. The large one (USB-A) can be used for powering a phone or other USB device from the scope’s internal battery.
The Unistellar documentation is not, well….stellar. It’s bare bones and basically covers taking the scope out of the box and setting it up and how to start the app. Then you’re pretty well on your own.
Spread the tripod and level with the integral bubble level. Plunk the mount/scope into the socket and secure with the two thumbscrews, take off the dust caps and the physical stuff is done. Maybe a minute - tops.
Press the power button about 2 seconds and it will initially turn Purple, and then to Red as it finishes its boot sequence and establishes its Wi-Fi network. At this point you can acquire the EVscope network on your phone or tablet, and then start the Unistellar app on that same device.
Use the app joystick to depress the scope to point at any open area of sky with visible stars.
A note on the joystick. The center yellow circle is the ‘tip’ of the joystick. Drag it onto any of the four direction arrows to move the scope. The further from the center you drag it, the faster the EVscope moves. Fine adjustments can be made by tapping just the arrows. I found it a little cumbersome to use in practice.
Tap the Autonomous Field Detection icon to start the alignment procedure.
Once the scope identifies the viewed star field with its internal database (called plate solving) it knows where it is and you’re good to go.
It seems to be very accurate, which it needs to be to land the image dead center on a small CMOS sensor. The only caveat is that it needs to see a star field, not just a single bright star, so you have to wait a little longer for the sky to darken before you can do an alignment.
Tap the ‘Explore’ icon on the lower menu bar to call up the GOTO database. Here you will find most of the popular Messier, NGC and IC targets grouped into several categories. If the selected object’s ‘GOTO’ icon is greyed out, this means it is not viewable at your time/location.
The EVscope is not a fast slewer, and during a GOTO, it seems to pause a couple of times along the way to review its plate solving algorithms in some wayward part of the sky, but whatever it is doing, it’s doing it well as the GOTO’s were spot-on middle-of-field when done, and they stayed there for as long as you want.
During slewing the ‘Live view’ will shows the stars as streaks until the scope settles down to tracking rates. Once on target, it stays in Live view mode unless you tap the EV mode icon. The Live view mode can be pretty grainy on dim objects. You can fiddle with manual controls for the live view mode to provide a less ‘boosted’ image. I don’t know if dimming the live view mode also dims the view for the EVscope’s Sony sensor.
So you’ll want to tap the EV icon and this is where the magic happens.
The EVscope then starts taking frames 4 sec apart, stacking and processing them to present a gradually improving image of dimmer astro targets. Brighter targets may only seconds to image, dimmer ones may run to several minutes depending on how dark your skies are.
In my fooling around the first time out, it only needed 20 sec to provide a nice pic of M42 and M82 – the Cigar Galaxy.
And I saw the Crab nebula for the first time ever….
And obviously, from this article, once you have the images on your phone or tablet, it’s easy to manipulate them.
The nice thing about all of this is that other than the preliminary setup, I was sitting comfortably in my den about 25 ft away while the scope was outside in freezing temperatures. I was able to move to the other end of the house which would have been about 40ft away at that point and still had a signal.
The scope seemed to be well focused and collimated when it arrived judging by the star images. Both the focus and collimation are manually adjusted with the app software providing the necessary feedback. There is an included Bahtinov focusing mask located under the front dust cap. Between the mask and the app-based cues for collimation, it is not difficult to do (easier than a standard Newtonian).
A couple of things seem to disorient the EVscope.
1. If there are clouds or obstacles in the way of the FOV, then the scope cannot see a ‘plate’ to solve. It’s not like a regular GOTO where you tell the scope where it is on the face of the earth and what time it is and the controller then predicts the target location from there on. That GOTO system does not care about obstacles, it will cheerfully point at your target on the other side of a barn. By comparison, the EVscope navigates by comparing star fields to its internal maps. If any of the FOVs are blocked when it drops out of warp to have a recon, then the GOTO is aborted, and it returns to tracking mode.
2. If excess vibration detected, the scope will drop out of EV mode. As mentioned, the rubber tripod feet or ‘squishy’ and there is excess play in the AZ axis that may be contributing to this issue…
So far, it is early days, but I am encouraged. The EVscope allows me to view the same old objects in a completely new light (no pun intended) and to save those views to my phone/tablet for use any way I want.
I am able to see things I could never see in my strictly visual scopes, or if visible, as my wife would say….meh...
So instead of doing a Messier marathon and saying ‘yeah, I think I saw it’, you can now have an image of each one for your Messier log. And like our hobby in general, the next night, the seeing or the next image could be better than the last.
The moon and planets can be viewed with the EVscope and indeed, they are GOTO objects in the Apps target list, but it is important to realize that this is not the EVscope’s intended purpose. The EVscope excels at aggregating light and detail from dim objects. The moon and brighter planets will require that you fiddle with the manual adjustments in live view mode. EV mode is not required. Just bear in mind that you are only dealing with 450mm of focal length so the planet views are going to be very small. However, for the moon and bright planets, any decent scope will do.
When it comes to looking for and viewing dim astro objects, there are basically two solutions:
a) Big aperture, with all the attendant problems with portability. And at the end of the day, most faint fuzzies stay exactly like that – faint.. even in bigger scopes.
b) Light stacking ie: Astrophotography. The EVscope is well along the way to astrophotography, albeit with limited resolution and light grasp compared to more professional setups. The meager 4.5” EVscope can show more of deep space objects than you could ever hope to see with direct vision. I’m sure there are some 24” newt owners that would dispute that statement, but please refer to my comment in point a).
So if you want to see more of deep sky objects than is possible with visual observing, and you’d like to be able to take pictures of these views, then this is perhaps a good fit for you.
I know that there are Astrophotographers out there that will sneer at this little scope, and there is no argument that for the money, you could get a much more capable telescope optically, and/or a better resolution AP setup - but you still have to carry it all out, hook it all up, learn how to use it, and accompany it with your computer while you’re taking the pics. And then you need to process the images through various software to tease out the details. I’ve done some basic webcam stuff and then processed it through a couple of stacking programs. I found it time consuming, tedious and not straightforward.
So the EVscope can get you into basic AP without the various components, wires, cables, computers, frostbite and steep learning curve.
I can take the scope outside, set it up and capture a decent image of M42 before the Pro AP guys have even finished carrying all their AP gear outside. And for now, I’m good with that.
· Good introduction to basic astrophotography. It adds another dimension.
· Accurate GOTOs and tracking
· Fully integrated package so no wires, hookups or compatibility issues.
· Works with any Android or Apple mobile phone or tablet with WiFi.
· Capable of revealing very faint astro objects and saving the image files.
· Good basic App interface. (would be better with a proper manual)
· Very portable (OTA and tripod less than 20lbs)
· No other accessories required.
· Small learning curve.
· Fully integrated package. If anything fails, you have a paperweight.
· Limited capabilities compared to more sophisticated setups. Reports are that Unistellar is working on upgrades to make their scope more AP friendly for those that want to have more control. After all, it uses the same Sony IMX224 sensor as a couple of popular aftermarket AP cameras.
· Sparse documentation for scope, and, in particular the Unistellar App. (to be fair though, they responded quickly to two questions I asked them)
· Not really intended for the brighter solar system targets (although they can be imaged…)
· Not good for terrestrial use.
- kc6zut, Bob Campbell, chazcheese and 39 others like this