Jump to content


* * * * *

Nexus II Review

Discuss this article in our forums

Nexus II Review


SUMMARY: The Nexus II is an outstanding piece of equipment that allows anyone to use their Smartphone or tablet and see where their telescope is precisely pointed. It is an extremely cost effective and easy way for someone to add digital setting circles and a “Push-To” function to just about any telescope.



Nexus-II - Digital Setting Circles | Astro DevicesThe Nexus II is one member of a family of digital setting circles devices developed by Serge Antonov, owner of Astro Devices. While the Nexus DSC product itself is a full featured DSC system consisting of the hardware/software and LED displays that enable anyone to dial in a selected astronomical object, the Nexus II is essentially the same thing, minus the digital readout. It takes the input from a pair of encoders mounted to the telescope and wirelessly displays where it’s pointed on a tablet or Smartphone. This is a review of only the Nexus II and to use it you also need an app that will interface with the unit. For my purposes I use Sky Safari 5+ on an Android device.

A quick background: I built my 12 ½” F5.2 Dobsonian telescope, described in a CN article here, with “manual” setting circles and by manual  I mean a printed 360° azimuth circle glued to a 18” diameter hardboard ring that encircled the rocker box of the telescope. For altitude I used a digital inclinometer. After going through a tedious alignment procedure to level the telescope and point it and the 0°/360° mark of the azimuth ring precisely north I would then look up the Alt/Az coordinates of an object I would want to view. Once the telescope was slewed to the specified coordinates I was usually in the neighborhood of what I was looking for but I still had to resort to old fashioned star hopping to zero-in on the object itself. It was far from a perfect system and I wanted something more efficient.

After a thorough search I selected Astro Devices for several reasons.

1.    Most important; Astro Devices provides a one-stop shop supplying everything I would need and by everything, I mean the encoders and mounting hardware specific to my type of telescope as well as the Nexus II itself. I felt in case of an “issue” I would only have to deal with one person, one company and not have several different vendors pointing fingers at anyone else.

2.    Serge’s customer support reputation, as described on CN, was outstanding. I expected at some point I would need some help (more on that later) and he did not disappoint.

3.    I saw no reason to spend the extra money for a DSC system with a digital readout. I reasoned that this era’s Smartphone or tablet has more than enough computing power to do that. The Nexus II basically tells the app on my phone where the telescope is pointing.

I emailed Serge the specifications of my telescope, he emailed me back with some specific questions regarding some needed dimensions such as the distance from the center point of the altitude ring to the base of the scope and I received the kit (from Australia) that included everything I needed, all for a total cost of $350.00 ($200 for the Nexus II + $150 for the encoders and hardware.)

IMG_20200808_225727 (2).jpgThe package included, in addition to the Nexus II device, a pair of 8196 step magnetic encoders with all the wiring and connectors as well as all the mounting hardware and instructions.  Installation was easy and accomplished in about an hour. It’s important to note, one critical piece of hardware needed and included with the kit is a modified stainless steel azimuth axis pivot bolt, one with a head that has a machined out socket for the encoder shaft, and a tapped setscrew to lock it in. For other scopes you might need something else but there are numerous kits shown on the Astro Devices website for different brands and types of telescopes. For my case, because it’s a home built scope I also needed to tell Astro Devices the exact length pivot bolt needed.

IMG_20200808_225907.jpgThe Nexus II itself is housed in a metal box roughly 3” x 5” x 1 ¼”, small enough to fit inside the base of the rocker without interfering with the bottom of the mirror box of the telescope when pointing at the zenith. It’s connected to both encoders with a single RJ-45 connector and that’s all there is to it. The internal battery is good for 11 hours of observing and since it’s a rechargeable battery, if and when it no longer holds a charge it can be replaced. (NCR18650B). It will also work with external power. After three years of use, I have not yet needed to replace the battery despite recharging it many times.

Once switched on the Nexus II creates its own little Wi-Fi network. With your smart device you connect to the Nexus network then once Sky Safari is opened and configured to the network’s IP settings, you click “Connect” and when you move the scope you will see the target on your device’s screen move. In my case, the first time I used it, when I moved the scope up the target would move down. I then simply had to change the Sky Safari encoder settings for the “Alt” axis from “+” to “-“ at which point it moved in sync with the scope in both directions.  You then go through the Sky Safari alignment process and you’re in business for the evening.

Now here’s the part where Serge’s support was critical. At some point, after two years of use with zero problems, all of a sudden Sky Safari wouldn’t connect with the Nexus II. It looked like the phone would connect with the Nexus network but once Sky Safari was launched there would be no connection. I thought it might be a battery problem so what to do? I emailed Serge and he called me on the phone (from Australia mind you, 16 hours ahead). We stepped through a couple of tests and he confidently diagnosed that somewhere along the line an Android update was causing my phone, because it detected no internet access, to automatically disconnect from the Nexus network and reestablish contact with my home network. Whether or not this would happen out at a remote site with no home network in range I wouldn’t know since I never tried it but the solution was to tell my phone to “forget” my home network. By doing this, the phone stayed in contact with the Nexus II without any issues. Once done for the evening I would simply reestablish my home network on my phone. Note: Android has since issued another update where a pop-up window now asks if I want to continue to use the Nexus network. If you don’t answer “Yes” you will lose the connection.   

Whenever I observe I’m always absolutely stunned with how well the whole system performs. When in use, the Nexus II is extraordinarily accurate. (And when I say “Nexus II” I mean the entire system, the device, the encoders and app). I can select whatever I want to look at on Sky Safari, move the telescope where indicated and the object, without fail, will be within the field of view of an 18mm eyepiece. I no longer need to even bother with my scope’s finder and it makes an evening’s observing session so much more efficient and rewarding. I have since removed both the azimuth circle and the inclinometer from my scope. They’re no longer needed.

I can highly recommend the Nexus II as well as the encoders supplied by the company for those who want to add a very accurate and reliable DSC system to their telescope but are looking for something a little more economical than a full blown self contained system.  For those who might be unsure about dealing with someone in Australia, rest assured Astro Device’s support is top notch but there are also several dealers that have been set up in the US as well as the UK, Europe and Japan. If you want a reliable, easy to install “Push-To” DSC system, this is the one to get.



  • Jeff Morgan, paul, markb and 11 others like this


I too just discovered Nexus and linking it with SS6 pro is the sole way I plan to use it, rather than toggle manually via Nexus device.


For alt az usage to find obscure targets on my observing lists, it is the perfect tool.

Thanks for the informative review.  With this info I’ll proceed confidently to chose a dob and add the Nexus 11 on.

Aug 30 2020 05:12 AM

This confirmed my decision also.  Waiting on my 10" dob to arrive, and I figured I'd wait till it showed up before ordering the Nexus II.  Now im going to go ahead and order it now.

Just verifying - I need internet access to use? Thanks-

Just verifying - I need internet access to use? Thanks-

No internet access required. The Nexus generates the wifi network for ipad or tablet or phone to connect to.

    • comabereni likes this

Thanks for an efficient and eye-opening review.


I first seen the Nexus as a Rowan add-on, but am not a fan of dedicated keypads etc (longterm reliabilty), I would not have picked up on the Nexus II as an alternative without your review!


I want to put DSCs on my mounts and this opens some affordable avenues, thanks!

I just got my Nexus II and encoder set for my AD10 last week - installed over the weekend, and gave it a quick whirl last night - LOVED it.  I am hopeful that it changes my observing habits.

Aug 31 2020 10:04 AM

Thanks for the heads-up! Just what I was looking for - I've ordered one for my 10" Dob.

Thanks for the review!  This will definitely keep me on the lookout for a cheap second-hand dob.

Newbie question here. Why not use a digital inclinometer sensor (like a dof sensor used in robotics) instead of encoding wheels.  Seems like this would be a one size fits all solution.  

Newbie question here. Why not use a digital inclinometer sensor (like a dof sensor used in robotics) instead of encoding wheels.  Seems like this would be a one size fits all solution.  

A device like the Nexus II allows the use of a tablet or phone with star charts and information at your fingertips. 

10K encoders (basic, and not the highest tick count available today) are accurate to about 2' of arc, or 1/30 degree. 

About the best you could get from an inclinometer would be about a degree.  And, it would necessitate EXACT leveling of the scope, not usually done.

And a higher level of orthogonality than is found in most commercial scopes.

Encoders are simple and relatively rugged and have been used on scopes for many decades.  


A note for potential Nexus II users: the Nexus DSC also has WiFi capability.  It's currently out of production, though, to give it multi-lingual capability.

I really like my Nexus II, but it was a hassle using it between my servocat and DS-Browser (which it required to set the alignment).  I came to hate using it all. I recently upgraded to the NexusDSC and it essentially saved an $8000 telescope for me.

I have one of the Next I devices - and it is great! I use it with my Half Hitch mount. So I would expect the Nexus II to be even better

Just ordered a Nexus II and encoders for my 8". Of course who knows when I'll receive them, but I'm sure it will be worth the wait.

They're expected before the end of the month.
The Nexus DSC is delayed for a bit.

Be aware for DIY that the manual has the pin outs for the DSC's reversed. In fact the picture is not correct at all. I am surprised he has not corrected it. 

Note that the pin outs diagram is correct, but the RJ jack is upside down.

Serge will reverse it in the future so wire #1 will be on the right instead of the left.


Right. The jack is upside down. Since Serge never answers emails, only phones you, you are left on your own to figure that out until the time difference is suitable. I had to use a scope to determine the signals. It should be fixed so the next poor soul doesn't spend a couple of hours or days figuring it out. He never did call or answer after I mentioned on a thread that be never answers emails. I guess, he took that the wrong way.

I'm hoping that someone can answer my question regarding the nexus ii.


I have placed an order but I can't seem a straight forward answer.


Will the Nexus ii be able to function if I travel to the  middle of no where in the desert without wifi?

And I see they make 2 type of Endcoders, which one goes to my explorer scientific 12 inch. The one that cost $249 or the $289. Just need to make sure I order the correct one.


Thanks for any help.

Sep 16 2020 02:42 AM

I'm hoping that someone can answer my question regarding the nexus ii.


I have placed an order but I can't seem a straight forward answer.


Will the Nexus ii be able to function if I travel to the  middle of no where in the desert without wifi?

Nexus-II creates its own WiFi access point and a smartphone/tablet connects to that network. Yes, you can take Nexus-II anywhere (but not underwater) and it will function.


Best Regards,


Sep 16 2020 02:46 AM

And I see they make 2 type of Endcoders, which one goes to my explorer scientific 12 inch. The one that cost $249 or the $289. Just need to make sure I order the correct one.


Thanks for any help.

Fo the 12" it might be better to go with the higher resolution azimuth encoder. If it was a 10" then it would not give you a lot of advantages.


Best Regards,


Thank you Serge and Thank you Xrayvizhen for this amazing review.


This made my purchase decision much easier to make.

     I also have had the pleasure of working with Serge to outfit two mounts built in the last Century made by Ed Byers.  He asked questions and had very good suggestions.  I settled on 311,000 tik encoders on both the Series One mount and the Byers 5-8 mount. This provides a much greater pointing accuracy than the 8k encoders I was using with a Lumicon DSC unit.


    Serge really helped us with the installation of the system by making some custom mounting brackets, using a 3D printer,   We just needed to give him a drawing with accurate dimensions. The mounting brackets fit perfectly and are very durable


    Personally I enjoy very much working with Serge who is helpful in every way.




(There are photos of my Byers Series One mount with the 3D printed attachments, on current the SHOW US Pictures of your mount forum )

Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics