Nexus DSC by Astro Devices , mini-review

On my ServoCAT driven 18” f/4.3 StarStructure LE Series telescope I installed new digital setting circles, the Nexus DSC from Astro Devices (, a drop-in replacement for my ArgoNavis. Some simple craftsmanship and Velcro got me a platform to replace the ArgoNavis’ cradle so my Nexus DSC sits in comfortable reach on my scope. For the past two and a half years I’ve been connecting my ServoCAT wirelessly to my laptop or tablet with the Skytools3 Pro program using another Astro Devices unit, the Nexus WiFi adapter.  The Nexus DSC has built-in WiFi which makes my older, less expensive Nexus WiFi adapter unnecessary. It has a “From Planetarium” menu selection to drive my scope wirelessly by interfacing with a tablet, smartphone or computer with any one of many programs such as, Astro Planner, Cartes du Ciel, DeepSky, Megastar, SkySafari Plus/Pro, Starry Night or the Sky 6. If the planetarium software of your choice supports the ASCOM platform then you should be good to go.  The Nexus DSC is more intuitive than the Argo Navis with superior catalogues of objects (almost 2 million) and more features. It has a numeric keypad and curser arrows for super- fast menu acquisition, access to catalogues and their objects, as well as, displaying information on magnitude, size, surface brightness, galaxy morphology and more, including rise, set and transit times with push-of-a-button ease.

There’s an on-board 5000mAh rechargeable lithium battery so there’s no worry about leaking cells. An external power port is also provided for any 5 to 16 volt power source. Operating temperature range is -5°F to +120°F. Most observers’ toes will give out before the Nexus DSC does.

Available catalogues in the Nexus DSC should satisfy even the most obsessive observers. They include: Abell Galaxy Clusters, Abell Planetaries, Arakelian, Arp Peculiar Galaxies, Asterisms, Barnard, Bayer, Bright Stars, Caldwell, Collinder, ESO, Flamsteed, Herschel, Hickson Compact Groups, King, LBN, Markarian galaxies, Messier, Minkowski planetaries, IC, Named Stars, NGC, Palomar Globular, PK, PN, Sharpless, Stock, Terzan, Trumpler, UGC,  HyperLEDA catalogue, MCG and SAO.  Mine came loaded with over 800 comets and a huge asteroid database, all of which are updatable from the MPC website. Are you a double star obsessive? Then you’ll love that the full Washington Double Star catalogue is included.  

Execute a go-to for any object then use the “Identify” function to display up to 128 nearby objects for exploring areas around your targets. Plus, on the off chance that an object is not in the database, or for some reason you just can’t find it in the Nexus DSC, then you can punch in the J2000 celestial coordinates by selecting “Object at RA/Dec.”

To keep your dark adaptation in check the clear OLED 3.12” display has 256 levels of brightness and the keypad has an adjustable backlight of 100 levels. If an observing companion complains about the display being too bright then it’s not the unit’s fault.  The OLED has no internal heater per se but it generates enough heat to help keep the display dew free. A glance at the display tells you if there’s a GPS signal present, current time, battery status and information from whatever menu you’re in. Consequently, the GPS negates the manual entry of location coordinates. The NEXUS DSC always knows where it is, even though you might not.

Initial set-up was easy. Turn it on, set the date and time zone and the GPS sets the time and finds your location. You set your mount type and encoder resolution (up to 999,999 steps) in the “Telescope Settings” menu. If you’re using a motor drive, then in “Communication Protocol” you can select ServoCAT, SiTech, Skytracker or the LX200 emulation. Then, establish an altitude reference and begin star alignment.  At subsequent set-ups you begin with the Altitude Reference and move right to star alignment, as long as you’re using the same scope and mount.  

I used a two star alignment on Polaris and Altair and GoTos were very good during a 7 hour observing session. Everything fell within the 1/2° True Field of View in my 13mm Ethos. Mostly, the GoTos were well-less than a 1/2° but consider that accuracy depends on a mount’s orthogonality.  If desired, one can use the “Mpoint” alignment function and add as many as 128 calibration stars for high precision performance. I haven’t tried Mpoint but I will in one of my upcoming observing sessions.

Menu navigation was quite natural and easily managed. First stop, from an observing list generated in Skytools3 Pro and downloaded at home to the Observing List file in the Nexus DSC, was M33. Yes, the Nexus DSC has the capacity to accept custom observing lists from various planetarium programs but it will only accept objects that are already in its catalogues.

Going deeper into the menus of the Nexus DSC I tapped in the “Tour” function which turned out to be a lot of fun. One can select either a constellation tour or a “Within” tour, the latter is what I used. I set it to find <14th magnitude galaxies within a 10° arc field of view from M33.  It took me to the NGC 507 Group of Galaxies on the border of Pisces and Andromeda. I was able to count 6 galaxies but my Interstellarum Deep Sky Atlas showed more than a dozen that should be visible in my 18” but sky conditions weren’t sufficient.  The Nexus DSC also brought up the NGC 382 Group in Pisces, also known as Arp 331. A chain group of 4 discernible galaxies were in my 9mm 100° AFOV eyepiece, but even more were shown in my atlas. Need to return to each of these under darker skies.

I think the Nexus DSC is nearer the proverbial “bees knees” than any DSC system I’ve used, that includes the ArgoNavis and SkyCommander. There are some down sides. Using it with gloves requires care as the numeric keys are close together. Without gloves I was quite accurate with my keystrokes. To register an alignment star, one must press the OK button on the unit which requires drift timing the stars, not a show stopper, but Astro Devices told me that a subsequent firmware update will address this by having the GoTo button on the ServoCAT hand controller perform the OK function to avoid drift timing. An anomaly crept up after about 5 hours of initial use. The GPS indicator, time display and battery status in the upper right of the OLED display disappeared but all else with the unit continued to function normally. Astro Devices told me that that happened once with their own unit but were unable to get this partial display failure to repeat. It hasn’t repeated for me either and all has been well since.  It appears that the internal lithium battery begins charging when an external power source is connected unless the unit is fully charged.  Although my unit was 100% charged at set-up, I guess the charge dropped slightly during the night triggering the charging from my external 12 volt battery after several hours in use.  Astro Devices says that the fully charged lithium battery should give 9 to 14 hours of use depending whether the WiFi used.

And there’s more…. Like parameters and analysis of the Mpoint calibration stars, some Equatorial Mount/Platform features, a Test mode, updating catalogues from the micro SD card, USB and Serial connections and a Daylight Testing procedure that Astro Devices told me can be used to find objects in daylight if you set up the scope pointing north.   But I’ve written over 1300 words for a “mini-review” on my use thus far and that’s enough to get anyone started observing. Astroimagers, you’re on your own.

The Nexus DSC, at this writing, has only one USA dealer, or you can purchase it direct through the Astro Devices link I provided earlier.

Clear, dark and steady skies to all.

Fred De Lucia

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