The Schmidt-Cassegrain telescope continues to evolve.
The 8-inch Schmidt-Cassegrain telescope revolutionized the hobby of astronomy 40 years ago when Celestron introduced the original orange-tube C8. Since then, the venerable telescope has kept up with the times. The latest edition adds a number of enticing features to appeal to the mobile-phone generation — indeed, to anyone now entering the hobby.
Software and Hardware Requirements
At $1,750, the NexStar Evolution 8 serves as a premium version of the popular $1,250 NexStar SE. Both NexStars feature the same excellent f/10 Schmidt-Cassegrain optics, and their tripods are similar and sturdy. What’s evolved is the mount.
The NexStar Evolution takes the Schmidt-Cassegrain telescope into the mobile computing age with the addition of built-in WiFi, allowing the telescope to be controlled wirelessly by an app on your smartphone or tablet. The Evolution does have a conventional hand controller with a simple two-line display, but that is so 1990s! You actually do not even need to connect the hand controller to use the Evolution. It can be aligned and operated strictly from the mobile app.
The app is free and can be downloaded from the Apple iTunes App Store (for iOS devices) or the Google Play store (for Android devices). You need to search for SkyPortal. As an alternative, you can also use Celestron’s SkyQ app ($5), which was adapted from Pocket Universe. SkyQ also works with Celestron’s add-on SkyQ Link accessory that allows adding wireless app control to other Celestron telescopes.
When I conducted the review, the Evolution did not connect to SkySafari, Starmap HD, TheSky HD or other planetarium apps that offer telescope control. SkySafari has since been updated to connect to Celestron WiFi scopes. Other apps might follow suit.
SkyPortal is actually a version of the popular SkySafari app, offering full telescope control, like the premium editions of SkySafari, but with a database of deep-sky objects limited to the Messier and Caldwell catalogues for 219 objects, just as with the lowest cost version of SkySafari.
SkyPortal requires at least iOS 7 or Android 4 to run, so don’t plan to use it with that old original iPad or Samsung smartphone still kicking around the house. I also found that I was not able to control the telescope with my four-year-old iPhone 4, even with the supported iOS 7 operating system. The app refused to complete an alignment or locked up, or the telescope spun out of control. My somewhat vintage iPad 3 (from 2012) had some initial difficulty seeing the Evolution’s WiFi network, but once connected, it ran the telescope fine. My conclusion: The app requires the latest mobile operating system (as stated in the product literature) as well as a fairly current mobile device.
To connect, you simply select the telescope’s WiFi network in your device’s preferences (it appears as SkyQLink-xx, with the xx being a unique two-character identifier). No device pairing or password is needed to log in. Just how an observing field full of Evolutions and iPad-wielding owners will get along remains to be seen. You could connect to someone else’s telescope by mistake — or evil intent — and vice versa!
You can also set up the Evolution and SkyPortal to connect to your home WiFi network (via the “Use Access Point” option), the same network to which your phone or tablet typically connects. The process involves entering the technical address info for your home network and flipping a hardware switch on the telescope. However, the other “Direct Connect” method is the default and is what you would need to use in the field far from home.
App Control
Once you are connected, the first order of the night is to align the telescope so that it knows where it is pointed in the sky. The telescope does not have GPS or even an internal clock. Your mobile device has all that information. The Evolution also does not use Celestron’s SkyProdigy technology, in which a side-mounted camera snaps images of the sky to auto-align the telescope. Instead, you must do the alignment.
To do that with the app, you have two choices: SkyAlign and Manual Align. With Celestron’s patented SkyAlign method, you have to use the app’s slewing buttons to slew to and centre three objects. They can be any three bright objects in the sky, and you don’t need to know what they are. The telescope figures that out for you. Celestron introduced SkyAlign several years ago, and it works amazingly well.
With Manual Align, you slew to one star you know, then tap on it in the app display to align on it. You then tap on a second star, and the scope slews to it or close to it (it’ll be off). You centre the object and align on it. Repeat for a third star. I prefer the Manual Align, as the telescope, not you, does most of the slewing. But you do have to know the identity of several bright stars.
When the scope is aligned, you can slew to any star, planet or deep-sky object displayed by SkyPortal by tapping on the object. A “Tonight’s Best” list takes you to a few dozen of the best of what’s up, a great start for beginners. You can also go to right ascension and declination coordinates you enter into the app, or you can scan the scope around using the hand controller’s four slew buttons.
What you cannot do is issue GoTo commands from the hand controller, because the controller thinks the telescope is not aligned and refuses to send the telescope anywhere. Nor can you align using the hand controller then switch to the app to issue GoTo commands. You must align and command the telescope with one system or the other: mobile app or hand controller. Once aligned, the Evolution found objects accurately, placing all targets nicely within the field of the 40mm low-power eyepiece.
The SkyPortal app is easy to use and offers access to many of the settings and status readouts (like battery level) that you would normally access through the hand controller. For many targets, there are excellent audio descriptions that tell you what to look for in the eyepiece — a coloured double star in a star cluster, for example. This feature is superb and really begins to make use of the media capabilities of the amazing computers we carry with us to enhance the observing experience.
But I hope Celestron will add more objects to SkyPortal’s modest database, bringing it on par with the SkyQ app, which offers all NGC objects as well as bright asteroids and comets. Another handy addition would be the ability to create custom observing lists offered by the advanced versions of SkySafari.
The Essentials
All the high-tech features would be for naught if the optics were fuzzy or the mount shaky. But not so. The Evolution is tack-sharp and rock-steady. Star images were textbook-perfect, and vibrations damped out in one second. The focuser is precise, with no image shift or greasy mushiness to hamper homing in on exact focus.
The other superb feature of the Evolution is its built-in lithium iron phosphate (LiFePO4) battery. It delivers 9.6 volts at 4.5 amp-hours, and depending on the amount of high speed slewing, it powered the telescope for 6 to 10 hours before requiring a recharge. (An AC charger is included, and recharging took about two hours.) To save battery power, you can limit the top slewing speed. External batteries are needed only for extended stays at dark sites away from AC power.
I loved the convenience of the internal battery, and I really like using a tablet to run a telescope. The large screen and star chart make it easy to see where the scope is pointed and what other objects lie nearby for exploration. Tapping on most objects and hitting the Info button brings up a wealth of science information, additional images and, for all the Messier and bright Caldwells, useful audio descriptions that will help you see more and understand what you are observing.
The late Tom Johnson, who designed the first commercial Schmidt-Cassegrain, would be amazed at how his telescope has evolved. Converging mobile computers with telescopes is a wonderful way to enhance observing and make the experience exciting to a new generation of stargazers. The Evolution takes the Schmidt-Cassegrain to the next level without any sacrifice in the quality of the optics or the mount.
Editor’s note: Regarding our statement in the above review about using the SkyQ app, Celestron has notified us of the following: “Shortly after the introduction of SkyPortal last year, the SkyQ app was no longer supported or available. SkyPortal was codeveloped by the makers of SkySafari and Celestron to work with Celestron WiFi compatible telescopes, including telescopes equipped with SkyQ Link 2 and the NexStar Evolution. The app is free and has undergone numerous improvements, with support for iOS and Android. SkyPortal may be upgraded to SkySafari Plus and SkySafari Pro to include a larger number of celestial objects to locate with a telescope.”
Associate editor Alan Dyer is an experienced user of amateur astronomy equipment. He is coauthor of The Backyard Astronomer’s Guide.
