Celestron StarSense Explorer™ DX 102AZ Smartphone App-Enabled Refractor Telescope

102mm f/6.5 Refractor Optics with XLT Coatings

The 102mm aperture and 660mm focal length give 212x the light gathering power of the eye, a limiting stellar magnitude of 12.5 and a resolution of 1.37 arc seconds (Rayleigh) or 1.14 arc seconds (Dawes). Celestron's XLT coatings on fully coated glass optics improve light transmission.

The aluminum tube is 812.8mm (32") long and 118mm (4.64") in diameter and weighs 5 lbs (2.26 kg). The included 90-degree erect image diagonal lets you use the telescope during the day to view birds, wildlife and landscapes. Expect sharp, bright views of Jupiter's four Galilean moons, its cloud bands and Great Red Spot, the rings of Saturn, the Trapezium in the Orion Nebula and the Pleiades. Even from a light polluted city, StarSense Explorer can pick out Jupiter, Saturn, Venus, the Orion Nebula, double stars and a few more of the most famous objects, and from even slightly darker skies more objects become visible, such as the Andromeda Galaxy.

StarSense Explorer: Your Phone Finds the Way

Celestron has reinvented the manual telescope with StarSense Explorer, the first telescope that uses your smartphone to analyze the night sky and calculate its position in real time, and it is ideal for beginners thanks to the app's user-friendly interface and detailed tutorials. StarSense Explorer uses patented sky recognition technology and your smartphone to work out where the telescope is pointed: a Lost in Space Algorithm (LISA), like the ones satellites use to orient themselves in orbit, matches the star patterns the phone detects overhead to the app's internal database.

Place your phone in the StarSense dock and launch the app. After you align the phone to the telescope's optics, a quick, 2-minute procedure, the app lists the celestial objects currently visible. Pick one from the planetarium view or the Tonight's Best list and arrows appear on screen to guide you; the bullseye turns yellow when the telescope has detected stars but is not yet on target, and green when the object is ready to view in the low-power eyepiece. Stop for a few seconds as you get close, so the telescope can sense the stars in its new position.

Setting Up the App and Phone

Download the StarSense Explorer app before your first night out; the app is large, so a Wi-Fi connection is recommended. The unlock code on the card in the box enables telescope control on up to 5 devices. The app works with most modern smartphones, and Celestron keeps a compatibility list on its site; on older phones the app can still be used, but it cannot be reinstalled once uninstalled.

To align the phone, which is best practiced during the day, insert the low-power eyepiece, place the phone in the dock and turn the knobs at the bottom of the bracket until the camera view is centered, unobstructed, in the dock's mirror. Point the telescope at a very distant object, at least a quarter mile away, such as a streetlight, a license plate, a stop sign or a treetop, center it in the eyepiece, then slide the camera view until the same object sits in the crosshairs. If you have removed the phone from the dock since the last alignment, the app suggests aligning again.

To attach the phone, remove the large cap over the dock's mirror, pull open the spring-loaded slider on top of the holder, set the phone flush with the bottom lip and release the slider slowly. Most phones fit with the case on, but a bulky or folio-style case may need to come off. The dock's bayonet mount goes into the port on the side of the mount opposite the dovetail clamp: line up the arrow with the alignment mark, press in and turn counterclockwise until the orange release button snaps into place. To remove it, press the orange button and turn the dock clockwise. A small clear plastic tab between the dock's battery and its contact keeps the battery from discharging in shipping; pull it out before use.

Altazimuth Mount and Tripod

The altazimuth mount is ultra-stable: slip clutches and geared slow motion controls in both axes let you move the telescope smoothly, zero in on a target and follow it as it drifts with a few turns of the knobs. For large movements, hold a tripod leg with one hand and push the tube with the other; for fine adjustments and tracking, turn the slow motion knobs. The knobs slip over the D-shaped gear shafts and are secured with the hex key stored in a slot at the front of the mount head.

The adjustable, full-height aluminum tripod comes preassembled with the mount: spread the legs, push down the center leg brace, extend each leg with its three hand knobs, and fix the accessory tray on the brace with three thumb screws. The tube slides into the dovetail clamp on top of the mount arm and is held by the hand knob under the clamp. The mount and tripod weigh 9.2 lbs (4.17 kg), with a maximum height of 1244.6mm (49").

Eyepieces, Diagonal, Focusing and the StarPointer

The 25mm eyepiece gives 26x and the 10mm 66x; the highest useful magnification is 240x and the lowest 15x. The erect image diagonal goes into the focuser and the 25mm eyepiece into the diagonal, each held by set screws, and focus comes from the knobs below the focuser. Magnification is the telescope's focal length divided by the eyepiece's. Find objects with the longest focal length (lowest power) eyepiece, which gives the widest field, then switch to the higher power eyepiece for a closer view. If bright stars twinkle or change color, the air is not steady enough for high magnification, and a lower power will give a steadier view.

Align the StarPointer red dot finder to the telescope during the day: center an easily recognizable object at least a quarter mile away in the low-power eyepiece, then, without moving the telescope, use the finder's two adjustment knobs to put the red dot on the same object. It should not need realigning unless it is bumped or dropped, and it is useful during the day or without the app.

Because the Earth rotates, objects drift across the eyepiece, faster at higher magnification. Celestron's Telescope Basics manual suggests positioning the telescope just ahead of the target and letting it drift through the field.