Celestron StarSense Explorer DX 5" Smartphone App-Enabled Schmidt-Cassegrain Telescope

Product Overview

The Celestron StarSense Explorer DX 5" is a 125 mm f/10 Schmidt-Cassegrain on a manual altazimuth mount and steel tripod, paired with a smartphone dock and Celestron's StarSense Explorer app. The app reads the actual star field through your phone's camera and matches it against its own catalogue to work out where the tube is pointed, then shows on-screen arrows that walk you to a target and turn the bullseye green once it is centred in the eyepiece. It packs 1250 mm of focal length into a 13-inch tube weighing 5 lb, with StarBright XLT coatings and a CG-5 compatible dovetail — the most focal length in the range, in the smallest optical tube.

Who It's For

This is a good match if the Moon, the planets and double stars are your main interest and you want long focal length without a long tube. The folded Schmidt-Cassegrain light path gives 1250 mm in something that fits in a daypack, which makes it the most travel-friendly high-magnification telescope here. It also suits an observer thinking a step ahead: the CG-5 dovetail means the optical tube can move onto a tracking or equatorial mount later without replacing the optics.

Key Features & Design

• 125 mm aperture at f/10: 1250 mm focal length, with a highest useful magnification of 295x, a lowest useful magnification of 18x and a limiting stellar magnitude of 13.
• Folded optical path: 1250 mm of focal length in an aluminium tube just 330 mm (13") long and 5 lb in weight.
• StarBright XLT coatings across the optical system.
• Two eyepieces supplied: a 25mm at 50x and a 10mm at 125x — both usefully higher than the same eyepieces give on the shorter telescopes in this range.
• Erect-image 90° diagonal (1.25"): a right-way-up, right-way-round view, which suits terrestrial daytime use as well as astronomy.
• Dual-axis geared slow-motion controls for fine tracking by hand at high magnification.
• CG-5 compatible dovetail: the optical tube fits standard CG-5 / Vixen-style mounts, so it is not locked to the supplied one.
• Steel tripod to 1320.8 mm (52") with an accessory tray, and 14.6 lb (6.62 kg) for the complete kit.

Optical / Mechanical Design

The Schmidt-Cassegrain design folds a long light path into a short tube: light passes through a Schmidt corrector plate at the front, reflects off the primary mirror, then off a secondary mounted in the corrector, and back out through a hole in the primary. That is how 1250 mm of focal length fits in 330 mm of tube. Celestron publishes 329 times the light-gathering power of the unaided eye, with resolving power of 1.11 arcseconds by the Rayleigh criterion and 0.93 arcseconds by the Dawes limit, and a 51 mm (2.0") secondary obstruction.

The consequences for observing are consistent: f/10 makes high magnification easy to reach with ordinary eyepieces, which is why the supplied 10mm gives 125x rather than the 65x it would give on a 650 mm telescope. The same focal length narrows the widest true field available, so this is a telescope for compact, bright targets rather than large sweeps of nebulosity. Unlike the Newtonians in this range, the optics are set at the factory and there is no routine collimation.

Recommended Uses

Lunar observing at high magnification, where 1250 mm and 295x are doing exactly what they are built for. Planetary observing — Jupiter's cloud bands and Galilean moons, Saturn's rings and the Cassini division on a steady night, the phases of Venus, the polar caps of Mars. Double-star work near the 0.93 arcsecond Dawes limit. Globular clusters and planetary nebulae, which suit a narrow field. Travel, where a 13" tube and 5 lb of optics matter. Daytime terrestrial viewing with the supplied erect-image diagonal. Guided touring with the app's object list and audio descriptions.

Compatibility and Accessory Notes

Eyepieces: the supplied erect-image diagonal takes 1.25" eyepieces. The 25mm and 10mm cover 50x and 125x; a 6mm takes you past 200x, with a 295x ceiling above.

Mounts: the CG-5 compatible dovetail fits standard CG-5 and Vixen-style saddles, so the optical tube can be moved onto a tracking altazimuth or an equatorial mount later. Ask us what would suit if that is the plan.

Smartphone: the StarSense Explorer app runs on Android 12 and later and on iOS 18 and newer, including iPhone XR and newer. Celestron lists the app alongside SkyPortal and Starry Night Basic Edition, and maintains the full device list at starsenseexplorer.simcur.com.

Power: none. The telescope draws nothing, and the app runs on your phone using its own GPS.

If you are unsure whether your phone will run the app, send us the model and we will check it against Celestron's list before you order.

Good to Know Before You Order

f/10 is a narrow-field instrument. Large objects — the Andromeda Galaxy, the Pleiades, big emission nebulae — will not fit in the field the way they do in the f/5 reflectors here. This telescope trades field width for magnification, which is the right trade for the Moon and planets and the wrong one for wide sweeps. If you want both, we can talk through pairing it with a short refractor.

A Schmidt-Cassegrain needs time to cool. The closed tube reaches ambient temperature more slowly than an open Newtonian, and images sharpen once it has. Setting it outside twenty minutes before you observe is enough at this aperture.

The app needs real starlight to work. It cannot orient itself in daylight and wants roughly an hour after sunset before there is enough star detail to match on. Cloud cover, haze, a bright Moon and heavy light pollution all reduce what it can lock onto. The telescope itself works by day; the app's sky-matching does not.

It shows tonight's sky only. There is no date or time control in the app, so it plans the session you are about to have rather than one next month.

Tracking is manual. Objects drift across the field as the Earth turns, and at 125x and above that is noticeable — the dual-axis geared controls are how you keep up with it.

Solar observing needs a purpose-made filter. Viewing the Sun through any telescope requires a proper solar filter fitted over the front of the tube — ask us and we will point you at one that fits this aperture.

Two-year Celestron warranty.

Frequently Asked Questions

Is it difficult to set up?

No. The mount and tripod arrive preassembled, the tube goes on its dovetail, an eyepiece goes in the diagonal and the phone goes in the dock. There is no collimation routine as there is on a Newtonian. Aligning the phone to the optics is a short procedure at the start of each session and the app's tutorials walk through it.

What is it best used for?

The Moon, the planets and double stars, at magnifications the 1250 mm focal length makes easy to reach. Globular clusters and planetary nebulae suit it too.

Can I use it during the day?

Yes. The supplied erect-image diagonal gives a correctly-oriented view, which is what makes terrestrial viewing usable. The app's sky-matching only works at night.

Does the app need a subscription?

No. The app is unlocked for use with the telescope, with nothing further to pay.

Which phones does it work with?

Android 12 and later, and iOS 18 and newer including iPhone XR and newer.

Can I put the tube on a better mount later?

Yes — that is what the CG-5 compatible dovetail is for. The optical tube detaches and fits standard CG-5 and Vixen-style saddles, so a tracking mount later is a mount purchase rather than a telescope purchase.

Can I use it for astrophotography?

The supplied mount is manual with no tracking drive, so long-exposure imaging is outside what this kit does. Planetary and lunar imaging with a short-exposure camera is practical, and the 1250 mm focal length suits it. On a tracking mount by way of the dovetail, more becomes possible — ask us what that would involve.

Bottom Line

A 125 mm f/10 Schmidt-Cassegrain with app-guided pointing: 1250 mm of focal length in a 13" tube, StarBright XLT coatings, 50x and 125x in the box, geared slow-motion controls and a CG-5 dovetail, at 14.6 lb complete. The high-magnification and most portable telescope in the range, built for the Moon and planets rather than wide fields.