Celestron CPC 925 GPS (XLT) Computerized Telescope

9.25" Schmidt-Cassegrain Optics: 0.49 Arc-Second Resolution with StarBright XLT

The diffraction-limited 9.25" optical system uses a Pyrex primary mirror and a crown glass corrector plate, with a Dawes resolution of 0.49 arc seconds, a Rayleigh resolution of 0.59 arc seconds and a limiting stellar magnitude of 14.4. The highest useful magnification is 555x and the lowest 34x, in a 559mm (22") aluminum tube 271.78mm (10.7") in diameter.

StarBright XLT is Celestron's coating system, built from three parts: enhanced multi-layer mirror coatings of aluminum, SiO2 and TiO2, with reflectivity fairly flat across the spectrum for both imaging and visual use; multi-layer anti-reflective coatings of magnesium fluoride and hafnium dioxide; and water white glass instead of soda lime glass for the corrector. Water white glass transmits about 90.5% of light uncoated, 3.5% more than soda lime glass, and reaches an average transmission of 97.4% with the StarBright XLT anti-reflective coatings.

The included 40mm Plössl eyepiece gives 59x (2350mm / 40mm). Focusing moves the primary mirror, which slides on the primary baffle tube; the focus knob sits on the rear cell just below the star diagonal, and it takes about 30 turns to go from close focus to infinity. Make the final focus turn counterclockwise so the mirror moves against gravity, which minimizes any mirror shift, and start on a bright object such as the Moon or a planet, since out-of-focus stars are very diffuse.

• Light Gathering Power: 1127x the unaided human eye.
• Secondary Obstruction: 85mm (3.35"), 36% by diameter and 13% by area.
• Included Accessories: Comes ready for observing with a 1.25" Star Diagonal, a 40mm eyepiece, and a 9x50 finderscope for easy object location.

Dual Fork Arm Alt-Azimuth Mount

The fully computerized dual fork arm altazimuth mount and the tube form one 58 lb unit that comes pre-assembled. DC servo motors drive both axes, and the manual lists fully enclosed optical encoders for position location among the CPC's standard features.

The dual-axis clutch system lets you move the telescope by hand even when it is not powered on, but both clutches must be tightened for GoTo use, and any manual movement invalidates the alignment. Leave both clutches somewhat loose when transporting, to reduce the load on the worm gear assemblies.

The mount slews at 9 speeds up to 5° per second and tracks at sidereal, solar and lunar rates in altazimuth, EQ North and EQ South modes.

Internal 16-Channel GPS and SkyAlign

The CPC's internal 16-channel GPS links with the orbiting satellites, works out the telescope's location to within a few meters and the time to the second, and enters them for you, so there is no need to enter the date, time, longitude and latitude or even know the name of a single star. SkyAlign, used with the telescope in altazimuth, then asks you to center any three bright celestial objects, including a planet or the Moon; the hand control has over 80 bright alignment stars down to magnitude 2.5. Auto Two-Star, Two-Star, Solar System, EQ North and EQ South alignments are also available.

GPS alignment only works outdoors with an unobstructed view of the sky. The first time, the CPC may take 3 to 5 minutes to link with its satellites; leave it powered on for at least 20 minutes so it downloads the satellites' orbital almanac, which it stores for future alignments. After moving a long distance, linking can take up to an hour.

NexStar+ Controller: A 40,000+ Object Universe at Your Fingertips

The included NexStar+ hand control puts a universe of celestial objects in the palm of your hand. Its database holds 40,000+ objects, which include customized lists of the best deep-sky objects, planets and bright double stars. Beginners can start with the built-in Sky Tour, which finds the most interesting objects in the sky for the current date and time and slews to each one.

The drive base has a hand control port, AUX ports, a PC interface port, an autoguider port, the on/off switch and a 12V input jack. The NexStar+ hand control's USB 2.0 port connects a PC, and Celestron includes Starry Night Special Edition and the SkyPortal app.

Power is 12 VDC at 1.5A, tip positive.

Weights and the Heavy-Duty Tripod

The kit weighs 77 lbs and breaks down into the 58 lb tube and fork mount and the 19 lb tripod. An ergonomic design lets you comfortably lift and move the telescope; carry it by the lower part of the fork arm on the hand control side and by the handle on the opposite side.

Celestron's newly designed heavy-duty tripod has sturdy 2" (50.8mm) stainless steel legs and makes attaching the telescope so easy you can do it in the dark. With the telescope, the height range is 1397mm to 1778mm (55" to 70").

The tripod's leg support bracket doubles as the accessory tray and is tightened against the legs with a tension knob, which increases stability and reduces vibration and flexure. The telescope base drops over the positioning pin on the tripod head, its three feet sit in the recesses on the head, and the three attached mounting bolts thread up from underneath. The tripod is less stable the higher it is extended; set it low for photography.

Visual Use and Astrophotography

The altazimuth fork mount sits directly on the tripod and moves up and down and left and right. The CPC can be used for short-exposure prime focus photography of the Moon and planets.

The CPC tracks precisely in altazimuth, but long-exposure astrophotography needs the fork arm aligned with the Earth's axis, which requires an optional equatorial wedge between the telescope and the tripod. Without it, stars slowly rotate around the center of the field; this goes unnoticed in the eyepiece but is very noticeable when imaging. On the wedge, EQ North and EQ South alignments and the Align Wedge routine help you polar align with the wedge's latitude and azimuth adjustments.

Periodic Error Correction reduces the amplitude of the worm gear errors to improve photographic quality, and is meant for advanced astrophotography with the telescope polar aligned on the optional wedge. Even with PEC, off-axis guiding is still mandatory for long-exposure deep-sky astrophotography; for filtered solar, lunar and piggyback photography up to 200mm, PEC can make unguided photography possible.