Celestron CPC 800 GPS (XLT) Computerized Telescope

The 8-inch Schmidt-Cassegrain: 2032mm Focal Length with XLT Coatings

The heart of the CPC 800 is its 8-inch (203.2mm) Schmidt-Cassegrain optical system, a zero power corrector plate, a spherical primary mirror and a secondary mirror that fold a 2032mm focal length into a 432mm (17") aluminum tube 238mm (9.37") in diameter. The highest useful magnification is 480x and the lowest 29x. 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.

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 secondary mirror obstruction is 64mm (2.5"), 31% by diameter and 9.77% by area.

Optical Power: 0.57" Resolution and 843x Light Gathering

The 8" aperture gathers 843 times more light than the unaided eye and reaches a limiting stellar magnitude of 14. The 40,000+ object database includes customized lists of the best deep-sky objects, planets and bright double stars.

Resolution is 0.57 arc seconds (Dawes) and 0.69 arc seconds (Rayleigh).

Dual Fork Arm Mount: DC Servo Motors and 5°/Second Slew Speeds

The fully computerized dual fork arm altazimuth mount carries the tube; together they weigh 42 lbs. 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 features 9 different slew speeds, ranging from a slow 0.5x sidereal rate for precise centering to a maximum speed of 5 degrees per second for moving quickly between targets. The mount 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 Database at Your Fingertips

The included NexStar+ hand controller puts a comprehensive catalog of over 40,000 celestial objects at your command. It stores 100 user-defined objects and has enhanced information on over 200 objects, on a 2-line by 18-character backlit display with 19 backlit buttons.

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.

The Heavy-Duty Tripod

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. It weighs 19 lbs; the kit totals 61 lbs.

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 Observing: A 51x View with the Included 40mm Eyepiece

The CPC 800 is ready for observing right out of the box. The package includes a 40mm 1.25" eyepiece, which provides a magnification of 51x. A 1.25-inch star diagonal is included for a more comfortable viewing position when observing objects high in the sky.

For precise object sighting, a 9x50 optical finderscope helps you find objects accurately, and it mounts in a quick release bracket.

Astrophotography: Autoguide Port, PEC and the Optional Wedge

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. The drive base has an autoguider port.

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.

Portability and Design: Assembling the 61 lb CPC 800 System

The ergonomic design lets you comfortably lift and move the telescope from place to place. It comes pre-assembled and breaks down into the 42 lb tube and fork mount and the 19 lb tripod. Carry the telescope by the lower part of the fork arm on the hand control side and by the handle on the opposite side.