Sky-Watcher Flextube 350P SynScan

GoTo on a Collapsible Dobsonian

The SynScan hand control can point the telescope at a chosen object or tour the sky at the touch of a button, and the motors track the object once found. Even an inexperienced astronomer can master its features in a few observing sessions.

356mm Paraboloidal Optics

The primary mirror is paraboloidal. Sky-Watcher USA lists 356mm at f/4.6; skywatcher.com lists the 14-inch at 355mm and f/4.5, with a highest practical power of 710x.

The included 20 mm and 12.5 mm 1.25-inch eyepieces give 82.5x and 132x with the focal length in Sky-Watcher USA's data.

Collapsible Tube: 1510mm to 970mm

The 23.5 kg tube is 500 mm in diameter and 970 to 1510 mm long (skywatcher.com).

Unlike other truss designs, Sky-Watcher's collapsible Dobsonian does not need to be disassembled between uses: it transports as two compact pieces, is ready to use in seconds, is easy to collimate once set up and holds collimation throughout the evening.

SynScan GoTo and Freedom Find

Sky-Watcher's patented Freedom Find dual-encoder technology lets you move the telescope by hand or electronically in either axis without losing its alignment or position information. Each axis has one encoder on the axis shaft and one on the motor shaft.

After you move to a new object, the telescope begins tracking it, with no re-setup in one observing session. DC servo motors give ten slew speeds, from 1x at Rate 0 to 1000x at Rate 9; the manual suggests Rate 4 for centering in the finderscope and Rate 3 or less in the eyepiece. Tracking is at sidereal, lunar or solar rate, on both axes.

Database and Alignment

The menu system slews automatically to over 42,900 objects: the complete Messier (110) and Caldwell (109) lists, 7,840 NGC and 5,386 IC objects, 29,523 SAO stars, 212 named stars, 55 double stars, 20 variable stars, the planets, and up to 25 user-defined coordinates. The TOUR key takes you on a preset tour of the sky you are under.

Before GoTo, level the base, align the finderscope and align the system on two stars. Brightest-Star alignment, recommended if you are new to the sky, asks you to choose one of eight regions and lists the stars brighter than magnitude 1.5 there; Two-Star alignment lets you choose two stars from a list, at least 60 degrees apart in azimuth. You center the first manually, and the mount slews to the second for you to center.

Computer Control

An RS-232 cable connects the hand control's RJ-12 port to a computer at 9600 bits per second. The manual says firmware version 3.00 and later work with the Celestron NexStar 5i/8i and NexStar GPS command protocol, which planetarium software can use to drive the mount. The firmware is user upgradable from version 3.0.

Power

The mount needs 10 to 15 V DC at 1 A through a 2.1 mm center-positive plug, into the Power jack on the altitude motor box. A 12V DC car-lighter power cable is included; the battery pack or power supply is sold separately.

To avoid tangling the power cable, the manual suggests placing the battery pack or power tank on the round base, behind the front panel.

Setting Up

Level the round base with a bubble level; better leveling gives better tracking. Loosen the three slider lock screws and pull the top tube out until it clicks, then tighten the screws without over-tightening. Remove the dust cap and front cover, lift the tube at the indicated positions onto the mounting platforms inside the side boards, and tighten the locking screw.

Connect the hand control and power cables to the altitude motor box, enter your location, date and time, and align on two stars.

Focuser, Finder and Eyepieces

The 2" dual-speed Crayford focuser comes with a 2" to 1.25" eyepiece adapter, and 20mm and 12.5mm 1.25-inch eyepieces are included.

A 9x50 straight-through finderscope, the hand controller cable, dust caps and a 12V DC car-lighter power cable are included.

Tube and Base

The tube weighs 23.5 kg (skywatcher.com) and the base 94 lb (Sky-Watcher USA), which lists the base at 36" x 31". They transport as separate pieces: retract the tube, loosen the locking screw and lift it off the base.

Solar Safety

Never use the telescope to look directly at the Sun, as permanent eye damage will result. Use a proper solar filter for viewing the Sun.

When observing the Sun, place a dust cap over the finderscope. Never use an eyepiece-type solar filter, and never use the telescope to project sunlight onto another surface: the internal heat build-up will damage the optical elements.