Sky-Watcher Flextube 250P SynScan

At a Glance

• Aperture: 254mm (10-inch)
• Focal length: 1200mm
• Focal ratio: f/4.7
• Focuser: 2-inch single-speed Crayford-style, 1.25-inch adapter supplied
• Finder: 9x50 straight-through
• Mount: Computerised GoTo Dobsonian, dual-axis tracking, 42,900-object database

Product Overview

The Sky-Watcher Flextube 250P SynScan is a 254mm (10-inch) computerised GoTo Dobsonian with a collapsible truss tube. It runs 1200mm of focal length at f/4.7 and gathers 1275 times the light of the unaided eye, with a SynScan hand controller and built-in Wi-Fi driving it to any of 42,900 catalogued objects.

The truss retracts for transport and holds collimation through the cycle. The telescope travels as two pieces — optical tube and rocker box — and goes together in seconds without taking the truss apart.

Who It Is For

This is a good match if you:

• Want 10 inches of aperture with the finding done for you — useful when observing time is short and the target list is long.
• Share the view, where tracking keeps an object centred while people take turns at the eyepiece.
• Drive to darker skies and need a 10-inch that fits in a vehicle without dismantling.
• Still like to star-hop — Freedom Find lets you push the tube by hand at any time without losing alignment.

Key Features and Design

• 254mm parabolic primary at f/4.7: the fast ratio buys a wide true field for a 10-inch instrument, suiting large nebulae and open clusters.
• 1275x the light grasp of the unaided eye: enough aperture to resolve globulars and pull structure out of brighter galaxies.
• Radiant Aluminum Quartz coating at 94% reflectivity: more of the collected light actually reaching the eyepiece.
• Patented collapsible truss tube: retracts for transport and storage while retaining collimation, and provides back focus for camera use.
• SynScan GoTo with built-in Wi-Fi: hand controller plus wireless control across a 42,900-object database.
• Patented Freedom Find dual encoders: move the telescope by hand whenever you like with no re-alignment afterwards.
• Patented tension control handle: adjusts friction between tube and sideboards to balance heavier eyepieces.
• Dual-axis tracking: sidereal, lunar, and solar rates on DC servo motors, with pointing accuracy published to 5 arc minutes.

Optical and Mechanical Design

Optically this is a fast Newtonian — 1200mm over a 254mm parabolic primary gives f/4.7. The fast ratio buys a wide true field for a 10-inch instrument, which suits large nebulae and open clusters, and keeps the tube short enough that the eyepiece sits at a comfortable height through most of the sky. Two mirrors and no lenses means no chromatic aberration at any magnification.

Mechanically, two patents carry the design. The truss system lets the upper cage slide down over the mirror box and return to the same geometry when extended, which is why collimation survives collapsing. Freedom Find places encoders on both axes that read position independently of the motors, so the GoTo system knows where the tube points even after you have moved it by hand. Computerised pointing you can override without penalty is the practical difference between this and a motorised mount that resents being touched.

Recommended Uses

• Deep-sky observing: globular clusters resolved to stars, galaxy groups, and planetary nebulae with structure.
• Guided touring: the controller will run a tour of the best objects above your horizon on the night.
• Outreach and club nights: tracking holds the target while a queue works through the eyepiece.
• Lunar and planetary imaging: tracking plus available back focus makes planetary camera work practical.

Compatibility and Accessory Notes

Supplied with a 9x50 straight-through finderscope, 12.5mm and 20mm four-element 1.25-inch Plössl eyepieces, and the SynScan hand controller. The 2-inch focuser accepts any standard 2-inch eyepiece, with the supplied adapter for 1.25-inch. At f/4.7 a well-corrected wide-field eyepiece earns its price at the edge of the field, and it is the upgrade most owners make first.

Power is 10 to 15 V DC at 1 amp through a 2.1mm centre-positive plug, so a field battery or regulated supply is part of the kit rather than an afterthought. A light shroud over the open truss controls stray light and dew, and a UHC or O-III filter lifts nebula contrast noticeably from suburban skies. If you would like help matching eyepieces, a power solution, or a shroud to this telescope, get in touch and we will work it out with you.

Good to Know Before You Order

• It needs power. The GoTo system runs on 10 to 15 V DC, so a suitable field battery is essential kit.
• Deep-sky imaging is limited by the mount, not the optics. The collapsible design does provide back focus for a camera and the mount tracks on both axes, but an alt-azimuth mount rotates the field over long exposures. Lunar and planetary capture suits it well; long-exposure deep-sky work does not.
• The truss section is open, so stray light and dew can reach the light path from the side. A shroud handles both.
• Two substantial pieces. Tube and rocker box carry separately, and a wheeled dolly helps considerably if it is stored indoors.
• Give the mirror time to cool before expecting the best planetary detail.

Frequently Asked Questions

Is it difficult to set up?

The physical side is quick — extend the truss, seat the tube in the rocker box, connect power. The GoTo then wants a brightest-star or two-star alignment, which is menu-driven and takes a couple of minutes. Sky-Watcher notes most people are comfortable with the controller within a few sessions.

Can I move the telescope by hand?

Yes. Freedom Find dual encoders read position independently, so you can push the tube to a target and the system stays aligned with no re-alignment needed.

Can I use it for astrophotography?

Lunar and planetary imaging, yes. Long-exposure deep-sky imaging, no — an alt-azimuth mount introduces field rotation however well it tracks.

What comes in the box?

A 9x50 straight-through finderscope, 12.5mm and 20mm 1.25-inch Plössl eyepieces, and the SynScan hand controller. You supply a 10 to 15 V DC power source.

How accurate is the pointing?

Sky-Watcher publishes GoTo pointing accuracy of up to 5 arc minutes, which puts targets well inside a low-power eyepiece field.

How is it different from the manual Flextube 250P?

Same aperture and collapsible concept. This version adds DC servo motors, dual-axis tracking, the 42,900-object database, Wi-Fi control, and Freedom Find encoders. The manual version needs no power and costs considerably less.

How is it different from the 300P SynScan?

The 300P steps up to 305mm and 1500mm focal length at the same f/4.7, gathering 1840x versus 1275x. Both share the identical SynScan electronics. The 250P is the more manageable of the two to move and store.

Bottom Line

In short: a 254mm f/4.7 collapsible Dobsonian with computerised GoTo, dual-axis tracking, and encoders that let you push it around by hand without losing alignment. Bring a 12 V supply and let the mirror cool, and it will find and hold 10 inches worth of deep sky all night.