Sky-Watcher Skyliner 300P FlexTube - Dobsonian Telescope

The Sky-Watcher Skyliner 300P FlexTube is a 305 mm Dobsonian telescope designed to provide substantial light-gathering capability while remaining easier to transport and store than a conventional solid-tube Newtonian of this aperture.

Its 305 mm parabolic primary mirror and 1500 mm focal length provide an f/5 focal ratio. This combination allows the large aperture to be used for observing the Moon, planets and a wide variety of deep-sky objects including galaxies, nebulae and star clusters.

The FlexTube system is one of the main features of this telescope. The optical tube can be extended or collapsed in seconds using three rigid support poles, without requiring the assembly and disassembly associated with conventional truss-tube structures.

When fully extended, the structure is designed to maintain tube rigidity and telescope collimation. A separate slightly shorter locking position is also provided for use with a binoviewer.

When collapsed, the optical tube length is reduced from 1400 mm to 920 mm. This makes transportation easier and allows the tube to be stored vertically in a smaller space.

The optical tube can also be quickly separated from the Dobsonian base by unscrewing the tension handles, allowing the two main parts of the telescope to be transported separately.

305 mm Aperture

Primary mirror diameter:

• 305 mm

This large aperture collects a substantial amount of light and is particularly suitable for visual observation of faint deep-sky objects.

Compared with a 250 mm telescope, the Skyliner 300P provides:

• 44% more light gathering

This increased light collection is particularly useful when observing galaxies, nebulae and star clusters.

Parabolic Primary Mirror

The primary mirror has a:

• Parabolic figure

A properly figured parabolic surface brings incoming light rays to the same focal point and eliminates the spherical aberration associated with spherical mirrors at fast focal ratios.

This design supports sharp, detailed and high-contrast images.

Low-Expansion Borosilicate Glass

The primary and secondary mirrors are manufactured from low-expansion borosilicate glass.

This material provides:

• Faster cool-down
• Improved mirror-shape stability during cooling
• Reduced thermal distortion

This thermal stability allows observing to begin sooner as the telescope adjusts from indoor temperatures to outdoor conditions.

RAQ Mirror Coatings

Both primary and secondary mirrors use Sky-Watcher RAQ Radiant Aluminium Quartz coatings.

The coating system includes layers of:

• Aluminium
• Tantalum pentoxide
• Silicon dioxide

Reflectivity reaches:

• Up to 94%

The coating is designed to combine high reflectivity with durability and long-term performance.

Secondary Mirror and Thin Spider Vanes

The secondary mirror is supported by four particularly thin spider vanes.

Vane thickness:

• 0.5 mm

This design minimises obstruction in the optical path and helps keep diffraction spikes around bright stars to a minimum.

1500 mm Focal Length

Focal length:

• 1500 mm

Focal ratio:

• f/5

This configuration combines the 305 mm aperture with a focal length suited to both deep-sky observation and detailed lunar and planetary viewing.

Deep-Sky Observation

The large aperture of the Skyliner 300P is particularly suitable for visual deep-sky observing.

Targets include:

• Galaxies
• Nebulae
• Star clusters

The 305 mm mirror collects enough light to reveal fainter objects than smaller-aperture telescopes.

Lunar and Planetary Observation

The Skyliner 300P is also suitable for observing:

• Moon
• Planets

The quality of the parabolic primary mirror allows the aperture to be used for detailed observation when atmospheric conditions permit.

Collapsible FlexTube System

The optical tube uses Sky-Watcher's FlexTube design.

The system incorporates:

• 3 rigid support poles
• 3-point tube locking system
• Extension without truss assembly

The tube can be extended or collapsed in seconds.

When extended, the structure is designed to prevent lateral movement and flexure while maintaining telescope collimation.

Binoviewer Position

A separate slightly shorter locking position is provided for:

• Binoviewer use

This reduces the optical-tube length when required by this observing configuration.

Tube Dimensions

Extended tube length:

• 1400 mm

Collapsed tube length:

• 920 mm

The FlexTube system therefore substantially reduces the telescope's size for storage and transport.

2-Inch Precision Crayford Focuser

The Skyliner 300P is equipped with a:

• 2-inch precision Crayford focuser

It accepts:

• 1.25-inch eyepieces
• 2-inch eyepieces

Both adaptors are supplied.

1.25-Inch Adaptor With Brass Compression Ring

The supplied 1.25-inch eyepiece adaptor uses:

• Brass compression ring

This prevents the locking screws from directly marking the eyepiece barrel.

Supplied Wide-Angle Eyepieces

Two 70° Super Wide Angle eyepieces are supplied:

• 12.5 mm
• 20 mm

Apparent field:

• 70°

With the telescope's 1500 mm focal length, they provide:

• 120x with the 12.5 mm eyepiece
• 75x with the 20 mm eyepiece

Highest Practical Power

Highest practical potential power:

• 600x

Actual usable magnification depends on atmospheric conditions and the observed target.

9x50 Finderscope

The telescope is supplied with a:

• 9x50 finderscope

It is mounted in a centring bracket and includes:

• Crosshair reticle

The finder assists with locating and centring objects before viewing them through the main telescope.

Direct SLR Camera Connection

The Skyliner 300P provides:

• Direct SLR camera connection

This allows a compatible camera to be connected to the telescope.

Universal Smartphone Adaptor

A universal smartphone adaptor is supplied.

Compatible phone width:

• 54 to 90 mm

The adaptor positions a smartphone behind an eyepiece for capturing images of celestial targets.

Manual Dobsonian Mount

The optical tube is supported by a wooden alt-azimuth Dobsonian mount.

It provides two movements:

• Horizontal azimuth rotation
• Vertical altitude movement

The mount is entirely manual.

It requires:

• No motor
• No slow-motion controls
• No electronic alignment procedure

The telescope is moved directly by hand towards the required part of the sky.

Low-Friction Bearings

The base uses low-friction bearing materials to provide:

• Smooth motion
• Easy manual slewing
• Stable positioning when released

This allows the telescope to be moved progressively while maintaining the selected position.

Adjustable Tension

The side handles control resistance on the altitude axis.

Tension can be adjusted according to:

• Accessory weight
• Eyepiece weight
• Telescope balance

The vertical axis can also be fully locked.

The tension handles additionally serve as:

• Carrying handles

OTA Easily Separated From Base

The optical tube can be removed from the Dobsonian base by unscrewing the tension handles.

This allows the telescope to be transported as two separate parts:

• Optical tube assembly
• Dobsonian base

This is particularly useful given the dimensions and weight of a 305 mm telescope.

Accessory Tray

The base includes an:

• Accessory tray

It keeps eyepieces and other small accessories close at hand during observing sessions.

Black Diamond Finish

The optical tube uses Sky-Watcher's:

• Black Diamond metallic finish

Contrasting white surfaces are also used to improve visibility of parts of the telescope in darkness.

This increased visibility can help reduce accidental contact with the telescope during nighttime use.

Optical Tube Construction

OTA material:

• Rolled steel

The structure incorporates the FlexTube mechanism and its three upper-cage support poles.

Weight and Transport

Optical tube weight:

• 21 kg

Dobsonian base weight:

• 17.8 kg

The optical tube can be separated from the base to make the two components easier to transport.

Base Diameter

Dobsonian base diameter:

• 520 mm

This dimension should be considered when planning storage and transportation.

Technical Specifications

• Manufacturer : Sky-Watcher
• Model : Skyliner 300P FlexTube
• Manufacturer product code : 10158
• Optical design : Newtonian reflector
• Mount type : Manual alt-azimuth Dobsonian
• Primary mirror diameter : 305 mm
• Primary mirror : Parabolic
• Primary mirror material : Low-expansion borosilicate glass
• Secondary mirror material : Low-expansion borosilicate glass
• Focal length : 1500 mm
• Focal ratio : f/5
• Light gathering : 44% greater than a 250 mm telescope
• Mirror coating : RAQ Radiant Aluminium Quartz
• Reflectivity : Up to 94%
• Secondary mirror supports : 4 spider vanes
• Spider-vane thickness : 0.5 mm
• Magnifications with supplied eyepieces : 75x and 120x
• Highest practical potential power : 600x
• Supplied eyepieces : 12.5 mm and 20 mm
• Eyepiece apparent field : 70°
• Eyepiece fitting : 1.25 inch
• Focuser : Precision Crayford
• Focuser size : 2 inch
• Eyepiece adaptors : 1.25 inch and 2 inch
• 1.25-inch adaptor : Brass compression ring
• Finder : 9x50
• Finder reticle : Crosshair
• Direct SLR camera connection : Yes
• Smartphone adaptor : Universal
• Compatible smartphone width : 54 to 90 mm
• Optical-tube system : Collapsible FlexTube
• Support poles : 3
• Tube locking system : 3 point
• Additional binoviewer position : Yes
• OTA material : Rolled steel
• Mount material : Wood
• Accessory tray : Yes
• Base diameter : 520 mm
• OTA weight : 21 kg
• Rocker-box weight : 17.8 kg
• Extended OTA length : 1400 mm
• Collapsed OTA length : 920 mm

Package Contents

• Sky-Watcher Skyliner 300P FlexTube optical tube
• Manual Dobsonian base
• 12.5 mm 70° Super Wide Angle eyepiece
• 20 mm 70° Super Wide Angle eyepiece
• 9x50 finderscope with crosshair reticle
• 1.25-inch eyepiece adaptor with brass compression ring
• 2-inch eyepiece adaptor
• Universal smartphone adaptor
• Accessory tray