Hubble Optics UL20 20" Premium Ultra Light Dobsonian Telescope

Hubble UL20 – A Lightweight 20" Dobsonian Telescope

The Hubble UL20 is a made-to-order 20-inch Dobsonian telescope designed for observers who want truly extreme aperture without the bulk and weight of traditional large Dobsonians.

With its enormous 20-inch primary mirror, the UL20 gathers over six times more light than an 8-inch telescope, and almost three times the light grasp of a 12-inch, revealing galaxies, nebulae, and fine structure at a level normally reserved for permanent observatory installations.

A Premium, Light, Compact and Portable Design

Despite its size, the UL20 is engineered to remain practical and transportable. The precision-machined all-metal truss construction delivers exceptional rigidity while keeping overall weight to around half that of traditional 20-inch Dobsonians.

The modular truss design allows the telescope to be broken down for transport, while the reinforced mirror box protects the primary mirror during storage and travel. This makes the UL20 a genuine “portable observatory” for dedicated deep-sky observers.

Optical Performance

At the heart of the UL20 is a premium parabolic primary mirror, individually tested and finished to achieve diffraction-limited performance (Strehl 0.95+). The secondary mirror is specified to 1/10 wave or better, ensuring excellent contrast and pinpoint stellar images across the field.

Both mirrors receive 96% enhanced reflective coatings, maximising light throughput while reducing scatter. This results in breathtaking deep-sky views, extremely faint object detection, and exceptional planetary performance even at very high magnifications.

Choose Your Telescope Control

The UL20 can be customised to suit your observing style. You can use it fully manually, or opt for Guided Push-To or Automatic Go-To systems.

Manual Mode
Even without electronics, the UL20 remains a precision Dobsonian with smooth, stable bearings and a well-balanced truss structure. This allows for classic hands-on observing with direct control and intuitive sky navigation.

Guided Push-To Version
The UL20 Guided Push-To version features the SkyHub2 digital setting circle system, providing accurate real-time telescope positioning without motorised tracking. High-resolution 8192 PPR encoders on both axes continuously update your telescope’s position in compatible planetarium software.

• Fast one-star alignment, with optional two-star alignment for higher accuracy

• Compatible with SkySafari, Stellarium, Cartes du Ciel, TheSky, and other ASCOM software

• Works on Windows, macOS, Android, and iOS devices

• Extremely low power consumption, up to 100 hours from a 15,000 mAh USB power bank

• WiFi and Bluetooth supported (WiFi only for iOS devices)

Automatic Go-To Version
The UL20 Go-To version adds fully motorised pointing and tracking for a hands-free observing experience. It includes a smart hand controller with a 30,000-object database and supports advanced 1–9 star alignment for high pointing accuracy.

• Built-in encoders and real-time clock maintain accurate sidereal, lunar, and solar tracking rates

• Control via WiFi or Bluetooth using SkySafari, Stellarium, or ASCOM/INDI software

• Compatible with Windows, macOS, Linux, iOS, and Android

• Adjustable slew and guide speeds, spiral search, and park/unpark functionality

Choosing Your Focal Ratio: f/3.3, f/3.7 or f/4.2

The UL20 is available in three focal ratios, allowing you to balance comfort, optical performance, and field of view.

Why choose f/4.2?

• Sharper images with almost 50% less coma than f/3.7

• Smaller central obstruction (3.5" secondary vs 4.0" on f/3.7)

• Easier to achieve perfect collimation

• Better suited for high-magnification lunar and planetary observing

• A coma corrector is helpful but not essential for many users

Why choose f/3.3 or f/3.7?

• No ladder required at all for f/3.3; only a small step may be needed for f/4.2 near zenith

• Extremely wide true field of view, especially with f/3.3

• Ideal for sweeping large nebulae and rich Milky Way fields

All three versions deliver extraordinary performance. A coma corrector is strongly recommended for the UL20 f/3.3, while the f/4.2 prioritises optical cleanliness and ease of use.

Thanks to Hubble’s two-section truss design for f/4.2 (single-section for f/3.3 and f/3.7), all versions remain equally rigid and transportable. Please note that counterweights may be required for balance, depending on configuration, and are not included.

Specifications (UL20)