20" Premium Ultra Light Dobsonian Telescope

f/3.3: $6,895

f/3.7: $5,995

f/4.2: $5,195

Order Info
  • A quantum leap in optical performance - the UL 20 Truss Dobsonian telescope's huge 20" diameter primary mirror gathers more than 6 times more light than popular 8" reflectors or almost three times of the light grasp of a 12" telescope
  • A Premium, Light, Compact and Portable Design - About half the weight of traditional Dobsonian telescopes
  • Outstanding Images - Premium quality, diffraction limited Newtonian optical systems will deliver stunning views of the heavens from dark sky sites
  • Light, Strong, Compact and Extremely Portable - The Hubble UL20 features a precision-machined all-metal construction. Fully assembled the UL20 weighs at about 90 pounds. It has 8 rigid truss tubes and extremely strong and portable folding ALT bearing structure. It features a real mirror box for safe mirror protection, and convenient storage and transportation
  • Exclusive Optical Technology - The UL20 features Hubble lightweight sandwich mirror with an optimized thermal design that cools up to 10 times faster than the regular solid mirrors
  • Fast Optics - The UL20 fast optical system delivers bright images and features a short tube keeping the eyepiece conveniently close to the ground
  • Enhanced Coating - The state of the art 96% Enhanced Coating on the primary and the secondary mirrors.
  • Modular and Compact Design: The Hubble UL20 is delivered in several preassembled modules. The entire systems can be assembled easily and quickly, as little as a few minutes.


UL20 Specs

  • Optical design: Reflector
  • Optical diameter:508mm
  • Focal length : ~1676mm (f/3.3), ~1880mm (f/3.7), ~2134mm (f/4.2)
  • Eyepiece height at zenith: ~1490mm(~59 in, f/3.3), 1745mm (~69 in, f/3.7), 2000mm (~79 in, f/4.2)
  • Optics type: Parabolic
  • Eyepieces: Not included
  • Optical quality: Diffraction limited++ (Strehl 0.95+ for the primary mirror, 1/10 lambda or better in PV for the secondary mirror)
  • Finder scope: Not included
  • Focuser: 2" dual-speed linear bearing Crayford
  • Secondary mirror obstruction: 100 mm (f/3.3, f/3.7), 90mm (f/4.2)
  • Secondary mirror obstruction by diameter: 19.7% (f/3.3, f/3.7), 17.7 (f/4.2)
  • Secondary mirror obstruction by area: 3.9% (f/3.3, f/3.7), 3.1% (f/4.2)
  • Mirror coatings/over-coatings: 96% Enhanced coating on both of the primary and secondary mirrors
  • Tube material: 6063-T6 Aluminum Alloy tubes with black zinc plated steel knob screws; Aluminum Alloy main structure (OTA and mount) and structure steel mirror cell.
  • Length of optical tube : 73 in (f/3.3, f/3.7), 83 in (f/4.2)
  • Weight, optical tube : 76 lbs (f/3.3,f/3.7), 77 lbs (f/4.2)
  • Weight, fully assembled : ~88 lbs. (f/3.3, f/3.7), ~89 lbs (f/4.2)
  • Additional, optional accessories: 8x50 Finder, Shroud, Wheelbarrow, Vinyl foam Cushioned Grips
  • Other features: Sling lateral support and deluxe push-pull brass knob collimation screws

Options (add-ons)

Options are optional add-ons that can be specified EITHER on the paypal special instructions section during payment OR - after payment - in an e-mail to:

E-mail: info@hubble-optics.com

Order Info
  • Light Weight Red Dot Finder Scope with Brackets and Dovetail: $45
    • Simple, effective, and easy to adjust 1 x Red Dot Finder scope. Free shipping when ordered with the system.

  • 8 x 50 Straight Through Illuminated Finder Scope with Brackets and Dovetail: $100
    • A top quality 50mm achromatic finder offering an inverted and reversed image, perfect for Newtonian Telescope. A deluxe quick release double-ring Finder Bracket including a dovetail base is included. There will be $15 additional charge for the surface delivery, or $25 additional charge the air delivery.
    • The scale markings and open center of the 8 X 50 Straight Through Finder allows you to measure distances and easily center an object in the field of view. The brightness of the reticle can be adjusted, which is nice when you are searching for fainter objects.
    • The illuminator screws into the end of the finder and can be removed easily to change batteries. The deep red illumination can be adjusted for brightness.

  • Truss Tube Grips: $7 each
    • 0.9m (35.5"), slid-on round cushioned grips, made of vinyl foam, they insulate, cushion vibration and protect the truss tubes. Free shipping when ordered with system.

  • Wheelbarrow: $120 +Shipping
    • The strong stainless steel handles, two top quality 6" pneumatic tires with ball bearing.  The shipping cost will be $100.

  • Shroud: $100 (f/3.3, f/3.7), $105 (f/4.2)
    • Made from the top quality Nylon/Lycra blended materials, it is one of the options you would really like to have. Free shipping when ordered with the system.

  • Truss Tube Carry Bag: $50 (f/3.3, f/3.7), $60 (f/4.2)
    • Made from the deluxe waterproof Nylon material with draw-string cord. Free shipping when ordered with the system.

  • 5-Star Artificial Star: $19.95 (free shipping if ordered with system)
    • It is really the time to have one, if you still don't have one yet!

  • Fan
    • Sorry, but It is not an option for UL20. You simply do not need one for our thin solid mirror!

  • Scope Storage Cover: $100 (f/3.3, f/3.7), $105 (f/4.2) (free shipping when ordered with the system)
    • Made with nice and strong polyurethane coated nylon fabric; light reflecting, water and dust resistant. A complete protection for your scope not only in the storage but also in the field. You don't need it if you store the scope in a luggage case or the custom made backpack.

  • Mirror Cover: $55 (free shipping when ordered with the system)
    • A very nice and strong plastic mirror cover

  • Light Baffle: $40
    • Free shipping when ordered with system

  • Hubble SkyHub Wireless Digital Setting Circle: $249 + $45 S&H
    • Breakthrough Wireless Digital Setting Circle with revolutionary high resolution, low power consumption ball bearing encoders at an inconceivable special price! Learn more here

  • Hubble SiTech GOTO: $1,995
    • Simply the most powerful GOTO system at an extremely affordable price. Learn more here

Features of the UL20:

Exclusive Sandwich Mirror Technology:

Our sandwich mirror technology has been used to manufacture research-grade optical elements and proven by over a half dozen years of successful applications at research facilities such as NASA, California State Polytechnic University San Luis Obispo, for the US Army, and in amateur telescopes around the world. Hubble sandwich mirror’s open core and close back design not only allows air to circulate through the mirror, but also provide the maximum structure strength to allow a simpler mirror cell design. Our sandwich mirror will reach thermal equilibrium up to 10 times faster than a traditional solid mirror and means the mirror can deliver great views even as the air around the telescope is changing temperature.

Why is thermal equilibrium so critical? The main issue is "mirror seeing," the turbulence seen through the eyepiece of the telescope when the air above the mirror is different from the mirror itself. Since a sandwich mirror cools far more rapidly than a solid mirror of the same thickness, this major source of distortion is eliminated quickly, giving you sharp and stable views. With ever- changing temperatures during observing or imaging, your thick and solid mirror may never reach equilibrium, and never reach its full optical potential. This is one of the major reasons why our lightweight-sandwich mirror has superior optical performance in real world situations, even without an active cooling system. (Active cooling systems, such as fans, introduce their own problems, such as micro vibration, which may seriously degrade the image quality.) Our sandwich mirrors reach equilibrium extremely fast, and without any external disturbing aid.

Enhanced Optical Coatings:

The Hubble UL20 primary mirror and the secondary mirror are coated with the state of the art 96% Enhanced optical coatings to assure it collects as many (while scattering as little) photons as possible to focus it into a bright and contrast-rich image. The optimal 96% Enhanced coating has multiple over-coating of precision controlled dielectric layers to maximize the reflectivity and provide excellent chemical and mechanical protection for the mirror coating.

A Real Mirror Cell In A Real Mirror Box:

The UL20 has an extensively modeled and optimized 18-point flotation system that provides more than adequate support for the sandwich mirror. The three-point Push-Pull collimation system is completely independent from the sling lateral support. It will totally eliminate the often-found potato chip astigmatism introduced by sling belt when using the simple 3 pivoted bolts collimation system. In a simple pivoted bolts collimation system, the collimation of the primary mirror may cause the sling belt to pull the mirror axially on the mirror edge, bending the mirror to a potato-chip shape, causing annoying astigmatism. It also comes with a real mirror box for easy and safe mirror protection and transportation.

All Metal Construction:

The UL20 mechanical structures have been extensively modeled via 3D CAD and advanced FEA to provide the optimal structure strength and stability. Machined with Computer Numerical Control (CNC) technology and hand fitted to assure proper fit and finish. Super strong T6063-T3 aluminum alloy truss tubes, structure steel mirror cell and aluminum alloy OTA and mount structure. Completed with deluxe and environmentally friendly black powder coating, it is such a pleasure to look at, not to mention the enjoyment to look through.

Dual-Speed 2-inch Linear Drive Crayford Focuser:

The Hubble UL20 comes with a precision dual-speed, 2-inch diameter focuser. It's a beautiful piece of precision machining that enhances the viewing experience as well as the overall impression of a premium quality instrument you'll have with this telescope. This focuser is robust! It is a zero-backlash "Crayford-style" design further enhanced with modern "linear bearings" meaning you get a rock-solid, super smooth focusing experience that can handle the weight of even the heaviest of modern eyepieces. Its tension, the pressure on the drawtube, is preset to a very reasonable level, but adjustable to lock heavy equipment in place if desired. The smaller stainless steel focus control adjusts focus at a rate 8 times finer than the larger focus wheels. This fine adjustment allows for critical focusing during high power visual observing or for imaging applications. The focuser has 50mm of travel distance.

If you've read enough, and want to just know how to buy it already, then click below!

Payment Info

Which UL20, f/3.3, f/3.7 or f/4.2?

Advantages of f/4.2:

  • Sharper images. It has almost 50% less coma than UL20 f/3.7; a coma corrector will still be helpful, but many people may live without it.
  • With the special introduction offer, you save $1,300 over UL f/3.7!
  • Smaller central obstruction, 3.5” (f/4.2) v.s. 4.0” (f/3.7) secondary mirror
  • Easier to achieve perfect collimation

Advantages of f/3.3 and f/3.7:

  • No ladder is needed for f/3.3 at all; while you may need one-step ladder for an f/4.2 when close to zenith direction.
  • Wider FOV for f/4.2, and even wider with f/3.3!

All f/3.3, f/3.7 and f/4.2 will provide you the excellent views. A coma corrector is recommended for the UL20 f/3.3.

With our unique two-section truss tubes for f/4.2 (one section truss for f/3.3 and f/3.7), f/4.2 is just as portable and strong as f/3.3 and f/3.7. At the end, it is really your personal preference.

Please note that some counter weight (real and/or a virtual spring counter weight) will be required for f/4.2 at the bottom(and for f/3.3 at the top), which is NOT provided

Happy Customers

Bruce's customized UL20. Charlie is holding the camera. Rich Mitchell is holding the secondary mirror

Hiroaki with his UL20.  "UL20 is working excellent. The mirror quality is excellent..."

Wanted to take the time and say thank-you for the excellent 20" f4.2. Wow is this mirror smooth and precise! Had one chance to see Saturn low in the sky, in September with stable seeing conditions. Uranus is finally getting higher, to chase good seeing. Where I am located south-west of Buffalo NY near lake Chautauqua, mostly have the jet stream overhead and never have stable seeing, except in the summer months. The site where the scope is, is dark and the deep sky views outstanding! I counted 26 galaxies in NGC 507 group at 200x in Pisces-Andromeda border. I'm using a Denkmeier 2 binoviewer and 3 power switch and A45mm OCS -1.2x 1.8x 2.25x with 24mm panoptics (107x 160x 200x ) and 35mm Baader eudiascopics I special ordered from Germany, just for this scope. Also color is brilliant as blue-greens are in planetary nebulae with this mirror ! Looking forward to seeing the pink rim in IC 418 this winter

- Thanks! Tom Bakowski

Instructions Manual

Click here for the instructions manual PDF - the Guide and Setup Process.


Click here for the UL20 dimensions when folded.

Order Info

Prices: (f/3.3) is $6,895- (f/3.7) is $5,995- (f/4.2) is $5,195

$3,447.50 (f/3.3), $2,997.50 (f/3.7), $2,597.5 (f/4.2) deposit at the order time, rest, including options and shipping will be paid before the delivery (about 60-90 days after the deposit) via a Paypal invoice.

Please note that the 60 days delivery is the estimated production lead time only which does not include shipping transit time.

Please specify your requested options in your payment for the deposit.

Choose your f /#

Shipping and Handling

We offer very reasonable worldwide shipping costs (at least for most of the countries) for the total system. Please understand the surface shipping is a great value, but may take more than additional 10 weeks for the delivery.

UL20 will be shipped in 6 boxes: the main structure 1 & 2, the truss tubes 1 & 2, the accessories and the primary mirror.

Country Economy(US$) Regular(US$)
US NA 995
US(Hawaii) NA 1062
Austria NA 894
Australia NA 965
Belgium NA 940
Brazil NA 2950(*)
Canada NA 915
Chile NA 1450
Denmark NA 850
France NA 875
Germany NA 860
Israel NA Contact Us(*)
Italy NA 910
Japan NA 590
Korea, South NA 565
Lithuania NA 1980
Mexico NA 1065
Netherlands NA 795
New Zealand NA 920
Norway NA 845
Portugal NA 965
Philippines NA 450
Poland NA Contact Us(*)
Romania NA 955
Russia NA 1495
Singapore NA 476
South Africa NA 1130
Spain NA Contact Us(*)
Sweden NA 830
Switzerland NA 860
Taiwan NA 510
UK NA 890

* Shipped via Fedex, the exact cost depends on your specific address.

For EU customers, please contact Astroshop EU for their wonderful services:

For Japanese customers, please contact Kokusai Kohki and Astro Street for their wonderful services:

For Indian customers, you may contact:

To see our listings of already stocked (miscellaneous) items, please visit our E-bay, by clicking here