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Why we love the Sky-Watcher Flextube 250P 10" Collapsible Dobsonian Telescope (S11720)
Product Description
Developed in the 1970s, the Dobsonian-style telescope is an inexpensive solution for bright, detailed visual observing using a simple design. The name '˜Dobsonian' comes from the telescope's inventor, John Dobson, a Vedanta monk who popularized sidewalk astronomy and dedicated his life to astronomy outreach. Dobson was well known for constructing large aperture reflecting telescopes capable of deep sky viewing, using low cost materials. These were often made with found materials, heavy cardboard tubes, recycled porthole glass, and plywood mounts. Dobson, who literally wrote the book on how and why to make amateur telescopes, encouraged other astronomers to assemble their own telescopes and taught workshops on telescope making.
The Flextube Dobsonian innovates on that original design, offering users the ability to collapse the optical tube using a proprietary truss-tube system while retaining its collimation. The optical tube uses a parabolic primary mirror, constructed of borosilicate, then polished and coated with our proprietary Radiant Aluminum Quartz (RAQ), producing a remarkable 94% reflectivity. With a 10-inch aperture, the Flextube 250P Dobsonian collects 1235 times more light than the human eye! This simple yet effective design is perfect for visual observation of faint objects, such as nebulae, star clusters, and galaxies.
Supporting the Flextube Dobsonian is more than just a simple rocker box. The base uses Teflon bearings for smooth, easy Azimuth slewing and a patented tension control handle to lock the telescope in place. Once locked on an object, the telescope can support both 1.25-inch eyepieces as well as the heavier 2-inch eyepieces, allowing you to use virtually any eyepiece on the market. All Flextube Dobsonians come with a slew of accessories, including: two 1.25-inch eyepieces, a 1.25-inch eyepiece adapter, a 2-inch eyepiece adapter, dust caps, and a 8x50 finderscope.
At Sky-Watcher, we stay true to the traditional John Dobson design, while offering a fresh look for the 21st century. Although we love computerized telescopes, using a star chart to find objects by hand can be far more fulfilling and will improve your knowledge of the night sky. Unplug your electronic devices, step outside, and become immersed in the wonders of the universe.
What can I see with a Sky-Watcher Flextube 250P 10" Collapsible Dobsonian Telescope (S11720)?
Here are some simulated views of common objects. Results with your telescope will vary with viewing conditions, obrits, equipment and more.
Jupiter with
25mm Eyepiece - 48x Magnification
(Included with This Telescope)
Jupiter with
10mm Eyepiece - 120x Magnification
(Included with This Telescope)
Jupiter with
5mm Eyepiece - 240x Magnification
Sold Separately
Moon with 25mm Eyepiece
48x Magnification
(Included with This Telescope)
Moon with 10mm Eyepiece
120x Magnification
(Included with This Telescope)
Moon with 5mm Eyepiece
240x Magnification
Sold Separately
Andromeda with 36mm Eyepiece
33x Magnification
Sold Separately
Andromeda with 25mm Eyepiece
48x Magnification
(Included with This Telescope)
Andromeda with 10mm Eyepiece
120x Magnification
(Included with This Telescope)
What's in the Box
Specifications
| Optical Info | |
| Optical Design | Newtonian |
| Mirror Coatings | Radiant Aluminum Quartz (RAQ) coatings with 94% reflectivity |
| Glass Type | Borosilicate |
| True Aperture (mm) | 257 |
| Primary Aperture (mm) | 254 |
| F/Ratio | 4.7 |
| Focal Length (mm) | 1200 |
| Secondary Diameter | 64mm |
| Secondary Obstruction (by diameter) | 25% |
| Secondary Obstruction by Area | 6% |
| Observational Info | |
| Dawes Limit | 0.46 |
| Rayleigh Limit | 0.55 |
| Limiting Mag. | 14.5 |
| Minimum Magnification | 36 |
| Maximum Magnification | 500 |
| Light Gathering (compared to next size down) | 57% |
| General Info | |
| Focuser | 2" Crayford |
| OTA Length (Retract/Ext.) | 31.5"/44" |
| OTA Outer Diameter | 11.375" |
| OTA Weight (with accessories) | 33 |
| Dob Base Weight | 26.5 |
| Dob Base Measurements | 29.5"x20" |
| Zenith Eyepiece Height | 48" |
| Accessories | |
| Included Finder | 8x50 RACI |
| Included Diagonal | No |
| Included Eyepieces | 25/10 Plossl |
| Magnification w/ Included Eyepieces | 48x/120x |
| Included Case | No |
| Corrector | No |
Additional Articles, Videos, and Links
5 Tips to Get the Most out of Your New Telescope
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Buying Your First Telescope - Part One: What's the Best Beginner Telescope?
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Buying Your First Telescope - Part Two: Making the Choice
Once you have become familiar with the sky and have been enticed by the views through other peoples’ telescopes, you will want your own. So what to buy?
Buying Your First Telescope - Part Three: Our Recommendations (2023)
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How to Pick the Best Telescope Eyepieces
Finding the right new telescope eyepiece can be a game changer. This post will help you to pick the best telescope eyepiece for your needs.