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Edmund Frick fits his 20" Obsession in his Vibe. Disassembled, it fits inside of a 2007 Pontiac Vibe (including all the necessary items needed to operate it along with 2 8 foot ramps to get the bottom section into the Vibe).
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Home > Telescopes > 20" Obsession
20" f/5
 20" f/4
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The Universe has just come into view!
The ultimate large aperture value
This is truly big aperture.
Thousands of deep sky objects will tempt you. In fact, nearly everything in Uranometria 2000 is within your grasp!
The Obsession 20" is the scope that in 1989 revolutionized the Dobsonian.
Our user friendly design, craftsmanship second to none, one person set up and super smooth operation have since made Obsession the standard by which all other Dobsonians are compared.
The 20" is the ultimate blend of cost, ease of use, and visual impact. If you want an instrument that will provide you with a lifetime of celestial enjoyment, the Obsession 20 is it. It's simply the telescope of choice for deep sky enthusiasts.
M104 by Glenn Schaeffer |
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20" f/5 vs 20" f/4:
The 20" Obsession can be ordered as an f/5 or as an f/4.
Eyepiece height at zenith for 20" f/5 is 8 feet.
Eyepiece height at zenith for 20" f/4 is 6 feet.
Advantages of f/5
- Crisper images, no Paracor coma corrector needed. Coma is inversely proportional to the cube of the focal ratio. In other words, the coma free field of view in a f/5 is twice as big as in an f/4.
- Easier to achieve precise collimation of primary mirror.
- Cost is less than an f/4.
- Slightly smaller 3.5" central obstruction (4" on f/4)
Advantages of f/4
- Smaller ladder, two steps shorter than an f/5.
- Easier to use for public viewing.
- Rich field of view. Great for star cruising the Milky Way and large deep sky objects. Easier to keep object in field of view.
In short, both scopes provide dramatic and exciting views. The f/5 is the ultimate personal scope. It yields better coma free images, but requires two more ladder steps. The f/4 is easier for public viewing, but requires a coma corrector like the Paracor.
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Dennis Dickerson with 20" and ServoCAT GoTo drive at Copper Breaks State Park near Quanah Texas getting ready for "Star Walk" public viewing night.
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Dick Latt with 20". Dick used his Argo Navis to down load and find the current comets at Okie Tex 2004.
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A cold night in Moscow. Mark Leonard with his 20".
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Mirror Options:
see the Optics page for more info
Obsessions are built with premium diffraction limited optics from Galaxy and OMI (Optical Mechanics Inc.).
Choose from Galaxy or OMI mirrors when ordering.
Obsessions are also available without optics if you already have your mirrors. Call, fax, or email for price and delivery.
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Standard Options and Accessories
- Choose from four great focusers
The JMI EV3 comes standard on all Obsessions. Or upgrade to the EV1, or EV1 with motofocus, or the awesome Feathertouch by Starlight Instruments. See the Focuser Options page for more focuser options
- Wheel Barrow handles
Comes standard on all Obsessions 15" through 25" at no extra charge.
Optional on the 12.5".
- Primary Mirror Coating
Enhanced Aluminum - 96% reflectivity, with dielectric overcoat (a supreme coating) standard on all primary mirrors.
- Secondary Mirror Coating
An Obsession exclusive - Super enhanced Brilliant-Diamond is standard on all Obsession secondary mirrors. This premium multi-dielectric coating has 98% reflectivity at 550 nm. The ultimate coating for the deep sky obsessed. This coating is standard on all Obsession secondaries at no extra charge. Brilliant-Diamond is just one of the reasons Obsessions out perform all others.
With 96% enhanced on the primary and our standard 98% Brilliant Diamond secondary, the optical system is equivalent to an extra 2" of aperture!
Optional Accessories:
See the Accessories page for more info on these items
- Telrad
- Ripstop Nylon light shroud.
- Barlow-Laser Collimator 2" barrel. Highly recommended. Includes 2" magnetic barlow lens and mask for the new barlowed laser collimating technique. Great visual aid and no better way to accurately align fast Newtonians. learn how
- Argo Navis digital setting circles with super res 10K encoders. more info
- ServoCAT Goto Drive System. more info
- Counterweight kit - (you supply the lead shot or sand) Recommended if you intend to use heavy barlow/eyepiece combinations, a Paracorr coma corrector, a traditional finderscope, or the Argo Navis digital setting circles.
- Dew heater for secondary mirror - Secondary mirror heating system automatically senses the air temperature and the mirror temperature, then maintains the secondary at a preset (adjustable) temperature above the ambient air temperature to prevent dewing or icing. more info
Ordering Information:
A Deposit is required to place an order ($2,000 for 20").
Mail the deposit to:
Obsession Telescopes
PO Box 804
Lake Mills, WI 53551
USA
You can e-mail your order, or mail it with the deposit.
- With your order, please list any options and/or accessories you want, your mailing address, e-mail address if any, and phone number(s).
- After we receive it, we will send you an order confirmation letter.
- Delivery is usually 1 to 2 months from time of order.
- Please e-mail for current delivery times.
- Balance due prior to shipment.
- Prices do not include shipping and crating. We ship throughout the world via UPS.
- Any questions, please call or e-mail.
- NOTE 10% order cancelation charge.
Need more information?
E-mail your postal address and we'll send you the Obsession brochure and video at no charge.
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