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Telescopes
18" f/4.2 UC (Ultra Compact)
- 18" UC Photos
- 18" UC vs 18" Classic
- 18" UC Specifications
- Mirror Options
- Standard Features and Accessories
- Optional Accessories
- Ordering Information
John R with his 18" UC at the Cadillac Star Party.
- Collapsed, the base is 25" x 25" x 13.5" high
- Weight of heaviest component is 72 pounds
- Eyepiece height at zenith is 5 feet 10 inches
- See more Specifications
18" UC includes:
- Feathertouch focuser
- Telrad
- Wheelbarrow handles
- Counterweight kit
- External light baffle
- See more Standard Options
Read Tom Trusock's review of the 18" UC - Birth of a New Classic
See what Gary Kopff at Wildcard Innovations had to say
18" f/4.2 UC $7,295
Plus Shipping & Crating
The 18" f/4.2 UC (Ultra Compact) is a revolutionary design. It is a large aperture telescope that collapses into a very small package. If you have limited hauling or storage capacity, (like the trunk of a small car) then this is the scope for you.
Our revolutionary Virtual Mirror Box (VMB) is the foundation of the UC design. It is a welded steel framework made from NC laser cut steel. It provides four main functions. It provides the primary mirror cell, the altitude bearings, the connection points for the truss poles, and a retainer for the wheelbarrow handles. To keep it as ultra compact as possible, the side bearing portion is foldable to reduce the height of the VMB by half.
In the transport mode the clearance height is a mere 14 inches. Or place the VMB (Virtual Mirror Box) next to the rocker in your car and reduce the height even more. Now everyone can have a big aperture scope and take it to their dark sky site. This telescope will appeal to those that like the ultimate in form follows function style. Lower eyepiece height means 90% of observing will be done with your feet on the ground. The UC is all black with a modern space frame construction. If your vehicle is small or you intend to put it in the trunk, then the Ultra Compact is the obvious choice. And if you want the ultimate in Dobsonian evolution, the Obsession Ultra Compact 18" is it.
No compromises. The UC uses the same proven design criteria and materials that made the Classic Obsession so successful and the most copied larger aperture dob on the market. We use the same premium optics from Galaxy and OMI that we do in our Classic series of telescopes. Diffraction limited and all figured and tested with interferometry. Ion deposition 96% enhance primary coating. Two inch flex free glass. One tenth wave 98% Diamond brite secondary mirror. As with our Classic series, you cannot get better optics at any price anywhere. Galaxy and OMI are so confident of their quality that they post the serial number and test data for ever mirror they make on their web sites for everyone to review. Nobody else does this.
Compare the Ultra Compact to the Classic Obsession 18 inch. Decide which best serves your observing needs. Both scopes provide stunning views, ease of motion, fast set up and a lifetime of observing enjoyment.
| 5 times the light gathering power of an 8 inch Schmidt-Cassegrain | Obsession 18" UC |
Typical 8" |
|---|---|---|
| Limiting stellar magnitude: | 16.0 | 14.0 |
| Rayleigh Resolution Limit: | 0.31 arc seconds |
0.68 arc seconds |
| Contrast limit: (minimum diameter before a nebular object fades from view) |
4.8 arc minutes |
11.0 arc minutes |
18" UC Photos
photos courtesy of Astronomy Magazine and Gary Kopff
See more photos from 18" UC owners
18" UC vs 18" Classic |
||
Obsession 18" UC |
Obsession 18" Classic |
|
| Eyepiece height at zenith | 70 inches | 78 inches |
| Set up time including nylon light shroud | Same for both | |
| Ease of use (setup, take down, collimation) | Same for both | |
| Ease of Motions (hand guiding) | Same for both | |
| Construction/materials | Same for both, except: | |
| components covered with satin black laminate | components are stained and have six coat polyurethane finish | |
| Bearing geometry and surfaces | Same for both, Ebony star on etched virgin Teflon | |
| Light baffling | Classic is better with 360 degree upper tube assembly baffle. UC 160 degree baffle opposite focuser. Views and contrast are identical unless there is a nearby street light in the area. If you only observe in the city at home then the Classic is the better choice. If you like to take your scope to a dark site the UC is an excellent choice, especially if you drive a sedan or have limited transport space. | |
| Optics (OMI) (Galaxy does not offer anything under 18 inches) | f/4.2 primary mirror requires a Paracorr coma corrector for optimum views. | f/4.5 Paracorr optional but not needed. |
| Secondary mirror | Same 3.1 secondary mirror for both. Central obstruction and image contrast the same for both under good skys. | |
| Coatings | Same for both. 96% on primary, 98% on secondary | |
| Mirror cell | Same for both, 18 point | |
| Wheelbarrow handles | Standard on both | |
| Truss poles | Six 1.25 inch diameter. Connected in pairs at apices. | Eight 1.25 inch diameter. All eight separate. |
| Stability | UC has 6 pole design and Baltic Birch steel reinforced segmented bearings. Much less mass than Classic. | Eight pole design and one piece cast aluminum side bearings. Mirror box and rocker have more mass. Total weight is about 50 pounds heavier than the UC. Classic is a better choice for CCD imaging. |
| Dimensions for transport | 24" x 24" x 13.5" high. Includes virtual mirror box nested in rocker (will fit in most trunks or hatchback). | 27" x 27" x 26" high (rocker and mirror box) Upper tube assembly placed next to lower unit. |
| Upper Tube Assembly weight (with Feathertouch focuser) | 8 pounds | 11 pounds |
| Weight of heaviest component (includes 2 inch thick standard thickness mirror) | 72 pounds. Includes the virtual mirror box, mirror, and dust cover | 82 pounds Includes mirror box, mirror, and dust cover. |
| Weight at wheelbarrow handles | about 10 pounds | about 15 pounds |
| Weight of complete scope | about 90 pounds | about 140 pounds |
| Clearance width required with wheelbarrow handles attached. (or minimum size of doorway needed to roll in or out with wheels attached) |
27 inches Clearance width needed when carrying UC virtual mirror box is 28 inches. |
30 inches |
| Optional custom foam lined ATA travel case (Holds everything except the truss poles) | UC uses a case 26 x 26 x 20 high (see below) | Classic - No way. |
18" UC Specifications:
Metric info shown in italics
Primary Mirror:
- 18" - 457 mm GALAXY, or OMI 2 inch thick mirror
- 96% reflectivity
- Enhanced Aluminum Coating and Dielectric Overcoat (a supreme coating)
- Center marked for precise collimation
- plus Interferometry certification
see Optics page for more info
Secondary Mirror:
- 3.1" - 79 mm United Lens 1/10 wave or better
- Interferogram included
- 98% reflectivity at 550 nm
- Super enhanced Brilliant-Diamond non-fading multi-dielectric coating
see Optics page for more info
Focal Length:
- 75" (± 2") - 1905 mm (± 50 mm)
Eyepiece Height at Zenith:
- (approximately) 70" - 178 cm
Mirror Cell:
- 18-point
Truss Pole:
- Length: 55" (± 2") - 140 cm (± 5 cm)
- Diameter: 1.25" - 32 mm
- Wall Thickness: 0.035" - 0.9 mm
Upper Assembly:
- Diameter: 22" - 56 cm
- Height: 13.5" - 34 cm
- Weight: 6 lbs. - 2.7 kg
Lower Assembly:
- Virtual Mirror Box alone folded for Transport
22" x 25" x 12" high - Virtual Mirror Box stacked in Rocker for Transport
25" x 25" x 13.5" high
Mirror Options:
Obsessions are built with premium diffraction limited optics from Galaxy and OMI (Optical Mechanics Inc.). See Optics page for more info.
Choose from Galaxy or OMI mirrors when ordering.
Interferometry certification included on all mirrors, both primary and secondary. Ion deposition 96% enhanced coatings standard on all mirrors.
Standard Features and Accessories:
Feathertouch focuser by Starlight Instruments
Standard on all Ultra Compacts
Low profile, Crawford type, 2 inch focuser, with 1-1/4 inch threaded adaptor for filters. Compression rings. Can be swiveled on it's base to the most convenient position. A joy to use and beautiful to look at.
Telrad
Standard on all Ultra Compacts
External light baffle
Standard on all Ultra Compacts
Counterweight kit
Standard on all Ultra Compacts
Wheelbarrow handles
Comes standard on all Obsessions 12.5" through 25" at no extra charge.
Primary Mirror Coating
Enhanced Aluminum - 96% reflectivity, with dielectric overcoat (a supreme coating) standard on all primary mirrors. See Optics page for more info.
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
Travel Case
White 26" x 26" x 20" thermo-formed, high-density polyethylene shipping container (foam lined) $549
Case meets the Air Transport Association's (ATA) Specification 300, Category 1 requirements.
Customer Comment:
"I took an 18 inch UC for 10,000 miles around the Australian outback in 2010 in an SUV - even drove it through the Gosse Bluff meteor crater, but it was in a great travel case. A week from now I take it and an 18 inch Classic to Ozsky at Coonabarabran 400 miles north of Sydney Australia in the same SUV for a week of southern sky observing with visiting US amateurs.
These scopes travel well."
Tony Buckley - Sydney Australia - March 1, 2013
Paracorr
$450 (Highly recommended at f/4.2)
Ripstop Nylon light shroud
(Highly recommended)
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
ServoCAT Goto Drive System
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.
Ordering Information:
A Deposit is required to place an order ($2,000 for 18" UC)
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.
Customer Comments
Jeffrey Kaszczuk, 18" UC owner in northeast Texas
February 27, 2012
Brief "first light" in my back yard last week, M42 and Jupiter. Then, we took the scope to our dark sky spot in the Caddo National Grassland in northeast Texas. Brought along a buddy with his 12" Skywatcher. His Skywatcher sat alone and unused all night. I couldn't peel him away from my scope HAHAHAHA!!! The feathertouch focuser is awesome. The entire scope is awesome. Once the crescent moon, Jupiter and Venus set, we started our galaxy hunting. Best one of the night was M51. I AM VERY, VERY, VERY SATISFIED WITH THIS TELESCOPE. Thanks Dave!! My friends may be contacting you about making one for them!! Some pics attached.
Read more 18" UC customer comments