| NOTE: THIS ITEM CANNOT BE SHIPPED STORE PICKUP ONLY SELECT PICK UP AT CHECKOUT |
Yes, our inventory is accurate!
SHIPPING NOT AVAILABLE - In Store Only
Condition: This is a used 18" Obsession Dobsonian from about 2015 in very good condition. You've heard of the quality that is an Obsession scope, now come see it for yourself.
The mirror is in good shape, but it is definitely dusty. See the photos, where we've tried to capture this - the dust you see in different areas is consistent across basically the entire surface of the mirror. In addition to the general dust, there are a couple of small spots on the edge of the mirror surface. One of these spots is where masking tape contacted the mirror. You may be able to clean this off yourself with GooGone, or its optical equivalent. (We have no idea if GooGone will work or will be worse for the optics.) You will definitely want to give the mirror a good and thorough cleaning after purchase.
The scope is in mechanically excellent condition - everything works. It includes a Feathertouch Focuser. This scope includes both the Nexus and Argo Navis digital setting circles as well as the ServoCAT goto drive/tracking system. We've tested the Nexus DSC system and the encoders are working. We've tested the ServoCAT system and the motors work in all four directions.
It also includes a shroud for the tube, as well as light shields for the primary mirror at the bottom of the tube, and for the secondary mirror at the top of the tube.
You will need to make sure that you can handle a scope of this size and complexity: it is over 6 feet tall, and you will need to work with the plugs and the cabling to make sure everything is functioning as it should. While we can't really assist you with this, as we don't know how everything works together, the previous owner has volunteered to give you some advice about disassembling and reassembling. We do have both the original manuals and the previous owner's cheat sheets to assist you in this regard.
Here's everything that's included - and it is loaded:
- Obsession 18” f4.2 UC (Ultra compact) OMI Primary and Astrosystems secondary
- ServoCat GOTO drive upgraded with Nexus DSC Pro (digital setting circles), powered ground board system installed and with ServoCat Hand controller. Scope is set up for three means of control:
- (1) using SkySafari as the Planetarium software for control and GOTO;
- (2) scope can also be used as PUSH/TO or
- (3) controlled by ServoCat Hand controller
- Feathertouch focuser with curved rotatable base, compression rings and feather touch 1.25” to 2.0” eyepiece adapter
- Markless Astronomy digital setting circle (DSC) mounting stalk
- Nexus DSC (digital setting circles)
- Pegasus Astro Pocket Powerbox Advance Gen2
- Argo Navis DSC
- Dew heater for secondary
- Telrad finder
- Astromania Cheshire collimator (long version)
- Astrosystems Laser Colllimator with Barlow attachment
- Apertura universal 10 Amp AC Adapter/power supply
- Pyramid PS-9KK Regulated 12 volt Power supply
- 12 volt cooling fan for primary
- Side bearing stabilizer bars
- 10K encoders and encoder arm assembly
- Robinson Jig
- Counterweight kit
- Ripstop Nylon Light shroud (with 2 fiber glass support sticks)
- Upper and lower light baffles
- Astrosystems Telescope cover for 18UC scope
- Astrosystems Truss Tube carry case
- Wheel barrow handles for scope with 10 inch pneumatic wheels
- White travel/storage case for 18UC scope
- Quick start Instructions and manual.
Also included is an old Mallincam system.
NO WARRANTY, GUARANTEE, OR RETURNS ON THIS ITEM. BUYER TO INSPECT PRIOR TO PURCHASE.
This is only available for in-store pickup.
Just your size. Large Aperture, no big ladder needed! Our most popular model.
The Obsession 18" is the ultimate compact scope for the discriminating enthusiast who wants big aperture in a small package.
There are no short cuts in construction or performance.
The Obsession 18" features the same quality craftsmanship and award winning design as found on our renown 20, 25, 30 and 36 inch telescopes.
A small step ladder is required when the scope is pointed near the zenith but most observing will be done with your feet on the ground.
We've done our homework - the 18" is easy to set up and a joy to use.
Fantastic deep sky and planetary images.
One look and you'll re-learn what it means to be excited about astronomy.
| 5 times the light gathering power of an 8 inch Schmidt-Cassegrain | Obsession 18" |
Typical 8" |
|---|---|---|
| Limiting stellar magnitude: | 16 | 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" Specifications:
Metric info shown in italics
Primary Mirror:
- 18" - 457 mm Ostahowski, or OMI 2 inch thick mirror
- Fused silica glass standard on all 18" Classic primary mirrors.
- 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:
- Pre-installed
- 3.1" - 79 mm United Lens 1/10 wave or better
- Interferogram included
- 96% reflectivity at 550 nm
- Super enhanced Brilliant-Diamond non-fading multi-dielectric coating
see Optics page for more info
Focal Length:
- 75" (± 2") - 1900 mm (± 50 mm)
Eyepiece Height at Zenith:
- (approximately) 71" - 180 cm
Mirror Cell:
- 18-point
Truss Pole:
- Length: 49" (± 2") - 140 cm (± 5 cm)
- Diameter: 1.25" - 32 mm
- Wall Thickness: 0.035" - 0.9 mm
Upper Assembly:
- Diameter: 22" - 56 cm
- Height: 12" - 30 cm
- Weight: 9 lbs. - 4.1 kg
Lower Assembly:
- A= 26" - 66 cm | B= 27" - 68 cm | C= 21" - 53 cm | D= 25" - 63 cm
Mirror Box weight:
- The heaviest component (what you don't lift): 80 lbs - 36 kg
- Weight at Handles: (what you lift at Wheelbarrow handles): 18 lbs - 8 kg
Standard Features and Accessories:
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 96% 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 96% Brilliant Diamond secondary, the optical system is equivalent to an extra 2" of aperture!
12 volt cooling fan
12 volt cooling fan comes standard on all Classic and Ultra Compact scopes.
Fused quartz
18” Obsessions use fused quartz for the primary mirror glass.
Argo Navis digital setting circles