Thinking About a New Scope? Think Big!
18" f/4.5 Classic
- 18" Specifications
- Mirror Options
- Standard Features and Accessories
- Optional Accessories
- Ordering Information
Plus Shipping & Crating
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
|Limiting stellar magnitude:||16||14.0|
|Rayleigh Resolution Limit:||0.31
(minimum diameter before a
nebular object fades from view)
Download PDF file of the complete Cloudy Nights review of 18" Obsession
Ted Forte, 18" owner in Virginia Beach, Virginia
My Obsession 18" is about to turn 11 years old. It's a little battle-scarred, a veteran of many, many, observing sessions, star parties and outreach events, but it still looks and performs great. I have logged thousands of objects with it, but more importantly, I have shared the heavens with more than 20,000 souls through it. I can truthfully say it is the best purchase I have ever made. I often tell novice astronomers that there is no perfect telescope – but the Obsession 18" comes pretty close.
Ted Forte is chair of the Astronomical League's Planetary Nebula Club. He has written "Flowers of the Night Sky" in the June 2010 issue of Sky & Telescope magazine. Watch for his next S&T article on exploring the Virgo-Coma galaxy cluster which will appear in the May 2011 issue.
Metric info shown in italics
- 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
- 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
- 81" (± 2") - 2060 mm (± 50 mm)
Eyepiece Height at Zenith:
- (approximately) 77" - 198 cm
- Length: 55" (± 2") - 140 cm (± 5 cm)
- Diameter: 1.25" - 32 mm
- Wall Thickness: 0.035" - 0.9 mm
- Diameter: 22" - 56 cm
- Height: 12" - 30 cm
- Weight: 9 lbs. - 4.1 kg
- 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
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:
Choose from four great focusers
The JMI EV3 comes standard on all Classic Obsessions. Or upgrade to the EV1, or EV1 with motofocus, or the awesome Feathertouch by Starlight Instruments. See the Focuser Options page for more information.
JMI EV3 (standard on all Classics)
JMI EV1 with motofocus
by Starlight Instruments
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!
See the Accessories page for more info on these items
(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.
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
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.
A Deposit is required to place an order ($2,000 for 18" Classic)
Mail the deposit to:
PO Box 804
Lake Mills, WI 53551
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.