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Made in the USA


12.5" f/5 Classic

12.5" Classic Obsession

James Book, in Ottawa, Ontario Canada with his 11 year old 12.5" Obsession - purchased October 2004.

22UC collapsed

Curved spider vanes: No diffraction spikes on stars and the ultimate in contrast for planetary work!

M13 Comparison


12.5" f/5$5,995

Plus Shipping & Crating

The Obsession 12.5 f/5 is a premium telescope for observers that want the best of all worlds.

Medium Aperture, fantastic f/5 images, no diffraction spikes!

2.5 times the light gathering power of an 8 inch Schmidt-Cassegrain Obsession
Limiting stellar magnitude: 15.0 14.0
Rayleigh Resolution Limit: 0.38
arc seconds
arc seconds
Contrast limit:
(minimum diameter before a
nebular object fades from view)
arc minutes
arc minutes

Sky & Telescope review - February 2009

Sky & Telescope logo

"Portability is definitely one of the 12.5 inch Obsession's biggest assets. The instrument is remarkably rigid. The optics in the Obsession really delivered. The views were remarkably crisp and bright. Star test showed the primary mirror (made by Optical Mechanic Inc.) to be first rate. The scope has a curved-vane secondary mirror support which means that bright stars are free of diffraction spikes, something I find quite appealing. The bottom line is that the 12.5 inch Obsession is a ruggedly built, portable scope that should delivery first-rate views for a lifetime."

Customer Comments

Ken M., 12.5" owner in Eugene, Oregon
December 28, 2015

12.5" Obsession

Hi Dave, This photo was taken last summer at Golden State Star Party in northern California and shows the scope with Telrad and Argo Navis mounted on it.

Now that I've had the scope for a little over two years I've come to really appreciate the wonderful views and the incredible smooth motion of the scope. Thanks again for creating such a great product.

Best to you in 2016,
Ken Martin

Read more 12.5" customer comments

12.5" Photos

Jerry Gilliam 12.5 Classic Obsession Jerry Gilliam 12.5 Classic Obsession Jerry Gilliam 12.5 Classic Obsession Jerry Gilliam 12.5 Classic Obsession

Jerry Gilliam

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12.5" Specifications:

Metric info shown in italics

Primary Mirror:

  • 12.5" - 317 mm 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:

  • Pre-installed
  • 2.14" - 54 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:

  • 63" (± 2") - 1590 mm (± 50 mm)

Eyepiece Height at Zenith:

  • (approximately) 60" - 152 cm

Mirror Cell:

  • 9-point

Truss Pole:

  • Length: 41" (± 2") - 104 cm (± 5 cm)
  • Diameter: 1" - 25 mm
  • Wall Thickness: 0.035" - 0.9 mm

Upper Assembly:

  • Diameter: 16" - 41 cm
  • Height: 10" - 25 cm
  • Weight: 5 lbs. - 2.5 kg

Lower Assembly:

  • A= 24" - 61 cm | B= 19" - 48 cm | C= 15" - 38 cm | D= 17" - 43 cm

see diagram

Mirror Box Weight:

  • (the heaviest component) 39 lbs. - 18 kg
    Weight at Handles (what you lift at Wheelbarrow handles): 7 lbs - 3 kg

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Standard Features and Accessories:

Wheelbarrow handles

Standard on all Obsessions 12.5" through 25" at no extra charge.

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 12.5")

JMI EV1 with motofocus

JMI EV1 with motofocus



Feathertouch by Starlight Instruments

by Starlight Instruments

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

telescope mirror cooling fan

12 volt cooling fan comes standard on all Classic and Ultra Compact scopes.

Optional Accessories:

See the Accessories page for more info on these items

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.


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 ultra res 32K encoders

more info

ServoCAT Goto Drive System

more info

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.

Pre-installed (if ordered).

more info

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Ordering Information:

A Deposit is required to place an order ($1,500 for 12.5" Classic)

Mail the deposit to:

Obsession Telescopes
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.