Thinking About a New Scope? Think Big!
Telescopes
25" f/5 & f/4 Classic
- 25" Specifications
- Mirror Options
- Standard Options and Accessories
- Optional Accessories
- Ordering Information
25" f/5
Dave Kriege with his 25" built in 1989
25" f/4
Chaco Observatory at Chaco Culture National Historical Park in northwestern New Mexico's San Juan Basin.
25" f/5$12,495
Orders received after April 1st price will be $12,995.
25" f/3.5$17,995
Plus Shipping & Crating
Forget averted vision. Globulars, nebulae, and galaxies will come screaming out of the eyepiece.
You won't believe your eyes. This is the cure for aperture fever!
Join the realm of Herschel whose famous NGC catalog of deep sky object descriptions are exactly what you will experience.
This is the telescope that Dave Kriege, founder of Obsession, uses for his personal observing.
The Obsession 25 is considered to be the ultimate telescope for the serious deep sky astronomer who can afford the best.
One person set up, one handed guiding, one incredible observing machine.
Try direct vision - you'll get used to it.
25" f/5 vs 25" f/3.5:
The 25" Obsession can be ordered as an f/5 or as an f/3.5.
f/5 (125" 3,175 mm focal length)
f/3.5 (87" 2,200 mm focal length)
Eyepiece height at zenith for 25" f/5 is 10 feet.
Eyepiece height at zenith for 25" f/3.5 is 7 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/3.5.
- Easier to achieve precise collimation of primary mirror.
- Cost is less than an f/3.5.
- Slightly smaller 3.5" central obstruction (4.5" on f/3.5)
Advantages of f/3.5
- 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/3.5 is easier for public viewing, but requires a coma corrector like the Paracor.
| 10 times the light gathering power of an 8 inch Schmidt-Cassegrain | Obsession 25" |
Typical 8" |
|---|---|---|
| Limiting stellar magnitude: | 17 | 14.0 |
| Rayleigh Resolution Limit: | 0.22 arc seconds |
0.68 arc seconds |
| Contrast limit: (minimum diameter before a nebular object fades from view) |
3.4 arc minutes |
11.0 arc minutes |
M13
by Dan Price
NGC 891
by Bob Brunck
M27
by Bob Brunck
Saturn
by Antonio Roman
25" Specifications:
Metric info shown in italics
Primary Mirror:
- 25" - 635 mm f/5 GALAXY, or OMI 2 inch thick mirror
25" - 635 mm f/3.5 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:
- f/5: 3.5" - 89 mm United Lens 1/10 wave or better
f/3.5: 4.5" - 114 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:
- f/5: 125" (± 2") - 3,175 mm (± 50 mm)
f/3.5: 87" (± 2") - 2,200 mm (± 50 mm)
Eyepiece Height at Zenith:
- f/5: (approximately) 10' - 305 cm
f/3.5: (approximately) 7" - 213 cm
Mirror Cell:
- 18-point
Truss Pole:
- f/5: Length: 87" (± 2") - 220 cm (± 5 cm)
f/3.5: Length: 60" (± 2") - 152cm (± 5 cm) - Diameter: 1.5" - 38 mm
- Wall Thickness: 0.049" - 1.2 mm
Upper Assembly:
- Diameter: 30" - 76 cm
- Height: 16" - 40.5 cm
- Weight: f/5: 15 lbs. - 6.8 kg
Weight: f/4: 16 lbs. - 7.2 kg
Lower Assembly:
- A= 35" - 89 cm | B= 35" - 89 cm | C= 28" - 71 cm | D= 32" - 81 cm
Mirror Box weight:
- The heaviest component (what you don't lift): 150 lbs - 68 kg
- Weight at Handles: (what you lift at Wheelbarrow handles): 40 lbs - 18 kg
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 25" f/5.
Only OMI supplies mirrors for our 25" f/3.5.
Obsessions are also available without optics if you already have your mirrors. Call, fax, or email for price and delivery.
Standard Options 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
JMI EV1
Feathertouch
by Starlight Instruments
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
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.
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
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 ($3,500 for 25" Classic)
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
Will O., 25" owner - January 14, 2010
I've only had one opportunity to get out to my dark site since I got the 25" but what a night! My most memorable views were of the Perseus galaxy cluster with NGC1275. I spent 30 minutes in this area and I kept seeing more and more the longer I looked. Thor's Helmet (NGC2359) was beautiful and seemed three dimensional. The detail is so astounding that it takes a while to have it all sink in!
I am most surprised at how easy it is to use a scope of this size. In spite of it's size, I setup and was ready for observing in less than half the time it took with my 16". Any doubts I had about using a large scope were removed after handling this for the first time. Great design and engineering! Will
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