Thinking About a New Scope? Think Big!


Why Buy an Obsession?

Contents of this page:

Consider these Obsession exclusives.

Optimum Design

Tim in Tucson

"I told you I donated my scope to the Tucson Astro Association last year but ended up getting it back when they couldn’t find storage for it. I am so glad. I’m having more fun with that thing than when I first got it!!" - Tim C,Tucson, Arizona

"I sure appreciate that you you’ve done such a service for those of us with an inclination to look up. I can say that the sights I’ve seen through that eyepiece have been a highlight of my life."
Many thanks, Dave.

Finally, the ultimate deep sky telescope is available to satisfy your obsession for the best performance and your demand for a superbly crafted instrument.

We design our telescopes to fit the optics -- not the other way around. Obsession telescopes are free from poor images caused by tube currents or oversized secondary mirrors used by others to accommodate large 'stock size' cardboard tubes.

All Obsessions deliver knock-your-socks-off images of deep sky objects. Many observers agree that the views in the 25" are as good or better than the astrophotos in Jack Newton's Deep Sky Atlas. Planetary views too are absolutely astounding.

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Industrial Construction

Obsession telescopes are built with aircraft grade ApplePly™ (see below), the finest plywood in the world for strength and beauty. Twice as many plys as the competition and twice as expensive as their so called "cabinet-grade" oak veneer plywood. (Ever wonder why they cover their end grains?) There are no voids or defects and the end grains are properly sanded and finished to show off their beauty. Extremely strong and light weight, Appleply™ damps out vibrations faster than all metal scopes.

This warm and beautiful wood is protected with Colonial Maple stain and five coats of polyurethane. Sanded between coats, our finish is applied with HVLP sprayer, not a crude brush job like most others. You'll be as proud to look at your Obsession as you are to look through it at night.

Ever wonder why there are no ugly nail or screw holes on Obsessions? The corner joints on our mirror boxes, rocker bottoms and sides are fully braced, glued and NC machine doweled every 2 1/2 inches (64 mm) for incredible strength. That's right, doweled. Cheap Dobs use nails or screws. In addition, Obsessions are constructed with a full Baltic Birch light baffle at the top edge of the mirror box to maximize image contrast and to increase the strength of the box. Others place the baffle (if any) inside the box close to the primary where is does little to no baffling and also leaves the top of the box wide open and unsupported. The result is a weak flexible mirror box and washed out images. No one builds Dobs as strong or as good as we do.


Why Baltic Birch?

Baltic Birch is a very special type of hardwood plywood from the Baltic region of Russia. The outer face veneers are a gorgeous birch species and the core laminations are all 1/16" hardwood birch veneers. With more hardwood core laminations, the resulting strength-to-weight ratio is unusually high. The competition uses cheap imitation birch or oak plywood with unsightly wide soft wood filler veneers. Baltic Birch is much stronger and resistant to flexure. It takes fasteners better than any other plywood and resists dings and bumps better too. Both the Classic and Ultra Compact Obsessions use Baltic Birch construction. The Classic Obsession receives six coats of polyurethane sanded smooth between coats to protect and show off the wood. On the Ultra Compact series we cover the Baltic Birch with black laminate for a more modern look. Baltic Birch is the ultimate construction plywood for a large aperture portable telescopes.

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Primary Mirror

2" thick primary mirror

Seeing is believing. The 12.5", 15", 18", 20", & 25" Obsessions use only premium diffraction limited mirrors from Ostahowski and OMI (Optical Mechanics Inc) and others (see Optics page for more info). Each mirror is thoroughly tested and meticulously hand parabolized. The surface figure is extremely smooth and free of astigmatism. There are no turned edges or zones. Each mirror is diamond edge ground, flat ground on the back, precision beveled and free of chipped edges. Ostahowski and OMI unconditionally guarantees every mirror to yield visually perfect diffraction limited images. All optics are coated with 96% enhanced aluminum so you get the highest refectivity and the brightest images possible. Because we use only the best optics on the market, our images will make you a believer in large aperture. Coupled with secondary mirrors that have a minimal 15% to 17% obstruction, image contrast on the planets is optimum. When the seeing is good, not only will you get exquisite views of deep sky objects, but you will also see large detailed views of the moon and planets that are better than photographs! It's no secret that at the big star parties, the lines are always behind the Obsessions.

Interferometry certification is included with each mirror. (No dreamed up test data like some others) In fact OMI is so confident of their quality that they post the serial number, test data and interferograms for every mirror they make on their website. Nobody else does this! Ostahowski Optics and OMI Pro-spec research grade mirrors are tested and certified with laser interferometry to be 1/4 wave or better Peak to Valley ACROSS THE FULL FACE OF THE MIRROR! There is no other way to meet this strict criterion without interferometry. Other opticians may claim their mirrors are 1/10 wave, 1/20 wave etc but don't believe it. Such claims are unsubstantiated and their mirrors often fail when analyzed by interferometry with astigmatism the most common error. There is no better way to test and figure a large aperture mirror than with interferometry. Other opticians measure the figure on the mirror using the Foucault test (there's nothing wrong with this). However this test measures only spherical aberration. From the data acquired in this test you can calculate a P-V wavefront error for spherical aberration only. However they often "infer" the P-V, RMS and Strehl values, as if they had measured the entire mirror and are able to report on all of the other aberrations. The RMS and Strehl values that they report are not valid because they are not collecting the data needed to calculate them. RMS and Strehl are the most important values to the customer, and rightly so. They tell you much more about mirror quality than the simple P-V measurement. Reporting bogus RMS and Strehl data is unscientific and useless. That's why we offer premium mirrors from Ostahowski and OMI. With a Ostahowski or OMI mirror you can be assured the P-V, RMS and Strehl data are accurate and real because they use interferometry in addition to the Foucault test.


Shown here are Foucalt and Ronchigrams for a 15" f/4.5 mirror made by OMI (Optical Mechanics Inc). Notice the exceptional smoothness and lack of ripple. Fully corrected figure all the way to the edge. In addition, we use only 2" thick glass so no bendy astigmatic thin mirrors like others may use.

Plus all 15” and 18” Obsessions use fused quartz for the primary mirror glass. Fused quartz is glass consisting of silica in non-crystalline form. It differs from traditional glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. The optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity. Its low coefficient of thermal expansion makes it one of the finest materials for precision mirror substrates. Fused quart is standard on all our 15” and 18” scopes, both Ultra Compact and Classic models.

Call, fax, or email for price & delivery.

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Secondary Mirror

secondary flats

secondary flats coating

Two dozen 3.1 inch flats with 98% reflectivity Brilliant Diamond exiting the coating chamber.

The secondary mirror is half the optical system. At Obsession we purchase all our secondary mirrors from Ostahowski Optics, THE leader in precision optical flats. Precision beveled and free of chipped edges, each Pyrex secondary mirror is guaranteed to be 1/10 wave or better and is certified with interferometry. That's right. Inteferogram with Peak to Valley wave front with every secondary mirror.

These optics have the finest specs on the market, are certified with laser interferometry and have ID (Ion Deposition) 96% enhanced coating.   Enhanced Ion deposition is the smoothest, most durable, most opaque (no pin holes) and most reflective coating possible.  Now  you  can have the best optics, the best coatings and the best delivery.   No one else offers this kind of quality.  With enhanced coatings on both mirrors, it’s like getting an extra inch of aperture for free! With Obsession you get the best reflectivity on the market. Enhanced coatings and precision flats from Ostahowski Optics are just two of the reasons Obsessions out perform all others. Our competition likes to compromise here to save money. Ask them where do they get their secondary mirrors. Ask them are they are tested and certified with interferometry. Ask them if they have enhanced coatings.

To enjoy visual astronomy, there is no substitute for aperture and quality optics. Proper annealing, thicker mirror blanks, diffraction limited optics, high performance coatings, and a slower focal ratio add up to the ultimate deep sky optical system. Quality optics and coatings cost a bit more, but if you are obsessed with the best, it's worth it. Our telescopes deliver the sharpest, brightest images you'll ever see in a commercially available telescope of similar aperture.

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Mirror Support

We support our primary mirror with a custom-made 9, 18 or 27-point stainless steel flotation cell, not with plywood cells like some other telescopes. Stainless steel doesn't warp and never needs painting. The support points are computer derived based on the thickness and focal ratio of the primary mirror. Each point supports exactly the same mass. Vertical support of the primary is achieved by a 180 degree Kevlar sling, just like on the optical bench where it was figured and tested. This custom support is a critical factor in providing the superior images seen with an Obsession. Some scopes omit the sling and use metal edge supports. Rigid edge supports deform the glass causing astigmatic images. (especially with 1.60 inch ulta-thin mirrors). As the scope is rotated downwards the glass is deformed more and more from the metal supports. These deleterious effects have been proven with interferometric analysis. Passive sling support is another reason why Obsessions outperform all other large aperture telescopes.

The flotation cell is secured by a welded steel framework with a built-in 12-volt fan (you supply power). This open 'tail gate' - an Obsession Telescopes exclusive - eliminates tube currents and helps the mirror rapidly reach ambient temperature.

The design also protects the mirror from unnecessary handling because it can be left in the mirror box at all times. No hernias, finger smudges, breakage or worry! Three lateral motion pins keep the mirror securely in place during transport and yet are non-contacting when the telescope is in use. Collimation of the primary is made simple by three built-in collimation knobs. No tools are required! Also, you can wash the primary right in the mirror box!

The above features mean that you'll be at the eye-piece while others with similarly large aperture telescopes are loading mirrors and waiting for their 'scopes to cool down.

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Upper Tube Assembly

Upper Tube Assembly

The upper tube assembly is ultra-low profile. This keeps it lightweight and allows us to use the smallest secondary mirrors possible which creates an obstruction of only 15% by diameter. Coupled with a super smooth 2" ultra-low profile Crayford focuser from JMI (the ball bearing DX3), the eyepiece is as close as possible to the secondary without vignetting the light path. These design choices produce the best image contrast possible for a strictly visual telescope with 100% illumination over a 5/8" field.

The upper tube assembly rings are manufactured from maple ApplePly™. Our rings are machined round so they look great, not cheap hexagons like some others. Struts are lightweight thin-wall aluminum tubing. Our telescopes have top quality stainless steel spiders and no tools spring-action secondary mirror holders for easy collimation and a lifetime of durability. Many companies cut corners here. The light baffle is black opaque Kydex. Kydex (an acrylic PVC) is non-warping, has a dull hair cell inside to reduced light scatter, and a beautiful shinny outside for looks. We don't use aluminum, cardboard, or cheap ABS plastic (styrene), so it won't ding, deteriorate or warp. Kydex is thermally and esthetically superior to these other materials. In fact since we discovered Kydex in 1990 it has become the most used light baffle material because it's the best. The focuser platform is made from multi-ply curved maple instead of the more common cheap flat board. It is rigid and attractive. Another example of using the best materials for optimum performance.

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Mirror Box & Rocker

mirror box

The mirror box is extremely strong - 5/8" ApplePly™, corner-braced and bolted to huge custom designed cast aluminum side bearings. On top, a functional Baltic Birch plywood light baffle minimizes reflections. The bottom has our unique steel mirror cell frame. The sides use our special altitude bearings that allow all the truss poles to be mounted on the outside of the mirror box where they belong to keep the box as small as possible. This is one of the main reasons Obsessions are more compact and user friendly than other 'scopes of the same aperture. Locating the pole clamps on the outside also makes insertion easier in the dark and prevents dirt from falling into the mirror box. The rocker assembly is constructed of double thickness side walls and is ultra-low profile. Extremely rigid, the rocker unit insures the best images possible when guiding at high power. Includes dust cover.

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Serrurier Truss Design

Serrurier Truss

The Serrurier truss is what makes large, portable telescopes possible. Used world-wide, it's incredibly stiff and lightweight. Because we want our telescopes to be the best, Obsession telescopes incorporate much larger diameter aluminum tubing than is commonly used (see statistics table for sizes). This prevents tube sag and deformation when the telescope is moved. Dark, closed-cell foam encases each truss member to reduce reflections and provide a warm grip for cold nights.

For optimum performance from your telescope, an optional custom-fitted light shroud is designed to increase contrast by keeping stray light from scattering across the field. The attractive shroud is made of ripstop nylon and has a drawstring at the top and bungee cords on the bottom for ease in attaching to the 'scope. Includes stuff sack.

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Side Bearings

We use our huge and exclusive strong cast aluminum side bearings (properly sized at 1.3 x the aperture) for each size telescope we build - slightly larger than the mirror box, and a beefy 1 to 3" wide.

Our design and choice of materials minimizes the difference between static and dynamic friction to allow subtle adjustments without excessive force or backlash.

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Buttery Smooth Tracking

Nothing moves like an Obsession. True one-handed guiding for easy movement right to the zenith in both axis. We wanted to make the smoothest moving large telescope available, and we didn't stop until we had completely redesigned the Dobsonian bearings.

Special glass and phenolic anti-friction laminates on all bearing surfaces glide across virgin Teflon resulting in nearly equal forces in both altitude and azimuth. These Glassboard/Ebony Star surfaces provide smooth "one finger" motion. Others cut corners by using "one size fits all" bearings made of flimsy laminate coated wood.

It took exhaustive testing of many surface combinations and we are convinced that ours provides unsurpassed motion in a giant aperture telescope. Ask any of our customers. Guiding at 600X is not an idle boast. After using an Obsession telescope everyone always says "It moves so smoothly!"

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Steel Wheelbarrow Handles

Wheelbarrow Handles

Standard on all Obsessions 15" through 25" at no extra charge. They're warp proof, stronger and lighter than wood handles and have 10" pneumatic tires.

Move quickly and easily from your vehicle to your observing site with the wheelbarrow handles. Don't be fooled by the "total weight" -- the wheels carry most of the weight, not you.

The mirror box, primary mirror, rocker and ground board are transported as a single unit. No heavy mirror cell with delicate primary to lug out and hassle with. No mirror box and rocker to carry around.

Why struggle lifting separate and heavy components one by one when you can easily and comfortably roll out everything all together on air filled tires. Set up is fast and easy so you can enjoy astronomy instead of a workout!

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Easy Transport

Roll around the entire assembly with less muscle than it takes to lift the primary alone!

You won't need a trailer to haul your Obsession telescope (15" through 25"). Our low profile design makes moving and storage of an Obsession a reality for many who thought they'd never own a 'scope this big. The lower unit can be rolled up ramps into a mini-pickup, minivan or even some of the newer hatchbacks.

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Quick & Easy Assembly

Assembly is fast and easy. No nuts, no bolts, no tools, no kidding! Others may stare in disbelief as you single-handedly assemble your Obsession telescope in less than ten minutes. Alone!

The process couldn't be simpler: truss tubes are inserted into solid maple split clamps on the mirror box and secured with hand knobs. The upper tube assembly is placed on top and secured with cam levered aluminum clamps. That's it! It's very precise, Collimation stays 'bang on' even after transport - only minor tweaking of the primary may be necessary. You are observing in minutes while others are still trying to figure out what goes where. And because you can place the upper tube assembly on top of the truss poles and let go, you can use your hands to engage the clamps. Other scopes require two people, one to hold the upper tube assembly and another person to engage fasteners, a real circus act. But with our cast aluminum pole seats anybody can set up their Obsession alone.

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Fast Delivery

Wheelbarrow Handles

fused silica primary optics ready to ship

Because we pre-purchase hundreds of large aperture optics from Ostahowski and OMI we have the fastest delivery in the business. All with the highest specs and reflecitivity on the market. Interferometry certification included.

Many apertures often in stock.

Email or phone for current delivery times.

We ship world-wide via UPS.

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"Obsession Telescopes - The Standard By Which Others Are Judged"