Obsession 18" Ultra Compact Reviews

• Obsession 15" Ultra Compact Review by Cloudy Nights (external link)
• Obsession 18" Ultra Compact Review by Cloudy Nights (external link)
  
• Obsession 20" Review by Astronomy Review
  
• Obsession 18" Review by Tom Trusock
  
• Obsession 18" and 20" Reviews by Ed Ting of Scopereview
  
• Obsession 20" f/5 Review
  

Obsession 20" Review
by Alan Dyer - Astronomy Magazine - March 1991
"The Obsession telescopes elevate the Dobsonian to a new level of quality and ease of use...Kriege's design is one of the finest we've seen for maximizing compactness in a giant-aperture 'scope...and example of craftsmanship we've rarely seen in any telescope, let alone a "light bucket"...mechanically, the 'scope works beautifully... it's easy to track objects even at high power and easy to move the 'scope when it was aimed at the zenith... each night I assembled the telescope the optical collimation was bang on. If big-aperture views are what you're after, this 'scope will deliver... (the 20" has) enough aperture to tackle any target in the visible universe..."


Obsession 18" Review
by Tom Trusock

Download PDF file of the complete Cloudy Nights review of Obsession 18"

I have been a visual observer for nearly two decades, and been fortunate to have opportunity to use a plethora of equipment - all makes, sizes and levels of quality. While there is no one perfect piece of equipment for every astronomer, there are those nights where everything comes together to give a near-religious and especially memorable experience. Last night was such a night. I spent many blissful hours with my 18" f4.5 Obsession with OMI-Torus Primary, StellarCat Drive and TeleVue eyepieces.

Everything just worked. Beautifully. I gazed dumb struck in wonder at a myriad of astronomical targets, through one of the finest optical systems I've been privileged to look through, let alone own. I saw detail last night that I'd only previously seen in pictures often taken with observatory size telescopes and expensive equipment. Amongst the targets I wondered at were: NGC 2392, the Eskimo Nebula, NGC 2438, IC 418, NGC 2371. These planetary nebula are some long favorites of mine and stood out against the night like stellar jewels. And yet, they were not the showpieces of the evening. By far the most awe inspiring view was the mighty Saturn. As I sat back and watched the ringed giant, I could make out far more detail than I'd ever seen visually, in any scope, no matter the size or quality. I couldn't help but laugh out loud. As I increased the power, it stayed rock solid in the center of the field and invited closer and closer inspection.

Gentlemen, without your contributions, I could not have enjoyed the evening nearly as much as I did. A long line of craftsmen made that evening possible. While I can’t thank everyone, I am would like to take a moment to thank the following principals: James Mulherin (OMI-Torus) you crafted a truly breathtaking mirror - the heart of the telescope. Dave Kriege (Obsession Telescopes), you've spent your time, effort and expertise in fashioning a well designed work of art for the sole purpose of holding that primary in perfect position. Gary Meyers (StellarCat), after a mere two sessions, I can no longer imagine observing without your drive system. And finally, Al Nagler (TeleVue), your eyepieces have consistently provided me with some of the most spectacular views I’ve ever known. Your spacewalk experience is alive and well.

Thank you. Thank you one, and all. I look forward to many more such nights under the stars. Clear Skies. Tom Trusock


Obsession 18" & 20" Reviews
by Ed Ting of scopereview

Obsession 18" f/4.5Jump to 20" review
This is a marvelous telescope and you're going to have a ball with it if you're not used to anything this large. You need a small stepstool to get to the eyepiece at the zenith, vs. a full-sized 5 foot ladder for the 20". The shorter truss poles and more compact mirror box makes the 18" (and the 15" for that matter) incredibly rigid and taut, given the unit's size. Tracking is buttery-smooth, even at 250X+. The secondary can now be collimated without tools, a nice improvement over the old system. Cool down, from a hot summer sun-drenched garage to a cool 60 degree summer night, takes about 45-60 minutes (faster if you run the fan.).

Dave Kriege jumps through hoops to make his telescopes as compact and light as possible. The weight on this unit is only 105 lbs or so, which you never lift - wheelbarrow handles bolt into the side of the mirror box, allowing you to move the scope easily (Obsession says the weight at the handles is 18 lbs.) The telescope looks impressively large and imposing while assembled, but when you break it down (a 7-10 minute operation) you would barely notice it's there. A telescope is mostly air, when you think about it. I've seen people fit two in their minivans.

Quality woodworking is the calling card of any Dave Kriege telescope, and this one is no exception. The choice of parts, selection of woods, and attention to detail are second to none. As an example, most other manufacturers attach their truss poles on the inside of the rocker boxes, which makes for larger rocker boxes. Obsession's truss poles attach to the outside, which allows the designer to shrink the size of the rocker box. It's barely larger than the mirror. As a result of design decisions like these, an Obsession is often a full frame size smaller, per given aperture level, than other similar telescopes. It's the one to get if portability is a big issue.

This sample was bought by a club member who had seen the 20" and its review last year (I am such a bad influence...) He ordered it with a Torus mirror (Nova is standard) and paid $300 for the enhanced coatings. The mirror's correction is excellent. This is impressive for such a large mirror. The surface figure looks very smooth as well. While looking at M13, the Ring, M71, etc., stars focus down to tiny pinpoints under good conditions. The color contrast on Albireo is immediately obvious.

I had the 20" and the 18" together one night and decided to test the old saying that there isn't much difference at a certain aperture level under light polluted conditions. Pointing both telescopes at a light-polluted area of the southern sky, the 20" did, in fact, still go deeper - noticeably. Tele- scopes gather light indiscriminately - light pollution and skyglow get sent up to the eyepiece right alongside your favorite deep sky object. So while the 20" goes deeper, the view is browner, and the sky background brighter, than the 18". How much this means to you depends on the individual. Several years ago, I would have found this intolerable. Now, I don't mind so much, and welcome the light grasp of a larger scope. Under dark skies, of course, it's all over - in good conditions, larger scopes always win on deep sky objects.

Having been a small-scope kind of guy for decades, I am slowly gravitating towards large-aperture telescopes again. I find I can use the 20" under most reasonable nights, and keeping the scope fully assembled on a rolling platform/ cart lets me deploy it within a couple of minutes. I can actually set up the 20" about as quickly as I can set up a 6" Dobsonian. Hey, if I can have 20", why settle for six?

A telescope like this 18" Obsession is going to be a revelation for anyone used to looking through a 6" Newtonian or an 8" Schmidt-Cassegrain. Even people accustomed to 10"-12.5" apertures are often amazed when they get a hold of a telescope of this size. In fact, there seems to be a threshold, somewhere in this 18"-20" range, where you start getting the feeling that you can do just about anything, given good enough conditions. You start looking at those tiny galaxies and planetaries plotted in your star atlas and seeing them as easy prey. Looking at the level of detail in the Veil with an O-III filter knocks my socks off every fall. I never get tired of looking at it.

The optics are of very high quality, the woodworking is top-notch, and the sheer aperture gain is going to be an eye-opener for the small-scope folks out there. Like all the Obsessions, this one gets the highest recommendation.


Obsession 20" f/5
20 inch Obsession Now that is a big telescope!

Readers have noted to me the relative dearth of premium, large-aperture Dobsonian reviews in these pages. All I can say is, you people writing to me from the clear, dry environs of Arizona, New Mexico, West Texas, and California have no idea how lucky you are. Here in the humid, cloudy Northeast, such telescopes are overkill much of the time.

Still, large Dobs are gaining in popularity out here. Take the case of friend David, who ordered this 20 inch model. He had it shipped to my house because he was out of town that week. I was glad to oblige -- since I cannot afford such a telescope (at least not now) I wanted to see what it felt like to take delivery of a 20 inch Obsession, even if it wasn't mine.

The scope arrived in 5 huge cartons. I opened the cartons to check for shipping damage, but that turned out to be something of a joke. The pieces are so well-packed, it became obvious within 5 minutes that there was not going to be any damage, not anytime soon. The scope parts come packed in bubble-wrap, and the whole thing is then covered with self-hardening foam and placed in the carton. If I had drop-kicked the cartons down the stairs, I still don't think there would have been any damage. As it is, it took me nearly one hour of steady work just to unpack everything.

After another half hour of or so or work, I had the scope assembled, and I did not even have the instructions. Egads, this is a huge telescope! On the day I put the telescope together, a bunch of guys from a contracting company were at the house, replacing my roof. One by one they stopped in the garage, and the response was pretty universal. They would look up at the scope, tip their caps back, and say "What the hell is that thing?".

Indeed, for a couple of days, it was hard to suppress a grin every time I walked into the garage. The eyepiece is something like 8 feet off the ground, and I need to climb four steps on a ladder just to reach the eyepiece when it's at the zenith. What's worse, although the scope comes with detachable wheelbarrow handles, I always place my big Dobs on rolling platforms, which raises the entire scope another 4 to 5 inches.

This telescope is extremely well-made, and as you look it over, the quality speaks at you everywhere you look. The woodworking on it is fabulous, much better than it has to be. It is almost a work of art. Other premium Dob manufacturers make wonderful telescopes, of course, and I love them all. But in terms of the quality of the woodworking, I still don't think any- thing touches the Obsession for sheer craftsmanship.

The Nova mirror arrived a few days later, and I spent about an hour installing it, adjusting the sling, and collimating the scope. For someone used to 4 inch refractors and 8 inch Newtonians, as I am, this 20 inch Obsession took some getting used to. While looking at M13 in twilight, I picked out NGC6207 nearby while the sky was still blue. This was going to be fun.

As darkness settled in, I toured the late summer and early fall deep sky objects. You can see much structure and detail in familiar objects like the Ring, Dumbbell, M13, M15, M11, M33, etc. The Dumbbell looks more like a Football Nebula than a Dumbbell. The various clusters in Cassiopeia and Cygnus take on real personality (in "normal" sized scopes, they tend to look like identical fuzzy blobs.) Planetaries like the Blue Snowball or the Blinking Planetary can be pushed to huge magnifications without image breakdown. To give you an idea of the light grasp of a scope like this, M56, the little globular in Lyra, looks like M13 in an 8 inch reflector.

The scope moves very smoothly on both axes - just a little nudge and it goes where you want it to. I got used to climbing the ladder. Also, I trained myself to sight through the Telrad from the ground (yes, from about six feet away.) This turned out to be a useful skill.

On the second night, I spent most of the evening looking at Stephan's Quintet, the Veil (with a 35 mm Panoptic and a 2 inch O-III filter) and the H-II regions in M33. The Veil, by the way, is absolutely spectacular, with its various tendrils and wisps twisting and intertwining with each other. Very beautiful. Night after night, I found myself looking up at the sky from my car on the way home, hoping it would be clear enough to use the Obsession.

Drawbacks? OK, so it's huge. Your wife is going to have a heart attack when she first sees it. Also, you really do need access to fairly dark skies to make the best use out of it (although a rural location like my Mag 5.0 driveway is adequate.) Being able to leave it fully assembled and on a rolling platform (i.e., the way I have it set up) will encourage you to use it. Finally, you are going to be a collimation expert after a few nights with this scope.

15, 18, 25, and 30 inch versions are also available (if you buy one of the 30" models, please invite me over!) There are too many options to list here; check Obsession's website for the latest updates and prices.

I was looking for a way to close this review by telling you how much I like this telescope. On the fourth clear night with the Obsession, several club members stopped by the house for a long evening of observing (I had this telescope at the same time as I had the Fluorostar, above, which made me a popular guy around here for a while.) After the session, I wheeled the scope into the garage and put the mirror box cover back on. At this point, one observer wrapped his arms around the truss tubes, looked lovingly up at the eyepiece end of the scope, and said, softly, ""Come to Pappa...".


Y'know...recommendations don't come any better than that.