The Big Easy: Obsession 15” Ultra Compact Dobsonian Review


Obsession Telescopes 15″ f/4 Ultra Compact Dobsonian. Credit Obsession Telescopes

In most of life’s endeavors, the more you pay, the more you get. More money buys a bigger house, a bigger car, a bigger boat. In other hobbies, however, the opposite is true. A $5,000 bicycle can weigh one-third what a $100 model does, for example. I had not thought to include telescopes in the latter category, until I saw Obsession Telescopes’ new UC (Ultra Compact) series. 


UC represents a radical departure from the traditional Dobsonian design, which Obsession itself helped to establish. Although it has the same basic parts of a conventional Dob, almost every part of the telescope has been rethought. Gone are the traditional mirror/rocker box assemblies, as well as the semi-circular truncated tubes on the upper truss. In fact, when you first see the scope disassembled, it hardly appears to be there at all. When I first got the scope in the garage, it was hard for me to believe an entire 15-inch telescope could arise from this odd-looking collection of parts. Obsession owner Dave Kriege said one of his goals was to make the scope small enough to fit in a compact car. 

The mirror box (which Obsession now refers to as a VMB, or Virtual Mirror Box; we are going to have to come up with some new terms) is the heaviest component, at around 53 lbs (24 kg) with the mirror installed. One caution – without a traditional mirror box around the mirror, the lowest part of the VMB is the side bearings, coated with rough flooring laminate. Be careful where you set it, or carry a blanket or towel if you need to set it down.

The complete telescope, ready to assemble. Credit: Ed Ting

Unlike many other truss Dobsonians, which use four or eight truss poles, the UC design uses six, and they are all joined together in one hinged piece. This has two advantages. First, there is only one piece to handle instead of four or eight, so assembly should go faster. Secondly, as one pair is shorter than the other two and attaches only one way in the front, gone are the debates as to which pole goes into which hole.

The scope’s back end showing the mirror, flotation cell, and personalized nameplate. Credit: Ed Ting

Perhaps the most radical part of the UC’s design is the upper truss – or, rather, the lack of one. The familiar truncated short tube is gone, replaced by a simple ring with the required parts bolted to it. The entire upper “truss” assembly, complete with secondary, Telrad finder, and Feather Touch focuser, weighs a mere 6.5 lbs (3 kg) in the version I tested. There’s a convenient handle that I used a lot for both assembly and during observing.

The barebones upper truss assembly. Note the handle. Credit: Ed Ting

Some have expressed concerns about dew problems with the scope’s upper components hanging out in the air. The telescope does come with a 9V battery-operated dew heater for the secondary. If further protection is needed, a separate dew removal system can be purchased. After attaching the upper truss to the truss poles, a traditional shroud can be placed over the scope, to prevent stray light from entering the scope, and for additional dew protection. With practice, the scope took me about six minutes to assemble and weighs about 75 lbs (34 kg) as shown.

The author with the assembled telescope sitting on a homebuilt rolling dolly for easy transport. Credit: Ed Ting

A 15-inch class telescope gathers enough light to the point where almost anything you want to see in a star atlas may be within your reach. The limiting factors are likely to be the quality of your observing location and your skill level, rather than the scope itself. Want to hunt down those obscure galaxies in Ursa Major, or the Virgo Cluster? Go for it!

The base price for the 15-inch UC is $5995, and delivery can range from six to 12 months. The scopes are made in the United States by hand, not on an assembly line, and you will likely have at least some contact with Dave Kriege himself at some point in the process. Also, keep in mind Obsession only makes the telescope’s structure; the mirror is subcontracted out to a specialist and will arrive separately. Finally, the $5,995 price can quickly balloon if you’re not careful. The shroud (mandatory in my opinion) is a $189 option. Since the telescope operates at f/4, the Tele Vue Paracorr ($500) should also be considered mandatory. Should you want an optical finder (in addition to the included Telrad) it will run you another $250. Add the full Argo Navis electronic package and be prepared to spend another $3600. Shipping at the time of this writing was $650. Before you know it, you could spend well over $10,000. Yes, it’s a lot of money. However, as the 15-inch Obsession UC can make a case as a “forever scope” I am sure some observers will gladly pay. Good hunting!

For more on the 15-inch UC Obsession, see Ed’s video at:

MSRP: $5,995


About Ed Ting

Ed Ting is a well-known amateur astronomer. His work has appeared in Sky & Telescope, Night Sky, Skywatch, Amateur Astronomy, Discover, and Popular Mechanics magazines. His web site,, is a widely-read telescope review web site. He is a National Science Foundation Ambassador to Chile and a NASA Solar System Ambassador.

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