Thinking About a New Scope? Think Big!
"Obsession telescopes are still the standard by which all other Dobsonain-style Newtonians are judged."
Star Ware by Phil Harrington
Obsession 22" Ultra Compact
by Tom Trusock - October, 2010
Ok, so I've got a new scope to lust after.
Dave Kriege with 22" UC
It's been a while since I've personally been interested in a large telescope. I mean a good observing buddy has a 30” Obsession, and I've got an 18” in my private observatory so lately when I've been heading to star parties I've either been taking a small telescope or relying on other folks to bring the big guns. While I spend a LOT of time with smaller scopes, there's no arguing that aperture will simply show you more.
But I've never been all that tempted by anything bigger than my 18”. I mean, lets face it – big telescopes are an exercise in logistics. You have to transport them, store them and – don't forget – set them up. If you're headed out by yourself, well – this task isn't exactly impossible, but it's not a particularly simple operation. (Think winches, tackle, ramps, trailers and teams of slaves…)
Dave Kriege's Ultra Compact scopes go a ways towards eliminating some of these hassles. The first out of the gate was the 18”, and that was a wonderful option in a super compact and portable large aperture. Especially for those of us who say - aren't as handy as some of the ATM'ers out there. (Me, I hardly know which end of the hammer to hold.) Still, let’s be frank: nothing's going to be the ticket for everyone, and the ultra compact / ultra light design isn't without a few trade offs. Hence Obsession's still booming market for what are now referred to as the “Classics”. (FWIW, Dave Kriege recently remarked that sales are split pretty evenly between the UC and the Classic models.)
Fast forward a year, and we see Obsession introduced a 15” UC for those that are looking for something a little smaller and less expensive than the 18”. The 15” UC really tempts me. It would be a fantastic little star party telescope, but my personal funding levels being what they are right now, well it's going to have to wait a while.
Not to mention my heart's been stolen by the latest iteration – the new 22” UC.
I spent a recent weekend in Michigan's Upper Peninsula at one of my favorite dark sky sites and had an opportunity to spend some time with Dave as well as play with his latest toy.
This scope is pretty much the evolution of the design, and has the features that you'd expect – at least for the most part. There are also some additions: like 8 poles instead of six. This adds to stability (a nice and needed touch for a larger telescope), but functionally – well – it's an Obsession Ultra Compact.
Collapsed the base is about 28”x29”x18” high, with the heaviest component around 90 lbs. The f4.2 mirror alone weighs around 65. Its eyepiece height at zenith is around 88 inches, putting it significantly shorter than the 20” F5 that's been so popular over the years. And for me, it’s just about perfect. But more on that in a bit.
The scope is rather deceptive – with the shroud off, it really does not look like a 22” inch telescope. I mean those are BIG scopes. No, this had a physical presence more like an 18” incher. The scope was solid, and well balanced (able to take heavy and light loads with aplomb). Settle time was minimal, and tracking was smooth. Setup is about the same as the others in the series at 5-10 minutes including collimation. I've got a video on the site of Dave putting one of the other UC's together if you're interested.
The OMI mirror delivered what I've come to expect from OMI – a top of the line viewing experience.
There's always an argument about Paracorrs. Do I really need one? Personally f5 is the breaking point for me, but many amateurs get down to f4.5 before they feel the need. The 22” is an f4.2. You will want a paracorr. I could definitely notice the difference with one in.
Using the 22” was an experience. Most of our observing was done flat footed, but there were a few targets that we had to go “up” for. But even then – it was only a step or two up a standard step ladder – no huge ladders required here. The scope was fairly stable in a 20-25 mph wind. While it did weathervane a bit (completely expected given it's smooth motions), the scope remained stable enough to use, and only when the strongest gusts came through was any vibration evident.
Some users have noted that there appears to be a noticeable “bump” when moving the scope over the hinged point on it's alt bearings. I don't know if Dave addressed that, if the added mass takes care of it, or if we simply weren't observing in portions of the sky where we'd notice it – but it just wasn't an issue for me.
While 22” isn't “that” much larger than my own light bucket, the difference in views were evident and obvious – not in part because of the location of the 22 inch (that place is black as pitch!). But you see, that's what the Ultra Compacts excel at. Portability. On the flip side – while any truss dob is portable, my 18” will probably never leave my observatory again and while my skies are good – that aren't THAT good.
The one clear evening we had, the weather was a little sporadic at best and we found ourselves observing through breaks and sucker holes. Every so often the sky would clear off completely, and when it did – WOW. Observing with a large scope is always a treat, but observing with a large telescope at one of the darkest sites this side of the Mississippi, and with the transparency that comes through after a storm – well, that’s just a jaw dropping experience. And to add to it – we also had a sample of the new 21 Ethos available for use. That eyepiece pretty much just stayed in the focuser all night. The combination of TFOV and magnification were stunning. It had a wide enough real field that we were able to use it as a finder, but provided enough magnification that we weren't all that tempted to switch it out for a different eye piece.
The 22” UC comes with a FeatherTouch, Telrad, External Light Baffle, CounterWeight system, and wheel barrel handles. I'd highly recommend adding – at the least - a light shroud (also known in Michigan as a “dew shield”), ParaCorr and an Argo Navis system to make the most of your time under the extremely dark skies your portable new telescope will allow you to reach.
At a price of $9995, I don't think any one would ever call it cheap, I do think it's a reasonable price for a 22” telescope – especially in this post pyrex world that’s careening towards us. If transport is a question, then it's most CERTAINLY worth a look - assuming you're in the market for a large scope.
You know the phrase “Think Happy Thoughts?” Well, I can tell you a 22” scope under ultra dark skies generates plenty of those. I know it's got me thinking. Unfortunately I suspect my wife isn't going to like the direction.
Obsession 22" Ultra Compact - First Light
by Eric T. de Jonckheere, 22" UC owner in Elko, Nevada - December, 2011
After putting my 22” UC together, I had to wait for three weeks due to the “new telescope curse” before getting it out for “first light”. Last Friday night the sky was finally clear. It was a little cold at around 4 degrees Fahrenheit. The transparency and seeing were on the good side of “okay”.
My skies are not the clearest, or darkest in the world, because of the proximity of where I live relative to town – however, I am not complaining one bit. Truly “dark skies” are only a 20 minute drive away, however, I wanted first light to be in my back yard. An estimated NELM for that night was around 6.0. I must admit that I was ill prepared for what I was going to see through the 22” UC. I knew it would be good, but I had NO IDEA of what I was about to see!
After allowing the optics to equilibrate with the cold night air for about an hour, I needed to finalize the collimation. I must say that I’ve never had a telescope that is this easy to collimate. The build of the telescope in conjunction with the barlowed laser technique made for an exceptionally easy collimation. It took only five minutes. At this point, the last thing I needed to do was to align the Telrad. I used Alnitak for this task. I also performed a star test on Alnitak and was quite simply astonished. It was as close to perfect as I have ever seen – I also had no idea that Alnitak had a “brother”. After doing the star test, I immediately noticed that it was a binary system. I was able to see a much smaller, fainter, star right next to it. I now know that it is actually a triple system.
The first object (and one of my favorites) I chose to observe was Betelgeuse. I love Betelgeuse because it is so close and bright. Once I had Betelgeuse centered in the Telrad, I took a look into my 31mm Nagler eyepiece. The sight that I saw was simply breathtaking! Betelgeuse was perfectly focused and ablaze with its’ brilliant orange light. It was so beautiful that it (truthfully) almost brought a tear to my eye. At this point, I knew I was in for quite a treat. Jupiter was my next target as it was very bright and high in the sky. People often say that there are no planetary views as good as through a top-notch APO refractor. While this may be true for some scopes, it certainly was not for my 22” UC. Jupiter literally snapped into focus. The view through my 17mm Nagler showed two, very distinct, very red, equatorial bands. They were bustling with detail. Swirls and notches within the bands were clearly visible. There were five moons visible in the eyepiece. My only complaint was that Jupiter was too bright, which is not really a complaint as it was easily remedied with a neutral density filter – after this the brightness/contrast was perfect. I have never seen Jupiter look like this, through ANY scope. I’d be happy to wager my view against the “best” planetary scopes out there. Because of the bitter cold, I only had two more targets for that way-too-short “first light” observing session. M42, the Great Nebula in Orion, was my next target. Once again, I’ve NEVER seen a view like this through any other scope. I was expecting a lot of detail, and a lot of detail is what I got. There were filaments and tendrils galore. I never realized that there were more than four stars in the trapezium. With my 9mm Nagler in, I counted seven, however, there were four more that were in extremely close proximity to the “main four” so I guess that the total would end up being eleven. There was one other surprising thing about that nebula – color. There was A LOT of it. The view I’ve had in EVERY other telescope I’ve looked through was grey. The view in the 22” UC displayed blues, greens, and even some places that appeared to be a reddish brown. These were also not “dull” colors. They were definite and beautiful. I NEVER imagined that I’d see color like this in a telescope. I was told, and thought, that you could only see color in astro-photographs. I was wrong! The last target of the night is something I’ve never seen before – the flame nebula. The famous dark nebula nicknamed the “horsehead” is on my observing challenge list -- I wasn’t even looking for it tonight. However, I did want to see if I could see the flame nebula. I had mentioned before that I performed a star test on Alnitak. At that point, I was centered in on the star, and not looking around. I re-centered the scope in on Alnitak. I also used my 17mm Nagler for this task. I looked through the eyepiece, and low and behold, there it was, as plain as day, just above and to the right of Alnitak. I could easily see the dark lanes (I counted three major dark lanes heading down and to my right of Alnitak – there were also several smaller dark lanes stemming from the three major ones). The flame nebula did not produce any color in my eye, however, I did not need a H-Beta filter to see it. I sat and studied the flame nebula for what felt like five minutes, but I am sure it was at least an hour. I could see some amazing detail in the nebula. After I was done observing the flame nebula, I did receive one final unexpected treat for the night. As I scanned around Alnitak, with direct vision, I noticed an even fainter nebulosity. Just above Alnitak, heading up and slightly to the left was a faint, grey strip. I had found IC 434! I never thought that I’d be able to see IC 434 on a night and location like this!. It was less than a minute after this that the seeing diminished for the night. In only a few more fleeting moments was I able to see IC 434. I could have put my H-Beta filter in and begun the hunt for the horsehead, but I was tired and cold, and I had seen way more than I had expected for my 22” UC’s “first light”. I would dream of seeing the horsehead nebula that night while I slept, and will continue the hunt on another night.
Dave, you produced an absolutely amazing telescope for me – a DEFINITE work of art. I COULD NOT be happier. Thank you SO much for fulfilling my dream. Not only did you fulfill it, you blew it away!!!!! I know that I will never own/buy a nicer telescope. I don’t want/need to own a better telescope, because I am pretty sure there isn’t one. The engineering of my 22” UC is amazing. The curves and edges of the wood-working are exquisite. The way the rockers and base are put together is simply genius. The look and function of the UTA is incredible. This telescope looks like it could be a piece of furniture in my living room, or a professional telescope in an observatory. You are a master at your craft and I will DEFINITELY more than recommend your telescopes to ANYONE who wants to by the best that there is. There is NO better than Obsession, which is probably why I see the majority of other scopes advertised as “Obsession like”. Oh, and thank you for your fantastic customer service. It was second to none. One final thought. I would NOT give a rave review like this unless it was 100% true and absolutely deserved. The Obsession 22” Ultra-Compact you constructed for me is definitely deserving of the best review I could give. Amazing Dave…simply amazing. Thank you so much! I hope to see you at a star party some time. If I do, you will have to take a look through the unbelievably fantastic piece of equipment that you produced. Oh, and the 22” UC telescope already has a name – “Inspiration”.
Eric T. de Jonckheere
by Sky & Telescope - February 2009
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.
First Look - Obsession 15" UC
by Tom Trusock - July, 2008
Dave Kriege with 15" UC
Last year, Dave Kriege of Obsession Telescopes released the Ultra Compact 18". At a clearance height of 14", the UC fits into places where large dobs have never fit before. However for various reasons 18" may still be a bit more than some folks want to handle, so this year Obsession is introducing a 15" version of the UC.
And I had a chance to play with the prototype last weekend at a gathering up in Michigan's UP.
To make a long story short, if you've seen the 18", you probably have a good handle on what the 15" is all about. It's smaller, lighter and less expensive - just what you probably suspect. The mirrors will be coming out of OMI as Galaxy makes nothing smaller than 18". The 15" UC follows the 18" UC at the f4.2 focal ratio. As compared to the 15" Classic (which I've also used), it takes up roughly half the height in transport and weighs around 25 lbs less.
According to Dave Kriege, the only significant differences between the prototype I used and the production models coming out in the fall are:
- Rocker box - the rocker box was NOT production, simply something that was slapped together quickly for a photo shoot and the trip, and frankly, it showed in both finish and utility. I'm told that the scope will be quite a bit more stable on the production base than it was on the prototype base.
- Lack of lower light shield - the 15" UC will have the same light shield around the primary as the 18" UC, there was no shield on the prototypes.
- Lack of shroud - the shroud was not ready for the prototype. Let me take a minute and note something - In this neck of the woods, shrouds are important not only for their ability to stop glare, but also as dew shields. Fortunately, in this case, the one evening we used the scope, the conditions were extremely dry and the primary did not dew over. However, a shroud is strongly recommended.
I had a chance to see Dave set it up, give it a good going over and then use it over the course of an evening. On the whole I was pretty impressed.
The scope can be quickly and easily setup by one person (see video at bottom of page), and stores into a relatively small space. While the (optional) storage container wasn't as small as I'd hoped (it appeared very similar to the storage unit for the 18" UC) it did appear to provide very good protection and assuming you have the clearance in your vehicle, allowed one to pack around it. If you have a tiny vehicle, then the storage unit probably won't be an option.
As standard equipment on the UTA you'll find the 2" FeatherTouch focuser, reverse counterweight system, foam covered handle (a thoughtful touch), light baffle and Telrad. The secondary is 2.6" - the same size as on the Classic - and uses three thumbscrews for adjustment. Note that a dew heater is not standard equipment. A quick glance at their website reveals that Obsession now sells a dew heater which automatically keeps the temp of the secondary a few degrees above ambient. (Most likely it's the same one as sold by Astrosystems, and I highly recommend it.) Further note that the 15" UC uses a three spider vanes rather than four, so on bright targets the diffraction spikes might be a little different than what most folks are used to. The light baffle velcros on, and does an effective job of blocking light directly across from the focuser.
The scope uses an "offset" six pole design where the tubes are already connected. The hardware is captive so you don't have to worry about getting to your dark site and having lost something. In the same train of thought, all assembly and collimation is "no tools" (excepting your laser, cheshire, etc..). The scope went together quite simply and in a matter of minutes.
Height to the eyepiece when you're observing at zenith is around 60". For me, this was a little on the short side and would require me to bring a chair. But then again, I'm a standard deviation (or three) to the right of the bell, so take that into consideration. In the photo above Dave Kriege (around 6' 1") gives a good size reference for the scope.
If you go with the Argo Navis option, you will be able to anchor it to one of the truss poles for easy access. I was informed the ServoCat will also be available as an option.
Moving down to the virtual rocker box, lets take a look at the cell. It's a nine point floating mirror cell, with three adjustments. Basically, its of the same design that's found in the other ~1,700 Obsessions that are in the field. It uses a Kevlar sling for edge support, and sports a small fan mounted in the middle of the cell. Note the fan does not come hooked up to anything. If it were me, I'd either buy a set of rechargeable batteries and attach them to the cell, or I'd opt for simply using a 9 volt battery. In my opinion, the key to this scope lies in keeping things as simple as possible. If you noticed that the rocker box in the photos is mismatched to the bearing size - remember again, this isn't a production rocker, rather it was simply something knocked together quickly with materials at hand.
You'll note the mirror cell attaches directly to the bearings. The bearing system utilizes the same ebony star and Teflon as found on other Obsessions, and the scope (for the most part - more on that latter) has inherited the standard Obsession motions, which is to say, there ain't much smoother. The bearings fold for transport and storage. In addition, they sport a set of handles to assist you in moving the scope, and holes for the (standard) wheel barrel handles. When moving the scope via the wheel barrel handles, there are going to be 4 attachments for the bearings and rocker box. Once again, not present on the non-production rocker.
The mirror cover sits atop the mirror and while somewhat flexible is quite thick and easily capable of supporting small objects which may get placed upon it during transport. It's not exactly pretty, but there's little danger of this one snapping or cracking - and that's really what you want.
One of the nice things about this little get together at a remote location in Michigan's Upper Peninsula was the gear. For a small gathering, there were several amazing products; a 30" Obsession, the new Binocular Photon Machine and the 15" UC Prototype just to name three. Although it wasn't a new moon weekend, we had about an hour and forty five minute window for true deep sky observing (1:45am to 3:30am), and a much longer observation window with the moon up. After moonset, we noticed that there was a slight aurora going on in the north but since (most) of the targets we were interested in were in the south it was of little import. Temps were around 45-50F, humidity was low, SQM was 21.56, and seeing was around Pickering 4.
Observations made with the moon up showed the glare you'd expect from the lack of a shroud. Although it's listed as an option, it's a necessity for anything other than dark, dark sky viewing. If you're thinking about one of these, add the cost of the shroud into the price.
Another item you'll want to budget for - a coma corrector like the Paracorr. My personal "œmust have Paracorr" point is when the focal ratio becomes faster than f5, although I can deal with it (if I have to) down to around f4.5. At f4.2 however, I feel that most observers really aren't getting everything they can out of the system without some form of coma correction.
With the moon down, the scope was an absolute joy to use. The spiral arms in M51 were obvious. M13 was a brilliant blue white ball of stars, resolved across the face. M71 was superb, as was the Ring.
Balance was not an issue with the two eyepieces we used that evening: Nagler 31 and Ethos 13.
While the lack of a Paracorr was obvious, the views (on axis) were sharp and had wonderful contrast. Fifteen inches is a significant amount of light gathering to use from a dark site, and this little guy makes for a wonderfully portable galaxy grabber and glob buster. Every OMI mirror I've looked through has been excellent, and this one looked to hold to that standard.
One issue I've noted with other ultra-light / ultra-compact designs is that due to the lack of mass, they often become a bit skittish and jump around as you move them. The UC exhibits that tendency, but to a lesser amount - most likely in part due to the 2" thick mirror. Note that Obsession touts this scope as Ultra Compact not, Ultra Light. In my opinion, everything is a trade off - the sheer act of making the telescope compact and light means you're going to lose some stability. While Obsession didn't manage to pull off a miracle, the 15" UC is actually better in this regard than I expected, and I'm told with the production rocker it should be better yet.
The UC is designed to provide a method for one person with a small vehicle to get a decent amount of aperture (and the rest of their stuff) to a dark site. It does so with aplomb. If you're like me; all thumbs when it comes to amateur telescope making, but still want a portable large aperture telescope and looking hard at the UC, then the natural question is which one to pick. If the height to your eye is 61 or 62 inches or more, and you absolutely do not want to haul a step stool to your dark site, then the 15" becomes the logical choice. If money and size aren't issues, personally I'd opt for the 18" UC. In terms of the views - 15" is nice, but 18" is better. Aperture rules.
The UC line has come on the market at an auspicious time. Now that we're in the realm of $4+ for a gallon of gas, I suspect we're going to see the end of many of the large vehicles we've used to transport our toys to dark sites. It's good to know that when the time comes to get rid of my truck I'll still be able to take along a large aperture telescope. I rather suspect these will be a sizeable success for Obsession.
The Obsession 18" f4.2 UC
Birth of a New Classic
by Tom Trusock - June, 2007
Gordon Pegue at Okie-Tex 2007
Albert Highe, Mel Bartels, Greg Babcock, John Hudek, and others have spent years trying for that perfect portable dob. If you're active in the ATM scene, you've had glimpses of several different lightweight designs, but for us poor schmucks who don't know a hammer from a drill, well, we're stuck dreaming. Yes, there's always been trade offs for an ultra compact design: shroud coverage, flexture, and an exposed mirror but for many of us the biggest is the lack of a major vendor. Till now, if you wanted a large aperture ultra compact scope you had some rather limited choices.
Obsession Telescopes has been around for a while. Owner Dave Kriege has been given his due for his hand in the current dobsonian revolution, and Obsession design is often imitated by ATM's. Some might not be too happy about that, but Dave's attitude is just the opposite - he helps where ever he can, even to the point of writing a how-to book and supplying parts to the do-it-yourself crowd.
The classic Obsession design grew out of a desire to make large aperture telescopes portable, and there is no doubt it's weathered the test of time quite well. Unfortunately, city dwellers can attest that skies have gotten worse, gas prices have increased, and the size of the average vehicle is decreasing to cope. Yes, taking an 18" classic Obsession to a dark site in a Prius is an entertaining thought, but reality is a bit more frustrating. Especially if like so many of us, you just don't seem to be getting any younger.
So say hello to Dave's little friend: the Obsession 18 f4.2 Ultra Compact or UC. The UC's aren't intended to replace the original Obsession (henceforth referred to as the "Classic"), but they are an addition to the product line for those who need an extremely portable scope.
Obsession Telescopes unveiled the design publicly at Texas Star Party this year, but only recently finalized the prototype. They've now entered the production stage, and we've got an exclusive first look at this revolutionary telescope. Early this summer, I spent 5 days at a gathering in Michigan's UP with some good folks - Obsession Telescopes Dave Kriege among them. He brought the final UC production prototype along for the ride, and not only proceeded to put on an excellent dog and pony show, but better yet - he let me and other amateurs actually observe with the scope.
We were impressed. But more on that later.
As I've mentioned, there are always design trade-off's involved in an instrument. Previous ultralight designs have sacrificed weight for stability - resulting in both flexture and, well, a skittishness in the motions. Lets face it, current non-ultralight scopes have spent 10-15 years evolving and are quite good. To take it to the next level as per portability, it seems logical that you'd have to give up something.
The UC gives up very little - except size.
Collapsed, the scope is absurdly small. The rocker box isn't more than a couple of inches off the ground (if that), and there really isn't a mirror box. (Kriege referrers to it as a virtual mirror box.) The bearings are reinforced with steel plate, and fold into two pieces for the ultimate in portability. All exposed steel is stainless. The primary support system utilizes a Kevlar sling, and an 18 point cell that has a small cooling fan attached. The mirrors are f4.2 and will be supplied by long time associates Galaxy and OMI. They are (what is termed as today) standard thickness mirrrors.
As you can see, the Obsession Ultra Compact is a six pole, single ring upper truss design. The six poles are fastened together at the ends and accordion to make life easier during transport - no loose poles floating around. They also do a darn good job of eliminating flexture. This scope stays in collimation both when parked or slewing.
On the single ring upper truss assembly (UTR) you'll spot a couple of interesting things. First off, the FeatherTouch focuser is standard, and it's mounted on top of the UTR. The foam covered handle is an excellent touch and is in the perfect location for most observers. The Telrad is mounted on a post that also projects above the UTR and in an interesting design move, the post is hollow and is used to hold the counterweights - three of which are supplied with the system. This setup allows the user to go from lightweight mono eyepieces to heavy binoviewers with a minimum of balance issues.
Those of you wishing to computerize the setup need not fear about clearance - a recess is provided in the ground board for the AZ encoder and provisions have been made for a virtual encoder mount for the ALT. The computer itself is mounted to a clip that attaches to the truss poles, placing it in a very natural position.
One of the major concerns dealt with the initial apparent lack of a shroud. Dave Kriege is well aware that most of us consider a shroud necessary (for a number of reasons), and has devised a system that keeps the shroud tight over the scope and out of the light path. The shroud will be an option for the production units. Because the focuser is mounted above the single ring UTA, a light shield is included as standard equipment.
The secondary sports tool less adjustments, and features an Astrosystems dew guard kit. (No, the high tech secondary cover shown in the images above is not included. You'll have to use your own sock.) The shroud ends a couple of inches above the primary, but thermal inertia should work fairly well to keep dew from forming on the primary until way into the early hours - at which point you'll most likely be asleep anyway.
As you can see, the mirror is more exposed to incidental dust and dirt than in a traditional design, but that's one of the few trade-off's for the ultra light weight and portability of the Obsession UC.
Wheel barrel handles are available for the observer who wants to keep the scope fully assembled and roll it out to observe. The scope can be locked into position using a Velcro strip. Additionally, the front and back edges of the rocker box are padded to help prevent you from dinging up the corners in storage or transport.
While it's not a done deal, Obsession is considering offering the transport case shown in the photos for resale. While increasing the room the scope takes up, it allows for "no worry packing" - a boon for those of us who have vehicles that are already crammed to the gills.
Initial setup and collimation took a matter of mere minutes (probably less time than it took you to look at the pictures). The collimation adjustments for the secondary are easily reached from the eyepiece, making that last bit of tweaking a snap.
Observing with the scope was a blast. The 18" UC is - hands down - the best star party scope I've had opportunity to use.
The shroud and shield worked well - contrast was very good, and there were absolutely no dew issues. Another fear; unwary observers would kick sand and dirt on the mirror proved to be pretty much a non-issue. But as the optics arrived a little dirty (this is the 5th prototype this optic set has seen light in) Dave Kriege demonstrated how the open design lends itself to cleaning the primary.
At f4.2 you really do yourself a disservice if you're not using a paracorr but with it, images are spectacular. The 31mm Nagler in particular makes an excellent low power eyepiece for picking off targets. It provided a true field of just over a degree and magnification around 70x.
We spent the first part of the evening with the telescope, and I had ample opportunity to put it through it's paces. The scope was at a decent height - I'm 6 foot 2 inches, and most of my observing was done with my feet on the ground. For targets within 10-15 deg of zenith however, a small step was necessary. In use, the UC didn't feel like an ultralight. For one reason or another, the ultralights I've used have been a little skittish. Not much of that here. And you're probably wondering about the patented "Obsession" motions - while the motions weren't quite as smooth as the classic Obsession, they were as smooth as or smoother than most of the other dobsonians on the market. I expect they can be tweaked a bit further, but as it stood, they were most certainly good enough. There was a slight bump evident in the alt motion at one vertical position, but Dave Kriege tells me this will be pretty much eliminated from the production scopes. The only other differences will lie in an improved fit and finish.
And speaking of production: the 18" Ultra Compact is expected sometime this fall. Pricing is (tentatively) set around that of the Classic with the FeatherTouch upgrade.
All in all I was very pleased with the performance and portability of the telescope - so much so that I'm giving serious consideration to one of the planned 15" versions for my own personal ultimate travel / star party scope. The 18" was lightweight, quick to setup and easy to use with very few drawbacks as compared to the classic design. Everything that a telescope is supposed to do, it did. And quite well at that.
Twenty years ago, Dave Kriege helped revolutionize the dobsonian telescope.
He's doing it all over again.
by Cameron Gillis - February 9, 2007
This review is based on my many "inspirational" observing experiences through my 18" Obsession. I hope you enjoy reading about my personal experience with this fine scope and even find it useful in helping you make your decision on selecting an Obsession as your own instrument of a lifetime.
Let's start by taking you back to the beginning of my quest for the perfect deep-sky scope; before Obsession. After many years observing through smaller instruments and cycling through "aperture fever", I was finally ready for my very own "final upgrade"! I determined there were two paths I could take: 1) high-tech computerized telescope with GPS and loaded with "features", or 2) pure simplicity and quality aperture. The former would take me down the path of digital astrophotography and merge my interest of computers with astronomy while the latter would take me down the path of observational deep-sky astronomy in one of its purest forms.
I seriously contemplated going for one of Meade's new-fangled RCX400s. This would satisfy all of my computerized astrophotography adventures for years to come. As I was going through my evaluation "soaking period", my thoughts swayed more and more towards the simple elegance of pure observational deep-sky astronomy. I began thinking it wise to let the faster-paced computer technology run its course while I maximized my visual enjoyment through larger aperture and simpler mechanics. Indeed, some time in the distant future, I fully intend on rounding out my astronomical portfolio with a "higher tech" scope (probably after they bring out the RCX5000) and then again, based on my experience with the Obsession so far, perhaps that distant future may remain very distant for many years to come.
As I was heading down the path of determining the one instrument that would give me my best mileage, I browsed the web and read the multitude of reviews on Dave's Obsession Web site (www.obsessiontelescopes.com/). It didn't take me long to realize that the Obsession was exactly what I was looking for. I had finally pegged my primary choice instrument: a beautiful 18" Obsession. As I continued my research, I came to the clear conclusion that there was really no substitute for elegant simplicity combined with pure quality. Let me just say now, based what I've experienced with my own 18" Obsession, I believe Dave's design has reached the epitome of the ideal "commercial" deep-sky observational telescope!
Yes, I had made my decision. I would purchase the beautiful, top-quality, fine-craftsmanship 18" Obsession Telescope. After many years of "star hopping" and getting to know my way around the night sky, I felt fully prepared for a high-quality large-aperture telescope. My last 14+ years of owning a beautiful Televue Genesis 4" have made me appreciate top quality optics and mechanics. Indeed, I was looking forward to "benchmarking" the mechanical and optical performance of the significantly larger Obsession!
Another key factor in my decision to go for the Obsession was my family moving to a new private "Dark Sky" location where I could "wheel" the Obsession straight out of the garage and enjoy my own private dark sky. The only limiting factor was the horizon was limited to -10 degrees dec. (just enough to catch Orion nebula and Rigel) due to very tall trees on my South horizon. Even if we eventually move from this location, the portability and set-up time of the Obsession are very attractive when considering I could easily pack it to go in our Minivan!
Of course, the final, final decision was made in consulting with my dear wife who gave me the "go ahead" that I should get the biggest scope I could practically use while providing me with a lifetime of quality astronomical enjoyment. Yes I love my wife very much and her "balanced" encouragement for my hobby :) I was now ready and confident to get the telescope of my dreams!
The Order, Arrival, and Setup
As soon as I made the decision, I e-mailed Dave with great excitement and anticipation. I was pleasantly surprised when he responded directly to me almost immediately! I placed my order on Friday, February 25th, 2005 including the following:
- Obsession 18" f/4.5
- 2" Barlow-Laser Collimator
- Starlight Feather Touch Focuser
Dave promptly replied with some great suggestions and feedback to further "calibrate" my order to my needs. Thank you, Dave!
The mirror arrived first, on Thursday, March 10th. It came directly from Galaxy in a secure, well padded ~50 lb box, about 2' square and 6" thick. I was amazed it only took about 1 week to arrive (shipped on Thursday, March 3rd). My very own beautiful 18" primary mirror arrived safe and sound and I dared not open it until I was ready to assemble the full scope.
Dave had my scope completed and ready for shipment by Monday, March 14th! Right after this, it was packed / shipped to my new home by Friday, March 18th. Dave was extremely helpful through the whole order and Margo was a great in arranging smooth packing and shipping.
My scope arrived in perfect condition a week later (Friday, March 25th) in 4 boxes from UPS: one box each for trusses, upper tube assembly, mirror box, and cradle. As I commenced the "unpacking "ceremony", I wanted to take it all in and enjoy building this instrument so I decided to do it all inside our living-room! I was impressed by the solid quality of the packing and as each piece revealed itself, it was quite clear to me the attractive quality of this instrument. What a beauty (I loved seeing the wood finish with my own eyes in my own house!)... I was ready and very excited about carefully assembling my Obsession.
Before getting too excited, I sat down and read all of the documentation and also watched the excellent video Dave produced on assembly and maintenance of his Obsession line. I successfully set-up and collimated my scope, enjoying every fine detailed step along the way.
After the scope was completely assembled in my living-room, I waited patiently for clear skies up here in the North West while Thunder Storms continued to roll through! It was already such a rewarding experience ordering and receiving my scope while appreciating the fine attention to details incorporated into the Obsession design! I was now a very happy and proud owner of a beautiful Obsession... Next step, "first light"...
After many patient days and nights (actually, weeks and months) of waiting for a good clear night here in the Northwest, the clouds finally cleared to give me a chance to "test drive" my new Obsession! I must say it is the most pleasing and joyful instrument to use with absolutely beautiful views through optical and mechanical excellence!!!
My first night was partly cloudy with a crescent Moon and Saturn in Gemini. I went through my new ritual of setting my Obsession up, letting it cool down and arranging my observing table with chairs in preparation for the nights observing with great anticipation. Using the barlowed Laser, I was able to collimate the scope very easily during the cool down period (actually, far easier than I would have thought). I gave my new Obsession about 1 hour to settle to ambient temperature then immediately pointed towards Saturn. As I was aligning the scope with the Telrad and scanning for Saturn, I couldn't believe my eyes to "accidentally" see the Eskimo Nebula casually pop into view so bright! What a wonderful surprise to see this so bright and distinct! I could clearly see the inner ring with outer "parka" smoke ring. From this point onwards, I knew my observing experiences would forever be changed to a new level of enjoyment!
I nudged my new scope over to Saturn and my first impression was how crisp and clear and intensely bright it was! Quite blinding actually. With this enhanced brightness came amazing clarity and color definition and contrast. I've never seen Cassini's division and the bands look so well defined. What also struck me was there was a "loose cluster of stars" hovering around Saturn that were clearly its moons! Wow, so enriching. I watched and popped in various eyepiece combinations and was able to push to 400x with my 5 mm Nagler. What amazed me was how transparent and smooth the mechanics were. I was able to easily nudge and track Saturn at this high power and capture beautiful moments of steady seeing where I couldn't believe the details that would reveal themselves to me. For the first time in using a telescope, I felt like I was purely observing and the telescope became a "transparent" extension to my vision. By the time I became conscious of myself expressing my amazement aloud, clouds started coming in too thick for the Obession to penetrate so I had to sigh and pack up for another night. However, I ended the night with a big smile on my face knowing that when the next time was right, this baby will reveal many more beautiful views of the heavens to my eyes.
I had to wait again for some time before I could go out a second time and again it was partly cloudy. Oh well. that's the Northwest for you. All the more reason to get the best view you can afford with what precious observing time we have. This time, I started in Leo. and let me just tell you that I stayed in Leo for as long as I could until the clouds came in again! The galaxies are simply beautiful through this scope. They appear everywhere :) I'm very familiar with star-hopping but I never thought I would be doing "galaxy-hopping"! You really need Uranometria 2000 (which luckily I had) in order to identify all of the galaxies you stumble upon while scanning. It really is a deep sky observers dream come true. Yes, the clouds game in again and another smile on my face :)
My third night was finally clear but with a full moon! I thought, "why not". let's see what the Obsession can do in the "worse conditions". I was not disappointed. I was still able to check out the galaxies in Leo and while the contrast was reduced, the views were very pleasing. It was simply great to be free to swing this scope around without any restrictions and have another night of fine observing.
Finally, the night I'd been waiting for had arrived. no moon and perfectly clear. Rather than write a single paragraph of my experience, let me just say it was awesome and I had the Obsession swinging from object to object like a dream.
Since those first couple of nights, I logged many hours and hundreds of objects (actually, 480 and counting) and enjoyed many repeated visits to my favorites (M51, Veil!!!, Cats Eye, Omega, Dumbell, Ring, Orion, 891, 4565, M5, M33, M81/82, M106). I am happy to say that the summer in the Northwest is absolutely beautiful (both in day and night) and I had many great nights letting myself become obsessed with my wonderful Obsession instrument.
The Experiences (of a lifetime)
Over the course of becoming a seasoned Obsession observer and developing a keen sense of what this instrument can do, I jotted down my inspirational thoughts as I logged my observing sessions. Here are the "highlights" for your enjoyment:
- Imagine starting out each observing session by using the detection of M51's spiral arms as your benchmark before diving into fainter deep sky objects.
- It's a great feeling when you know your way around the sky (I think it is an essential part of astronomy). What's really cool is when you're able to swing this baby through the "Gems of the sky" by heart.
- Honestly, you quickly adapt and become accustomed to the consistent enjoyment of an Obsession! It never lets you down.
- With it's great aperture, I often find that the sky rotates too fast since I can easily spend 1 hour observing 10's of objects in one quadrant of a constellation.
- The views this scope give to me are often so breath-taking that I often find myself talking to myself aloud saying things like "nice", "very nice", and "just beautiful". Indeed, I have entered into the "Obsession Zone" :)
- Imagine pointing your telescope and finding galaxies not shown on Sky Atlas 2000... You're talking U2000 and "galaxy hopping" (not only star-hopping). We're talking cruising the heavens in "style" :) Galaxy groups and clusters are within your grasp...
- Galaxies are everywhere! You start to get used to easily seeing NGC 6207 in Hercules near M13 and NGC 6552 near Cat's Eye Nebula which is, by the way, absolutely beautiful in my 11 mm Nagler at 184x, taking on a 3D perspective...
- Beautiful Planetary Nebulas, Galaxies, the central star and structure in the Owl Nebula, M81/82, 4565 dust lane, M51 Whirlpool!!! M64 Black Eye... Galaxies galore in Leo! The list goes on forever and so does the enjoyment.
- Imagine observing your favorite deep sky objects at 400 x comfortably and with pleasure on nights of steady seeing. Life is good with the Obsession :)
- Dave's recommendation for getting the OIII was excellent! I cannot tell you enough how superb observing the Veil Nebula is with this scope and filter. Talk about "cruising the Veil in style". Tendrils, twisting, turning, islands, protrusions, inlets, waves, knots, and every possible word you can use to describe nebular structure :) You simply have to see this with your own eyes.
- Good and sturdy. With the mechanical performance of this scope, I find nothing is missing like I though might be without tracking. So smooth at 404x with my 5 mm Nagler!
- "Easy on the eyes" both in day and night. Very comfortable viewing for long nights you feel relaxed while observing.
- As I re-observe objects from my past (before Obsession), I find myself reclassifying "bright" on my observing notes! Objects that were barely discernable or invisible in smaller scopes are distinct and "comfortable" to view even at higher powers through the 18".
- You don't even think about the scope you just observe... The instrument is so seamless you simply focus on the joy of viewing rather than "fiddling" with the instrument wishing for this or that... what a joy!
Here are some hints I can offer based on my experience to maximize the enjoyment of your Obsession experience:
- You'll want to read the instructions on this baby :) You'll be pleasantly surprised as the "zip-lock" bag unveils its secrets as you assemble the scope. Quite an enjoyable experience and all part of the pleasure of owning such a grand instrument :) Dave has his Obsession "bill-of-materials" package down pat...
- No need for counter-weight. The natural tendency without eyepiece is to slightly pivot upwards. I ended up using the "shroud bag" around one of the support rods at the upper tube assembly filled with the barlowed laser and the tube has perfect balance.
- Dave commented that he's been using Galaxy for 17 years and Torus for the last 7 years and both have top notch quality while complimenting and supporting the supply while keeping up with demand.
- The Feather Touch focuser is absolutely perfect supporting all my range of eyepieces and barlows (from 40 mm PENTAX to 5 mm Nagler or 11 mm Nagler with 3x Barlow). Solid performance with incredibly smooth movement, long range of focus, robust for holding heavy eyepiece combinations and adjustable base. The way I see it, why not match mechanical excellence together if you're going for the best (no compromises). Werner (Starlight Instruments) was extremely helpful with helping explain how to rotate the focuser.
Memories and Closing Comments
To give you an idea how excited and how much anticipation / patience I had about getting my very own 18" Obsession, I still remember the first time I looked through such a large telescope. It was a 17.5" Dob around 1986 (when I was a teenager) at a star party up in Canada. This first experience had left such a big impression on me that I still remember viewing the "Eskimo Nebula" with detailed structure in the "face" and outer ring. It was such a long time ago, I forgot the name of the pair of interacting galaxies I was looking at but I remember seeing clear structure and "antenna" along with other galaxies showing clear mottling, spiral structure and well defined features using direct vision rather than averted vision... I also remember that I wanted to see much more and point the telescope myself to whatever I wanted. This lasting impression has been with me all these years and now that I'm all "grown up" and have "earned" my very own Obsession, there is no more rewarding experience than to own such a top-notch telescope that allows me to dig deeper into the sky for many years to come!
After 20+ years of observing through smaller instruments, nothing beats the combination of quality optics, elegant simplicity, mechanical excellence and pure aperture! What can I say, I allowed myself to indulge and become fully Obsessed :)
Thank you so much Dave, for creating this wonderful instrument for my lifetime enjoyment and the enjoyment of many other fortunate amateur astronomers around the world!
by Alan Dyer - Astronomy Magazine - March 1991
M104 by Glenn Schaeffer - 20" Obsession
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...
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"
by Ed Ting of Scopereview
Obsession 18" f/4.5 - jump to 20" review
M51 by Johannes Brachtendorf
in Rottenburg Germany - 18" Obsession
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!
Bubble Nebula by Glenn Schaeffer
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.