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Tom Trusock
Reged: 02/26/02
Posts: 29969
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22" Obsession Telescopes Ultra Compact
Edited by Mike Loffland (10/13/09 03:36 PM)
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stevecoe
"Astronomical Tourist"
Reged: 04/24/04
Posts: 2642
Loc: Arizona, USA
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Tom;
I have had a chance to use two of the 18 inch UC scopes and I was not impressed. I found them both to be very "twangy". Just touching the focuser at 150X made it difficult to find focus because the scope what moving so much. You would take a guess at focus and then wait for 10 seconds for the image to settle down and guess a new focus point. It is possible that something was done with the setup of these scopes or that there has been an upgrade that will help this problem, but I certainly came away being sorry for my friends who had spent all that money for such a poor instrument.
Clear skies;
Steve Coe
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TeleVue 102 refractor on CGEM mount
10 inch f/4.7 Newtonian
Author "Deep Sky Observing" Springer-Verlag
Author "Nebulae and How to Observe Them" Springer
Canon Xt astrocamera with Hutech modification
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skyward_eyes
Carpal Tunnel
Reged: 12/12/06
Posts: 2101
Loc: Arizona
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I too know someone who owns one of the 18" UCs, he had to add a few upgrades to get it to where he wanted it. I hope the 22" UC is better.
I will also like the Classic Obsession though!
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auriga
scholastic sledgehammer
Reged: 03/02/06
Posts: 794
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Quote:
Tom;
I have had a chance to use two of the 18 inch UC scopes and I was not impressed. I found them both to be very "twangy". Just touching the focuser at 150X made it difficult to find focus because the scope what moving so much. You would take a guess at focus and then wait for 10 seconds for the image to settle down and guess a new focus point. It is possible that something was done with the setup of these scopes or that there has been an upgrade that will help this problem, but I certainly came away being sorry for my friends who had spent all that money for such a poor instrument.
Clear skies;
Steve Coe
Steve,
My complaint is with the design itself.
The heaviest component is 90 lbs. The mirror itself weighs 65 lbs.
Two errors in design from an ergonomic viewpoint:
1.Keeping almost all the weight in one place, a mistake Portaball also makes. Any design that combines the rockerbox with the mirror box, or has a non-removable mirror, does this.
2.And using a thick 2" mirror, which is Dave Kriege's position. A 1.6" mirror, or better, a 1.25" mirror would save a lot of weight. And the mirror should be made removable.
Many people don't mind the ergonomic issues and don't mind lifting 90 pounds, or they try to finesse it with wheelbarrow handles, or winches, but I consider putting almost all the weight in one place with components that don't separate easily, to be a blunder *from an ergonomic point of view.*
I like the idea of compactness, which this scope achieves. I respect many of Dave Kriege's innovations in telescope making. I appreciate that he has made and sold thousands of quite good Dobs and that they are justly widely admired.
When I was 21 I did construction work and lifted 94 lb. bags of cement all summer. But I am no longer 21. If you are young enough, the weight of the heaviest component may be trivial for you, and my ergonomic critique may not apply to you at all.
I can see that for many people, compactness is of much greater importance than the weight of the heaviest component. For them, the design may be just what they want and need.
But not for me. I think that for anyone over 40, lifting this scope may be asking for trouble.
IMHO.
Bill Meyers
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Tom Trusock
Reged: 02/26/02
Posts: 29969
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Quote:
Tom;
I have had a chance to use two of the 18 inch UC scopes and I was not impressed. I found them both to be very "twangy". Just touching the focuser at 150X made it difficult to find focus because the scope what moving so much. You would take a guess at focus and then wait for 10 seconds for the image to settle down and guess a new focus point. It is possible that something was done with the setup of these scopes or that there has been an upgrade that will help this problem, but I certainly came away being sorry for my friends who had spent all that money for such a poor instrument.
Clear skies;
Steve Coe
Hi Steve,
There are definately trade offs with any ultra compact or ultra light design - this is one of the reasons that the classic design is still on the market - and stability is probably the biggest. There's just no substitute for mass. On the other hand, mass translates into size, and that translates into increased issues with portability. FWIW, there sure didn't seem to be much "twangy" in this one. A 13mm ethos w/ paracorr combination (about 200x) left nothing to the imagination as per focus. And vibration wasn't an issue for that matter either - even with some wind action going on.
Personally, having used all three of the models in the UC lineup, I certainly don't think I'd call them "poor" instruments. But I guess YMMV, right along with what you're looking for. Everything's a compromise. Always best to try things out firsthand if you're shopping around and see what you can live with and what you can't.
Personally, I sure could live with this scope. Well, until my wife found out I spent 10 K that is. 
T
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Hyperbole - undoubtedly the best thing ever.
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turtle86
professor emeritus
Reged: 10/09/06
Posts: 683
Loc: Red Sox Nation
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Thanks for the review. The 22 certainly sounds promising, as it appears to be stable enough and not "twangy." One thing I like about the design is that it is low profile and takes a few inches off the height. I do wish the heaviest component didn't weigh 90 pounds...
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Hi Steve,
There are definately trade offs with any ultra compact or ultra light design - this is one of the reasons that the classic design is still on the market - and stability is probably the biggest. There's just no substitute for mass. On the other hand, mass translates into size, and that translates into increased issues with portability. FWIW, there sure didn't seem to be much "twangy" in this one. A 13mm ethos w/ paracorr combination (about 200x) left nothing to the imagination as per focus. And vibration wasn't an issue for that matter either - even with some wind action going on.
Personally, having used all three of the models in the UC lineup, I certainly don't think I'd call them "poor" instruments. But I guess YMMV, right along with what you're looking for. Everything's a compromise. Always best to try things out firsthand if you're shopping around and see what you can live with and what you can't.
Personally, I sure could live with this scope. Well, until my wife found out I spent 10 K that is.
T
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skyward_eyes
Carpal Tunnel
Reged: 12/12/06
Posts: 2101
Loc: Arizona
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The UCs were made to be Ultra Compact not Ultra Light.
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Tom Polakis
scholastic sledgehammer
Reged: 12/20/04
Posts: 767
Loc: Tempe, Arizona
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Tom
I purchased an 18" U-C about 18 months ago, and after some considerable modifications, have been able to make it work out for me. At the risk of belaboring points that I have made on this forum and others, let me add my two cents.
I don't find the telescope's vibration due to focusing to be too objectionable. I routinely use it at 500x and above, and find that the vibrations damp in a couple seconds. Contrary to your review -- and perhaps this was fixed in the 22" model -- any breeze at all, much less 20-20 mp,h makes the scope vibrate unacceptably. Like most large Dobs with low bearings, the oscillation frequency is rather small, on the order of 2 or 3 cycles per second.
You say that the tracking is smooth, but that was anything but my experience regarding altitude. Due to the continuous Teflon strip, the starting friction caused me to overshoot the target repeatedly until I eventually would luckily get it to the center of the field. Fortunately, replacing the strip with two pads put the appropriate pressure on the bearing, and the problem is now solved.
There are a large number of issues with the 18" that Kriege elected to leave to the customer to address, and I won't go over them again here. What I find unfortunate is that he did not consider remedying any of them in his new 22" design. None of the issues have anything to do with compromise of a compact design; they are merely oversights that would have cost little in the way of effort or expense to fix. But there they are in the 22" model, as if the 18" represented perfection.
You state that the "21mm Ethos eyepiece pretty much stayed in the focuser all night." Maybe this was part of the reason for your favorable review. Observing at 112x in a 22-inch telescope may have masked some of the problems that are more evident at higher magnifications. In my humble view, the number one reason to buy, haul, and set up a large telescope is its ability to easily handle high magnifications. In other words, a 2mm exit pupil corresponds to 280x in that 22-inch U-C. Use it to your advantage!
Tom
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Tom Polakis
Tempe, AZ
Visual observing, DSLR photography, lunar & planetary imaging
http://www.pbase.com/polakis/
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auriga
scholastic sledgehammer
Reged: 03/02/06
Posts: 794
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Quote:
The UCs were made to be Ultra Compact not Ultra Light.
Hi,
Exactly. It is a mistake of design, not of execution.
Ultra-light was sacrificed to ultra-compact.
Or, to put it another way, weight of the heaviest component was a free variable in the design, free to take whatever value was dictated by the design goals in the rest of the system.
Clear skies,
Bill Meyers
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Tom Trusock
Reged: 02/26/02
Posts: 29969
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Quote:
Tom
I purchased an 18" U-C about 18 months ago, and after some considerable modifications, have been able to make it work out for me. At the risk of belaboring points that I have made on this forum and others, let me add my two cents.
I don't find the telescope's vibration due to focusing to be too objectionable. I routinely use it at 500x and above, and find that the vibrations damp in a couple seconds. Contrary to your review -- and perhaps this was fixed in the 22" model -- any breeze at all, much less 20-20 mp,h makes the scope vibrate unacceptably. Like most large Dobs with low bearings, the oscillation frequency is rather small, on the order of 2 or 3 cycles per second.
You say that the tracking is smooth, but that was anything but my experience regarding altitude. Due to the continuous Teflon strip, the starting friction caused me to overshoot the target repeatedly until I eventually would luckily get it to the center of the field. Fortunately, replacing the strip with two pads put the appropriate pressure on the bearing, and the problem is now solved.
There are a large number of issues with the 18" that Kriege elected to leave to the customer to address, and I won't go over them again here. What I find unfortunate is that he did not consider remedying any of them in his new 22" design. None of the issues have anything to do with compromise of a compact design; they are merely oversights that would have cost little in the way of effort or expense to fix. But there they are in the 22" model, as if the 18" represented perfection.
You state that the "21mm Ethos eyepiece pretty much stayed in the focuser all night." Maybe this was part of the reason for your favorable review. Observing at 112x in a 22-inch telescope may have masked some of the problems that are more evident at higher magnifications. In my humble view, the number one reason to buy, haul, and set up a large telescope is its ability to easily handle high magnifications. In other words, a 2mm exit pupil corresponds to 280x in that 22-inch U-C. Use it to your advantage!
Tom
Hi Tom,
Good to hear from you!
From previous discussion, I seemed to recall that you weren't satisfied with the motions (the ones I remember were a bump in the teflon where the bearing hinge was, and you saying you had a tendency to overshoot) and therefore I made a point to look at that with this one. It may have been the increased mass of the primary, something unique to your setup or just not something I ran into (for whatever reason) but I didn't see a problem with this one.
I agree completely that lower powers aren't nearly the test that higher powers are, and that this may indeed have masked some issues with stability. FWIW, In addition to the 21 we also used the 31 Nagler and the 13 Ethos. The 13 Ethos provided around 200x with the paracorr in place. We didn't go higher, but that had everything to do with the weather conditions that evening. Still, at the powers we used, tracking and locating were both quite smooth, and I didn't notice any tendency to overshoot. Nor did I see anything that would lead me to believe that I'd run into this down the road. I unfortunately don't have long term access to the telescope so I won't be able to investigate in more detail. However, my thoughts are that it simply won't be as stable as say an obsession classic (I observe at 800-1200x on a routine basis) or as well baffled, but for the design goals of portability and the trade offs inherent therein, it seems adequate. Is there room for improvement? Probably.
I don't think I've seen too many dobs over the years that haven't been tweaked for improved performance in one way or another. I'd be surprised if one hadn't done anything. I am glad to hear that you finally got the motions to your liking, thank you for noting your solution. Given your background, I was (and still am) somewhat surprised that you hadn't built your own highly portable scope, as that's the only real way to ensure it's design is 100% adequate to your own personal requirements from the ground up. Me, I'm all thumbs when it comes to that so it's not really an option.
No non-ATM dob is perfect for any one user (and some folks are more demanding than others). IMO, It's extremely important that anyone considering purchase of an expensive piece of gear like this make it a point to travel to a few large star parties, use one themselves and talk to everyone on the field to see if the trade off's are ones they can live with! Obviously there are folks who are not fond of this design. OTOH, from what I've seen, I could certainly could. YMMV.
I did not intend to give the impression that it was rock steady during the strongest breezes. But as per damping, it was usable even then, and was nothing worse than I've seen in any other dob. One problem I noted was a tendency to weather vane in the strongest breezes. When that happened, we usually waited till the wind had died a bit. Frankly I didn't even consider it worth mentioning as any dob with free motions and a shroud would have done the same thing.
Tom
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Hyperbole - undoubtedly the best thing ever.
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Tom Trusock
Reged: 02/26/02
Posts: 29969
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Quote:
But not for me. I think that for anyone over 40, lifting this scope may be asking for trouble.
That's a good point.
As you acknowledge, there's workarounds. In addition to what you mentioned you could also remove the primary for transport. But even though I'd rather transport this than my 18" classic truss, I completely agree - that's a lot of weight. And it's very important to consider that it may be a better option for an individual to use a trailer and winch for loading and transporting.
Mirror weight as the final unreduceable component is going to be an issue with any large telescope until honeycomb mirrors become a viable amateur option. And then you've got some increased stability issues staring you in the face, but perhaps some of those could be overcome by tension in the right places...
Anyone used a string dob?
T
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Hyperbole - undoubtedly the best thing ever.
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Tom Polakis
scholastic sledgehammer
Reged: 12/20/04
Posts: 767
Loc: Tempe, Arizona
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Quote:
From previous discussion, I seemed to recall that you weren't satisfied with the motions (the ones I remember were a bump in the teflon where the bearing hinge was, and you saying you had a tendency to overshoot) and therefore I made a point to look at that with this one. It may have been the increased mass of the primary, something unique to your setup or just not something I ran into (for whatever reason) but I didn't see a problem with this one.
Hi Tom,
Actually, there is no 'bump' with the continuous Teflon strip in the U-C, and I'm pretty sure that's why he went with the strip rather than pads. By replacing the strip with pads as I did, you create a bump at one discrete altitude, but have vastly superior altitude motion, resembling the Obsession Classics. Kriege's own book recommends a pressure on the Teflon of 10 to 15 psi, and then he violates his own criterion with the strip. Out of the box, it was impossible to center objects in altitude with the strip. I can't see how it would be any different in the 22-inch, but maybe it is.
Quote:
However, my thoughts are that it simply won't be as stable as say an obsession classic (I observe at 800-1200x on a routine basis) or as well baffled, but for the design goals of portability and the trade offs inherent therein, it seems adequate. Is there room for improvement? Probably.
My point that is often being missed is that it is trivial to make the U-C every bit as well baffled as the Classic. Just make that piece of Kydex on the upper cage the proper length! I can see by the photos that it's too short, and light is going to shine right into the focuser, as it did with mine. I had to go to a place that sells Kydex, and have them cut a piece that's a few inches longer. That's not a "compromise of a compact design" as much as just ignoring an obvious oversight. He should fix it rather than ignore it. It's not just the baffling, but also other problems that I had to fix on a $7K scope. None of these were examples of me tinkering and making it perfect, as I don't dabble in the ATM side of the hobby at all. They were all things that I had to grudgingly do because the U-C was deficient.
Quote:
Given your background, I was (and still am) somewhat surprised that you hadn't built your own highly portable scope, as that's the only real way to ensure it's design is 100% adequate to your own personal requirements from the ground up.
My background is that I am a mechanical engineer who mostly does flow, thermal, and stress analysis in the aircraft engine industry. I have no desire to make astronomy equipment work properly in my free time. Hence, the rather pricey Dob purchases over the years. I expected an Obsession to work out of the box. If I liked to tinker, I would have saved big money by buying a Meade or something, and modified it.
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Obviously there are folks who are not fond of this design. OTOH, from what I've seen, I could certainly could.
I like the design in concept. What I find frustrating is that there was no attempt to address the deficiencies in the 22-inch model. Again, these could be addressed with little effort or expense on Kriege's part. Me, on the other had... it took better part of some weekends to address them.
Quote:
But as per damping, it was usable even then, and was nothing worse than I've seen in any other dob.
There I will agree with you. I suppose I'm spoiled with the number of clear nights I get in that I just stop using a big scope if the wind exceeds 5 or 10 mph.
Tom
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Tom Polakis
Tempe, AZ
Visual observing, DSLR photography, lunar & planetary imaging
http://www.pbase.com/polakis/
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Tom Trusock
Reged: 02/26/02
Posts: 29969
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Quote:
it was impossible to center objects in altitude with the strip. I can't see how it would be any different in the 22-inch, but maybe it is.
Maybe, as you alluded to earlier, the issue comes back to magnifications used. I've used the 15, the 18, and the 22 - and while I don't think I've had any of them over 300x, I do not recall experiencing the issues you state as significant - or at least as significant as you make them sound. Perhaps this is much worse at higher magnifications?
Quote:
My point that is often being missed is that it is trivial to make the U-C every bit as well baffled as the Classic. Just make that piece of Kydex on the upper cage the proper length! I can see by the photos that it's too short, and light is going to shine right into the focuser, as it did with mine.
I'm guessing you're not judging the size by the photos I've posted of the 22 as the baffle is not even on the scope in those. Nor is the shroud. Nor was the mirror skirt. You must be getting the photos from elsewhere?
Baffling certainly can make a difference in contrast - particularly if you're observing from a light polluted area. As we weren't - I didn't see any problems. We could probably have observed sans baffle and shield as a matter of fact - it was that dark. So yeah, I'd agree that may be significant in some locations.
Quote:
I had to go to a place that sells Kydex, and have them cut a piece that's a few inches longer. That's not a "compromise of a compact design" as much as just ignoring an obvious oversight. He should fix it rather than ignore it. It's not just the baffling, but also other problems that I had to fix on a $7K scope. None of these were examples of me tinkering and making it perfect, as I don't dabble in the ATM side of the hobby at all. They were all things that I had to grudgingly do because the U-C was deficient.
Tom, FWIW - that's exactly what I mean. IMO, every single dob (unless you build it yourself) has things that can done to it to make the experience more pleasurable for the end user or to fit their specific needs. Choice is about picking the scope with the least compromises for your intended use. I don't think people intend this, but some of these comments almost make it sound like the scope is flat out unusable out of the box. That's not even remotely been my experience.
I'd ask you to consider writing up an article on all the modifications/improvements you've done to your 18 inch and submit it as an article for the benefit of the community. It could be a wonderful resource for people who own or are considering purchasing or manufacturing a compact travel scope.
Quote:
I have no desire to make astronomy equipment work properly in my free time.
Boy am I with you on that one. And the older I get the more intense that feeling seems to grow.
Thanks for your comments.
Clear Skies - I really envy you those... Especially this time of year! 
T
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Hyperbole - undoubtedly the best thing ever.
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osbourne one-nil
professor emeritus
Reged: 07/03/06
Posts: 710
Loc: Cumbria, England 54.5ºN 2.5ºW
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I don't know about the telescope, but it looks like your lawn needs a good water.
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Celestron NexStar 6SE
http://www.greatasby.co.uk
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Tom Polakis
scholastic sledgehammer
Reged: 12/20/04
Posts: 767
Loc: Tempe, Arizona
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Quote:
I'm guessing you're not judging the size by the photos I've posted of the 22 as the baffle is not even on the scope in those. Nor is the shroud. Nor was the mirror skirt. You must be getting the photos from elsewhere?
Yeah, the pictures are on Obsession's site.
22" U-C Pictures
Note the upper baffle length. You can imagine drawing a line that goes over the top of it, and directly into the focuser.
Quote:
Baffling certainly can make a difference in contrast - particularly if you're observing from a light polluted area. As we weren't - I didn't see any problems. We could probably have observed sans baffle and shield as a matter of fact - it was that dark. So yeah, I'd agree that may be significant in some locations.
In my experience, the only baffling that is really necessary is across from the focuser. You just can't have light from the sky directly entering the focuser, and that applies at the darkest site. I discovered the upper cage baffle issue a few miles from Lowell Observatory's Discovery Channel Telescope site, where the SQM reading is around 21.5 mag/sq. arcsec. The darkest sky in the world is light gray, and that light floods the view if you're using a wide-field eyepiece that focuses far in.
Quote:
Tom, FWIW - that's exactly what I mean. IMO, every single dob (unless you build it yourself) has things that can done to it to make the experience more pleasurable for the end user or to fit their specific needs. Choice is about picking the scope with the least compromises for your intended use. I don't think people intend this, but some of these comments almost make it sound like the scope is flat out unusable out of the box. That's not even remotely been my experience.
But it was pretty close to unusable. I had to go out and find lead shot to make a counterweight. Then in the field, I couldn't get a decent view with three of my eyepieces without cludging together an upper baffle extension from duct tape and a cereal box. The altitude bearing was not unusable, but practically so when you attempted to center objects at high power. When the equatorial tracking platform was at either end of the travel, the mirror slid around between the posts, changing collimation during the night until we made shims to bring that excessive lateral clearance to an acceptable level. These are not compromises inherent to a compact design.
I don't buy into the notion that modifying something just to make it work properly begins to compare to "souping it up" to make the experience more pleasurable. Now I did add a nice finder in place of the lead shot counterweight, and that indeed does fall into that latter category. I wouldn't expect them to provide a finder in addition to the Telrad.
Quote:
I'd ask you to consider writing up an article on all the modifications/improvements you've done to your 18 inch and submit it as an article for the benefit of the community. It could be a wonderful resource for people who own or are considering purchasing or manufacturing a compact travel scope.
That is a good idea, and I have thought about it. Since I still feel burned about paying $7K for this product, I don't know how to do that without it dripping with attitude (as my posts about it do). Let me think about giving it a try. What would be the proper vehicle for publishing such a piece?
One other thing that has been interesting is -- and I swear I'm not just being contrarian - that the very things that annoy everybody else about the U-C don't annoy me. The primary's full thickness makes the scope much less tipsy near the horizon. Sometimes, a lot of inertia is good thing. I can put in a heavy eyepiece or no eyepiece and it stays put. In my unit, the laser dot stays very well centered on the primary at all altitudes, so I don't have that flexure problem. And as long as there's no wind, the scope settles down nicely, as it did just this morning when I was imaging Mars with it at 0.17" per pixel.
Tom
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Tom Polakis
Tempe, AZ
Visual observing, DSLR photography, lunar & planetary imaging
http://www.pbase.com/polakis/
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Tom Trusock
Reged: 02/26/02
Posts: 29969
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Quote:
Yeah, the pictures are on Obsession's site.
22" U-C Pictures
Note the upper baffle length. You can imagine drawing a line that goes over the top of it, and directly into the focuser.
I think I see the picture you're talking about but I also think the angle on that one makes it deceptive. It didn't stand out as being that bad in reality. My recollection on the 22" was more like the one a couple up.
Quote:
In my experience, the only baffling that is really necessary is across from the focuser. You just can't have light from the sky directly entering the focuser, and that applies at the darkest site. I discovered the upper cage baffle issue a few miles from Lowell Observatory's Discovery Channel Telescope site, where the SQM reading is around 21.5 mag/sq. arcsec. The darkest sky in the world is light gray, and that light floods the view if you're using a wide-field eyepiece that focuses far in.
Last time I took my SQM to the site we were at last weekend, I got a reading of 21.56. There were no issues noted with stray light with the 31 nagler, 21 ethos or 13 ethos.
I've used the 22, 18 and 15 UC's up there. (I'm giving a lot of consideration to purchasing the 15" as a star party scope, but economic factors aren't favorable for me at the moment.)
Quote:
I had to go out and find lead shot to make a counterweight.
Then in the field, I couldn't get a decent view with three of my eyepieces without cludging together an upper baffle extension from duct tape and a cereal box.
The altitude bearing was not unusable, but practically so when you attempted to center objects at high power.
When the equatorial tracking platform was at either end of the travel, the mirror slid around between the posts, changing collimation during the night until we made shims...
Lead shot - I questioned Kriege on this myself when I ordered a classic from him years ago. Like counterweights, it cost more to ship the lead shot then than it did for me to go out and buy some locally. It wasn't hard to locate.
Baffling - see above
Alt Bearing - noted in previous post
Platform issue - It's not confirmed (the thought of checking for mirror slop didn't even remotely cross my mind) but putting some conversations together in my mind, I have a rather strong hunch that's been taken care of on the latest models with the addition of some o-rings on the posts.
Quote:
What would be the proper vehicle for publishing such a piece?
Write it up and send it a copy to submit@cloudynights.com and another to administrator@cloudynights.com. I don't know if you'd even want my assistance, but I'd be willing to help if you like.
T
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Hyperbole - undoubtedly the best thing ever.
Edited by Tom Trusock (10/15/09 09:42 PM)
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tmol2003
newbie
Reged: 07/07/08
Posts: 1
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10,000 dollars for that.
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TimNott
newbie
Reged: 09/10/06
Posts: 3
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Thanks Tom for a good review of this and the other models.
For those who are interested, I completed a 22" version of this design earlier this year before Obsession themselves released this model:
http://www.iceinspace.com.au/forum/showthread.php?t=41554
It has a lighter 1.7" thick mirror and shorter focal ratio of F3.6 by Steve Kennedy. So, I was able to get away with using 6 X 32mm diameter poles instead of 8.
In the design and construction process I came across a few things that may help potential or current owners of this type of scope.
The scope is an easy 2 person lift, but wheelbarrow handles and planks are necessary for a one person setup. Wouldn't have been able to get a 22" classic design in and out of my wagon though! It is about the same weight as a traditional 18 incher.
You'll notice looking at the pics that I used a full sized, flocked baffle opposite the focuser as I did not want to use a shroud. The half-sized one supplied by Obsession seems to be designed to be used with a shroud only, so If you don't have one I'd calculate the size needed and cut a full circle out of black plastic. I used black polypropylene and covered it with Protostar self adhesive flocking. This will stop nearly all the stray light getting in the eyepiece. You can also use a baffle just below the focuser but the bottom of the focuser tube was doing the same job in this case according to my calculations so I left it.
The diameter of the Altitude bearings on these newer compact scopes is often much wider than the classic design to make the scope balance, which will automatically mean a firmer motion up and down than a scope with smaller diameter bearings. The flip side is it is less prone to balance problems when changing eyepieces.
As noted, the join in the fold-over bearings is smoothed over by using the single strip of teflon and by rounding over the tips of the arc on the rocker. This has the potential to make the motions firmer again. If however, the diameter of the arc in the rocker is very slightly less than the mating curve of the altitude bearings then, instead of the laminate resting evenly on the whole strip of teflon, the pressure is concentrated on the outside tips. I don't know if Obsession has already done this trick, or even whether this varies between scopes.
What I did when I was not happy with the motions on mine was peel off the teflon (it is usually just fixed on with contact glue) find an appropriate thickness strip of plastic then contact glue it on, followed by the Teflon on top. This reduced the effective diameter of the arc in the rocker enough to concentrate the weight on the tips and the motions were improved.
If you replace the strip with the more traditional 4 pieces of teflon instead then you could round off the edges slightly with sandpaper or a dremel to avoid having multiple bumps. Cutting the teflon at an angle would also help.
I like the first option though as it has the advantage of both methods.
As far as vibration goes, I found the biggest potential for flexure was in the join in the altitude bearings. Making sure the adjustable latches are really tight helps a great deal. Having steel supports running across the tips of the altitude bearings like Obsession has included in the 22" version will also reinforce this join and the U-shaped bearings. It is easy to construct-just a strip of steel with a couple of holes drilled in it, some matching holes in the tips of the bearings, bolts and wingnuts.
I must admit, though, that I have mainly been using mine with Servocat, so I am not bothered by either vibration or problems with motion in altitude anyway.
I hope some of this helps, though I appreciate that people could be annoyed at having to fiddle with a product they have paid for.
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Thomas44
super member
Reged: 10/26/09
Posts: 101
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That was huge mate. Looking good and it looks worth all the money you paid for it too.
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www.laserpointers.co.uk
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