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Obsession Optical quality

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#1 helpwanted

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Posted 04 July 2019 - 02:43 PM

A question for Obsession owners, or those that have done a side-by-side comparison.

 

If you have a 15" Obsession next to an Orion xx16g.... or a 12.5" Obsession next to an Orion xx12, are you seeing a noticeable difference in optical quality, and if so, please describe.

Are you seeing fainter? Sharper?

 

Please... only looking for answers from those with experience, not speculators. 

 

Thank you,

 

David



#2 Stellar1

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Posted 04 July 2019 - 03:51 PM

For what i can contribute, ill say that higher end dob's usually come with far better mirrors than what you would find in mass produced scopes. Custom scopes like Obsession, Starmaster, Teeter, and the like utilize smaller secondary mirrors which provide better contrast. I have a Starmaster with a 10" Zambuto mirror, i also had a 12" Meade Lightbridge, i can attest that the contrast in my Starmaster is on a whole new level, it would wipe the floor with the Lightbridge even having a 2" smaller mirror. Theres no substitute for a finer mirror, especially assuming both mirrors are the same size. Im sure others with far more experience will weigh in but, i can bet dollars to donuts that if you compared M13 side to side in my 10"starmaster with a .95 strehl and my Lightbridge, you'd see the difference without a doubt. in that sense im confident in saying that yes, a 16" obsession will certainly provide a better image than a 16" lightbridge or Skywatcher.


Edited by Stellar1, 04 July 2019 - 03:58 PM.


#3 The Ardent

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Posted 04 July 2019 - 03:59 PM

Former Obsession owner here. 

 

I would ask: 

Does Obsession make the mirrors and control the optical quality? 

Do they test the optics for you before delivery? 



#4 helpwanted

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Posted 04 July 2019 - 04:29 PM

I don't know Ray, that's why I am asking, it looks like they sub out the mirrors. 



#5 Don W

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Posted 04 July 2019 - 04:52 PM

Obsession buys premium mirrors from well known makers. Dave does not test them.


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#6 junomike

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Posted 04 July 2019 - 05:03 PM

IME the premium mirrors are guaranteed to be of a certain Strehl, but at the eyepiece I rarely see a difference, especially for DSO's.

I'd take a decent non-premium mirror over a premium one if It was at least 20% larger.

IMO  (for DSO's mainly), you can't re-write the laws of physics so mass produced 14" mirror will show you things a premium 10" could only dream about


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#7 CHASLX200

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Posted 04 July 2019 - 05:07 PM

I had two Obsessions. 15" and 12.5" with OMI mirrors and both were super.  Dave does not test them before shipping like Rick did with the Starmasters.



#8 niallk

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Posted 04 July 2019 - 08:35 PM

Teeter/Webster/New Moon/etc partner to source mirrors - similarly to Obsession. Obsession relies on the interferometry test reports supplied with the primary and secondary mirrors from their suppliers. The website details the min guaranteed spec. Some other suppliers do a check under the stars.

I can't compare equal apertures, but fwiw, my 15" Obsession has delivered better views with finer details of Jupiter, Saturn and indeed the moon than my Skywatcher 10" - if you want to take that as a subjective optical quality data point. No comparison on DSOs - aperture rules ;)

The Obsession moves beautifully - and this makes a huge difference in use at the EP at high powers. The optics also make the longer cool down required worth it for planetary observing, imho.

Edited by niallk, 05 July 2019 - 05:59 AM.

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#9 George N

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Posted 05 July 2019 - 01:42 PM

A question for Obsession owners, or those that have done a side-by-side comparison.

 

.....

 

David

A month ago I had my 2001 era Obsession 20 F/5 with OMI mirror at a star party (dark skies, with good/excellent seeing) next to 16, 18, 20, and 22 inch "premium" Dobs. Both I, and some other long-time observers concluded that my scope was clearly showing more pin-point stars and better detail on Jupiter. My scope has a history of great optical performance, and very smooth movements - while encoder accuracy is sometimes not so "super" - thanks I think to the mirror box sliding sideways in the rocker box.

 

However -- I had very carefully checked the positioning of the primary in its Glatter cable sling - to make sure it was moving freely and the primary and secondary cells were working properly. I also took my time with collimation - and checked it a 2nd time after it was fully dark - trying to be very precise. My conclusion was - my scope's apparent "superior performance" was more a result of good cooling and precise collimation that superior optics! Learn to collimate and insure a cool mirror first before worrying about mirror quality!

 

A friend who makes well-known "premium Dobs" - and will sell you one with a premium mirror or a Chinese GSO mirror (at lower price, with quicker delivery time) - told me about a year ago "The latest batch of GSO mirrors I've had come in were all pretty good!" Yes, he does star test the completed scopes, and will not sell you an optical "dog".

 

So -- why do I want to sell my Obsession 20???

 

Well, at nearly 72 now - I need to get rid of the ladder, get an easier-to-handle F/3.2 or something 20 to 22 inch -- but after this last experience with the old Obsession 20 -- I'll probably keep it for another year! cool.gif

 

When I do sell it - a very lucky 40-something person who can handle ladders, transport heavy scopes, etc, will be getting a great scope that will perform for years!


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#10 CHASLX200

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Posted 05 July 2019 - 06:07 PM

I always wanted a 20" Obsession if it could roll out my 36" wide door all set up. A 18" Tectron would fit all set up.  The OMI mirrors seemed to be very good on avg.


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#11 Don W

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Posted 05 July 2019 - 06:47 PM

I built a 20" f/5 in the early 90s. Great scope but it was so heavy. I needed a friend's help to set it up. In 2005, I bought an 18" Obsession Classic. It was so easy to set up and I didn't need a ladder. Had a small step stool. It was probably the most fun scope I've ever had, since it got used a lot. The OMI mirror was excellent. Sad to see them go out of business.


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#12 George N

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Posted 07 July 2019 - 08:33 AM

I always wanted a 20" Obsession if it could roll out my 36" wide door all set up. A 18" Tectron would fit all set up.  The OMI mirrors seemed to be very good on avg.

 

For years I had problems with getting my Obsession 20 out the door. It was maybe an inch too wide, so it required some "creative" twisting. That door was what prevented me from getting a 25-inch!

 

Then, about 4 years ago, we replaced that sliding-glass door with "French" ( bat-wing ) doors. Now it opens up wide enough that I could get a 50-inch scope in and out. It took a while for my wife to figure out why I was so enthusiastic about that "door replacement project"!  ;)

 

Today I also have a garden shed that will hold all the lawn stuff, plus the fully assembled Obsession 20. I can simply roll it about 15 or 20 feet to observe. However, the few times I've left it in the shed the primary dewed up in the morning -- and so far I don't have AC power to the shed (other than running a long cord) so I can't put a heat gizmo on a timer. It remains a "future project".

 

Altho I mostly do imaging from home - when I do want to observe with the Obsession 20 I just leave it out on the lawn for up to 4 nights.



#13 Chesterguy1

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Posted 07 July 2019 - 10:27 AM

I never was able to compare my 10” Orion, with my 8” Teeter because I sold the Orion years before I got the Teeter. The Orion Premium Deep Space Explorer had an excellent Terry O mirror and put up quite good images despite my nascent collimating skills. It held collimation well, but the secondary had bolts that had to be loosened with a wrench for adjustment. I expect that it would have held its own against other premium dobs of similar size although it had a thick mirror.

 

My 15” Obsession has an OMI mirror. The best upgrade I did to the 15” was replacing the awful mirror strap with a Glatter cable. There was so much shifting, stretching and folding of the original strap that it allowed the mirror to bump up against  the mirror clips and put tiny little divots on the mirror edge. NOT GOOD. It’s amazing how much better the primary holds collimation now. I didn’t realize how much I was struggling to maximize the potential of that mirror. It’s due for a recoat, but is still great and my only complaint is the mirror thickness (for portability and acclimation)

 

I will say that my Teeter with a Carl Z mirror is stunning. When well collimated it does a superior job on everything, reaches ambient temp fairly quickly and is only limited by sky conditions.

 

Chesterguy



#14 cuzimthedad

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Posted 07 July 2019 - 04:50 PM

I'm going to chime in by saying that IMHO it's a combination of optics that make the difference. Today's mass produced glass is much better than it was 10-15 years ago. Is it on par with an OMI or Zambuto? No. Where I think the difference is told is in the eyepiece quality used. If you take an Orion 12" dob using TeleVue eps and put it up against an Obsession of similar aperture using Explore Scientific eps, the visual quality gap is narrowed. By the same token, if you use high quality eps in an Obsession and use lesser in the Orion, the quality gap will be seen. If I were asking the question, I would ask is the much higher cost of a special order 15" dob justified as opposed to buying a much less expensive 15" mass produced scope. The question is one of personal preference. Do you want a Ferrari or do you want a Corvette...well maybe IROC Camaro. What truly matters is that you're happy with what you buy and have no regrets of doing so.


Edited by cuzimthedad, 07 July 2019 - 04:52 PM.

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#15 Markovich

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Posted 08 July 2019 - 02:25 PM

Well, couple of things to consider:

First of all, a premium scope is typically built better than a "mass market" dob of equivalent size. So you generally have less issues and a longer life span, plus the ability to withstand the bumps and bangs of transporting a large scope. The optical set ( primary and secondary) also tend to be of higher quality.

 

On most nights, the casual observer is not going to be under ideal skies and local conditions that will display that extra edge from a premium mirror. But on those rare nights, yes you will see a difference with the right eyepiece and experience. However, it will also take an experienced, trained observer to notice it.

 

Ive never had a mechanical issue with my Obsession, and the Swayze mirror is outstanding. The scope is pampered, sits in a corner of my living room with my other gear. But it has had it shares of bumps and ooopsies over the close to 20 yrs now, and it still looks brand new. I think my knuckles have taken more of a beating trying to get it out of the door. I seriously doubt a mass market dob will give you that same long term value.

 

I always tell potential buyers to look at used premium dobs, from Obsession, Starmaster and Teeter etc. Those are excellent choices and usually competitively priced, and usually "dialed in" by now.



#16 Richard Whalen

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Posted 08 July 2019 - 04:48 PM

My 18" UTC came with a report. Had a Galaxy primary which was very good for a 18". On a good night you can see the difference in optical quality in larger dobs pretty easy. 



#17 The Ardent

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Posted 10 July 2019 - 03:36 PM

Read this ad from today , touches directly on the topic

 

https://www.cloudyni...ssion-125-inch/



#18 Solar Ken

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Posted 14 August 2019 - 12:42 AM

I can give the original poster exactly what they asked for. I had an Orion XX21i for several years, and it provided very good views. More experienced observers said it was a very good mirror for what it was and for what the price point was. After several years I sold the Orion and bought an Obsession 12.5. Yes I did notice a brighter image with more contrast with the Obsession. The mirror was from OMI and the report data shows it to be an excellent mirror. I believe Dave at Obsession now gets his mirrors from other suppliers, but no doubt the mirrors he provides in all his scopes are top of the line. The real pleasure comes from the buttery smooth movement of the Obsession. Every time I use it I'm immediately reminded of what a joy it is to use.


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#19 GShaffer

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Posted 14 August 2019 - 04:34 AM

Obsession has never used in house glass to my knowledge, prior to settling in on OMI for a long run they used others.....My 20" Obsession came with a Nova Optics primary which is a fine mirror as well though as I understand it wasnt consistent enough in quality to suit the Obsession folks so they went to OMI. I eventually sold the Obsession body and and Tom at Midnight Telescopes did the wood work on a new scope to my specs which I transferred the glass to.....Dont know who's glass they use now but an email or a phone call would get that info in short order.



#20 CHASLX200

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Posted 14 August 2019 - 05:20 AM

Obsession has never used in house glass to my knowledge, prior to settling in on OMI for a long run they used others.....My 20" Obsession came with a Nova Optics primary which is a fine mirror as well though as I understand it wasnt consistent enough in quality to suit the Obsession folks so they went to OMI. I eventually sold the Obsession body and and Tom at Midnight Telescopes did the wood work on a new scope to my specs which I transferred the glass to.....Dont know who's glass they use now but an email or a phone call would get that info in short order.

My Nova mirror in my 18" F/5 Tectron was very bad.



#21 Mike Wiles

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Posted 14 August 2019 - 08:49 AM

I've had a 15" Obsession classic since 2001 that has provided hundreds of hours of satisfactory viewing for me.  After 18 years, I recently undertook a project to freshen up the scope.  I sent the mirror in for recoating and had it independently tested at that time by a mirror maker with far more experience than I'll ever have.  My 2001 vintage OMI mirror tested out at 1/5 wave (Peak to Valley) with a strehl ratio of 0.944.  It has a wider than normal bevel, a remnant of an attempt to correct a rolled edge on the mirror which is visible in the interferometry results.  It's always been considered a good performer among my circle of observing friends and the difference in performance has always been obvious when placed next to the Meade 16" Starfinders that ushered in the wave of large, cheap dobs of the 2000's.  

 

Second, and I've learned this through experience, the quality of the structure is equally as important as the quality of the optics.  We don't give it enough time on these forums, obsessing more about the quality of the optics than the structure that's housing them.  I'm adding fans to the mirror box and a SIPS focuser, but I don't want to do anything that compromises the structure.  As others have pointed out, the Obsession has it's own quirks that have been improved by the newer generation of builders - but nothing moves like an Obsession.  All that talk about their buttery smoothness is not hype, and no telescope from any other builder that I have ever used - including my newer, much more expensive 20" - moves like an Obsession.  They are a joy to use and in today's market, probably represent the sweet spot between quality and price.  They're much better built, with consistently better optics than any of the mass market dobs out there.  They're much less expensive and nearly the equal (and better in some cases) to the current crop of premium quality dobs that have a matching price tag and extraordinarily long wait times.  

 

My 15" Obsession classic was a premium priced scope at the time that I bought it back in 2001, and it was a large chunk of money to spend.  I've never regretted it.  It's been worth every penny for all these years. The only thing that made me consider a new telescope was that a new generation of opticians surfaced who brought an ability to make extremely fast, thin, large aperture mirrors of exceptional quality - so it became possible to upgrade aperture without having to add a ladder to the mix.  Another point not to be overlooked - I could put the Obsession on Astromart right now and price it for not much less than I paid back in 2001 and it would sell quickly.  It's rare to even find a mass produced dob from that era that's still intact, and they're sold at fire sale prices when they do surface.  


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#22 azure1961p

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Posted 14 August 2019 - 09:17 AM

I recall reading some really unhappy Obsession owners who despite a nice big reflector had shoddy optics.  This was pre-Lockwood where I think bigger glass may have suffered QC more than today where the bar is raised higher.  Still with regard to the Lightbridge line, even if Obsession slipped some poor ones through I HAVE TO believe their QC record was far far better than that. I mention Lockwood not because he had anything to do with those earlier scopes but simply that he was one of the key figures turning out proper big optics.

 

Pete



#23 George N

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Posted 14 August 2019 - 10:31 AM

I recall reading some really unhappy Obsession owners who despite a nice big reflector had shoddy optics.  …..

 

Pete

The 98% with great optics from Obsession, like mine, are much less likely to post about it on the forums. cool.gif 

 

A number of folks have commented on the quality of my OMI mirror ( including two S&T Editors, and the owner of a "famous" eyepiece and refractor company). As reported in S&T about two years ago, they used my scope to test eyepieces for an article in the mag. cool.gif 

 

Dave's Obsession "business model" has always been to place large orders for mirrors with several suppliers (and to pre-stock most, or all scope parts too) - and he has been able to negotiate lower prices, which he passes on to buyers (same on eyepieces too). That way, he almost always has a mirror in stock from one maker or another - and that means ( or use to mean ) - you could get a 25-inch "premium" Dob delivered to your house 2 to 4 weeks after ordering it. On the other hand - he has noted that he has several million dollars tied up in inventory - which I suspect other premium Dob makers do not. Not being a small business owner - I have no idea what the economic implications of that is - other than, as a dentist and clinic owner, he had the money to invest.

 

At one point 'in the early days' - you could order a 'regular' primary - or pay more for a 'premium' one. Dave himself never tested them - and if you had a warrantee problem with your mirror, you needed to deal with the mirror maker, not Dave. Add to that his insistence on using 2-inch thick mirrors - which he considers superior.

 

As far as "buttery smooth" moves -- my Obsession 20 moves smoother than any other Dob I've personally used. It does have a clunky method to keep the mirror box from sliding sideways in the rocker box - stick-on furniture sliders! They need to be replaced every few years or the DSC pointing accuracy goes down to the point that moved-to objects are no longer in a high-power eyepiece. I have no experience with the movement of Obsession UC scopes - so I defer to those who do.


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#24 Don W

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Posted 14 August 2019 - 10:53 AM

That was 20 years ago and the mirror maker made good on all claims. Time to put that one to rest!!


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#25 GShaffer

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Posted 14 August 2019 - 01:11 PM

My Nova mirror in my 18" F/5 Tectron was very bad.

 

Kinda fits with what I said about consistency huh? :)


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