Obsession/Starmaster comparaison

This is my first post and I'm looking for advice on purchasing my next scope. I own an obsession 12.5" and looking to jump to a 18" or 20" truss scope and I am currently balancing between Obsession again or Starmaster type.
As far as Starmaster is concerned, i am pleased with the focal ratio (4.3 avoiding ladder) and the possibility to get the mirror off the rocker and thus reducing weight to lift and avoiding the need for Wheelbarrow handles. I have been also told that Zambuto mirors are better than OMI or GALAXY, which is the accuracy one can expect from Zambuto mirrors?
Talking about Obsession, i am quite satisfied with the one i have, specialy with the mechanicals and they are quite famous here in France.
So could someone advise me how Starmaster compare to Obsession?
Please note that my observing style is pure visual.
Thanks for sharing.
Bernard

I think that both scopes are well made. The Zambuto mirrors are as good as there is out there, perhaps better.
Starmaster scopes are made to transport, with removable mirrors and transport box, to aid it getting the weight down on the mirror box.
Starmaster has triangular trusses that are quicker to assemble and hold collimation well. The woodwork is nice and attractive. The movements are smooth and predictable. Good support after purchase. Reasonable weight and height makes for a nice overall scope.

Obsession is also well made. Weights are not posted for all parts but look similar to the Starmaster. Price is less by $500, but I no Feathertouch focuser, Telrad or mirror transport box as standard equipment makes the cost about the same.

I have not owned an Obsession, but have used them and they seem like a nice scope.

I do own a Starmaster and would stand it up against any scope for performance and ease of use and transport.

I own an 11 Starmaster and love it.
From what I can tell, woodworking on the Starmaster is excellent and is even better on the Obsession.
The Obsession moves on its axes with a lighter touch, just one finger will do it, but the Starmaster also moves very well on its axes and is more resistant to losing the object when you change eyepieces.
I don't care for the mirror sling that Obsesson uses. No on else seems to use it.
To me the ability to remove mirror and cell to lighten the mirror box for transport is very important and I would insist on that if I went to a larger scope.
Obsession sells more scopes than Starmaster.
Starmaster has superb, indeed unmatched, support after purchase. Better than any other scope in my opinion.
Rich Singmaster star tests each telescope against a known comparative telescope under the stars before he will ship it.
Zambuto mirrors are famous for their superb quality, no exceptions.
Obsession ships the mirror to you separately directly from the mirror maker so Obsession has never seen your mirror, I am told.
Starmasters are a bit ovrebuilt, sturdier than they need to be, because their builder used to design bridges. The builder of Obsessions is a dentist and his woodworking skills are even better than the fine woodworking of Starmasters, I am told.
Obsession hints at invidious comparisons to other telescopes, including SCTs and Dobs other than Obsessions. Starmaster does not.
Both are top quality scopes. I have never heard of a disappointed user of either.
Since the truss tubes are attached to the outside, rather than the inside, of the mirror box, the Starmster mirror box and rocker box are a bit larger than the Obsession, but the Focuser assembly stacks easily within the rocker box, saving space for transport.
I think the mirror box on Starmaster is probably heavier than that of Obsession if you leave the mirror in, but considerably lighter if you take the mirror and cell out (easily removable) and put it in the mirror storage box that you can keep in your car.
All this is what I have been able to figure out, plus some personal experience with 18 inch Obsessions, and of course with
the Starmaster I own.
Two excellent scopes. I don't think you can go wrong with either.
I am sure other posters will be quick to correct any errors of fact I have made.
I hope this will be helpful to you.
Bill Meyers

I now own my third Starmaster scope and I like everything about it. Several years ago, when I purchased my first new Starmaster, I asked Rick Singmaster why I should buy a Starmaster and he quickly said, "the Zambuto mirror". It is not that others do not make great mirrors, too. It is just that if Carl Zambuto makes the mirror, you know it will be superb. Actually, I like the Starmaster structure, too. It has an industrial strength look and feel that appeals to me.

The Obsession scopes are beautiful and I am sure I would be just as happy with it. They do have a sort of furniture like appearance about them, though I would rate them just below Starmaster in every other dimension. I would love to have a premium dob with Feathertouch focuser, Starmaster's wiffle-tree mirror cell, Zambuto primary, Rick Singmaster's support and Obsession's sexy lines and that cool little brass plate.

Bernard,

I recommend an AstroSystems Telekit with a Zambuto primary. That's the best woodwork with the best mirror! They ship internationally also.

Thanks
Bill

Being my first post and from reading many answers i got, I'm pleased to have got many responses and detailed advices. So thanks to Flyod, Bill, Randy, Jim, Hart, Bob and Ron.

I have a few questions pending:
Bill, what do u mean by : » Obsession hints at invidious comparisons to other telescopes, including SCTs and Dobs other than Obsessions. Starmaster does not. »
Hart, your suggestion is very attrative « Actually, if you're buying new you may be able to get an Obsession with Zambuto primary, since you can buy an Obsession without a mirror, and Carl announced last year that he is selling mirrors to the public » but I still not found any Zambuto website and i am a bit afraid about focal length and final adjustment to be made and, as mentioned by Bill, « issues because of mirror box depth and mirror thickness"
Ron, i understand that the faster SM optical design (with an f/4.3 Zambuto) will show coma enough for me to be obliged to get a Paracorr, is that correct ?
About mirror precision (PV, RMS) is it possible to get anywhere data to demonstrate the quality of Zambuto mirror compared to other diffraction limited mirrors?

I noted that both scopes have their strengths and weaknesses but i will decide mainly on eyepiece height, as mentioned by Ron, and also on Quality miror.
On both items SM has a plus. On opposite that will lead to less magnification and use of Paracor.
At last i understand that based upon mechanical design and smooth move O has a plus.

Thanks again for looking
Bernard Chevalier

...

Ok, a bit late to the game, but I'll chime in. Reading through the posts, there are some very good points. I own a 15" Obsession with a wonderful Swayze mirror. Steve also doesnt publish test results, merely saying that he was happy with the figure of the mirror and how smooth it was. Carl recommned him to me as a good choice for an Obsession.First light was jaw dropping to say the least. I looked at SM when deciding, but really had lusted for an Obsession for years. I prefer the look of the truss tubes on the outside of the box, it also makes the box smaller and lighter. I have helped set up and observed with a 25" Obsession. That was an easy set up for a scope that huge. My 15 is a breeze to set up and collimate. Collimation stays dead on all night. There a number of dob builders that use the mirror sling, as well as other methods such as the wiffle mount,etc. Ive always been happy with Dave's support ( rarely needed tho), and he is very active on the Obsession group. He and Richard Berry wrote the book on how to build an Obsession clone. If you've read the book, you know that the first few chapters are all about those who innovated the truss design before Dave got started. He freely aknowledges those ideas he used to start Obsession. I personally feel that both gentlemen did the hobby a great service by publishing the book with the incredible detail about building similar scopes. Ive seen a number of "Obsession clones" built as a result of that book.
Finally, there are a number of other dob builders to consider. T-Scopes, Plettstone, Nightsky and a few others I'm obviously forgetting. My club has a 16" Astrosystems that is very nice.I would bet that any of these builders offer a scope that would be of high quality and provide years of great views.

The Obsession-SM debate is eerily similar to the Mac-PC debate ( Macs win!!) LOL!!!


Mark

I'm in a similar boat to the one you are in - looking to upgrade from a 12" Dob to a premium 18" Dob.

I too have been waffling between Starmaster and Obsession.

I don't think that the f/4.3 focal ratio of the 18" Starmaster is meaningful in assessing which scope is ladder free. In fact, neither the f/4.5 Obsession nor the f/4.3 Starmaster are flat footed scopes near zenith.

Starmaster lists the 18" f/4.3's eyepiee height at zenith as 78" or 6.5 feet. Obsession's 18" f/4.5 has an eyepiece height at zenith of 6' 5" - about the same (or actually one inch lower) than the Starmaster.

I prefer the more compact Obsession rocker box and use of Appleply rather than red oak plywood for the wood work. I prefer the wiffle tree mirror cell on the Starmaster to the kevlar sling based cell on the Obsession. Zambuto vs. Galaxy vs. OMI is a tough call. Zambuto mirrors are thinner (1.6" vs. 2.0") for faster cool down. Starmaster uses quarz overcoated aluminized primaries rather than the dielectric coatings used on Obsession mirrors. Some claim the thinner mirrors are more prone to astigmatism. Some claim that the enhanced coatings change the figure of the mirror too much.

On balance, I am leaning toward the Obsession, though certain aspects of the Starmaster appeal to me. Now I am waffling between 18" and 20". Hmm...

Regards,

Jim

Bernard,
My apologies for chiming in late here, but I've been away for a few days. I believe this little story tells a lot:
I have a friend with an 18" Obsession that I was very impressed with. I was looking for one of my own, but got sidetracked by a 14.5" Starmaster, here on Astromart. After much deliberation, and similar forum advice (thanks guys), I purchased the Starmaster, and have been thrilled with it ever since.
My friend, who is more qualified than I, was very impressed by my Zambuto mirror, and declared it to be the best star test he had ever seen. Shortly thereafter, he had his OMI/Torus mirror tested, and the results were not good. Nowhere near the numbers claimed by the maker. He masked off the turned edge, and continued to use it, but he was not happy.
He had just made arrangements to return the mirror for a refund, when Carl Zambuto announced he would be selling to the ATM market again. He jumped on the opportunity, placed the first order with Carl, and is now extremely happy with his ZOC-equipped Obsession. I am once again, jealous of his scope!
Linton