Obsession 15" f/4.5

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Brand and Model:Obsession 15" f/4.5
Price ($USD):$3495
Attributes: un-checked Go-To un-checked PEC
Aperture:381mm (15")
f Ratio:f/4.5
Focal Length:1714mm
Electric Power:N/A
Mount:Truss-tube Dobsonian
Weight (lbs):apx. 75 lbs.
Dimensions (w/h/d):72"x 23"x 23"
Description:Comes standard with wheelbarrow handles for easy transportation of the mirror box. Comes standard with 89% reflective primary and 99% reflective secondary. For $250 extra, primary is 96% reflective. Has a JMI DX3 Crayford focuser. Telrad is a $45 option. Light shroud is a $129 option. Eyepiece height @ zenith is 5' 5".

Observer.org's review

Vote Highlights Vote
Obsession 15" f/4.5
First off i did not rate the optics yet'They seem to be very good.Better than any i have used yet.I have this 15in obssesion for almost 6 months now.I ordered it back in may 2003 took only a month to get.I have the torus mirror with great numbers.This mirror was made after some of the torus problems were fix,This scope is so easy to put together and move.I have the kevlar sling and the scope stays collimated all night in all types of weather.I got the jmi dx-1 focuser and extra counter weight kit,I use a denkmeier bino and the views are breataking stars are pin point up to about 200x.I live in the ohio valley where seeing can be both good and bad.I have yet to really do a good startest but the optics seem very good.I look though alot of good scopes at starparties and my optics seem to be as good as the best.The movement of a obssesion is smooth as butter the best i have used.One needs no ladder with this scope and it only takes a few minutes to take down or put up.The finish is high grade.This scope is a keeper and gets alot of use.Total cost with shipping was about$4300.Will update later.THANKS BOB HART

Overall Rating: 9
Mount:9 Ease of Use:10 Value:6
Weight: 10 (Trustworthy Vote)
By: indybob
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=329630

Obsession 15" f/4.5
At this time I do not want to give a rating on the optics, mount and other for the 15" Obsession. I just want to give my initial impressions of the scope. I believe it will take about a year of use with this scope before I could give an honest rating on this equipment. I live in the Great Northeast and good to excellent seeing conditions are not common. It will be some time before seeing conditions will allow this optic to be evaluated. I have an observing buddy that has a 15” Obsession with a known excellent Nova mirror, which I will use as a reference.

I received my new Obsession with a Torus mirror back in October of 2002. The scope came just 7 weeks after placing the order. The crating, insurance and shipping cost was just under $400, which I thought was kind of high. This is the first new DOB I ever ordered so I really have no idea what the other DOB manufactures are charging for shipping. I must say that Mail Boxes Etc did an excellent crating and shipping job.

The first package I open was the Torus mirror. I was excited to see what kind of mirror specs I had gotten. I was shocked and thrilled when I saw the interferometric test results. I had a mirror with a strehl ratio of 0.994! I couldn't expect a better mirror. A couple of weeks later my bubble was burst with reports on the internet of a Torus mirror with TDE, poor optical performance and independent test results that didn't agree favorably with Torus's. At that point I became very skeptical about my mirror and mirror manufacturers and there claims in general. I no longer had confidence that I had a great mirror and only time behind the eyepiece will determine if I did or not.

Unpacking and assembling the scope was straightforward and uneventful. The design, finish and construction of the scope are very good. Much better than the Compact II Starsplitter I owned previous to this scope. The new spring loaded secondary collimation screws are an excellent design change and this makes collimating the scope a joy. By far this is the easiest scope to collimate precisely and easily. The alt/az motions are smooth and the scope is very well balanced. Once completely assembled the scope is beautiful, functional and extremely rigid and stable. I have noticed in some other DOB designs a lack of rigidity that would cause backlash in its motion and loss of collimation due to shifting truss poles. The 15” Obsession is rock solid in this aspect. The scope is also very compact when apart and fits easily in the back seat of my Toyota Camary. This is most likely the largest truss DOB that a strong and healthy individual can pick up and carry with no assistance. Also anybody over 5’ 10” will not require a ladder.

I have had the scope out only a couple of nights due to the great weather we have here in the Northeast. Sky conditions were fair to bad and therefore I could not evaluate the optics. My last scope was a 12.5” Starsplitter and so far the most obvious difference is the brightness and color of stars. Stars are much more brighter and colorful in the 15” Obsession. At this time I have no more feedback on the Torus optics.

Things I didn’t like about the scope, some are minor, are as follows:

1. The plastic standoffs for the secondary collimation screws are white and should have been finished flat black. This is most likely minor but some day I will do this myself.
2. The truss poles had very sharp edges on the inside ends. The tube cutter caused this edge when the tubes were cut and for the money these scopes cost the edges should have been finished off with a file. I did finish off the edges myself right away to avoid being sliced and bleeding like a pig all over my new optics.
3. The mirror cell sling design does have problems with holding exact collimation. The mirror can swing side to side and the belt at times seams to stretch and shrink. For the typical seeing conditions in the Northeast exact collimation is not that critical but when the seeing is good and you want to observe Jupiter or Saturn you better check your collimation. Again this scope is very easy to collimate.

My final comments are about previous reviews and comments about the 15” Obsession on this site. First of all I cannot believe any telescope review with just a few lines of basically emotional comments with a rating of 10. I think most people just get too emotional with their new telescope purchase and then their objectivity just goes out the window. There will always be problems with design, construction and workmanship with any scope no matter who makes it. If these reviews were truly objective they would point out these issues and you would never see ratings of 10. You cannot expect perfection from these scopes for the money they cost. Just remember that the Hubble’s initial cost was about a billion bucks and it had its share of problems.

With all this said, I hope for one day to witness jaw-dropping views of Jupiter and Saturn with this scope. The kind of views you read about on these discussion groups. Until then I’m going to reserve my final review and rating of the 15” Obsession for a later date.

UPDATE 8/7/2003

It has been over 10 months since I have received my 15" Obsession. After many months of observing, star testing and performing side by side comparing with another 15" Obsession with Nova optics and other large DOBs I came to the conclusion that I had a mirror with a significant turned down edge. The other Obsession with the Nova mirror that I was comparing with also had a turned down edge.

After weeks of being in a state of denial I finally contacted James Mulherin at Torus and discussed my findings with him. He was convinced that I really had a problem with my mirror and that he would take care of it right away. In less than 6 weeks my scope had a fantastic mirror that would focus bright stars to a fine point with only 4 diffraction spikes from the spider. I was very satisfied with the optic now, but I wanted to see Mars with it before I gave it the okay.

Observing Mars this year in any scope has been amazing so far. I have never seen so much detail on this planet until now. My new optics seemed to be performing as good on Mars as any other known good optics in my club.

The final test was at the Rockland Astronomy Club's summer star party in Savoy, Massachusetts. Here there were at least 50 or more scopes on the field. During the early morning hours of August 1 the sky seeing conditions become very steady for the Northeast. I was observing Mars with my 15" Obsession using a 2.5x PowerMate with a 13mm SW Lanthanum eyepiece. This gave me about 330 power. The images of Mars were amazing. Never saw anything like it in my life. People who came by to take a peek were so impressed that they were telling other people in the field to come over to my scope to take a look. Soon there was a line of people who wanted to look through my scope. Everyone who did come over were also amazed at what they saw. They were also saying to themselves that my scope was giving the best Mars images of any scope on the field. At that moment I knew I had a very good optic.

Later on that evening there was news of a 25" Obsession using a bino viewer with a Torus mirror that was giving even more impressive views of Mars than my scope. I went over to take a peek, but there was already a long line. I decided to came back later to look. By the time the line was gone also the seeing had gone. When I looked through the 25" it was a nice view but nothing compared to what I saw through my scope. After talking to several people who looked through both scopes it appears that about half were split between which scope had the better views.

Now you may wonder why I only gave the scope a rating of 9. I figure nothing is perfect and there will always be something better out there. In my book a 9 is about as good as it gets.

Overall Rating: 9
Optics:9 Mount:9 Ease of Use:10 Value:9
Weight: 10 (Trustworthy Vote)
By: iamadobman
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=173549

Obsession 15" f/4.5
Just got my new 15# scope, WOW! Best newt. Dob. I've ever had! Worth every penny. Great mirror from Torus, Great woodwork and finish. It glides effortlessly, perfectly balanced, even with heavy eye peices! The views I have gotten of galaxies planets nebulas are incredible, it seems that there is nothing I can't reach with this scope!(given the right conditions) Set up takes about 5 Min. that includes collimation, I rate it a 10+

Overall Rating: 10
Optics:10 Mount:10 Ease of Use:10 Value:10
Weight: 10 (Trustworthy Vote)
By: nick
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=79277

Obsession 15" f/4.5
All in all a very good telescope. Nevertheless, the fit and finish are not consistent with the price tag. Example, I bought Dave's counterweight kit and the pipe sections were cut too long to fit. Dave's response was along the lines of, "well, just go to the hardware store and see if they'll cut it for you." Well, ok, but if I wanted to DIY the solution, I wouldn't have needed to send him the extra $25 for his kit. I ordered it to save the hassle, but I still got the hassle. Don't get me wrong, Dave is a great guy, but he is the ultimate DIY'er and forgets that his customers are not. When you spend $6K for a telescope, you want all the parts to fit. There were 4-5 little details like this. Additionally, I can't say that I was pleased to find out that I received the only mirror with less than a .90 strehl from the production run in question. Can I tell the difference--no--but if you saw that the rest of the mirrors were .90 and most were .95, I doubt you'd feel much like "Obsession" was the right name. Note, I'm not dinging the mirror on the ratings, but Obsession markets a Ferrari/Cadillac experience and doesn't really deliver.

Overall Rating: 8
Optics:8 Mount:9 Ease of Use:8 Value:6
Weight: 5 (Veritable Vote)
By: egage
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=581700

Obsession 15" f/4.5
I was able to look through/use two 15" Obsessions at our recent Swiss Starparty, both with primary mirrors from LOMO. Excellent images with and without Zeiss/Astrophysics binoviewer. Very smooth tracking and still easy to lift without handles.

Overall Rating: 10
Weight: 1 (Unreliable Vote)
By: Anonymous (xxx.xxx.140.178)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=41208

Obsession 15" f/4.5
The very best! Excellent portabilitt and craftsmanship

Overall Rating: 10
Weight: 1 (Unreliable Vote)
By: Anonymous (xxx.xxx.242.13)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=41207

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