New Obsession UCs

Post by **rcj** » Wed May 16, 2007 2:56 pm

Hi all,

This might be good news for some of us here who are obsessed with Obsessions

Dave has released news of the new UC line (Ultra Compact) for 15 and 18 inchers at the recent TSP.

Some of the excerpts (features) are:

- made in 15" (airline portable!) and 18" diameters.
- UC stands for Ultra Compact.
- Cost for the f/4.2 18" will be the same as for the Obsession 18" classic with Feathertouch focuser upgrade.
- It's a 6-truss design with folding altitude bearing, and goes about 14" high. No mirror box. Reverse mirror cell (designed for clearance issues) Full 2" thick mirror by OMI, reverse mirror cell (Dave Chandler design) with two collimation knobs on the lower end of the cell.The Feathertouch focuser fits on a specially-made bracket, so there are no other focusers available yet. The tube near the Telrad is for insertion of weights to balance the scope. Rather than put 5 times the weight of a 31 Nagler down near the mirror to balance binoviewers and heavy eyepieces, the scope is bottom heavy, and you place aluminum tubes filled with sand or lead shot up in the UTA to balance the scope.
- The 6 truss tubes are 1" diameter, and all attached to one another so you can't lose one. Production tubes will be 1.25" diameter. Availability of the 18" is expected by the end of the year, with the 15" available some time in 2008.
- OMI will make the first primary mirrors for the UC. Only the f/4.2 focal ratio will be available at this point. Don Holcolme with Scope Guard may make cases for the scope, which means Obsession can ship them right to you!

Reference:
Cloudynights TSP

Canopus Lim · Post by **Canopus Lim** » Wed May 16, 2007 3:19 pm

Wow Remus beat me in posting this!

The new Obsession Ultra Compact is real small! 15" to be airline portable. Wow. If it incorporates servocat and Argo Navis, it would be really the smallest GOTO dob in the market. There is no heavy mirror box and it is a very minimalist design. The issues I see is that it should allow the use of shroud and more light baffles since it is rather 'exposed' to ambient light.

For the portability and size it is really great. The 18" is smaller than my 12.5"!

Post by **rcj** » Wed May 16, 2007 4:40 pm

Dave has done it again!! My....*drool*

Post by **VinSnr** » Wed May 16, 2007 5:50 pm

Finally someone did an Ultra-light dob for consumer sale.. Long overdue for this kind of scope.

Just make sure don't kick sand onto that mirror because it's so low. Also, the truss looked triangular, which means implementing a shroud would be difficult. Over here might need a dew heater for the primary if we can't put a shroud there.

ariefm71 · Post by **ariefm71** » Wed May 16, 2007 6:39 pm

Looks like a copy of other similar ultralight design, e.g. http://www.xmission.com/~alanne/DS4Main.html

The trade-off for such scopes are stability, very difficult to get high magnification without vibration problem. A waste of the premium primary mirror, imho. I'll take the old-style obsession any day

Post by **acc** » Wed May 16, 2007 8:28 pm

But imagine how nice it would be to take this scope to the aussie outback. Or even NZ. I can't do that with my portaball

Canopus Lim · Post by **Canopus Lim** » Wed May 16, 2007 11:24 pm

If it can incorporate servocat, stability is non issue since it is tracking. For that portability, a trade off in stability is reasonable. At least for DSOs it will perform very well due to much lower magnifications and since most people travel to dark sites, planetary is of least importance for the tremendous aperture gain. Even better still is the 15" which is airline portable. Which 15" scope can be brought on the airplane? I for sure cannot bring my Obby on the airplane

Even the portable SCTs loses to it in portability.

Post by **weixing** » Wed May 16, 2007 11:48 pm

Hi,
Hmm... Seem quite complicated to set it up... and may be a bit too dangerous at night... I mean dangerous for the mirror:

Scope Owner: "Quick... come here, look at the awesome M51 though my Obsession UC!!!"
Obs Buddy: "Here I come!!! Where??? I can't see anything??"
Scope Owner: "Err... You are stepping on the Mirror... "

Have a nice day.

PS: Hope it's won't happen.... touch wood!!

ariefm71 · Post by **ariefm71** » Thu May 17, 2007 12:49 am

The best is to have both the old-style structure as well as the airline portable version. I have a feeling someone here (initial "T"?) will order the UC version as well to complement the conventional structure for his 15" Z mirror.

Arief

Post by **rcj** » Thu May 17, 2007 12:58 am

guys, think it is still early to say for sure how the UC version performs. Some other UK based manufacturers have been doing this for years too, but the exposure in the States with regards to such minimalistic structures are still embryonic. It would be advisable to wait for the 'dust to settle' and have more user feedback and experience before any serious 'embarkment'.