Ursa Major 8" f/6 Dobsonian

Worth knowing before you buy

How does the Ursa Major 6" Dobsonian compare to a basic 80mm refractor for planetary viewing?

Multiple forum members assert that a properly set-up and collimated Ursa Major 6" should significantly outperform an 80mm refractor, given its larger aperture and 1200mm focal length. However, one user's real-world experience showed the opposite result until collimation issues were identified, highlighting that out-of-the-box performance may disappoint if the scope arrives needing collimation.

Does the Ursa Major 6" or 8" Dobsonian arrive in good collimation, or will it need adjustment straight away?

Several forum members identified collimation as the likely cause of one new owner's very poor initial views, where the Ursa Major 6" appeared worse than a 20-year-old 80mm refractor. Forum members recommended checking and correcting collimation before first serious use, with a link to a beginner's guide by Gary Seronik cited as helpful.

How does the Ursa Major Dobsonian's Crayford focuser work — which screw is for locking and which is for tension?

This question came up across multiple threads, with users confused by the focuser's three screws and unclear instructions. A forum member clarified that the bottom screw is the focus lock and the top is the tension adjustment, adding that one screw can restrict full travel if left in place.

Do the GSO mirror cell springs and collimation screws on the Ursa Major Dobsonian need to be upgraded with Bob's Knobs?

This is discussed across threads, with some members recommending Bob's Knobs thumbscrews for the secondary and stiffer springs for the primary. However, FLO directly clarified in one thread that the springs fitted to current GSO-manufactured scopes sold under the Ursa Major and StellaLyra brands are not the same weaker springs as earlier models, and that older internet advice about replacing them may no longer be relevant.

Is the straight-through finder scope on the Ursa Major Dobsonian adequate, or should it be upgraded?

Multiple users found the stock straight-through finder awkward, particularly at higher elevations, with one user describing it as "almost unusable" due to the uncomfortable viewing angle. Forum members consistently recommended upgrading to a right-angle correct-image (RACI) finder, and one member suggested pairing a cheap red-dot finder with a RACI to locate objects quickly.

Is the Ursa Major 8" Dobsonian better value than the 6" given the same 1200mm focal length?

At least one experienced forum member noted that both the 6" and 8" Ursa Major share a 1200mm focal length, and recommended the 8" for its significantly greater light-gathering power — nearly twice that of the 6". The 8" StellaLyra version was also highlighted as coming better-equipped with a two-speed Crayford focuser, smoother alt-az motion, a RACI finder, adjustable balance points, and a cooling fan, which members said more than justified the price difference.