JMI Sky Trekker 400 Wheeley Bar — Large Dobsonian Telescope Dolly

Product Overview

The JMI Sky Trekker 400 Wheeley Bar is a Dobsonian dolly for telescopes in the 14″ to 16″ class, built around ground boards measuring 28″ to 32″ across. The assembled Dob sits on a welded steel frame carried on four 10″ pneumatic all-terrain tires and steered with a tow handle, which lifts the telescope roughly 4″ to 5″ off the ground and moves it out in one piece. The frame measures 33″ wide at the rear wheels by 53″ front to back including the wheels, and weighs 30.0 lb. JMI designs and builds it in the USA.

Who It's For

This is a good match if you own a 14″ or 16″ Dobsonian and the rocker box is heavy enough that moving it by hand shapes how often the telescope comes out. It suits large truss-tube Dobs kept assembled in a garage, shed or observatory, and setups where the telescope travels a meaningful distance to a dark-sky pad rather than a few feet onto a driveway.

Key Features & Design

• Sized for 14″–16″ Dobsonians: Built around ground boards of 28″ to 32″ outside diameter.
• Four 10″ pneumatic tires: All-terrain air-filled tires at all four corners.
• Tow handle: Steers the loaded frame from the front rather than pushing it from the rocker box.
• 4″ to 5″ of lift: Raises the telescope clear of grass, gravel and standing water.
• 33″ × 53″ footprint: 33″ across at the rear wheels and 53″ front to back with the wheels included.
• Locking wheels and leveling bolts: Lock the frame at the observing position and bring the base flat.
• Welded steel: Designed and built by JMI in the USA.

Mechanical Design

The Sky Trekker 400 is specified by the outside diameter of the Dobsonian ground board — 28″ to 32″ — rather than by the spacing of the feet beneath it, which is how the larger Sky Trekkers differ from the 200 and 300. The tow handle is the piece that changes how a 16″ Dob moves: pulling from the front of a 53″ frame steers the load along a line, where pushing a tall telescope from behind tends to steer it into whatever it was being aimed away from. Four 10″ pneumatic tires spread the mass and take the shock of ridges and ruts in the air rather than through the frame into the optical tube, and the 4″ to 5″ of lift keeps the board clear of the ground on the way out. Once the telescope is placed, the wheels lock and the leveling bolts take up the slope of the surface.

Recommended Uses

• Moving an assembled 14″ or 16″ truss-tube Dobsonian from a garage or shed to an observing pad
• Towing a large-aperture Dob across a longer run of ground to a dark-sky position
• Keeping a large Dob permanently on its dolly so the rocker box is never lifted
• Crossing grass, gravel and uneven surfaces on air-filled all-terrain tires
• Repositioning a heavy telescope during the night to work around obstructions

Compatibility and Accessory Notes

The Sky Trekker 400 is specified for Dobsonian telescopes in the 14″ to 16″ class whose ground board measures between 28″ and 32″ outside diameter. JMI names the Meade LightBridge 16″ and the Orion SkyQuest XX12g, XX14g and XX14i among the telescopes it fits. The outside diameter of the ground board settles the fit rather than the aperture printed on the tube. The loaded frame is 33″ wide and 53″ long, which is the dimension that has to clear doorways, gates and the route to the observing position. Smaller Dobsonians are covered by the Sky Trekker 200, 300 and 350. Tell us your telescope model or the outside diameter of its ground board, and we'll confirm the fit before you order.

Good to Know Before You Order

• Fit is set by ground board diameter. The published range is 28″ to 32″ outside diameter, and a board outside that sits outside the published fit.
• The frame is 33″ by 53″ including the wheels. The 53″ length matters as much as the width for doorways, turns and storage.
• This is a Dobsonian dolly. It carries a Dobsonian ground board; tripod-mounted telescopes are served by the Universal Wheeley Bars.
• The tires are pneumatic. Air-filled tires hold pressure and are topped up like any other pneumatic tire.
• Lift is 4″ to 5″. The eyepiece rises by the same amount at a given altitude, which raises the observing height on an already tall telescope.
• The dolly weighs 30.0 lb on its own, before the telescope is added.
• The 350 and 400 share a published footprint and board range. JMI lists the same 33″ × 53″ frame and 28″–32″ board range for both, with the stated aperture class being the difference — we are glad to sort out which model suits your telescope.

Frequently Asked Questions

Is it difficult to set up?

The dolly is a welded steel frame, so setup means placing the Dobsonian's ground board onto it, winding the leveling bolts until the base sits flat, and locking the wheels once the telescope is where you want it.

How do I know whether my Dob fits?

By the outside diameter of its ground board, specified at 28″ to 32″ for this model. The Meade LightBridge 16″ and the Orion SkyQuest XX12g, XX14g and XX14i are named fits, and we are glad to check any other telescope against that range.

What does the tow handle do?

It lets the loaded frame be pulled and steered from the front, which gives more control over a tall, heavy telescope than pushing it from behind.

How does it differ from the Sky Trekker 350?

JMI publishes the same 33″ × 53″ frame and 28″–32″ ground board range for both, and specifies the 350 for the 12″ to 14″ class and the 400 for the 14″ to 16″ class. Where a telescope sits near that boundary, we are happy to work it out with you.

Are there wheel options to choose?

No. Four 10″ pneumatic all-terrain tires are standard on this model, so there is no wheel upgrade to add.

Does the telescope stay on it between sessions?

It can, and on a Dob of this size that is the usual arrangement, since it removes the rocker box lift from the session entirely.

Bottom Line

In short: the Sky Trekker 400 is the Dobsonian dolly for the 14″ to 16″ class — a 33″ × 53″ welded steel frame on four 10″ pneumatic all-terrain tires with a tow handle, 4″ to 5″ of lift, locking wheels and leveling bolts, at 30.0 lb and built by JMI in the USA. Fit comes down to a ground board of 28″ to 32″ outside diameter, and we will happily check that figure with you.