What is cof-to-cof distance on a Dobsonian, and how do I measure it?

cof-to-cof means center-of-foot to center-of-foot, the straight-line distance between any two of the three feet on the bottom of your Dobsonian's ground board. Turn the rocker box upside down so the feet point up, identify the three foot positions, and measure between any two. The Sky Trekker 200 fits cof-to-cof distances of 10.875 to 12.0 inches (276 to 305 mm) or 14.3 to 15.4 inches (363 to 391 mm), corresponding to its two mounting positions.

Will my Dobsonian fit the JMI Sky Trekker 200 Wheeley Bar?

The ST 200 is designed for 8 to 10 inch Dobsonians. Confirmed-compatible models include the Meade LightBridge 8 inch, Orion SkyQuest XT8, and Celestron / Sky-Watcher 10 inch collapsible Dobsonians. If your Dob isn't listed, measure your cof-to-cof distance and confirm it falls in one of the ST 200's two ranges. The ground board must also be 22 inches in diameter or less.

Will the Sky Trekker 200 fit through my doorway?

The Sky Trekker 200 is 27 inches at its widest point (rear wheels) and 37 inches long front-to-back, and rides about 3.5 inches off the ground. Most interior doors of 30 inches or more easily accommodate the 27 inch width with a Dob mounted; check garage door tracks and any oddly-shaped passages. The layout drawing on the product page has full dimensions.

JMI Sky Trekker 200 Wheeley Bar for 8-inch Lightbridge Dobsonian, product photo

JMI Wheeley Bar with Dobsonian telescope, customer photo

JMI Sky Trekker 200 Wheeley Bar with 8-inch Lightbridge Dobsonian, view 3

JMI Wheeley Bar with Dobsonian telescope, product detail

JMI Sky Trekker 200 Wheeley Bar with 8-inch Lightbridge Dobsonian, view 1

JMI Sky Trekker 200 Wheeley Bar with 8-inch Lightbridge Dobsonian, view 2

JMI Wheeley Bar with Dobsonian telescope, product view

JMI Sky Trekker Wheeley Bar for Dobsonian telescopes — demonstration video

Sky Trekker 200 Wheeley Bar for Dobsonian telescopes

SKU: TPWLB8

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Sky Trekker Series · For Dobsonian Telescopes

Save your back — roll your Dobsonian out in one trip.

The JMI Sky Trekker 200 Wheeley Bar makes moving a heavy or awkward Dobsonian telescope a breeze. Roll your scope from storage to your observing spot, level the base on its built-in leveling screws, and start observing — the whole process takes about a minute, nearly effortlessly. You’ll observe more and enjoy the hobby more when setup is this quick. Built on a sturdy welded-steel frame by JMI (part of the CXB Astro family) and made in the USA.

The ST 200 is the smaller member of the Sky Trekker series, designed for 8″ to 10″ Dobsonians. It offers two mounting positions on the base to accommodate the two most common foot-spacing patterns in this size class. If your Dob is in the 10″–12″ range, compare against the Sky Trekker 300 below.

Specifications

Fits Dobsonian class

8″–10″ Dobsonian telescopes

Foot-to-foot (cof-to-cof) range

10.875″–12.0″ (276–305 mm) or 14.3″–15.4″ (363–391 mm)

Maximum ground board

22″ diameter

Wheels

10″ pneumatic tires — all-terrain, all-surface (no upgrades needed)

Lift height

Raises the setup ~3.5″ off the ground

Footprint

27″ wide (at rear wheels) × 37″ long

Construction

Welded steel, locking wheels, leveling bolts. Made in USA.

Which Sky Trekker Fits Your Dob?

The Sky Trekker series comes in two sizes — match your Dob to the right one. Don’t know your foot-to-foot distance yet? Jump down to How to Measure.

Model

Fits

Fit measurement

Sky Trekker 200This model

8″–10″ Dobs

cof-to-cof: 10.875″–12.0″ or 14.3″–15.4″

Sky Trekker 300

10″–12″ Dobs

cof-to-cof: 15.75″–16.875″ or 19.5″–20.625″

Sky Trekker 350

12″–14″ Dobs

ground board: 28″–32″ diameter

Sky Trekker 400

14″–16″ Dobs

ground board: 28″–32″ diameter

Have a Triangle-base Dob or a different mount style? See our full Wheeley Bars range.

Telescopes Known to Fit the ST 200

Meade LightBridge 8″
Orion SkyQuest XT8
Celestron / Sky-Watcher 10″ Collapsible Dobsonian

If your Dob isn’t listed, measure your foot-to-foot distance (instructions below) and compare it to the spec box — if your number falls inside one of the ST 200’s two ranges, you’re good to go.

See the Sky Trekker in Action

JMI Sky Trekker Wheeley Bar in action — watch the demonstration video

Watch a Sky Trekker carry a Dobsonian across the yard. The video also plays in the product gallery above.

How to Measure Your Dob’s cof-to-cof Distance

“cof-to-cof” is center-of-foot to center-of-foot — the straight-line distance between any two of the three feet on the bottom of your Dob’s ground board. To measure:

1. Turn the rocker box of the telescope upside down so the ground board is on top and the feet point up.

2. Identify the three foot positions on the underside of the ground board.

3. Measure the straight-line distance between the centers of any two feet. Be reasonably accurate — within about 1/8″.

4. Compare your number to the ranges in the spec box above (and to the comparison table for ST 200 vs ST 300).

Example: measuring Dobsonian ground board center-of-foot to center-of-foot distance

Example of a ground board cof-to-cof measurement — click to enlarge.

Frequently Asked Questions

What is cof-to-cof distance, and how do I measure it?

cof-to-cof stands for center-of-foot to center-of-foot — the straight-line distance between any two of the three feet on the bottom of your Dobsonian’s ground board. To measure, turn the rocker box upside down (feet pointing up), identify the three foot positions, and measure between any two. The ST 200 fits cof-to-cof distances of 10.875″–12.0″ (276–305 mm) or 14.3″–15.4″ (363–391 mm), corresponding to its two mounting positions.

Will my Dobsonian fit the Sky Trekker 200?

The ST 200 is designed for 8″ to 10″ Dobsonians. Telescopes known to fit include the Meade LightBridge 8″, Orion SkyQuest XT8, and Celestron / Sky-Watcher 10″ Collapsible Dobs. If your Dob isn’t on that list, measure your cof-to-cof distance and confirm it falls in one of the ST 200’s two ranges. Your Dob’s ground board must also be 22″ in diameter or less.

Why doesn’t the Sky Trekker come with wheel options?

The Sky Trekker series ships standard with 10″ pneumatic tires — these are designed for all-terrain use straight out of the box (concrete, sidewalks, grass, dirt, and gravel). The wheel-swap upgrade path used on the Universal Wheeley Bars isn’t needed for the Dob-specific Sky Trekkers. Take care on soft or wet ground, where pneumatic tires can sink in.

Will it fit through my doorway?

The Sky Trekker 200 measures 27″ at its widest point (rear wheels) and 37″ long front-to-back, and rides about 3.5″ off the ground. Most interior doors (30″+) easily accommodate the 27″ width with a Dob mounted; check garage door tracks and any oddly-shaped passages. The PDF layout drawing below has full dimensions.