Explore Scientific 6-inch Dobsonian Reflector Telescope

The Classic 6-inch Dobsonian: Aperture and Simplicity

This telescope follows the classic Dobsonian idea: a reflector on a simple base you move by hand. It suits a first telescope that goes beyond the Moon to planets and bright deep-sky objects, and a quick-setup scope for experienced observers.

The Dobsonian concept is about simplicity and direct connection to the sky. There are no electronics to master or polar alignment to perform. You place the base on the ground, set the tube on it, hook the two springs onto their posts, and move the tube by hand. This manual approach is a fantastic way to learn the constellations and develop the fundamental skill of locating celestial targets on your own.

154mm f/7.6 Parabolic Mirror System

At the heart of the telescope is a 154mm (6-inch) parabolic primary mirror. A paraboloid figure avoids the spherical aberration of a spherical mirror. The 1170mm focal length gives f/7.6, and a slower focal ratio like this is generally more tolerant of small collimation errors and easier on eyepieces than a fast one.

The optical system also includes a 37.5mm secondary mirror, giving a central obstruction of 24.4% by diameter. The mirror coatings have 90% reflectivity with an SiO2 overcoat.

What You Can See with a 154mm Aperture

Start with bright, easy objects such as the Moon or Saturn. The Moon shows craters, rilles and mountains. You will see the rings of Saturn, track the four Galilean moons of Jupiter, and spot its main atmospheric cloud belts. Under good conditions, you can even identify the polar ice caps on Mars when it is near opposition.

In deep space the Orion Nebula (M42) shows its glowing cloud, the Andromeda Galaxy (M31) shows its bright core, and higher power starts to resolve the outer stars of bright globular clusters such as the Hercules Cluster (M13).

A 1120mm Tube on a Simple Dobsonian Base

The optical tube assembly is 1120 mm long with a 185 mm outer diameter and comes fully assembled. The base is assembled once from wooden panels with the included tools and, per the manual, does not need to be taken apart except for shipping or long-term storage.

The Dobsonian base sits on bearing pads. It moves in two directions: altitude (up-down) and azimuth (left-right). Its spring tension system uses two springs that hook from the tube's altitude bearings to spring posts on the base. The system maintains tube balance and accommodates optional accessories, and the tube moves smoothly while staying in place when released.

2-inch Crayford Focuser and 25mm Plössl Eyepiece

The telescope has a 2-inch Crayford focuser with a focus lock thumbscrew. Removing the 1.25-inch adapter from the 2-inch collar lets you use 2-inch eyepieces (sold separately).

The telescope includes a 25mm Plössl eyepiece in the 1.25-inch format. With the telescope's 1170mm focal length, this eyepiece provides a magnification of 47x. That is a good starting power for locating objects and viewing open star clusters. An extension tube is also in the box.

Locating Objects with the Included Red Dot Scope

To help you aim the telescope, a red dot scope is included. It projects a small red dot onto a clear glass window. To use it, you turn it on, look through the window with both eyes open, and move the telescope until the red dot appears to be on top of your target in the sky.

Before your first observing session, you must align the red dot scope with the main telescope. Center a distant object in the 25mm eyepiece, move the red dot onto the same object with the finder's adjustments, and check on a second object. It stays accurate unless bumped or removed.

Aligning the Primary and Secondary Mirrors

All Newtonian reflector telescopes require occasional optical alignment, a process called collimation. The optics were collimated in the factory but may have moved during shipment.

The process involves two main adjustments:

• Secondary Mirror Tilt: Looking into the empty focuser, tilt the secondary mirror with its three collimation screws until it appears round.
• Primary Mirror Tilt: Loosen the three small lock thumbscrews by no more than two turns, then turn the three spring-loaded knobs at the bottom end of the tube a quarter turn at a time until the secondary mirror's reflection is centered on the primary. The primary mirror is center-marked to aid in precise alignment with optional collimation tools.

Tube and Base Weights

The optical tube weighs 11 lbs 14.3 oz and the base 19 lbs 6 oz. A handle attaches to the base during assembly.

To carry it, unhook the springs from the spring posts on the base; the springs stay on the tube so they are not lost. Let the telescope cool outdoors for 20 to 30 minutes before observing.