How to Test an Orion Telescope

One test of a tescope is observing the moon.

Orion sells telescopes and binoculars at two retail locations in California, by mail order and online. Since 2005 the company has been a division of the Imaginova Corporation which makes digital media including a popular virtual planetarium named "Starry Night." Orion sells optical telescopes in most configurations including refractor, reflector, Dobsonian and Schmidt--Cassegrains. The company also provides free lifetime customer support by email and by phone for their products.

Instructions

1. Set up the telescope in a location away from light pollution on a full moon night. Wait at least 20 minutes for the telescope to cool to the ambient temperature.

2. Focus on the full moon. The moon should be perfectly sharp and free from false color under low magnification.

3. Increase magnification and look for image blurring. Image blurring may indicate only atmospheric turbulence so repeat the blurred image test several times.

4. Focus on a bright star high in the sky. Move the eyepiece in and out slightly. As you defocus the star should become an evenly illuminated and perfectly round disk in reflectors and refractors. In Schmidt--Cassegrains and other catadioptric telescopes the secondary mirror should appear as a shadow.

5. Repeat the defocusing test by moving the eyepiece. If the image is not identical when you defocus the eyepiece in both directions the telescope is slightly astigmatic.

6. Look for a short line as you focus and defocus the eyepiece in and out. Rotate the eyepiece if a line appears. If the line rotates with the eyepiece the eyepiece is defective.

7. Find a double star if you are an advanced enough astronomer to know how to do that. Search for defects by repeating the defocusing test on a double star.

References

• "Observing Double Stars"; Orion Telescopes and Binoculars
• "Testing your telescope -- Part 1"; Skymania Astronomy and Space Guide
• "Testing your telescope -- Part 2"; Skymania Astronomy and Space Guide