Celestron AstroMaster 90EQ Refractor Telescope User Manual

1. Introduction

The Celestron AstroMaster 90EQ is a refractor telescope designed for both astronomical and terrestrial observation. It features 90mm fully-coated optics, providing clear views of celestial objects such as the Moon, planets, and brighter deep-sky objects, as well as land-based targets. This manual provides instructions for the assembly, operation, and care of your telescope to ensure optimal performance and longevity.

Image 1: The Celestron AstroMaster 90EQ Refractor Telescope, fully assembled on its equatorial mount and adjustable tripod.

2. What's in the Box

Verify that all components are present before beginning assembly:

• Optical tube
• Tripod and equatorial mount (preassembled)
• 20mm eyepiece
• 10mm eyepiece
• StarPointer red-dot finderscope
• User Manual (this document)

3. Setup Instructions

Assembly of the AstroMaster 90EQ is designed to be straightforward and tool-free. Follow these steps for initial setup:

1. Tripod Setup: Spread the tripod legs outward until they are fully extended. Secure the accessory tray to the center brace of the tripod. Adjust the leg height to your desired viewing position using the leg clamps.
2. Mounting the Optical Tube: Locate the dovetail bar on the optical tube. Slide this bar into the dovetail clamp on the equatorial mount. Tighten the clamp knob securely to prevent the tube from slipping.
3. Attaching the Finderscope: Slide the StarPointer red-dot finderscope bracket into the receptacle on the optical tube. Tighten the small screw on the receptacle to hold it in place. Ensure the battery is correctly installed in the finderscope.
4. Inserting Eyepieces: Loosen the thumbscrew on the diagonal (the angled piece at the end of the optical tube). Insert the desired eyepiece (e.g., 20mm for lower magnification) into the diagonal and tighten the thumbscrew to secure it.
5. Balancing the Mount: For an equatorial mount, proper balance is crucial for smooth tracking. Adjust the counterweight along its shaft until the telescope is balanced in Right Ascension (RA). Similarly, adjust the optical tube within its dovetail clamp until it is balanced in Declination (DEC).

4. Operating Instructions

Once assembled, follow these steps to begin observing:

1. Aligning the Finderscope: Before using the telescope, the finderscope must be aligned with the main telescope. Point the main telescope at a distant, stationary object (e.g., a streetlight during the day). Look through the finderscope and adjust its alignment screws until the red dot is centered on the same object that is visible in the main telescope's eyepiece.
2. Focusing: Once an object is centered in the eyepiece, turn the focus knob slowly until the image appears sharp and clear.
3. Using the Equatorial Mount:
   • Polar Alignment: For astronomical tracking, roughly align the mount's polar axis with Polaris (the North Star) in the Northern Hemisphere. This allows for easier tracking of celestial objects.
   • Tracking: After polar alignment, celestial objects can be kept in view by turning only the Right Ascension (RA) slow-motion control knob. This compensates for the Earth's rotation.
4. Observing Tips:
   • Start with the lowest magnification eyepiece (20mm) to locate and center objects.
   • Switch to higher magnification (10mm) for more detailed views once the object is centered.
   • Allow your eyes to adapt to darkness for better night sky viewing.
   • For terrestrial viewing, ensure the 90° erect image diagonal is used to provide a correctly oriented image.

5. Maintenance

Proper care will extend the life and performance of your telescope:

• Cleaning Optics: Use a soft, lint-free cloth or a specialized optical cleaning kit. Avoid touching optical surfaces with bare hands. Dust can be removed with a camel hair brush or compressed air.
• General Care: Keep the telescope covered when not in use to protect it from dust and moisture. Store it in a dry, temperature-controlled environment. Avoid exposing the telescope to extreme temperature changes.
• Mechanical Parts: Periodically check all screws and knobs for tightness. Do not overtighten.

6. Troubleshooting

If you encounter issues, refer to these common solutions:

• Image is blurry: Adjust the focus knob slowly. Ensure the eyepiece is fully inserted and secured. Check for condensation on the optics.
• Cannot find objects: Verify that the finderscope is properly aligned with the main telescope. Start with the lowest magnification eyepiece. Ensure the lens caps are removed.
• Telescope wobbles: Ensure all tripod leg clamps and mount knobs are securely tightened. Extend the tripod legs only as far as necessary for stability.
• Red dot finderscope not working: Check the battery. Ensure the power switch is on.

7. Specifications

8. Warranty and Support

The Celestron AstroMaster 90EQ Refractor Telescope is backed by a 2-Year US Warranty. For technical assistance, support, or warranty claims, please contact Celestron's US-based customer support team. Further information can be found on the official Celestron website.

For additional resources and astronomy software, visit the Celestron Store on Amazon.