20/25/28/30/35/40/42/45/ 50/54/60/70/80/90mm Astronomical Telescope Secondary Mirror

Key Benefits

• Elliptical shape matches Newtonian telescope optical design for accurate light reflection
• Aluminum coating with protective film ensures high reflectivity and long-term durability
• Short axis sizes from 20mm to 90mm allow compatibility with a range of main mirror apertures
• Tolerance of ±0.5mm ensures precise fit and alignment in the telescope tube
• Surface accuracy of 1/4-1/6λ PV delivers sharp, low-distortion image quality
• Single-piece construction simplifies assembly and reduces alignment errors

Application Scenarios

• Building a custom Newtonian reflector telescope with a 76mm to 203mm main mirror
• Replacing a damaged secondary mirror in a DIY telescope without buying a full assembly
• Matching a secondary mirror to a specific main mirror aperture for optimal light collection
• Testing optical alignment during telescope assembly with a known, accurate secondary
• Using in educational or amateur astronomy projects requiring a precise, low-cost mirror

Who It Is For

• Amateur astronomers building or upgrading Newtonian reflector telescopes
• Educational institutions teaching optics and telescope construction
• DIY hobbyists assembling telescopes from component parts
• Science outreach programs requiring low-cost, functional optical components
• Small-scale telescope makers sourcing individual mirrors for custom builds

Problems It Solves

• A mismatched secondary mirror causes light loss and image distortion in a Newtonian telescope
• A poorly coated mirror reduces reflectivity and increases image noise
• Lack of tolerance control leads to misalignment and focus issues during assembly
• No protective film causes surface oxidation and degradation over time
• Buying a full telescope assembly when only the secondary mirror needs replacement

Technical Features

• Elliptical plane mirror shape for Newtonian reflector systems
• Aluminum coating with protective film for high reflectivity and environmental resistance
• Short axis length ranges from 20mm to 90mm, with 20mm, 25mm, 28mm, 30mm, 35mm, 40mm, 42mm, 45mm, 50mm, 54mm, 60mm, 70mm, 80mm, 90mm available
• Tolerance: ±0.5mm on short axis dimension
• Surface accuracy: PV 1/4-1/6λ
• Single piece construction, no assembly required
• Designed for use with main mirrors from 76mm to 203mm aperture

Specifications

Specifications are taken from the AMADA product data for this item. Confirm critical dimensions with us in writing before ordering.

Customization Options

• Select from 14 available short axis sizes: 20mm, 25mm, 28mm, 30mm, 35mm, 40mm, 42mm, 45mm, 50mm, 54mm, 60mm, 70mm, 80mm, 90mm
• Standard aluminum coating with protective film is included
• No custom coating options or surface shapes beyond the elliptical plane

Comparison With Other Options

Use Guide

• Verify the short axis size matches your main mirror aperture before assembly
• Handle the mirror only by the edges to avoid fingerprints on the coated surface
• Clean the mirror only with a soft brush or compressed air; do not use solvents
• Align the mirror in the telescope tube with the optical axis using a laser collimator
• Ensure the protective film is intact before final installation to prevent damage