Classic 6-Inch f/5 Concave Telescope Primary Mirror

Outstanding vintage 6-inch f/5 concave spherical primary mirror on premium Pyrex low-expansion borosilicate glass – authentic surplus optic with an excellent underlying figure, perfect for building or upgrading a versatile Newtonian reflector.

The mirror shows some insignificant light surface haze on the protected aluminum coating – a common and completely normal characteristic of well-used vintage mirrors from years of faithful service and storage. This light haze is purely superficial (no scratches, pits, or damage to the glass figure) and actually presents a fantastic opportunity: many telescope makers love these mirrors precisely because they can be gently cleaned or professionally recoated (~$100–$150 at services like Spectrum Coatings or Galaxy Optics) to achieve like-new brilliance and even higher reflectivity. The result? A top-tier Pyrex parabolic mirror performing at its full potential – sharp, high-contrast views of the Moon, planets, star clusters, and deep-sky objects – all at a fraction of the cost of a new mirror.

This is classic ATM (amateur telescope making) gold – a thick, stable Pyrex blank ready for your personal touch and restoration!

Key Specifications:

• Diameter: 152 mm (~6 inches)

• Focal Length: ~762 mm (~30 inches – standard f/5)

• f/ratio: f/5 (most common modern balance of wide field and performance)

• Edge Thickness: 25 mm (thick low-expansion Pyrex blank ensures superior thermal stability)

• Curve: Spherical concave

• Material: Pyrex low-expansion borosilicate glass (classic pale ground back)

• Coating: Protected aluminum first-surface (bright broadband reflectivity)

• Condition: Excellent surplus figure – light surface haze/fuzz on coating (easily cleanable or recoatable); no optical damage

Popular f/5 ratio delivers bright, wide views with good planetary detail in a portable all-purpose scope.

Applications:

• Primary mirror for 6″ Newtonian telescope (deep-sky, planetary, or rich-field observing)

• Compact tube design with standard eyepiece compatibility

• High-speed focusing mirror for experiments

• Vintage surplus quality – stable and reliable for years of use

Pyrex f/5 6-inch mirrors are telescope-making favorites – this thick example ensures excellent figure retention and is ready for your next build.

Perfect for amateur telescope makers (ATM), astronomers, or anyone wanting a proven, versatile 6-inch primary!