N /A 114mm D114 F900mm Newtonian Primary & 25mm Secondary

This D114F900mm replacement main mirror with a 25mm short-axis secondary mirror is a K9-glass optical component set designed to restore or upgrade small Newtonian telescopes for clearer planetary and deep-sky viewing.

If you need a direct-replacement or spare optical train for a beginner Newtonian or travel scope, this pair gives you a 114mm diameter primary mirror with a 900mm focal length plus a 25mm short-side secondary mirror. Both optics are made from K9 glass and receive an aluminum reflective coating with an aluminum-oxide protective layer. The components ship in separate packaging so they arrive protected and ready to install in compatible focuser and secondary holder assemblies.

What performance can I expect from a 114mm K9 primary with a 900mm focal length?

This mirror delivers a mid-aperture light-gathering area suitable for bright planets, the Moon, and many brighter deep-sky targets. The f/7.9 focal ratio balances magnification potential and eyepiece compatibility for general observing and simple astrophotography.

• 114 mm aperture gives improved resolution versus small toy scopes
• 900 mm focal length (f/7.9) supports medium to high eyepiece magnifications
• K9 glass substrate provides stable figure for visual use
• Aluminum + protective oxide coating enhances reflectivity and durability

How does the 25mm short-axis secondary mirror affect views and setup?

The short-axis 25mm secondary presents a compact obstruction that keeps the light path efficient for small Newtonians and reduces weight in travel setups. It’s sized to match small-diameter primary mirrors and is suitable for adult or children’s beginner telescopes that use a similar secondary holder geometry.

• 25 mm short-axis minimizes central obstruction while fully illuminating common eyepieces
• Spherical secondary is simple to align in collimation procedures
• Aluminized with protective film for handling and installation safety

How easy is installation and what accessories do I need?

These optics are replacement components intended for users familiar with collimation and basic mechanical installation in Newtonian tube assemblies. Installation requires a compatible secondary holder, focuser, and basic collimation tools; no specialized adhesives are necessary if the scope already has standard fittings.

• Fits telescopes designed for a 114mm primary with a 25mm-compatible secondary
• Requires a collimation cap or laser and a screwdriver for mounting adjustments
• Packaged separately to reduce dust and handling damage during shipping

Who is this for: This mirror pair is intended for amateur astronomers replacing or upgrading optics on entry-level Newtonian reflector telescopes, travel scopes, and educational telescopes. It’s a practical choice for hobbyists wanting a robust K9 glass primary with a compact secondary for planetary observation and casual astrophotography experiments, as well as for telescope builders needing standardized mirror sizes for custom tubes.