Best Telescope Diagonals (2026 Guide)
We selected diagonals by combining user rating and review volume with construction features (barrel size, coating type, prism vs mirror) and mechanical quality
The Verdict
- Best Overall: Astromania 1.25 — Best for terrestrial viewing: Amici prism provides upright images for daytime and casual sky observing without image reversal
- Best Premium: Celestron 2 inch LT Diagonal Mirror for SCT Telescope — Best for SCT users: 2" mirror diagonal built for SCT telescopes with a robust mirror design for heavier eyepieces
This guide compares top-rated telescope diagonals across common types (Amici, mirror, dielectric) to help you choose a diagonal that matches your telescope and observing goals. Picks were chosen based on aggregate user ratings, review volume, construction type (Amici/prism vs. mirror), and available barrel sizes and coatings
Top Picks
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1
Best Overall Astromania 1.25
Best for terrestrial viewing: Amici prism provides upright images for daytime and casual sky observing without image reversal
1.25 inch Amici prism diagonal delivering upright, non-reversed views with enhanced brightness. Users note crisp image clarity, sturdiness, and good value for the price
- Amici prism for upright images
- multi-layer coatings for brightness
- durable build for extreme temps
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2
SV188P Dielectric Mirror Star Diagonal 1.25in 90°
Best budget dielectric mirror: compact 1.25" diagonal with dielectric coatings and brass compression ring for reliable eyepiece fit
Dielectric-coated 90-degree star diagonal with brass compression rings for 1.25
- >99% reflective surface
- built-in brass ring for secure eyepieces
- upright image with left-right reversal in 90° mode
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3
SVBONY SV188P Dielectric 2" 90° Star Diagonal
Best 2" dielectric option: larger 2" mirror increases light throughput for wide-field and deep-sky eyepieces
SV188P dielectric star diagonal with 99% reflectivity for bright 2-inch optics. 90-degree viewing with brass compression rings and protective anti-damage features. Customers note clear optical alignment and good value
- 99% dielectric reflectivity
- aligned optics with anti-stray-light treatment
- durable brass compression rings and protective features
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4
SVBONY SV223 1.25" Dielectric Star Diagonal
Best compact high-reflectivity 1.25": premium dielectric coating and solid build focused on contrast and accurate star images
SV223 1.25" star diagonal with 90° design and 99% dielectric coating for clear, bright imaging. Clicklock locking mechanism ensures stable eyepiece installation
- 99% dielectric coating for bright images
- 90° star diagonal for comfortable viewing
- stable try-lock clamping with clicklock
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5
Best Premium Celestron 2 inch LT Diagonal Mirror for SCT Telescope
Best for SCT users: 2" mirror diagonal built for SCT telescopes with a robust mirror design for heavier eyepieces
2 inch SCT diagonal with high performance XLT coatings and precision housing. Supports clear, brighter views with quality alignment; noted for good optical clarity and fit
- 1/10 wave mirror quality tested
- precision machined housing for alignment
- includes adapter and carry case
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6
SV223 90° Diagonal Mirror with 2 in & 1.25 in adapters
Best adapter flexibility: includes both 2" and 1.25" adapters for quick switching between eyepiece sizes and setups
SV223 diagonal mirror with 99% dielectric coating for erect image. 90-degree design improves observation; sturdy aluminum build with clicklock locking for stable eyepiece attachment. Customer insight: stable fit reduces chance of component detachment
- 90-degree erect image design
- high-reflectivity dielectric coating
- secure clicklock locking mechanism
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7
SVBONY 90 Degree Diagonal Mirror 1.25" Telescope Diagonal
Best midrange 1.25" mirror: straightforward 90° diagonal that balances portability and optical performance
SVBONY SV222 90-degree diagonal mirror for refractor telescopes. 1.25 inch thread allows attaching filters; high reflectivity supports good imaging. Customers note good quality and clear images, with mixed build quality feedback
- 90-degree observation comfort
- 1.25" filter compatibility
- high reflectivity for clear images