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Diagonal Mirror 90 Degree Comparison - April 2026
| 1 Best Choice  9.9Exceptional | 2  9.7Exceptional | 3 Best Value  9.6Exceptional | 4  9.3Excellent |
| View DealOn Amazon | View DealOn Amazon | View DealOn Amazon | View DealOn Amazon |
ModelSVBONY SV188P Dielectric Mirror Star Diagonal, 90 Degree Mirror Diagonal, 99% Reflectivity Dielectric Coatings with Brass Compression Rings (2 inch) | Model SVBONY SV188P Dielectric Mirror Star Diagonal, 90 Degree Mirror Diagonal, 99% Reflectivity Dielectric Coatings with Brass Compression Rings (1.25 inch) | Model Astromania 1.25 Inch Telescope Diagonal with Amici Erecting Prism - 90° Fully-Coated Star Diagonal for Upright & Clear Astronomical Viewing, Metal/Plastic Construction, Enhanced Optical Transparency | Model SVBONY SV221 90 Degree Diagonal Mirror, Telescope Diagonal 1.25 inches with Brass Compression Rings, Telescope Accessory for Refractor Telescope |
BrandSVBONY | Brand SVBONY | Brand Astromania | Brand SVBONY |
Reviews | Reviews | Reviews | Reviews  |
Tech Specs | |||
product dimensions4.4 x 2.4 x 3.3 inches | product dimensions 4.4 x 3.3 x 2.4 inches | product dimensions 4.42 x 2.8 x 2.11 inches | product dimensions 3.94 x 1.97 x 2.36 inches |
item weight1.43 pounds | item weight 7 ounces | item weight 4.6 ounces | item weight 3.17 ounces |
Available On | Available On | Available On | Available On |
Our Top 3 Picks
Here are the top 3 recommended products with more information to help you find the right product for you
9.9
1SVBONY12% OffSVBONY SV188P Dielectric Mirror Star Diagonal, 90 Degree Mirror Diagonal, 99% Reflectivity Dielectric Coatings with Brass Compression Rings (2 inch)
Main highlights- The interior of the SV188P has been specially treated to eliminate stray light; spray matte paint; the side burgundy cover is made of aluminum plate; and matte velvet is attached; it can effectively eliminate stray light; get a bright image
- The diagonal is made of aluminum alloy; the lens uses a high-precision plane mirror with a 1/4 wavelength error; and the surface is coated with a dielectric film with a reflectivity of up to 99% to improve the performance of the reflector; the surface of the lens barrel is treated with black bright oxidation; beautiful and generous
- Star diagonal adopts a side screw locking design; there is a brass pressure ring inside the barrel; so that the eyepiece surface will not be damaged when locking the eyepiece; it has an eyepiece anti-contact block design; better protect your eyepiece from damage
- SV188P diagonal uses a high-reflective dielectric coating; more durable and more reflective than enhanced aluminum coating; reflectivity is up to 99%; for maximum field of view brightness and clarity
- 90 degree viewing angle; provides a more comfortable viewing angle to observe the starry sky above; provides an upright image; comfortable observation; reducing the steps of post-image processing
- 2-inch dielectric mirror diagonal; suitable for 2-inch telescopes and eyepieces; supports 2-inch filter installation; comes with a 2-inch to 1.25-inch converter; can be connected to 1.25-inch eyepieces; barlow and other telescope accessories
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9.7
2SVBONY10% Off
SVBONY SV188P Dielectric Mirror Star Diagonal, 90 Degree Mirror Diagonal, 99% Reflectivity Dielectric Coatings with Brass Compression Rings (1.25 inch)
Main highlights- Dielectric coatings; super flat mirror with dielectric coatings to reduce reflected light loss; provide an over 99% reflective surface; good for astronomical viewing
- Correct upside down and left right reversed image; the view image is upright; but left and right reversed if use the 90 degrees to your telescope
- Brass compression ring; Built in brass ring and thumbscrew accessories avoid eyepiece to rotate during adjustments; effortless fixes more firmly and will not scratch your eyepieces barrels
- 90 degree viewing angle; diagonal reflects the telescope’s light path 90 degree to provide a more comfortable viewing angle; best for observing objects overhead
- 1.25 inches nosepiece fits 1.25 inches telescopes; accepts standard 1.25in filters; eyepieces; Barlow lenses and other accessories with a 1.25in insert barrel
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9.6
3Astromania20% Off
Astromania 1.25 Inch Telescope Diagonal with Amici Erecting Prism - 90° Fully-Coated Star Diagonal for Upright & Clear Astronomical Viewing, Metal/Plastic Construction, Enhanced Optical Transparency
Why we love it
Clear, sharp images with BK7 glass.
Ideal for both day and night use.
Secure eyepiece with metal barrels.
Main highlights- Sophisticated Aesthetics & Ergonomics: The high-gloss finish resists fingerprints and scratches, while the compact lightweight design ensures portability for field astronomy
- Resitant 1.25 Inch Telescope Diagonal Build: Combining an premium-grade aluminum barrel and impact-resistant ABS housing, this diagonal withstands extreme temperatures from -20°C to 60°C while fitting all 1.25" focusers
- Premium Fully-Coated Diagonal for Optimal Clarity: Multi-layer dielectric coatings on prisms and lenses ensure 89% reflection for a bright image; surpassing standard mirrors in brightness and sharpness for Star Diagonal applications
- Erect Image Diagonal with Amici Prism Technology: The integrated Amici Prism Diagonal BK7 optical glass corrects image orientation; delivering upright & non-reversed views—perfect for birdwatching and deep-sky exploration
- Enhanced Compatibility & Versatility: Utilize the M28.5×0.6mm filter thread to attach 1.25 inch moon filters or nebula filters, expanding your telescope diagonal’s functionality across celestial and terrestrial targets
- Control Engineering for Crisp Imagery: Internal glare-eliminating threads and dual rubber dust caps minimize glare and debris; ensuring to improve brightness of image and reduce dark edge formed
- 90° Telescope Diagonal for Comfortable Viewing: Experience effortless astronomical observation with Telescope Diagonal Mirror featuring 90° angle design; Maintain an upright & comfortable posture, whether observing planets or terrestrial landscapes
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