# Best Star Diagonals for Comfortable Viewing (2026) Source: https://stargazernest.com/best/star-diagonals Updated: 2026-10-06 Publisher: Stargazer Nest. Our score is an editorial rating out of 10 (fit 35%, features 25%, build 20%, value 20%), not a customer rating. Method: https://stargazernest.com/how-we-research#our-score A star diagonal bends the light path 90 degrees so you look down into a refractor or SCT instead of crouching behind it. The two types are dielectric mirror diagonals, which offer very high reflectivity and neutral color, and prism diagonals, which can give excellent contrast in smaller scopes. Check the barrel size, 1.25 inch or 2 inch, whether it fits your focuser or SCT thread, and that it produces a correct right-side-up but mirror-reversed image, standard for astronomy. Star diagonals suit refractor, SCT, and Maksutov owners who want a comfortable viewing angle for targets high in the sky. A practical tip: a quality 2 inch dielectric diagonal with a 1.25 inch adapter covers both eyepiece sizes and loses almost no light, making it a good long-term buy. If you also glance at terrestrial scenery, consider an erecting prism diagonal that corrects the left-right flip for a natural daytime view. ## Picks ### 1. Celestron 93573 Dielectric Star Diagonal 2 inch with Twist Lock and 2 inch to 1.25 inch Step-Down Adapter Our score: 8.8/10 (Fit for the job 9/10 · Features and specs 9/10 · Build and materials 9/10 · Value 8/10) Celestron 93573 2 inch dielectric star diagonal with twist lock and 2 inch to 1.25 inch step-down adapter. Pros: - Step-down adapter supports both 2 inch and 1.25 inch eyepieces - Twist lock secures heavy eyepieces safely - Dielectric coating provides bright, contrasty views Cons: - Heavier than 1.25 inch diagonals, so small refractors may tip on light mounts - Premium price compared with budget 2 inch diagonals Details: https://stargazernest.com/product/B07VNHDHFL ### 2. Celestron Dielectric Star Diagonal 1.25 inch with Twist Lock 58 Layer Coating 99% Reflectivity Our score: 8.6/10 (Fit for the job 9/10 · Features and specs 9/10 · Build and materials 8/10 · Value 8/10) Celestron 1.25 inch dielectric star diagonal with twist lock and 58 layer coating for 99% reflectivity. Pros: - 58 layer dielectric coating reaches 99% reflectivity for bright views - Twist lock holds eyepieces securely without marring barrels - Celestron quality suits refractors and SCTs Cons: - Priced above basic diagonals with similar coating claims - Small-barrel format rules out wide-field 2 inch eyepieces Details: https://stargazernest.com/product/B07VRSL37R ### 3. SVBONY SV188P Telescope Diagonal, 2" 90°Mirror Diagonal 99% Reflectivity Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10) SVBONY's SV188P 2 inch, 90-degree dielectric diagonal with reflectivity stated at up to 99% and a 2 inch to 1.25 inch adapter included. A budget way into 2 inch wide-field eyepieces. Pros: - Dielectric coating with reflectivity up to 99%, described as more durable than an enhanced aluminum coating - Comes with a 2 inch to 1.25 inch converter and supports 2 inch filters, so both eyepiece sizes work - Brass pressure ring protects eyepiece barrels, and the interior is matte treated to cut stray light Cons: - Uses a side screw lock, not the twist-lock collar found on the pricier diagonals in this guide - Mirror accuracy is stated as 1/4 wavelength, a looser figure than premium diagonals quote Details: https://stargazernest.com/product/B0DLL5W5Y3 ### 4. SVBONY SV223 90 Degree Diagonal Mirror 99% Reflective Dielectric Star Diagonal 2 inch with 1.25 Adapter Our score: 8.4/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 7/10 · Value 9/10) SVBONY SV223 90 degree 2 inch dielectric star diagonal, 99% reflective, with 1.25 adapter. Pros: - 99% reflective dielectric coating delivers bright views - 1.25 adapter provides compatibility with smaller eyepieces - Affordable 2 inch upgrade for refractors and SCTs Cons: - Build finish may not match Celestron or Orion diagonals - Larger size adds weight to small telescopes Details: https://stargazernest.com/product/B0CFQBZWJM ### 5. SVBONY SV188P Telescope Diagonal 1.25" 90°Mirror Diagonal 99% Reflectivity Our score: 8.1/10 (Fit for the job 9/10 · Features and specs 7/10 · Build and materials 7/10 · Value 9/10) A 1.25 inch, 90-degree dielectric mirror diagonal with a stated reflectivity of over 99%. A low-cost upgrade for the diagonal on small refractors and Cassegrains with a 1.25 inch focuser. Pros: - Dielectric coatings on a super-flat mirror reduce reflected light loss, with the surface stated at over 99% reflective - 1.25 inch nosepiece accepts standard 1.25 inch filters, and the body takes 1.25 inch eyepieces and Barlow lenses - Brass compression ring with thumbscrew holds the eyepiece firmly without scratching the barrel Cons: - 1.25 inch format only, so it cannot take 2 inch wide-field eyepieces on a larger focuser - The view is upright but reversed left to right, as the listing notes, which is normal for a mirror diagonal Details: https://stargazernest.com/product/B08QRY4V97 ### 6. Astromania Telescope Diagonal 2" 90° Diagonal Mirror 99% Reflective Coating Our score: 8.0/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 6/10) A 2 inch, 90-degree dielectric mirror diagonal with a stated 99% reflectivity and a Pyrex glass mirror. It ships with an SCT adapter and a 2 inch to 1.25 inch adapter for refractors and Cassegrains. Pros: - Multi-layer dielectric coatings on a super-flat Pyrex mirror, with reflectivity stated at over 99% for brighter images - Includes both an SCT to 2 inch adapter and a 2 inch to 1.25 inch adapter, so it takes both eyepiece sizes - Listed as suitable for refractors, Schmidt-Cassegrains, ACF, EdgeHD and Maksutov-Cassegrain telescopes Cons: - The listing says it is not recommended for reflectors, especially Newtonians, so it is no use on a Dobsonian - Costs about twice as much as the budget 2 inch dielectric diagonal in this guide for the same stated reflectivity Details: https://stargazernest.com/product/B01M3P1S4B ### 7. SVBONY SV223 1.25” Telescope Diagonal, 90 Degree Dielectric Mirror Our score: 8.0/10 (Fit for the job 9/10 · Features and specs 8/10 · Build and materials 8/10 · Value 6/10) A 1.25 inch, 90-degree dielectric diagonal with a clicklock collar and a coating stated at 99% reflectivity. For observers who swap eyepieces often on a 1.25 inch focuser. Pros: - Clicklock mechanism clamps the eyepiece with a fast locking action for a stable, secure fit, per the listing - Thick precision optical flat mirror with an enhanced dielectric coating stated at 99% reflectivity - Aluminum body with internal antireflection baffling and a brass compression ring to protect eyepiece barrels Cons: - Priced well above basic 1.25 inch dielectric diagonals, so the clicklock collar is what you are paying for - 1.25 inch only: wide-field 2 inch eyepieces need a 2 inch diagonal and focuser instead Details: https://stargazernest.com/product/B0CFLM6RNZ As an Amazon Associate I earn from qualifying purchases.