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Buying Your First Telescope Part One: What’s the Best Telescope? Part Two: Making the Choice Part Three: Our Recommendations (2022)
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New Additions

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Telescopes
Best of Telescopes
Best Telescopes for Kids Best Telescopes for Beginners Best Telescopes for Astrophotography Best Telescopes for Viewing Planets Best Telescopes for Eclipses Best Telescopes Under $500 All Telescopes Telescopes on Sale
By Type
Celestron NexStar Celestron StarSense Explorer Refractors Reflectors Dobsonians Scmitd Cassegrain - SCT GoTo and Computerized Table Top Spotting Scopes Guide Scopes Solar Telescopes Optical Tube Assembly - OTA Astrographs All Telescopes
By Brand
Askar Celestron Explore Scientific Meade Orion SharpStar Sky-Watcher Tele Vue Unistellar William Optics All Telescopes
Start Here
Buying Your First Telescope So You've Got a Telescope: Now What?
Astrophotography
Cameras
Deep Sky Planetary and Lunar Guiding Cameras Solar All Cameras
Filters
LRGB Filters SHO Filters 3nm Filters Light Pollution Dual Band UV/IR Cut All Filters
Accessories
Auto Focusers and EAF Filter Wheels Filter Drawers Focusing Masks Off Axis Guiders - OAG Smartphone Adapters
By Brand
ZWO Optolong Antlia QHY Orion Baader Planetarium Sharpstar Astrophotography William Optics Astrographs All Astro PrimaLuceLab
Start Here
Astrophotography for Beginners How to Use a Star Adventurer Tracker How to Shoot the Moon
Solar Photography
Daystar Instruments - Quark Meade PST, Coronado Lunt
Mounts and Tripods
By Type
Alt Azimuth Equatorial GoTo and Computerized Harmonic Manual Star Trackers All Mounts and Tripods
By Brand
iOptron Sky-Watcher Celestron Tele Vue Explore Scientific All Mounts and Tripods
Accessories
Counter Weights Mounting Hardware Hand Controllers Mini Piers Polar Scopes Vibration Pads GPS and Wifi Modules All Accessories
Eyepieces
By Size
Zooms 0-5mm 6-10mm 11-15mm 16-20mm 21mm and Up All Eyepieces
By Type
Barlows and Powermates Diagonals Visual Filters Eyepiece Sets and Cases Visual Filter Sets
By Brand
Pentax Tele Vue Celestron Baader Planetarium Explore Scientific All Eyepieces
Need Help?
Help Picking Eyepieces
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Astronomy Binoculars Kids Binoculars Birding Binoculars Giant Binoculars Monoculars Solar Binoculars Spotting Scopes
Birding
Birding Binoculars Binoculars for Kids Birding Field Guides
Straps and Accessories
Birding Field Guides
Accessories
By Brand
ADM Antares Baader Planetarium Celestron Kendrick Astro Lunt Solar Orion Pacific SharpStar Sky Instruments Sky-Watcher Starfield Starizona Stellarvue Tele Vue Telrad Thousand Oaks All Accessories
By Type
Auto Focusers and EAF Battery Packs Books Carry Cases and Bags Celestron NexStar Accessories Dew Management Diagonals Flashlights and Laser Pointers Microscopes Mounting Hardware Planispheres Polar Scopes and Alignment T-Rings and T-Adapters Reducers and Flatener Smartphone Adapters Solar Filters
All Accessories Essential Astronomy Accessories
STEM
Microscopes Rock Tumbling STEM Toys CMY Cubes
Learning Center
Helpful Articles
Astrophotography for Beginners Series Choosing the Best Beginner Telescope Upgrading Your Telescope Eyepieces Is the Celestron NexStar the Best Telescope?
Videos
Nexstar Videos
Astrophotography
Step 1: Using the Star Adventurer Tracker Step 2: How to Shoot the Moon Step 3: Choosing Gear for Deep-Sky Imaging Step 4: Shooting Deep-Sky Images
Buying Your First Telescope
Part One: What’s the Best Telescope? Part Two: Making the Choice Part Three: Our Recommendations (2022)
Using Your First Telescope
Part One: Tips for Happy Stargazing Part Two: Aligning a GoTo Scope
Birding
How to Buy the Best Binoculars for Birding Get the Most Out of Your Binoculars Bird Watching 101: Your Essential Guide
Brands
Visual Astronomy
Baader Planetarium Celestron Coronado Explore Scientific iOptron Kendrick Astro Lunt Meade Orion Sky-Watcher Tele Vue Unistellar
Astrophotography
Antlia Askar Daystar Instruments Founder Optics Optolong Pegasus Astro PrimaLuceLab QHYCCD Sharpstar William Optics ZWO
Birding and Binoculars
Kowa Leica Pentax Zeiss
New Additions
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Home / Telescope Diagonals

Telescope Diagonals

Diagonals are the pieces at the back of your telescope that make it easy to look through the eyepiece.  We have a few upgrade options with high quality, high transmission dielectric mirrors and twist lock or compression ring systems for securing your valuable telescope eyepieces.  We also have erect image options that will make it easier to use your telescope for terrestrial viewing.
Sky Instruments
Antares 2" Diagonal, Mirror, Dielectric Machined, Twist-Lock (2MD-DTL)
2 reviews
$159.95

2" Mirror Diagonal with Twist-lock retainer and multilayer dielectric coating with 99% reflectivity in green (546nM) light. Reduces or eliminates vignetting, and allows for use of any 2" accessory. Please note: does not include adapter...

In Stock
Celestron
Celestron Dielectric Star Diagonal 2" Twist-Lock (93573)
2 reviews
$337.95

Ensure maximum light transmission without loss of optical quality with the Celestron Dielectric Star Diagonal, 2” with Twist-Lock. Upgrade your existing star diagonal to this premium one and enjoy brighter, sharper images without purchasing an...

In Stock
Celestron
Celestron Dielectric Star Diagonal 1.25" With Twist-Lock (93571)
$209.95

Ensure maximum light transmission without loss of optical quality with the Celestron Dielectric Star Diagonal, 1.25” with Twist-Lock. Upgrade your existing star diagonal to this premium one and enjoy brighter, sharper images without replacing your...

In Stock
Celestron
Celestron 1.25" Star Diagonal (94115-A)
1 review
$70.95

The Celestron 1.25” Star Diagonal slides into the focuser (1.25”) of your refractor or catadioptric telescope and accepts standard 1.25” eyepieces, allowing you to view objects more comfortably. A diagonal that is angled at 90º...

Special Order
Sky Instruments
Antares 2" Diagonal, Mirror, Dielectric for SCT (2MDS-DTL)
No reviews
$159.95

2" Dielectric mirror diagonal with twistlock, for SCT threads, 99% reflectivity at 546nM 2" Mirror Diagonal for Schmidt-Cassegrain thread-on with Twist-lock retainer and multilayer dielectric coating with 99% reflectivity in green (546nM) light. Reduces or...

In Stock
Tele Vue Optics
Tele Vue 2" 90 Diagonal Everbrite Satin (DDP-8004)
1 review
$512.00

Whiter and brighter images. Simply put, that is the benefit the Everbrite mirror coating. This exotic, dielectric, nonmetallic coating is 99% reflective across the full visual spectrum, resulting in the "whitest," most natural image available....

In Stock
SharpStar
Askar M54/M48 Backfocus Adjuster (BFA)
No reviews
from $169.95

The M54 backfocus adjuster's front telescope interface is female thread M54x0.75 and the rear camera interface is male thread M54x0.75, the overall thickness is 18mm and offers ± 2mm adjustment range. The M48 backfocus adjuster's...

Sky Instruments
Antares Verascope Finder (VS60F)
$107.95

VS60F is a 1.25" right angle correct imaging package with EID90 prism and W25-X eyepiece for using VS60 as a finderscope. Magnification is 9X and true field is 6.5 degrees. It works with the Antares...

In Stock
Celestron
Celestron 45-Degree Erect Image Diagonal 1.25" (94112-A)
$70.95

Did you know that most telescopes work well for daytime viewing as well as for astronomy? If you have a refractor or a catadioptric telescope (the Schmidt-Cassegrain is the most popular example), and you would...

Special Order
Baader Planetarium
Baader Planetarium Zenith Prism Diagonal T-2/90° with 32mm Prism (2456005K)
No reviews
$227.95

Containing: T-2/32 Diagonal with focusing 1¼" eyepiece clamp (#2458125) and 1¼" nose piece (#2458105) Connection objective side: T-2 internal thread 1¼ "barrel Connection eyepiece: T-2 external thread and focusable 1¼ "eyepiece Excellent for Baader Maxbright...

In Stock
SharpStar
Askar 2" High-Precision Diagonal (HPD2)
No reviews
$239.95

The high-quality CNC machined diagonal, with its matte interior coating and gloss oxidized surface, brings a more premium texture and a more comfortable feel. The all-black colour gives you the impression of stability. The integrated,...

In Stock
Tele Vue Optics
Tele Vue 1.25" 90 Diagonal Everbrite Satin (DPC-1250)
$385.00

Whiter and brighter images. Simply put, that is the benefit the Everbrite mirror coating. This exotic, dielectric, nonmetallic coating is 99% reflective across the full visual spectrum, resulting in the "whitest," most natural image available....

In Stock
Sky Instruments
Antares 45 Degree 2" Prism Diagonal (2EID45)
1 review
$179.95

 A 45 degree 2" precision polished correct image amici prism that allows for terrestrial viewing with 2" eyepieces. MgF2 coated, It is also suitable for astronomy.

Special Order
Founder Optics
Founders Optics 1.25"/2" Mirror Diagonals (DIA1.25-M/DIA2-M)
No reviews
from $139.99

Specifications Model: DIA1.25-M DIA2-M Barrel Size: 1.25" 2" Eyepiece Holder: Twist-up Tension Type - 1.25" Twist-up Tension Type - 2" Viewing Angle: 90° 90° Features: Dielectric coating, >99.99% reflectivity, aluminum anodizing

Special Order
iOptron
iOptron 1.25" Dielectric Mirror Diagonal (6231)
No reviews
$105.95

Use the iOptron 90° Dielectric Star Diagonal to place your head in a comfortable viewing position when your refractor or catadioptric optical tube assembly (OTA) is aimed at or near the zenith. Built with a...

Special Order
iOptron
iOptron 2" Dielectric Mirror Diagonal (6232)
No reviews
$194.95

Use the iOptron 90° Dielectric Star Diagonal to place your head in a comfortable viewing position when your refractor or catadioptric optical tube assembly (OTA) is aimed at or near the zenith. Built with a...

Special Order
Meade
Meade SERIES 5000 2" ENHANCED DIAGONAL MIRROR (07680)
No reviews
$242.99

Meade Series 5000 2" Enhanced Diagonal Mirror -- Our best diagonal for Meade LX90 and LX200 models. Features an incredible 99% reflective surface across the visual spectrum. For spectacular views of the universe, use the...

In Stock
Baader Planetarium
Baader Planetarium 2" BBHS Mirror Diagonal with 2" ClickLock Clamp (2456115)
1 review
$669.95

Specifications SKU (#) 2456115 EAN CODE 4047825033543 NET WEIGHT (G) 450 OPTICAL DESIGN Mirror Diagonal INNER CONNECTION (LENS SIDED) Thread, M48, M55, 2" (50,8mm) OUTER CONNECTION (LENS SIDED) Barrel, Dovetail ring, S58, 2" (50,8mm) INNER...

Sky Instruments
Antares Dielectric 1.25" Diagonal (MSD-DTL)
$129.95

Premium dielectric coatings in a carbon fibre body and twist lock adapter to prevent marring of eyepieces.

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