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Your cart is empty.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 entirely new telescope. This star diagonal reflects the telescope’s light path 90° to provide a more comfortable viewing angle. In addition, the glass has 58 layers of dielectric coatings, which provide an over 99% reflective surface, delivering the maximum amount of light to the eyepiece. This 2” star diagonal has the added benefit of allowing you to use larger 2” eyepieces with your telescope, providing a wider field of view, or standard 1. 25” eyepieces with the stepdown adapter. The twist-lock eyepiece holder secures eyepieces while keeping them centered in the diagonal, thus providing best opto-mechanical alignment between the telescope and eyepiece. Unlike traditional thumb screws, the twist-lock cannot scratch or engrave the barrel of your eyepieces. The diagonal has an integrated 2” barrel stop that prevents 2” accessories with long barrels from damaging the mirror. All the diagonal’s mechanical parts are made of machined black anodized aluminum, except the twist lock rings, which are orange anodized for visibility. The interior of the Schmidt-Cassegrain adapter and 2” barrel are glare threaded and painted flat black to prevent glare. With all its features and these high-end finishes, the Celestron Dielectric Star Diagonal, 2” with Twist-Lock is one of the highest quality 2" star diagonals that Celestron has ever offered. This diagonal also comes with two interchangeable barrels to provide flexibility in connecting the diagonal to a wide variety of telescopes without the need for additional adapters. For telescopes, like refractors, which accept 2” barrels in their focuser, a standard 2” barrel is included. For Schmidt-Cass grains (SCTs) that use a threaded connection to the focuser, a barrel with SCT threads is included. Both barrels thread onto the diagonal housing, providing a secure connection to the diagonal. The key specifications for a star diagonal are its reflectivity and its optical quality. This diagonal delivers top performance in both categories, with an over 99% reflective mirror and diffraction-limited optical quality. This ensures that virtually all the light collected by the telescope will reach the eyepiece without the diagonal affecting optical performance. Using a lower quality star diagonal can both dim the view and degrade optical quality. You can enjoy better views from your telescope by simply swapping out its diagonal for a premium one, like the Celestron Dielectric Star Diagonal.
Robert McDaid
Reviewed in Canada on January 31, 2025
A must have of you own 1.25 and 2 inch eyepieces
Go Bills
Reviewed in the United States on September 28, 2024
The "Celestron Dielectric Star Diagonal 2" with Twist Lock" I just received I installed on my Celestron Nexstar 8SE. I have been using the 1.25 Diagonal and I am very impressed with the improvement. This is worth the investment.
Male
Reviewed in Japan on September 26, 2024
天頂ミラーの方向を簡単に変更できるよう、C8 にbaader の2インチClicklockアダプターを付けて使用。天頂ミラースリーブに2インチフィルターを付けられるので、付属の1.25インチアダプター使用時に別途フィルターを用意する必要がない。光学性能は特に問題なし。
Ted Bohrer
Reviewed in the United States on September 11, 2024
I do not have an expensive telescope (a 5" Maksutov) but the telescope glass is pretty good. The problem is the 5" aperture which only allows so much light to come in. This means the optics attached to the telescope need to be as high quality as you can afford so you can get all the light possible to the eyepiece. For this I purchased Celestron's dielectric star diagonal because it is much better than the original cheap diaganol. It is easy to work with, too, because of the special twist lock it has which lets me change eyepieces easily and safely. I'm surprised more amateur astronomers don't start with buying a better diagonal like this one. When I upgrade my telescope the Celestron Star Diaganol can work with the new scope too.
R. C. Seaton
Reviewed in the United States on June 16, 2024
This fit my Astro Tech AT115EDT perfectly.. I like the fact that it includes twist lock adapters for both 2” and 1.25” eyepieces. Basically it’s a complete package, with everything needed to fit a large variety of telescope.
Rick Evans
Reviewed in the United States on December 1, 2024
Nice diagonal for $200, especially if you own a SCT. The only issue like others have mention, is it does not have enough thread depth for the 6.3 focal reducer corrector. Others have swapped the SCT ring from the 1.25 stock visual back. This does work fine and I got 1.5 turns onto the focal reducer. The solution I prefer is to purchase the Astromania adapter. This will convert SCT threads to M42 or M48 with M48 adapter. The diagonal uses M48. The adapter does not reduce the light path diameter to the diagonal. I use the astro adapter to attach all kinds of stuff to my C8. The really nice thing is it provides two full turns to the focal reducer. This allows significant more weight bearing. One star off for not thinking about the 6.3 reducer connection ahead of time.https://www.amazon.com/gp/product/B01M5BQAC5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
LUIS SILVA
Reviewed in Mexico on October 4, 2024
Gran construcción y diseño perfecto. Funcionamiento confiable y muy buena óptica
SocKeTPupPet 🤖
Reviewed in the United States on July 24, 2023
Let me start by saying this is an excellent star diagonal with excellent retention performance on the twist lock rings for 1.25" -2" barrels. Solid construction and manufactured in Taiwan. Holds all my eyepieces from the heaviest to lightest with installation ease on a Celestron Nexstar 8SE.Why the 3 star you may wonder? Well, the SCT adapter ring that free floats and attaches to your telescope/ corrector/ reducer doesn't have deep enough threads! Full thread engagement is only exactly 1/2 turn onto the Celestron brand f/6.3 reducer, but has about 3 turns (if diagonal is threaded directly) to engage the back of the telescope. I had it come loose a few times (even with the eyepiece and diagonal leaning with a right bias), but luckily the threaded ring only clamps and free floats to clamp the diagonal when tightened. Very scary to have only half thread revolution to connect a very expensive Pentax eyepiece with this star diagonal and sometimes utilizing a 2x Barlow!The way I resolved this was to take the original factory 1.25" visual back from the 8SE and reuse that ring, since it has a full set of threads up to the edge that allows at least 3 full turns of thread engagement once installed on the 2" dielectric diagonal. The original threaded ring from the diagonal was reused on the visual back and offered a good 1.75 turns of engagement. Overall diameter of the knurled section is smaller, but I'd rather have the security and peace of mind with more than just half a set of threading engaged. If you're up for swapping, it was not exactly an easy task, since the threads on the SCT adapter ARE THREADLOCKED! I had to heat up the smaller end of the adapter (non-floating ring section with thinner knurling) that goes into the star diagonal to get the floating adapter ring free. Don't use tools with this, as it can and likely will mar the anodized aluminum finish.I hope that Celestron fixes this as this $200 diagonal should be better thought out about safe fitment conditions and full compatibility with more than just a half thread of security for some expensive and often times, heavy glass and aluminum optics attached to the other end. 3 stars for this oversight, on an otherwise excellent dielectric diagonal.
TomInIll
Reviewed in the United States on July 19, 2023
Changed from 1.25 to 2" diagonal. The twist locks make changing eyepieces a breeze.This is an excellent eyepiece, and compared to buying separately, a very good deal!
G.Mac
Reviewed in the United States on June 17, 2023
This thing is beautifully made. I hate buying stuff made in China but you can't argue that they aren't making a very good optical product. 5 stares for QC.
Mathias
Reviewed in Germany on May 1, 2023
Gekauft dan günstigem Preis von Amazon US.Leider nicht zum Betrieb mit Reducer und Spiegelreflex geeignet, der Lichtweg ist zu lang.Ohne Reducer funktioniert es.
Rob
Reviewed in Australia on October 1, 2022
Product was as expected and delivered very promptly. Would highly recommend.
SC
Reviewed in the United States on October 24, 2019
I use this with my 1999 Celestron Celestar C8 SCT. Nice upgrade much brighter views. Also Using with the Celestron f6.3 focal reducer, 2” eyepieces ok on focus, only my 40mm 1.25” eyepiece would come into focus, any 1.25” eyepieces below 40mm would not focus. I bought a William Optics SCT Adapter for Standard 2 Diagonal - Gold - D-SCT-TA that is shorter than the one this 2” diagonal came with to shorten the light path. Now all my 1.25” eyepieces come into focus range. Celestron should have tested this more, and included a shorter front. Before release.
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