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GSO 2" 90-deg 99% Quartz Dielectric Mirror Diagonal for SCTs

4.6 (15 Reviews) Read Reviews Write Review
Brand GSO
Part Number GS2QSCT
Availability available

Product Info

Manufacturer Description

If you want a high-end mirror diagonal for your Schmidt-Cassegrain telescope, this GSO 2" Quartz Dielectric Diagonal Mirror is an excellent choice. GSO's 2" SCT diagonal features dielectric coatings with 99% reflectivity across the visible spectrum and a 1/12 wave quartz mirror. The all metal diagonal body is CNC machined. The combined result is a superb diagonal offering excellent mechanical and optical quality at a great price. Dielectric coatings are more durable than regular or enhanced aluminum coatings, so you will enjoy years of excellent performance from this product. Diagonals with comparable quality and specifications often sell for $200 or more in today's astronomy market.

High quality diagonal mirrors are usually made of BK7 glass. Quartz glass goes a notch higher - it offers greater thermal stability, resulting in minimal thermal expansion and contraction as compared to other glass types. The result is a minimal, if any, shift in focus due to temperature changes over long observation sessions, making this quartz diagonal ideal for photographic and imaging applications.

You can attach this diagonal directly to Schmidt-Cassegrain telescopes and many Maksutov-Cassegrain telescopes, as long as there is a SCT male thread on the telescope. The standard SCT thread is a 2"x24 tpi thread.

A 1.25"-2" adapter is included so you can use this diagonal with 1.25" or 2" eyepieces. The 1.25" and 2" holders both feature a brass compression ring, so your eyepiece barrels will not be scratched by the set screw. The 1.25"-2" adapter is also threaded to accept 2" filters. The clear aperture is 38.2mm. The diagonal comes in a very nice foam-fitted storage box and includes 2 end caps. Weight = 1lb-4oz. (with 1.25" adapter); 1lb-1oz. (without 1.25" adapter). Made in Taiwan.

Reviews

4.6 (Based on 15 Reviews) 100% of reviewers recommended this product.
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    1. Guest

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      Review by HARRY H.
      1547639860
      Jan 16, 2019

      5.0 Quality Quality Quality

      Pros:

      Cons:

      Comments:

      Makes the stock diagonal feel and look like a toy...

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Review by Jon L.
      1533093903
      Jul 31, 2018

      5.0 GSO 2” diagonal

      Pros:

      Cons:

      Comments:

      Very nice heavy duty, works much better than standard Meade diagonal

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Kevin C
      1505767143
      Sep 18, 2017

      4.0 GSO 2" Quartz SCT Diagonal

      Pros:

      Cons:

      Comments:

      Bought this to attach to a 102mm Mak-Cass telescope. Bought an SCT adapter for the back of the telescope barrel, attached a 2" 0.63 focal reducer to the adapter, then the 2" GSO diagonal to the reducer.

      Works well. Had to make a gasket as the threaded ring of the SCT band on the diagonal was too deep. Made up a plastic ring about 0.3 mm thick to compensate and it works ok, but that would be why I give it a 4 star rating.

      Works great for both my 1.25 in and 2 in eyepieces.

      Would recommend.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Ron H.
      1501269235
      Jul 28, 2017

      5.0 High quality

      Pros:

      Cons:

      Comments:

      This quartz diagonal out performs my old mirror star diagonal, using it to view the sun.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Walter D.
      1494530222
      May 11, 2017

      5.0 Very well made diagonal. Well

      Pros:

      Cons:

      Comments:

      Very well made diagonal. Well worth the cost.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Peter of Charlotte, NC.
      1412726400
      Oct 7, 2014

      3.0 Funky tightening ring

      Pros:

      Strong Construction,Quality Lenses

      Cons:

      Difficult to Use

      Comments:

      My threaded ring didn't tighten correctly. You could tighten it and then it would not want to come off. As I see it, the threaded ring was too close to the hardness of the Meade threads and would cause this galling. Agena sent me a new front piece to try and it perectly solved the problem. It even made it quiet while screwing on rather than squealing. I gave it three stars because of the hassle; however, it would have been worse had Agena service not been so great. They are great!

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by slipfit of Millersville, TN.
      1348272000
      Sep 21, 2012

      5.0 New scope

      Pros:

      Accurate,Easy to Use,Strong Construction

      Cons:

      Comments:

      Got this to use with my CPC 800. What difference this thing makes, its like having a new scope. Much better than the stock diagonal.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by AhBok of Tennessee.
      1320451200
      Nov 4, 2011

      5.0 Why Pay More?

      Pros:

      Strong Construction,Accurate,Quality Lenses

      Cons:

      Comments:

      I've used the more expensive brands and I cannot tell any distinct difference in build or optical quality. You can pay over twice as much and get the same exact views and durability.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Review by Chris-SD of Rapid City, SD.
      1320451200
      Nov 4, 2011

      5.0 Great product!

      Pros:

      Strong Construction,Easy to Use,Accurate

      Cons:

      Comments:

      I bought this for a 10" Meade SCT f/6.3 I purchased. It is a beautiful product; from the packaging all the way to the finish on it is amazing. I never tried a 'regular" mirror so I can't say whether it really has a "brighter" return but it does provide a beautiful picture.

      Standard wonderful product from GSO at a good price. I'd buy it again given the choice.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Stacy of Seattle, WA.
      1287014400
      Oct 13, 2010

      4.0 Nice Diagonal!

      Pros:

      Performance,Value

      Cons:

      Comments:

      Really nice diagonal. Very bright and performs well. Great deal from Agena. Recommended!

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Review by Bob of El Paso, TX.
      1286755200
      Oct 10, 2010

      5.0 Works with Meade Series 4000 f/6.3 Focal Reducer

      Pros:

      Short light path

      Cons:

      None

      Comments:

      The Meade Series 4000 f/6.3 Focal Reducer/Field Flattener for Schmidt-Cassegrain Telescopes is a nice accessory but it has limitations when used with some 2" diagonals as you can't ever reach focus.

      Because of the shorter light path of the GSO 2" diagonals for SCTs I can now easily reach focus with all my 1.25" and 2" eyepieces, unlike my older Meade 2" diagonal that is now in retirement.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Bob of El Paso, Texas.
      1286150400
      Oct 3, 2010

      5.0 One small problem to be aware of...

      Pros:

      Quality Lenses

      Cons:

      Comments:

      From the product description: "The 1.25"-2" adapter is also threaded to accept 2" filters."

      Yes you can screw a 2" filter into the adapter but some 1.25" eyepieces may contact the filter and damage it. A parfocal ring on the eyepiece or a short 2" spacer is needed to prevent this problem.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by Patmon of La Habra.
      1257811200
      Nov 9, 2009

      4.0 It works for me.

      Pros:

      Strong Construction

      Cons:

      Heavy

      Comments:

      The only reason I gave it 4 stars instead of 5 is because of the threaded front has to be loosened in order to adjust the eyepiece closer to the viewer. Furthermore, when adjusting this diagonal it might cause damage to the threads on the SCT from constant tightening and loosening-especially when using a heavier eyepiece like the Ethos series that I use.

      Good note is that both the front thread and the rear eyepiece adapter can be removed for easy cleaning of the quality dielectric coated mirror.

      Bottom Line: Would you recommend this item? Yes
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      This review was provided courtesy of AgenaAstro.com

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      Review by "The ancient Astronomer" of Tucson AZ.
      1243382400
      May 26, 2009

      4.0 Quality at a great price

      Pros:

      Quality workmanship

      Cons:

      None

      Comments:

      This diagonal compares well with units costing much more money. Construction is first rate and the mirror is very well polished. Very usable in Sct type scopes of various manufacturers.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Review by sonoranviewer of Tucson, Arizona.
      1238112000
      Mar 26, 2009

      5.0 GSO IS A GOOD CHOICE

      Pros:

      QUALITY MIRROR,Strong Construction

      Cons:

      Heavy

      Comments:

      Very bright mirror, well constructed diagonal, you tighten the ring around your lens barrel so you are not digging a hole into your beautiful lens barrels as you are with the diagonals supplied with most scopes from the factory. The body is very heavy so remember you must make sure your balance is correct if you are using motors to go to and slew. It was not to large for the 8" sct I put it on and it fit under the fork comfortably when packed away. Found the 2" diagonal will allow you to use your 1.25 lenses as well as my 2" lenses so there is no reason not to upgrade your sct to a 2" and get all the light comming down the 2" tube from the secondary lens. OVERALL I found a difference from the 1.25 that I could notice and the gso mirror after being cleaned upon arrival was just beautiful and the price was great for what you get. I do not believe any 2" diagonal is any better then this gso model at this very low cost.

      Bottom Line: Would you recommend this item? Yes
      Was this review helpful? Yes / No

      This review was provided courtesy of AgenaAstro.com

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      Specifications

      Manufacturer GSO