GSO 2" 90-deg Mirror Diagonal for Refractors

5.0 2" GSO 90* Mirror Diagonal

Great deal for price. Using on my 102mm, F/6.5 RFT refractor with a GSO 30mm Superview eyepiece. Love it.

This review was provided courtesy of AgenaAstro.com

5.0 Great product

Totally impressed with the performance of this 2 inch diagonal.Well built and a great value for the dollar.

This review was provided courtesy of AgenaAstro.com

5.0 Good diagonal, great price

Easy to Use,Strong Construction

Until now I have used my Orion ED80 mostly for prime focus DSLR photography of wildlife so I didn't need a diagonal. But I wanted one for occasional casual observing of the moon, planets, etc. without spending too much for a 2". I am very pleased with this purchase and the quality of the diagonal, which has expanded my use of the ED80. In addition to astronomy viewing, I have found it to be very convenient for bird and wildlife videoing using afocal coupling of a GoPro to a Baader Hyperion eyepiece, being able now to look down for live view focusing and recording, allowing a lower tripod height.

This review was provided courtesy of AgenaAstro.com

5.0 A must have for refractor.

Accurate,Strong Construction,Easy to Use

The 90* diagonal allows a user to avoid some of the uncomfortable viewing positions encountered using a refractor telescope.
The MIRROR in this diagonal is excellent. Only a little loss of light. Hardly noticeable.

This review was provided courtesy of AgenaAstro.com

5.0 Great Diagonal!

Quality Lenses,Strong Construction

Very good diagonal. Not Dielectric but performing very good. Strong construction. Just what I needed.

This review was provided courtesy of AgenaAstro.com

4.0 Excellent quality and materials

Easy to Use,Accurate,Strong Construction,Exceeds My Expectations,Lightweight

No Dialectric Mirror

Most of my experience has been with 1.25 focusing equipment and oculars.
2 inch equipment adds another dimension to each telescope domain whether it be astrophotography, long night observing, or terrestrial viewing.
The cost of each piece of course is more but the results of using larger pieces and lenses is near extraordinary.
My latest refractor is the Orion 5 inch on the motorised EQ mount. I had been using 1.25 inch. 2 inch weighs more and I had to rebalance the scope and mount. The added weight has not been a problem in fact added weight has reduced some vibration in the wind.
Most of the additional weight comes from the larger eye pices and large glass.
I'm excited to be at the 2 inch stage of focus equipment.
2 inch lenses are more expensive but it's the only way to get the images we all see in magazines and on TV.

This review was provided courtesy of AgenaAstro.com

4.0 Great product.

Good Quality Diagonal,Strong Construction

None

This is a nice diagonal. I use it with my Celestron 6" Refractor and my Orion 120mm ST Refractor. It performs well.

This review was provided courtesy of AgenaAstro.com

5.0 Quality at a bargain price

Accurate,Easy to Use,Strong Construction

I've had a couple of these over the years, the design has been modded to some degree but the great bang for the buck remains unchanged, the latest was bought for use in a ED80, to be honest in the visual sense I can't see any difference between it and a high end dielectric I own,recommended and it won't empty the wallet, GSO make great stuff at a very modest price.

This review was provided courtesy of AgenaAstro.com

5.0 None better at any price!

Superb Quality Mirror,Compact,Strong Construction,Easy to Use,Solid - Built Like A Tank,Accurate

I'd put this 2" Diagonal up against any from the expensive name brands like TeleVue and Astro Physics any day of the week. It's that good!

Have another one for my NexStar 5 SE SCT as well.

This review was provided courtesy of AgenaAstro.com

4.0 Good Diagonal

Strong Construction,Accurate,Quality Lenses

Heavy

This is a whopper of a diagonal. It's durable enough to have withstood a tragic fall of about two feet onto concrete without any damage or misalignment, and it feels like it. Big, heavy, but excellent views.

Unless you're using a really wide view eyepiece, I'd go down to 1.25" prior to the diagonal.

This review was provided courtesy of AgenaAstro.com

4.0 Excellent Diagonal

Strong Construction,Quality Lenses,Excellent contrast

This is a excellent diagonal for the money. I have a GSO 90mm refractor for what I bought this for what a difference from the factory 1.25" diagonal. Far sharper and brighter images.The only negative is the eyepiece can catch on the way down the diagonal you always have to make sure it's fully seated. Excellent diagonal.I recommend both.

This review was provided courtesy of AgenaAstro.com

5.0 Great diagonal for the money

Quality Lenses

Great diagonal for the money, no need to spend a lot to get great performance

This review was provided courtesy of AgenaAstro.com

5.0 Why Pay More?

Solid Construction

None

This is by far the best upgrade I have done for my Orion 120ST; there is simply no comparison to the stock diagonal that comes with it. I read quite a number other other reviews on two inch diagonals and this seemed like the best value and it hasn't disappointed me. Two inch filters screw onto the end very easily. The views of the beehive cluster through a GSO SuperView 20mm were outstanding.

5.0 Best diagonal for the money

Great build quality, optically excellent 1/12th wave mirror.

Nothing meaningful.

This diagonal is as good as any out there, for a fraction of the price. Build quality is excellent and rock solid. The body of the diagonal is machined from a single piece of bar-stock aluminum, and has a nice, hefty feel. But the GSO isn't really heavy by comparison with other high end 2" diagonals--only the carbon-fiber ones like the William Optics' are noticeably lighter. GSO rates the mirror at 1/12th wave, and even at very high power (over 200X) images are bright and free of distortion. GSO also makes a quartz version of the diagonal, it's optically identical to the dielectric, the only difference is that the quartz version is less vulnerable to temperature changes. You can spend more than the $100 the GSO dielectric costs, but realistically you can't get much better performance.

4.0 Very Capable Product

Strong Construction

I wanted a 2" diagnonal but felt the high prices for some of the "99%" reflectivity diagnoals was difficult to justify and based in part on hype. I am not an optics expert but I have doubts the human eye can really discern the difference between a 92% reflective surface and a 99% reflective surface. I have other GSO products and they are all well built and perform capably.

This diagnonal is no different. It is very well made and is very professional looking. It has nice large set screws and uses a compression band which holds even heavy eyepieces tightly. The only issue I have with it is the 11/4" adaptor. The adaptor is also very well made, but I find getting it in and out of the barrell is a real bear. It is a tad bit too tight. You have to remove the diagonal from the scope and wiggle the adaptor out. Even this is not easy. I find that this really detracts from an otherwise great product at a great price.

This review was provided courtesy of AgenaAstro.com

5.0 Excellent diagonal at a winning price

Solid build. Excellent surface accuracy. Excellent image brightness and contrast. Low price.

Unanodized focuser insert tube. Thin translucent plastic end caps, not thicker plastic or metal caps.

This 2" 99% reflectivity dielectric mirror diagonal from GSO is a great performer. I compared it head to head with a buddy's William Optics 2" 99% dielectric diagonal using my Sky90. The William Optics diagonal is touted to have a 1/10th wave substrate surface accuracy while the GSO diagonal is advertised with 1/12th wave substrate surface accuracy. Sometimes if the multilayer dielectric coatings are not evenly applied to the surface the advertised surface accuracies will no longer be valid. Happily it appears that both WO and GSO use the latest multilayer dielectric coatings application technology which does not impact the surface accuracy to any great extent. This is clear in the star testing done on my optically superb Sky90. Comparing the star test with and without these diagonals, the star test remained identical. Hence these diagonals clearly do not introduce any additional optical errors in the light path.

Views of DSOs using either diagonal and a quality Panoptic were identical. For example, I easily detected M76 with direct vision under Mag 5.5 skies using either diagonal and the 15 mm Panoptic using the Sky90. When a Lumicon OIII filter was used, the extent of the faint "wings" was the same using either diagonal. Image contrast provided by either diagonal appears to be identical. For example, the knot of dark dust that juts into the Trapezium in the Orion nebula shows identical wispiness and mottling using either diagonal under the same Mag 5.5 skies using a 7mm Nagler. Image brightness provided by either diagonal is the same. For example, using the 7 mm Nagler, M15 resolved almost 50% of the way into the core using either diagonal and the globular had identical brightness graduation beginning from the center and moving out. In addition, the angular extent of this somewhat compact globular was identical using either diagonal. The build quality of this diagonal is quite good but the William Optics just has a slightly more solid feel to it. In addition, I did notice that the focuser insert tube on the GSO was not anodized black unlike on the William Optics. Mind you, these are mere cosmetic trifles only. Performance of either diagonal was identical and so I'd heartily recommend this diagonal as the better bang-for-your-buck.

5.0 Great diagonal

Great quality, sharp views, nice features

None

I got this to compare against the Astro-Physics Maxbright. In short, I kept the GSO and sold the Maxbright.

The GSO had excellent fit and finish, and it has views which were every bit as sharp and bright as the Maxbright. The GSO also has the ability to remove the nose piece and replace it with a version which can screw onto SCT threads which is a nice feature. The GSO also comes in a nice foam-lined box with end caps and a 1-1/4 to 2-inch adapter which, because of its design, is a 0-height adapter...in other words it does not raise the height of the eyepiece at all because the part that holds the 1-1/4-inch eyepiece is actually recessed a bit. This is a neat feature.

This is a great quality diagonal with tough dielectric coatings that is 1/3 the price of the Maxbright. The GSO is definitely recommended.