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The SVBONY SV188P Dielectric Mirror Star Diagonal features a super-flat mirror with advanced dielectric coatings that reflect over 99% of light, ensuring brighter and clearer astronomical views. Designed with a 90-degree viewing angle, it offers ergonomic comfort for observing objects overhead. Its 1.25-inch nosepiece fits standard telescopes and accessories, while the brass compression ring secures eyepieces firmly without damage. Highly rated and a bestseller, this diagonal is a must-have upgrade for serious amateur astronomers.















| ASIN | B08QRY4V97 |
| Best Sellers Rank | #1 in Telescope Diagonals |
| Customer Reviews | 4.8 4.8 out of 5 stars (323) |
| Date First Available | December 16, 2020 |
| Item Weight | 7 ounces |
| Item model number | FF9171B |
| Manufacturer | SVBONY |
| Product Dimensions | 4.4 x 3.3 x 2.4 inches |
D**4
A Must-Have Optical Upgrade - Say Goodbye to Ghosting!
I’ve been using this for a few weeks now with my refractor, and the difference between this and the "stock" diagonal that came with my scope is night and day. If you're looking for one single part to improve your viewing experience without breaking the bank, this is it. Brighter, Sharper Views The 99% reflectivity dielectric coating isn't just a marketing gimmick—you can actually see the difference. The blacks are deeper, and the stars are much "tighter." I noticed a significant reduction in light scatter when looking at bright objects like Venus or the Moon. Everything just looks crisper. Protects Your Gear My favorite feature is the brass compression ring. Most cheap diagonals use a simple screw that digs right into your eyepiece barrels, leaving ugly scratches. This ring applies even pressure all the way around, holding my heavy Celestron zoom securely without marking it up. Built for the Long Haul The body is solid metal and has a nice weight to it. It feels like a piece of professional equipment. The 90-degree angle is perfect for those high-altitude targets; no more neck strain trying to get under the tripod to see the Zenith. Bottom Line: It’s an Amazon's Choice for a reason. Great price, excellent build quality, and a noticeable jump in image clarity. It fits any standard 1.25-inch setup perfectly.
A**V
Would definitely buy it again
Have used it just a few times so far, but it appears of higher quality and is well made. Definitely better than the stock diagonal that originally came with my telescope! Images are bright and sharp.
O**Y
Sturdy and sharp
This Chinese brand of optical goods continues to impress me for value. So far, the telescope and accessories I have purchased through Amazon have delivered very good performance, allowing me to put my heavy 8" Newtonian telescope in storage in favor of a much lighter 102mm refractor that accepts 2" eyepieces. This star diagonal delivers sharp, contrasty views of both bright objects and starfields.
B**N
2" angle. Very good quality at ridiculously low price.
Exactly as advertised. Super fast shipping with Prime.
J**A
good value, shorter path length than premium $100 diagonals
Bought this as I have a small f/5 modified scope with limited infocus travel. My premium diagonals have a longer optical path length and don't work in this scope. This SVBONY diagonal has a shorter path and will allow my eyepieces to focus. This is pretty decently made, although my use is not optically demanding (low power only) the difference in reflectivity when compared to a non-dielectric diagonal can be seen. This diagonal is marked "99% dielectric coated" which refers to the mirror reflectivity. The side plates on this diagonal are blackened on the inside. SVBONY may have corrected the design or the ones mentioned that are red on the inside slipped past quality control, which is spotty with China manufacturing. Hopefully the coating on this is more durable than a conventionally aluminized mirror, since at this price point it's not worth reconditioning. The mirror appears to be glued in place, so if the collimation is off it's not really fixable. Check it with a laser collimator in the eyepiece port and place a flat mirror on the telescope side, facing the mirror and collimator. The laser spot should reflect dead center on the collimator target. This particular diagonal checked out fine, but since the mirror is likely installed by hand it should be checked when you get yours. IMPORTANT: there are similar SVBONY diagonals with silver side plates that are described as Dielectric. If they are, the specified reflectivity is VERY LOW for a dielectric mirror. Most likely it's incorrect information, and that's why they are about $10 cheaper. Getting a straight answer out of China makers is hard because of the language barrier. I think those have the same metal parts with a conventional non-dielectric mirror.
S**S
Image correct, good fit, super happy.
I have an orion 90mm telescope w/ equatorial mount, $130ish setup. Basic. This SV diagonal is an upright correct image. It has metal framework, and everything fits tightly. I feel more comfortable using this diagonal to hold my Barlow, filter, and eyepieces compared to what came with the telescope (combo plastic/metal). To me, the picture is somewhat of an improvement over what came with the telescope. I really just like the fitment! Oh, it didn't arrive broken!
A**S
As described
I replaced original 45° it came with for this 90° red one corrected the issue I had And you don't get a weird pinch in your neck like the 45 gave ya. And it's red I like red
B**D
Another fine product from SVBONY
I had a diagonal with my Meade 6 inch refractor along with a complete set of Meade series 4000 Plossl eyepieces. After reading about various degree of light transmission through diagonals, I decided to test the one I had. I looked through it at my computer desk which has wood veneer on it. The desk is brown color but through the existing diagonal it came out as mostly grey. Having purchased a diagonal finder from SVBONY and been happy with the product. I decided to pick this up which is about 1/3 of the cost of a similar diagonal from more well known companies. I took it out of the box and tested it against the desk and it is the same brown that the eye sees. Ironically a friend (who I bought the telescope from) found a 2 inch diagonal in a discount store for $5. He gave it to me. It was in its original box and looked brand new. It had no brand name or any other writing on it. I did the test on the desk and it and the SVBONY one both produce the same sharp, brown image. P.S. It was black inside and not red.
D**N
Much better than stock diagonals, brighter and clearer views
I didn't expect a 55$ diagonal to blow me away, but here we are. I recently purchased a Skywatcher 102mm StarTravel, the included 45 degree diagonal is perfectly usable for terrestrial, but for sky observing with objects high, it's much more of a problem. I was recommended this diagonal from a friend, and I was blown away with the difference in brightness and clarity of viewing. I have purchased a few SVbony products and they never fail to impress. This diagonal is no different. The mirror is huge compared to cheaper diagonals, and the dialectic coatings make it much brighter. If you need a diagonal buy this one with confidence. It comes with a brass band and not just a screw, so your eyepieces shouldn't get scratched up. Getting used to left and right being backwards, takes some getting used to, but it's definitely not a deal breaker. An unexpected side benefit, is the mirror is very easy to clean. (with a microfiber cloth) That was a problem with the default one that came with the scope.
1**2
Confio comprar na Amazon, eles nunca me deram canseira, são pontual
Produto original, a qualidade do material é excelente, amei
R**Y
Great value for money
This product gives full value for the money.It is a part of the telescope which can really make a difference,especially if the one being replaced is stock ,which came with the telescope.
E**K
Recomendado
Cumple con lo ofrecido y es una mejora a la diagonal que me vino con el telescopio, se percibe mucha calidad en la construcción del producto al ser completamente de metal.
K**L
Good quality diagonal, came quickly
I've generally been happy with the various SVBONY items I have purchased. This diagonal seems well made, and does seem a bit brighter than older diagonals I have.
Trustpilot
2 weeks ago
2 days ago