You hate reversed views of your star diagonal but no prism will do it for you?
This new 2" 90 deg. erecting prism by William Optics is our reply to your needs! High quality prism, coating and finish, for good correct-image views of celestial objects. Perfect for daytime observations. Will turn your refractor into a 24/7 friend! This prism is particularly suitable for astronomical usage.
• Image erecting BaK4 prism with anti-reflection coating.
• Fully multi-coated.
• Minimized light loss and high accuracy to make possible critical night-time observations.
• Internally matte blackened and threaded for no internal stray light reflection.
• Threaded for 2" filters.
Ready to Go
• 1.25" adapter with brass compression ring included in the price.
• Large, chromed thumbscrews.
• Entirely aluminum, black anodized.
• Silver sandblast finish with William Optics logo laser engraved.
• Prism: High quality BAK4 with new FMC coating
• Materials: Entirely machined aluminum
• Angle: 90 degree
• Prism clear aperture: 40mm
• 2"-1.25" adapter with brass compression rings
• Weight: 19.8 oz
Feb 24, 2012
Williams Optics 2" Erecting DiagonalPros:
Accurate,Quality Lenses,Strong ConstructionCons:
I use this with my Baader 36mm aspheric to get the full Moon in the field of view in my F/10 SCT. Excellent for low power correctly oriented Moon viewing up to about 150X for me. There is another erect image diagonal by another manufacturer more suited for higher power astro viewing of planets and Moon but is only rated for 1.25" use as the nose piece opening is about 10mm smaller.
This review was provided courtesy of AgenaAstro.comJan 9, 2012
Quality product, excellent opticsPros:
Quality Lenses,Strong ConstructionCons: Comments:
I bought this with some apprehension, I wanted a correct image diagonal but was unsure of the quality of the view. I am 100% satisfied..I can't see any difference in the EP, images are bright, sharp and light transmission appears excellent. I have enough trouble navigating the stars without having to try to decipher backwards/upside down stars. This has made my stargazing a real pleasure..what you see is exactly what the star maps and planetarium programs display. Takes all the hassle out of figuring out what you're looking at. Two thumbs up for this product.
This review was provided courtesy of AgenaAstro.comNov 4, 2011
Star searchers friendPros:
Strong Construction,Accurate,Quality Lenses,Easy to UseCons: Comments:
O.K. I'll admit it, I have a hard time finding the things I want to look at (i.e. mostly Messier items ). I really enjoy my binoculars as the large view and correct image are such an aid. I have a 80FD , f 555 , f 6.9 scope with NO computer control. It takes me forever to find things with the small scope and reversed image. Enter the WO 90
This review was provided courtesy of AgenaAstro.comJul 4, 2011
Strong Construction,Quality LensesCons: Comments:
Use binoculars a lot for astronomy. Love the correct image and match view of star charts. Tired of spending the night struggling to find things with the 80mm scope, due to the small field of view and reversed image.. The write up of the CI diagonal and the option to return it, plus I really like the W.O. products I own, made me give it a try. It's a keeper! I also have a W.O. 2" enhanced diagonal to compare it with. There is so little difference for most viewing that it is no contest the C.I. diagonal is the best way. Even on the moon, I could see no reason to go back to the reversed diagonal. When I viewed Saturn, at 111x,139x, & 186x, the reverse diagonal gave sharper views with more apparent depth. Therefore the C.I diagonal will be used for ALL viewing, with the exception of Saturn and Jupiter, and then, only if I have the reverse with me. These results may not be the same for more capable scopes, as mine is only an 80 mm f 555, but I am VERY happy with the C.i. diagonal for my use.
This review was provided courtesy of AgenaAstro.comMay 26, 2009
Excellent, but. . .Pros:
Strong Construction,Quality LensesCons:
Can not handle high powerComments:
I purchased this because I wanted to see if the traditional wisdom about prism diagonals for astronomical use was still true. It is true, but . . .
The traditional wisdom is that prisms can be used as a star diagonal to give you an erect image, but only at low power. I found that it worked for me at low and moderate - almost high - power. Where it broke down was in doing double star work at higher than usual powers. In that case, the traditional mirror star diagonal is a significantly better choice.
Want specifics? I was splitting the close double star Izar in Bootes using a 120mm apochromatic refractor. A 5mm eyepiece - 180X - could just do the job on this night and the split was OK with both diagonals. With a 3.5 mm eyepiece (257X) the split was acceptable with both diagonals - but better with the mirror. And with a 2.5mm eyepiece - 360X - there was no contest - the mirror star diagonal gave a much cleaner split with perfect diffraction rings around each star.
So what good is this prism diagonal? Well, if you like looking at the moon it's a lot easier finding your way around if you have a correct image - especially easier for beginners. But I have half a century experience as an amateur astronomer and I prefer a correct image, all other things being equal, not just for the moon, but for star clusters as well. So this diagonal is fine for most of the astronomy I do and delivers that correct image.
But - when the chips are down, when conditions are ideal and you want to see detail on the Moon, planets, or in stars - you want high power and this diagonal is a poor choice.
Obviously for day time use it's a must.
And, of course, most of us use two-inch eyepieces because we want low power views and they work fine with this diagonal. I like seeing the Pleiades as they appear to the naked eye and binoculars - except they look better with a larger telescope and this correct image diagonal. But then, that does mean changing diagonals when I want to crank up the power.
I should add that others might notice the quality difference at a lower power than I did. I did also use it when pursuing faint galaxies and I did not notice a difference in light through-put between it and a mirror diagonal.
Bottom line - this diagonal is fine and well made and while the correct image is nice, you still need a mirror diagonal for really sharp views at high power.
I would recommend this to a friend as long as they understood the inherent limitations of a prism star diagonal.
This review was provided courtesy of AgenaAstro.com
AstroGuy1 New Member
- Skill Level
- Time with Product
Nov 27, 2008
- User Notes:
- Review by telenaut of Texas.
WO 2" Erecting DiagonalPros:
Excellent optical quality,Excellent buildCons:
A bit priceyComments:
This product allows correctly oriented views of both sky and land in all directions, up/down and right/left, as opposed to the eyepiece view of a (mirror or prism) "star diagonal", which is right side up but reversed-looking, right to left. Some backyard astronomers feel the eyepiece view should match that of most star charts and maps (which are often printed as if viewed with the naked eye), and is especially important for lunar work. Birders also prefer to follow the critter with proper right/left movement of the telescope, relative to the target. In the past, most of these devices were optically abysmal, rife with distortion, aberration and cloudy views.
The William Optics 2" erecting prism diagonal is a very solid affair, well machined with close tolerances and an overall feel of quality. Included is a 2"-1 1/4" adaptor. Inspection of the prism disclosed nice multicoatings. One issue that was encountered was the shorter than expected clearance between the prism face and the top rim of the eyepiece insertion barrel. At least one of my oculars, possessing the dual 2"/ 1 1/4" design (think Orion Stratus/Baader Hyperion) actually made contact with the prism if inserted without the 1 1/4" adaptor in place. Be sure and check the mating of eyepiece/diagonal before proceeding in the field.
Optically, this prism teamed with a 17 mm Orion Stratus/ WO 80mm Flourite Doublet, while not waterproof and a tad bulky, absolutely blows the doors off most (if not all) other birding scopes. I compared this setup to a friend's Swarovski 65mm HD spotter, and the WO combo showed better resolution of fine detail, a brighter image, greater color saturation, and overall a more relaxing, easier view. This at about 1/2 the price of the Swarovski.
While undoubtedly one of the better products of its type on the market, it did suffer in a head-to-head showdown with the same company's Dielectric Mirror Star diagonal. In high contrast situations (bare twigs or limbs against a bright cloudy background), even at relatively modest power (32X), some purple or green etching around the limbs and twigs was noted. That tack-sharp apo scope "wow factor" was not as great thru the erecting prism diagonal as thru the star diagonal. There is also a small, but present, form of field distortion (curvature?) that is most apparent when panning or adjusting the scope. Although I have not used the erecting prism extensively for astronomy, these shortcomings would still remain, but I cannot directly comment on their bothersome-ness.
All this is understandable when considering a mirror diagonal asks the light to make one surface reflection, and a prism is contorting the beam more severely thru a hefty thickness of glass.
So do you need one? For the moon, utilizing a book, map or software program (there are several) that provide landmark orientation as seen thru a refractor/star diagonal pairing can be used. I would certainly avoid employing this erecting prism with high powers. Star-hoppers would benefit most from an erecting prism/ short-focus refractor, when using the main scope as both primary instrument and finder- as long as the power is kept low to low-moderate when wishing to examine an object in greater detail.
For terrestrial use, if you are accustomed to a regular birding scope with correct reading right-left eyepiece fields, the choice is a bit tougher, but having experience with both I would recommend a star diagonal. I submit it's easier to get used to reverted images than to lesser optical performance. After a while, it's just second nature to move the scope right if your quarry is moving left. In fact, having used a mirror diagonal for many years on my trusty 'ol Pronto as a birding/astronomy scope, I was constantly disoriented and moving the "wrong" direction when I switched to the erecting prism!!!
Having said all that (really more than anyone probably wanted to read!), if you must have a eyepiece field that is both rightside up and rightway 'round, this is one of the few products that won't give you a headache when looking thru it.
This review was provided courtesy of AgenaAstro.comSort by