2" diagonals differences between manufacturers?

[yagon]

Bintel advertises a 2" quartz dielectric diagonal at 99% reflectivity and 1/12 wave accuracy for $149, manufactured by GSO.

Andrews advertises a William Optics 2" dielectric diagonal at 99% refelctivity and 1/10 wave accuracy for $239.

Based on the advertised numbers, the performance should be similar or (very) slightly better for the Bintel diagonal.

What is the justification for the higher price of the WO? Is it the fit and finish only?

[MikeyB (Michael)]

WO diagonals are of different design/construction to the Bintel/GSO unit. The WO body is like a slice of triangular tube, with the sides attached separately, so the mirror position/angle is fixed and non-adjustable. WO claim that their patented design ensures perfect alignment of the mirror for the life of the diagonal. Full details are on their website:

http://www.williamoptics.com/diagona...2_features.htm

Myself, I bought the Bintel which is a beautiful piece of workmanship for the price and provided a noticeable improvement on the standard Celestron 1.25" prism diagonal in my N8i.

[MortonH]

I may be wrong, but I think the GSO diagonals are made of two or three pieces (excluding the mirror) that are 'stuck' together. The WO models (and even more expensive ones like TeleVue, Lumicon, etc) are machined from one solid piece of metal, which means the alignment is permanent.

Having said that, if you treat the diagonal carefully there is no reason it should go out of aligment, but if you were to drop it one day...

There may also be differences betwen the optical coatings used on the mirrors, e.g. the more expensive models may have 'harder' coatings that are more resistant to wear and will last longer.

I just bought the WO $239 model today and I must say it is a beautiful piece of engineering, and is so much brighter than my old (non-dielectric)model it's like I've gained an inch of aperture!

If you're just starting out and you don't want to spend too much, then GSO equipment generally is very good for the money, and I would hope that their diagonals are too. Where I would be more careful is with cheap eyepieces. For focal lengths under 15mm, I reckon you need to pay at least $150 for decent performance. At longer focal lengths you can get away with cheap eyepieces a bit more. All my humble opinion of course!

Morton

[shredder]

In the past I've had a good WO 2" diagonal, a good 1.25" diagonal, a medium 1.25" diagonal and a very cheap 1.25" diagonal (you tend to collect them after a while).

In terms of quality and engineering skill the WO is easily the best made of all of them. It has that WOW factor, and while the good 1.25 was of similar materials it just didnt look as good.

In terms of performance I was certainly hard pushed to see much difference between the best and worst. At least for visual observing they all performed well, maybe for imaging you can see the difference, but not visually (and I am reasonably experienced, over 10 years observing).

I also thing alignment is an interesting topic. I dont see the point of the arguement about the casing, and alignment. You dont align to the casing, you align to the optical path, so while being aligned to the casing might help it wont be right. All diagonals, by their design, wont sit flush when in a focuser, tighten the locking screws (in the focuser) and they all move a fraction, tightening the locking screws on the eyepiece and they move again, if you then add the 1.25" adapter you again get movement. While none of it is huge, and is generally ignored, it all plays up on alignment. If you are buying something that is 99% reflective you probably get more value playing with this alignment than anything else. Interestingly though none of my good diagonals alowed you to align them... the cheap ones did (but I never bothered).

For me one of the big advantages of the WO over the others was that it had a beveled edge cut into it, so that if the focuser locking screw came loose it didnt slide right out and hit the ground. Most of my others didnt have this and after having one hit the ground on a cold night I ended up getting them cut into them. That said having it added cost about $5, so not worth the extra $100 to have it.

For me, and this is just my personal opinion, I think the question should be asked why 2"? When I bought my WO 2" I assumed it would give amazing views and huge improvement, and that I would amass a number of 2" eyepieces. Well the image was no real improvement, and as I already had good/vgood eyepieces in the 1.25" variety I never did get many good 2" ones. So I was continually stuffing around with the 1.25" adapter, and on the occasion I did use a 2" ep having to remove it and then find it again later. In the end I would the whole 2" diagonal a bit of a gimic rather than a good add on. Most high quality low focal length eyepieces are 1.25", and when talking about long focal length going much over 30-35mm is wasted due to the puple size (from memory its a limiting factor) so the useable rang eof the 2" ep over the 1.25 is from 25mm-35mm, or generaly 1 ep.

But that was just my experience, everyone is different, and certainly the WO will make you smile whenever you see it, and soon forget about the cost. Also remember the WOW factor, lots of people will go "Wow a WO diagonal" but you will wait a long time before anyone goes "Wow a Bintel diagonal".

[acropolite (Phil)]

Ditto what Michael says, I have the $149 SCT dielectric Bintel diagonal, it's beautifully made and performs very well for the money. I haven't had the chance to compare with other dielectric diagonals but I suspect that you wouldn't pick any difference in performance. In my case too there was a noticeable improvement over the standard meade 1.25 diagonal.