Diagonal's - worth the extra?

[scottydog]

Hello out there.....can anyone tell me, are these diagonal's really worth the money? Are they much better than the supplied one's?

Revelation Quartz Dielectric Diagonal

or the

William Optics 1.25" Carbon Fibre Dielectric Diagonal

Would the Quartz be better than the WO carbon fibre?

I have the SW 127 Mak............

Thanks in advance

[Moonshane]

the build quality is likely to be better and you get nice compression ring fittings but in all honesty I doubt you'd actually see a difference between them.

[John]

I directly compared the views with an expensive diagonal (Tele Vue Everbright) with those through a standard Skywatcher diagonal a while ago and there was hardly, if any, difference.

The higher standard of construction is worth having though, especially if you are going to put heavy and expensive eyepieces in there

[Damo636]

I use the William Optics diagonal you mention and its definately a quality product.

[great_bear]

I saw a substantial difference between the William Optics 1.25" Carbon Fibre Diagonal and the Revelation (GSO) Quartz 2" Dielectric Diagonal when used with my Skywatcher Skymax 180 Pro.

It was not a small difference.

It was like buying a new telescope.

The Revelation 2" Quartz Dielectric Diagonal revealed details in Jupiter that I'd never seen before. The thin, wispy edges on the cloud bands are simply not visible in the William Optics Carbon Fibre 1.25" Diagonal. The Revelation Diagonal is a marvel of rock-solid, precision engineering. It's a delight to own, and I can't see myself replacing it any time soon.

The William Optics Diagonal is a nice product in many respects, but it's not in the same league as the Revelation/GSO one.

[Macavity]

The Baader "T2" diagonals are nice "mechanically" (and expensive?) for the MAK127. But, are "screw on", lighter & more compact than a 2" diagonal AND (with their interim 35mm aperture) useful with MOST 2" eyepieces for that slightly increased true field of view.

http://www.teleskop-express.de/shop/index.php/language/en/manufacturers_id/5/filter_id/9

[F15Rules]

Hi Scotty,

I comes down I think to cosmetics and aesthetics, ie touchy feely as much as performance. I posted a diagonal thread discussion last year which you can find here:

http://stargazerslounge.com/equipment-discussion/103777-can-we-have-discussion-diagonals.html which you might find helpful and interesting..

Having come down on the size of "function" rather than "form" myself, I've just bought a used Everbrite 2" and the construction is a step above the Revelation (which I've just sold, and was a very good diagonal). Whether the views will be much better is too early to say, although the Everbrite's field of view is definitely bigger than the Revelation in my 6" refractor, noticeably so.

There is no doubt that the Williams is a nicely built piece of kit. But I sold mine and stayed with my tal 1.25 diagonal (which I still use in my Mak as it only accepts 1.25" diagonals) as the Tal view was just as good, and it is built like a tank.

I also think that the benefit of dielectric coatings is dubious, to say the least..so there!

you pays your money and you takes your choice:icon_scratch:!

good luck

Dave

[michael.h.f.wilkinson]

I have a WO 2" dielectric quartz diagonal and it is so much better than the standard Celestron 1.25" job. The difference in optical quality is large. I did not buy the "SCT-thread" one but the 2" plug-in type, along with a Baader 2" Visual back for SCTs (which I needed for a flip-mirror anyway). The plug-in type also works with the refractor I recently added, and allows a bit more free opening. I can even use a 40mm super wide angle (1.38 deg true FOV) without discernible vignetting.

Note that mirrors have the best quality surface in the centre, as a rule, and therefore a big mirror, of which you only use the centre at high magnification, gives better views.

[Rob Severn]

I had the Revalation 2" diagonal and found there to be a very marked difference between that and the original 1.25" Meade. Possibly one of the first things to buy when upgrading bits and pieces ?

[obscura]

I have the WO dielectric 2" also and a good buy. You can also use 1-1/4" eyepieces etc with it. Some £s more but gives you more flexibility later on. Threaded for 2" filters too.

[cs1cjc]

I have both the Revelation 2" quartz diagonal and the WO Carbon Fibre 1.25". They are both very high quality. The Revelation is surprisingly big and heavy. I take the WO for grab and go, but it has the disadvantage that internally it is limited to 25mm which is less than the 27mm field stop of some 1.5" eyepieces.

[John]

..... I take the WO for grab and go, but it has the disadvantage that internally it is limited to 25mm which is less than the 27mm field stop of some 1.25" eyepieces...

I've noticed that issue with the WO 1.25" and it's clones as well. It's a shame really as otherwise it's a very nice piece of kit

[scottydog]

I've noticed that issue with the WO 1.25" and it's clones as well. It's a shame really as otherwise it's a very nice piece of kit

Sorry to ask and expose my ignorance but in what way does the 'issue' effect the image?

And what do you mean by 'clones'?

Thanks in advance

[John]

Sorry to ask and expose my ignorance but in what way does the 'issue' effect the image?

And what do you mean by 'clones'?

Thanks in advance

These diagonals use a rather thick internal ring to hold the eyepiece tube onto the body of the diagonal. This ring sits just below the eyepiece and, where the rings aperture is smaller than the field stop of the eyepiece, the ring restricts the field of view that is visible.

You can see the ring at the bottom of the eyepiece tube in this picture:

http://www.williamoptics.com/diagonalPrism/images/dielectric125_04.jpg

By clones, I was referring to other diagonals made to the same pattern but with different branding.

[scottydog]

These diagonals use a rather thick internal ring to hold the eyepiece tube onto the body of the diagonal. This ring sits just below the eyepiece and, where the rings aperture is smaller than the field stop of the eyepiece, the ring restricts the field of view that is visible.

You can see the ring at the bottom of the eyepiece tube in this picture:

http://www.williamoptics.com/diagonalPrism/images/dielectric125_04.jpg

By clones, I was referring to other diagonals made to the same pattern but with different branding.

Thank you, that was well put

I'm still not sure though if I'll see much of a difference between the supplied diagonal & a more expensive one?! :)

[Falcon]

I've read that there is no detectable difference for the human eye if you reduce the brightness by 10% (supplied ones's - 90%, dielectric and quartz - 99% light transmission). In my private opinion if you work on maximum possible magnification for the scope (about 250x) when image becomes dimmer it makes sense to have 10% more light transmission. Maybe in that case it will be detectable but I don't know. The best way to decide is it worth (optically) or not, is to remove the supplied diagonal and to put the eyepiece directly on the diagonal's place - now you'll have 100% light transmission, and you could compare. You have to rotate a little bit more the knob to reach the focus, and be careful about your neck .

Good luck and don't forget to share the results

[great_bear]

The other problem with the William Optics 1.25" is all those contrast-robbing internal reflections off the polished components. The photo jahmanson linked to, shows them well (the concentric rings of light). You can't flock them away since the small diameter of those stops is already past the limits of tolerance as already discussed.