2" Dielectric Comparison

[Nightspore]

 

Above, left to right top row: Tele Vue Everbrite, Baader Planetarium ClickLock. Left to right bottom row: Sky-Watcher, Altair Astro Posilock.

 

 

 

At 390g the ‘Sky-Watcher’ 2” dielectric diagonal is the ‘no frills’ plainest and lightest of the four dielectric diagonals featured here. I have no idea who the OEM is. It may actually be manufactured by the Suzhou Synta Optical Company. The main body appears to be an unpainted anodised silver coloured metal plate, probably consisting of pressed aluminium. The two plain black metal side plates are each secured to the main housing with three Allen screws. Mine now has a replacement GSO thumb screw in the eyepiece holder. There’s nothing inherently wrong with the original screw, I just prefer the longer Guan Sheng Optical one. Interestingly, both screws have the same size threads. My version of this diagonal was actually bundled with my 80ED DS Pro Evostar.

 

 

The nosepiece features a slight flare, is well baffled and includes a filter thread. I make about 44~45mm of clear aperture. I’m guessing the nosepiece is threaded into the body but mine is too tight to loosen and I don’t want to force it to discover how it is actually attached. The metal eyepiece holder is almost certainly brazed into the main housing body and features a brass compression ring. The diagonal feels solid and well made. Its dielectric mirror gives a bright image with no defects or aberrations that I can detect. In my experience light scatter is not a real issue and no better or worse than my other dielectrics.

 

 

As these diagonals are often bundled with Synta-made telescopes they don’t have a particularly sparkling reputation and many people seek to upgrade them as soon as possible. Although in my experience there is nothing wrong with the diagonal and it performs admirably.

 

 

As a decent basic 2” dielectric diagonal it compares well with anything else on the market. My only real concern is with the eyepiece holder itself. The compression ring isn’t particularly problematic but I am always wary of brazed holders. There is always the concern that they have the necessary strength to hold heavy eyepieces securely. Having said that I believe it would take a lot of brute force to physically detach the holder from its housing. I’m pretty sure mine came supplied with a 1.25” adapter. As I rarely used the original adapter I’m not sure of its present whereabouts. Although it was perfectly usable.

 

 

The adapter I regularly use with it now was originally supplied with my Altair 60 EDF ED doublet. There are no compatibility issues with the Altair adapter. The Sky-Watcher diagonal is still used a fair bit, although now predominantly with my modified ST80.

 

 

The Altair Astro Premium ‘Posilock’ dielectric is in many respects a very similar design to the Sky-Watcher diagonal. It comes supplied with a 1.25” adapter. The main housing body is most probably cast anodised aluminium equipped with carbon fibre side plates. The aesthetically pleasing black and silver twill weave plates are attached to the main housing with three screws. This appears to be virtually identical to the mounting of the side plates on the Sky-Watcher diagonal body. The three Allen screws used in both diagonals are possibly the same size and thread. The nosepiece also features a similar slight flare, internal baffling, and a filter thread. The baffling appears more ‘matte’ black than the Sky-Watcher nosepiece which is a tad more ‘gloss’.

 

 

The Altair nosepiece definitely threads off from its respective housing. The positive lock mechanism is probably responsible for the diagonal’s 525g overall weight (not including the 1.25” adapter). Making it a good 100g heavier than its Baader ClickLock diagonal equivalent. The Altair positive lock mechanism features two pillar holders rather than a collet and is identical to the mechanism shown below in an APM Amici.

 

 

In use the positive lock is precise and secure. For extra safety the metal screw at the top of the eyepiece holder can be rotated and tightened/loosened along its own axis as a form of safety lock. I make the clear aperture to be the same as the Sky-Watcher at about 44~45mm.

 

 

In use this is a perfectly decent dielectric and to be honest I can’t tell any difference with my other 2” dielectrics. Apart from the carbon fibre sides feeling peculiarly sharp to the touch, my only real gripe is its excessive weight. It is only 75g lighter than a 2” APM Amici prism diagonal equipped with the same type of positive lock eyepiece holder. Mirror diagonals are usually a fair bit lighter than their prism equivalents. This weight is quite noticeable on lightweight mounts combined with small aperture short tube refractors. Oddly, these Altair diagonals usually retail at exactly the same price as the 2” Sky-Watcher dielectric. After sitting in a cupboard for a couple of years my Altair dielectric is now regularly used with my modified ST102 on a Vixen Porta II mount and a Vixen APP-TL130 tripod combination.

 

 

The Baader Planetarium ClickLock #2956100 weighs in at a reasonable 425g. It is supplied without a 1.25” adapter. Baader states that it has 46.6mm of clear aperture, and I believe them. The housing body is white in appearance and feels comfortable to the hand in a tactile sense. Overall it is very well constructed with a high build quality. The oversized 1/10 wave mirror is held in place with a metal base plate separated from the main housing by what appears to be a red rubber gasket.

 

 

The plate is held in with four screws. The removable nosepiece sports safety kerfs and uniquely both ends of the nose contain M48 filter threads. Furthermore, the rubber gripped click lock eyepiece holder can also be removed from the housing. Like most Baader products this diagonal can be customised somewhat to individual tastes and applications. Unlike the ‘posilock’ type the Baader locking eyepiece holder utilises a brass compression ring. Using a compression ring rather than the ‘pillar’ type of retainers is its only apparent Achilles’ heel. I say this as I once got a 19mm Celestron Luminos eyepiece well and truly stuck in this diagonal. Requiring both eyepiece and diagonal to be partially disassembled to completely extricate them from each other.

 

 

The culprit undoubtedly being the undercut on the Luminos barrel that had become enmeshed in the compression ring. The Baader ClickLock diagonal holds every other 2” eyepiece I own perfectly well. Although it has to be stated that most of them don’t have undercuts. This is an aesthetic and ergonomically satisfying diagonal to use and performs very well in every telescope I own that has a 2" focuser. The click lock mechanism itself is smooth and secure in use. Although there is no safety mechanism like the one featured on the ‘posilock’ type. Out of the four featured diagonals this is my personal favourite.

 

 

It mainly gets used in my 60mm Altair EDF. As the diminutive doublet gets out far more than any of my other scopes, the Baader ClickLock gets to see (or reflect) a great deal more of the night sky than the other diagonals.

 

 

The Tele Vue DDP-8004 Everbrite diagonal weighs in at 455g (without the adapter). I make the Everbrite to have a clear aperture of 46mm. This is the most expensive diagonal reviewed here. It costs about two thirds more than the Altair and Sky-Watcher dielectrics and up to a third more expensive than the Baader ClickLock. However, there is also a slightly less expensive version on the market that utilises a mirror constructed of enhanced aluminium. The build quality is very high, like all Tele Vue products. That, and the fact that it is almost certainly manufactured outside of mainland China, probably accounts for its high retail price. Apparently the dielectric coating is applied to Pyrex with a 1/10 wave flatness. The housing is finished in matte black and well baffled. Unusually it has a body machined from a solid block of aluminium with the mirror being held in place by a base plate. The solid block design is to ensure that the nosepiece or eyepiece holder cannot accidentally be unthreaded in use.

 

 

It also possibly contributes to its relatively light weight. Without its adapter it is only around 30g heavier than the Baader ClickLock diagonal. Both the adapter and the eyepiece holder itself feature brass compression rings. The rings and the screws for them are high quality and the long thumb screws are very smooth to operate. Neither of the thumb screws are captive. The overall ergonomics of the design are well thought out and the diagonal is a pleasure to use. Unfortunately the nose features a relatively deep undercut. I originally bought the Everbrite for my Altair 60 EDF.

 

 

The undercut has given me problems when used in the focuser of the 60mm ED doublet which features a three screw compression ring. Smooth or flared nosepieces don’t get caught on the 60 EDF’s compression ring. Another slight point of concern with the 2” Everbrite is that the base plate appears to be made of a plastic polymer or resin material. This is unlike the 1.25” Everbrite and Enhanced Aluminium models which have metal base plates. Whether this plastic is employed for reasons of weight or economy is not known. It is slightly disconcerting on a diagonal costing just over three hundred quid though.

 

[+Bino-viewer]

An enjoyable review once again @Nightspore and thanks for posting.

 

You are becoming the UKs version of Bill Paolini with your extensive eyepiece and diagonal expertise ! 😀

You may recall Bills own diagonal review he posted over on CN in 2014. Below is a link to it.

https://www.cloudynights.com/articles/cat/articles/mirror-vs-dielectric-vs-prism-diagonal-comparison-r2877

 

My current (and only) 2" diagonal is the Baader BBHS mirror with Clicklock.

It was expensive but i've been very impressed with it when i've used it in my larger 140mm refractor.

 

It actually looks fairly nondescript (model #2456115) and you wouldn't think it cost over £300 !

 

Interestingly when i ordered it Rother Valley Optics actually sent me the wrong one after waiting for a few weeks and i received the while #2456110 white diagonal

instead. I had a good look over it and i thought the build quality was stunning. Much 'plusher' than the more expensive option i had originally ordered and slightly bigger

and heavier (Baader state 480g for the white and 450g for my BBHS)

I actually thought about keeping that one and asking RVO to credit me the difference, but i didn't and had already set my stall out on the BBHS.

So i sent the white one back and a week or two later the black BBHS arrived. It didn't actually get used alot for the first year with me predominantly bino-viewing,

but i'm starting to do mono a quite bit more now since investing in the Docter UWA 12.5mm. And they make a formidable combination, and have given me some stunning views.

 

I like yourself am a big fan of Baader Planetarium, and when you see more than 10 different diagonal models on their website you know they are firmly committed in giving us

the best aberration-free views possible.

 

Heres my current line up of 5 with the Herschel wedge. For a 2" mirror, i think its actually fairly small with an optical lightpath length a stated 112mm, a big chuck of 

which is taken up by the Clicklock. I've never had a single issue with a Clicklock ; all the ones i've ever used have performed flawlessly.

 

 

Finally, i have decided to order my latest toy : the New APM superzoom 7.7 - 15.4 mm

Its listed as being available on July 9, although when i ordered it in mid June, Marcus Ludes quoted me a 6 - 8 week delivery. 

Just in time for Jupiter and Saturn then.....

 

 

[Nightspore]

12 hours ago, Bino-viewer said:

An enjoyable review once again @Nightspore and thanks for posting.

 

You are becoming the UKs version of Bill Paolini with your extensive eyepiece and diagonal expertise ! 😀

You may recall Bills own diagonal review he posted over on CN in 2014. Below is a link to it.

https://www.cloudynights.com/articles/cat/articles/mirror-vs-dielectric-vs-prism-diagonal-comparison-r2877

 

My current (and only) 2" diagonal is the Baader BBHS mirror with Clicklock.

It was expensive but i've been very impressed with it when i've used it in my larger 140mm refractor.

 

It actually looks fairly nondescript (model #2456115) and you wouldn't think it cost over £300 !

 

Interestingly when i ordered it Rother Valley Optics actually sent me the wrong one after waiting for a few weeks and i received the while #2456110 white diagonal

instead. I had a good look over it and i thought the build quality was stunning. Much 'plusher' than the more expensive option i had originally ordered and slightly bigger

and heavier (Baader state 480g for the white and 450g for my BBHS)

I actually thought about keeping that one and asking RVO to credit me the difference, but i didn't and had already set my stall out on the BBHS.

So i sent the white one back and a week or two later the black BBHS arrived. It didn't actually get used alot for the first year with me predominantly bino-viewing,

but i'm starting to do mono a quite bit more now since investing in the Docter UWA 12.5mm. And they make a formidable combination, and have given me some stunning views.

 

I like yourself am a big fan of Baader Planetarium, and when you see more than 10 different diagonal models on their website you know they are firmly committed in giving us

the best aberration-free views possible.

 

Heres my current line up of 5 with the Herschel wedge. For a 2" mirror, i think its actually fairly small with an optical lightpath length a stated 112mm, a big chuck of 

which is taken up by the Clicklock. I've never had a single issue with a Clicklock ; all the ones i've ever used have performed flawlessly.

 

 

Finally, i have decided to order my latest toy : the New APM superzoom 7.7 - 15.4 mm

Its listed as being available on July 9, although when i ordered it in mid June, Marcus Ludes quoted me a 6 - 8 week delivery. 

Just in time for Jupiter and Saturn then.....

 

 

 

Thanks, and you're welcome. Bill's reviews are a bit more technical than mine lol. I'm more the 'average bloke on the Clapham Omnibus reviewer'. 

 

 

I have the 1.25" BBHS mirror. Although I believe it will actually hold a 2" nosepiece and eyepiece holder. 

 

 

Unfortunately I haven't had much chance to test it properly. Like you, I'm looking forward to the Saturn and Jupiter oppo's and I plan using it with my 102mm Altair Starwave then.

 

 

The white 2" 'bog-standard' Baader is a really nice diagonal. Baader tend to overestimate the weights of their products in my experience. Either that or they're using faulty scales. It's interesting that the 2" BBHS mirror is even lighter than the white one. You shouldn't have told me that as I'll really want one now! Basically all dielectrics are the same to me in performance, and I can't distinguish between my TV 1.25" Everbrite and Enhanced Aluminium diagonals. The Baader BBHS do seem to have an edge though. I think Bill Paolini is a fan of their silver coatings as well. Apart from the Luminos incident I've not had any problems with the Baader ClickLocks. If anything would get stuck it would be a bloody Luminos lol. I think Baader have the best selection and quality diagonals on the market. I use their 1.25" Zeiss Amici a lot for lunar viewing. The APM zoom sounds really special. 

Edited July 1, 2021 by Nightspore

[+Bino-viewer]

Heres another 'Bill P' review looking at the Baader BBHS mirror #2456115 (you may have seen it)

 

https://www.cloudynights.com/articles/cat/user-reviews/the-baader-bbhs-sitall-silver-diagonal-r3038

[Nightspore]

On 06/07/2021 at 16:04, Bino-viewer said:

Heres another 'Bill P' review looking at the Baader BBHS mirror #2456115 (you may have seen it)

 

https://www.cloudynights.com/articles/cat/user-reviews/the-baader-bbhs-sitall-silver-diagonal-r3038

 

Just seen this, thanks. I really want one now! lol