Quality of dielectric diagonals?

[Marvaz]

Good evening everyone.

I've bought few months ago refractor Meade 5000 127 ed apo. This scope comes with 5000 series 2'' dielectric diagonals. Just wondering. There is any visible difference between this one and for example Televue everbrite dielectric diagonal or William Optics or any other top notch diagonals?

Should I have to change my Meade or not?

Thanks for any advice given.

[M4lcs67]

Would be interested to know this also. I am currently in the market for a 2" diagonal to go with my C9.25 and the smart money is on the Williams Optics 2" dielectric at the moment.

[MadAlbert]

Would be interested to know this also. I am currently in the market for a 2" diagonal to go with my C9.25 and the smart money is on the Williams Optics 2" dielectric at the moment.

pssst! That's the one I opted for..

[E621Keith]

I'd keep using the Meade. WO is just another mass produced dielectric diagonal, you probably won't notice any difference.

Televue's housing is made from a single block of aluminium, so you won't have to worry about the barrel unthreading with heavy accessories. Optically, it will be very hard to tell the difference between it and a cheaper dielectric under normal skies. You may see a very small difference if you are a very critical observer, have crystal clear skies, the perfect scope and the best eyepieces. (PS. there are some reports on CN saying the GSO enchanced mirror diagonal is optically better than TV)

[russ.will]

I was asking a similar question in this thread.

Russell

[John]

... This scope comes with 5000 series 2'' dielectric diagonals. Just wondering. There is any visible difference between this one and for example Televue everbrite dielectric diagonal or William Optics or any other top notch diagonals?

Should I have to change my Meade or not?.....

I've posted in Russells thread but, in summary, I'd say no performance difference. FWIW I reckon the Meade is at least as good as the William Optics. Might even be the same unit with a different colour scheme in fact !

The premium diagonals such as Tele Vue Everbright and Astro Physics Maxbright offer superb one-piece construction so are secure platforms for very heavy eyepieces but I've not been able to discern optical benefits over the likes of William Optics and Revelation / GSO dielectric diagonals, at least to my eyes.

[bomberbaz]

I can only say that my sct came with a bog standard 1.25 celeatron diagonal. I needed a 2" diagonal and so opted for the WO one. All I can say is the weight and feel of it is verry nice but in view of what John and Keith have said I doubt its worth shelling out a lot of sheckles for.

[E621Keith]

I can only say that my sct came with a bog standard 1.25 celeatron diagonal. I needed a 2" diagonal and so opted for the WO one. All I can say is the weight and feel of it is verry nice but in view of what John and Keith have said I doubt its worth shelling out a lot of sheckles for.

The OP's diagonal is already a 2" dielectric, so there is no need to change, but if the diagonal is a standard 1.25" I'd change it immediately. Last week, I forgot to bring my 2" visual back when I observed with my C8, so I had to use the kit 1.25" diagonal that was installed in my finder. I really regretted it because when I zoom my Pentax 8-24mm the eyepiece rotated in the diagonal and the set screw put a big scratch on the barrel of the otherwise mint eyepiece.

[bomberbaz]

The OP's diagonal is already a 2" dielectric, so there is no need to change, but if the diagonal is a standard 1.25" I'd change it immediately. Last week, I forgot to bring my 2" visual back when I observed with my C8, so I had to use the kit 1.25" diagonal that was installed in my finder. I really regretted it because when I zoom my Pentax 8-24mm the eyepiece rotated in the diagonal and the set screw put a big scratch on the barrel of the otherwise mint eyepiece.

Ouch!

[alan potts]

I have the Meade 5000 diagonal sitting in the cabinet beside a Televue Everbrite, apart from the diffence in feel and build quality I can't see a difference with any eyepiece. That though has not stopped me selling it and buying another Everybrite. The Meade is a very good diagonal, highly recommended by the Sky at Night magazine.

I just like Televue, i"m ill.

Alan

[Stargazer_00]

I use the 2" meade 5k de. I think it's really good. Beyond showing a brand name off I can't see how investing any more money for visual use is worthwhile. The meade report 99% reflectivity so any further investment would be at great expense to eat into that final 1%.

That is the pure definition of diminishing returns.

I'd use the money on another eyepiece myself.

[alan potts]

I don't know what the most costly diagonal on the market is but Astro Physics make one at about 300 quid so that would fit nicely into the diminishing returns definition. I know it's a waste but it just seem nice to me, televue eyepieces televue diagonal. I have had the Meade though for a good while and I don't have one complaint with it.

Alan.

[Stargazer_00]

It makes sense if you buy s/h in my opinion. not new though. each to their own though, hobbys are meant to be obsessions and therefore logic doesnt really apply to the economics of it all. It's not like food shopping, utility bills etc where you look for savings. you're meant to make stupid, or rather illogical and emotional decisions in hobbys!

[E621Keith]

When you mention the AP and other premium diagonal, it reminds me of this shoot out in CN between a TEC140 and a premium Mak Newt

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4774348/page/0/view/collapsed/sb/5/o/all/fpart/all/vc/1

They were worried about local air temperature variation within 12ft, eddies coming off trees, and warm pavement slab before they started worrying about the diagonal. That's how unimportant the diagonal was.

[alan potts]

Keith,

That has got to be one of the best things I have ever read on this site, I am still having a laugh 20 mins after seeing it.

Looking at the name the local Mafia was there too.

Alan

[Stargazer_00]

That is a hilarious report Some people really do live in a luxurious end of the scale dont they. I can't imagine ever being able to be in a financial position to scrutinise optics to that level.

[bomberbaz]

Would be interested to know this also. I am currently in the market for a 2" diagonal to go with my C9.25 and the smart money is on the Williams Optics 2" dielectric at the moment.

Is the current diagonal a 1.25" Celestron one with screw retainers for the EP, then if so and as mentioned by Keith, do look for a better quality 2" one. I bought a WO as mentioned, find it to be superb and was a decent price. Depends on your budget really but the WO quotes 99% reflectivity so what do you want.

[bomberbaz]

There is a 2" Diagonal on ABS. http://www.astrobuysell.com/uk/propview.php?view=68168 made by Ascension. All the Meade and WO ones are sold.

[Marvaz]

Apparently I have saved few hundred quid.

Good for me. TeleVue Ethos 13 mm is next on the list.

[John]

Apparently I have saved few hundred quid.

Good for me. TeleVue Ethos 13 mm is next on the list.

Well I guess an ES 14mm / 100 would save you even more. But it's not (quite) a Tele Vue of course

[russ.will]

That is a hilarious report Some people really do live in a luxurious end of the scale dont they. I can't imagine ever being able to be in a financial position to scrutinise optics to that level.

The thing that struck me (after I wiped the tears from my eyes) is that at no point did two scopes ever have the same brand of EP in them during the same test, by which I mean object observed.

Now, whilst I appreciate that it's going to be hard to match magnifications, FOV and exit pupils between two differing scopes, surely the sheer difference in number of glass surfaces and individual manufacturers coatings will make a significant difference? A UO Ortho v Pentax XW - What am I supposed to learn about the 'scopes? I'm discounting the diagonal at this point, even if part of me does wonder about the significance of a mirror so close to the focal plane.

Whilst I'm an complete an utter amature in this hobby, I am a paid reviewer in another sphere. If there's one thing I've learned, there is nothing to tell from a single evening of use - A reliable impression is built upon many evenings of use and in as many different locations as possible. What changes with the circumstances, is as important as what doesn't when it comes to a well rounded review, as that nails down the innate character of the equipment under scrutiny.

Russell

Russell

[jerryTheC]

My favourite 2" diagonal is the Baader Clicklock one - but that's mainly down to build quality and the fact I like the Clicklock clamp better than the usual thumbscrews. As far as performance goes, I've used a number of 2" diagonals, from the standard celestron mirror version, and budget to premium dielectric ones - and I haven't noticed a significant optical difference between them; different build quality, yes, but they've all worked fine. For visual use, I don't think you'd notice the difference in reflectivity normally - maybe if you were pushing the fringes of what you can detect, you might see a difference, but for normal use we just aren't good at spotting absolute brightness differences.

[E621Keith]

The thing that struck me (after I wiped the tears from my eyes) is that at no point did two scopes ever have the same brand of EP in them during the same test, by which I mean object observed.

Now, whilst I appreciate that it's going to be hard to match magnifications, FOV and exit pupils between two differing scopes, surely the sheer difference in number of glass surfaces and individual manufacturers coatings will make a significant difference? A UO Ortho v Pentax XW - What am I supposed to learn about the 'scopes? I'm discounting the diagonal at this point, even if part of me does wonder about the significance of a mirror so close to the focal plane.

Whilst I'm an complete an utter amature in this hobby, I am a paid reviewer in another sphere. If there's one thing I've learned, there is nothing to tell from a single evening of use - A reliable impression is built upon many evenings of use and in as many different locations as possible. What changes with the circumstances, is as important as what doesn't when it comes to a well rounded review, as that nails down the innate character of the equipment under scrutiny.

Russell

Russell

I think the magnification difference can have greater effect on the perceived image than the number of glass elements in an eyepiece, especially when you observe near the seeing limit. I guess it's acceptable when they try to find which scope offer the overall image, money no object. They had all the best wide field eyepieces money can buy on site, XW, Delos, Ethos, Tak UW, Nikon .... you name it, they had it. (This is a totally alien concept to me and probably to most of us. I wouldn't even dare to dream about having an eyepiece collection like that turning up in a observing session). It didn't matter which eyepiece performs better on its own, all that mattered was the final results when both eyepiece and scope works together. However it did sound odd they chose a 6mm ortho rather than the 6mm Delos in the comparison against the XW.

Anyway ignoring the rest of that review, the point I wanted to make was the difference between a good dielectric diagonal and a premium dielectric diagonal is negligible. There are a lot of equipment and environmental factors to consider, before someone should think about whether they need a £300 AP or TV diagonal.

[Stargazer_00]

I think its a glaring ommision that they didn't count for the colour of the paint on the cars parked nearby. If there was a mean average of red cars instead of blue cars then the approximate absorption of heat from the air would have given a direct effect on the local air pressure immediately around the tyres and lower hanging metallic parts of at the rear of the car. This would in turn create slight updrafts which could generate local air turbulence and thus effect local seeing conditions.

God forbid someone farted during the test. I think I would've bent over lauging/crying!

In case it isn't obvious i'm agreeing with what russ.will said. they were scruitinisng some things to a rather pathetic level but were really skipping over some really obvious things. For instance if the OTAs were being assessed then they should've taken the diagonal and eyepiece out of one scope and put it in the other to eliminate some variables. If they didnt give the identical magnficiations then at least the diagonal should've been moved.

[E621Keith]

In case it isn't obvious i'm agreeing with what russ.will said. they were scruitinisng some things to a rather pathetic level but were really skipping over some really obvious things. For instance if the OTAs were being assessed then they should've taken the diagonal and eyepiece out of one scope and put it in the other to eliminate some variables. If they didnt give the identical magnficiations then at least the diagonal should've been moved.

This is an interesting point someone made later in that CN thread, but I don't agree with it. If you are looking for the overall performance, you should configure the scope as it would be used in a normal observation. Unless you are Japanese, the 'normal' configuration for a refractor is OTA-> diagonal -> eyepiece. To eliminate the diagonal variable, they should choose one recommended or made by the OTA manufacturer. Astro-Physics scope should use AP/Baader Maxbright diagonal, TEC 140 with the TEC eyepiece turrent, Televue scope with a TV Everbrite and Takahashi should be used straight through etc...

As for eyepieces, if both scopes were at 165x and a 6mm Delos in the Mak Newt beat a 5mm XW in the APO, the Mak Newt beat the TEC at 165x. The result may favour the TEC if it had a 5mm Delos, but 5mm Delos don't exist. Anyway, scrutinising scope at that level is way beyond me, so I'd read that shootout is just for fun, like watching Top Gear.