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Upgrading My Diagonal


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Hi,

I got my EdgeHD 8" a month ago, and a couple of nights ago I had a really great session (observing from my balcony in a red zone), I was able to see some amazing globular clusters.

Anyhow, I am interested in upgrading my diagonal to a 2”, in order to buy my first set of eyepieces, (I am considering the ES 82* eyepieces). For the last few weeks, I was trying to settle on a specific brand but still not sure. I have read the report written by William Paolini and it is a good and an informative article. The prism diagonal is way over my budget, as I'm only considering diagonal in the range of $100-150 (if new). The three brands that I am currently looking at are the Meade 5000, Sky watcher and the William optics. There are other few brands that I am not sure about, like the Antares, Olivon, ES, TPO, Astro-Tech and GSO. Please note that I'm going to buy  2” visual back, therefore, I'm not limited to diagonals with SCT female thread, as I like the Idea of threading the eyepiece directly into the visual back (if I need to overcome the scattering or the 1% light loss).

So, my question is how would you rank these brands, or are they all similar (as all have the same specifications). Although, I have heard that some are supplied by a the same manufactured, so would that mean that they have similar quality standards.

Also, some diagonal like the TPO and GSO have the Quartz Dielectric, would that mean that they perform better than the others or they are more durable.

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I can't help with your diagonal question but as regards to fitting the eyepiece straight into the back of your OTA remember that in order for you not to have to contort yourself into all sorts of awkward positions you will probably need your mount fully extended. This can induce vibrations, especially if it is windy, which will spoil your view. It also takes a lot of distance out of the focusing chain. I've got a Revelation Superfocus 2" R&P focuser on the back of my C8 XLT so that makes up for the lack of a diagonal. Not sure if the SCT will reach focus with that extra distance missing or not?

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I have a Revelation 2" diagonal, a Meade 2" diagonal and a Tele Vue 2" diagonal, these range from about £80.00 GBP through £150.00 GBP to £240.00 GBP.

The difference between them when used in 10"SCT is marginal and the main thing that affects the view is the sky quality, as with eyepieces once they start costing more than £150.00 the increase in quality of the view is marginal, but still noticable in a fast scope, not so much in long focal length SCT.

Dave

Edited by Davey-T
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Of the first 3 I would have said WO, Meade, Skywatcher.

Antares seem to produce good equipment, not sure where the bits come from but Antares are in Richmond BC if I recall.

Olivon will be a rebrand (GSO I half suspect), ES could actually be the same as the Meade - they still seem to work together however Meade used to source from GSO, TPO I am not familiiar with, Astro-Tech seem to source a lot from Barsta who equally seem to make some good optics. GSO are possibly the weakest.

The Meade/ES relationship is likely the question. If not working with Meade ES seem to be producing some good items at good prices.

Meade is now owned by Sunny Optics so their diagonals could come from the Sunny factory in which case they are somewhat unknown.

Quartz is generally more for thermal changes - I think - I was looking at a 2" diagonal and eventually made up my mind on the Altair 2" offering in glass. The quartz was nice but I very much doubt the cost difference would result in any visual improvement to me.

WO still would be my blind choice simply as they make some nice bits like diagonals that seem to work well, so maybe it is just a bit safer choice, you are most likely to get a good one, or less likely to get a bad one.

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Thanks all for the reply,

I was checking WO website and two statement caught my eyes.

http://www.williamoptics.com/diagonalPrism/2Carbon-Fiber-Diagonal-Dura-Bright_features.php

The first is that they are polished to have a 1/12th wave accuracy, and they end the statement with a (*) as if there would be some kind of a note at the end of the page but there is it.

The second is that it shows that they have a patented design that would save you the effort from ever needing to collimate the diagonal.

How accurate are these claims? especially on there online shop they don't have these claims and it shows only that they have a 1/10 lambda surface. 

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I really wouldn't be swayed by claims of 1/10th wave etc etc. Not saying they are telling porkies but these optical specs can mean different things according to how the tests were done, and how consistent manufacturing runs come out.

I'd avoid the cheapest made to a rock bottom price.

Hope you find something suitable, Ed.

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I have the WO carbon fibre 2", it's made very nicely and very solid but light.

I had a Revelation one which was also very good as is the TeleVue one I replaced it with.

To be honest I can't tell much difference between them.

Not sure what the Meade is like but I have some 5000 EPs which are really good.

I'd say my order of preference is WO, Meade, SW but personally would not bother with the SW, mainly as I wouldn't put one on my Tak!

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Not sure if the SCT will reach focus with that extra distance missing or not?

Bryan It shows in the manual that l could thread my eyepiece directly into the 1.25" visual back with out the diagonal if desired, and I was able to do that and get it in focus with the 40mm eyepiece it came with. However, it is a really a neck breaker the closer the target to zenith, but still it is a chose that I might consider from time to time for planetary observation, as I find no difference when viewing stars and clusters.

A read on a number of threads that there is no obvious differences in the optical quietly between most of the brands, and the major factor is the mechanical build and which is the best to securely hold the huge 2" eyepieces. For that the WO as many of you have recommended do excel, and it going to be my first choose. Unless I find a cheaper second hand diagonal from Meade or ES.

Thanks all for your advice, most appreciated.

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