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1-1/4" Diagonal. 99% Dielectric....AT or GSO or ?

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#1 spongebob@55

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Posted 10 May 2013 - 09:50 AM

Hi Everyone,
I have to buy a 1.25" diagonal for both my ST80 and my f/15 Mak Cass that's coming. I'm visual. Could possibly be holding a binoviewer too. Any input on these two or would you suggest another? The specs look the same....
Thanks
Sbob.

#2 Binojunky

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Posted 10 May 2013 - 10:01 AM

Most are coming out of the same couple of factories in the far east,the Orion,Stellarvue, Williams etc, go with the best price and shipping charges, the exception is the TeleVue, costs a good bit more but has superior mechanics,its milled from a solid billet of aluminum,DA.

#3 csrlice12

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Posted 10 May 2013 - 10:10 AM

The GSO one is fine, the Televue if you want to eek out those very, very, very tiny details when the viewing weather is perfecto (those 1000X nights), then, there'll be a small difference. For AP, I'd probably go with the Televue, but the GSO is even fine for AP. I got the Orion one, same diagonal, different label, and it works great. Unfortunately, I just gave away the 1.25" XLT diagonal to someone.

#4 DaveJ

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Posted 10 May 2013 - 10:37 AM

I have to buy a 1.25" diagonal for both my ST80 and my f/15 Mak Cass that's coming. I'm visual. Could possibly be holding a binoviewer too. Any input on these two or would you suggest another? The specs look the same...


Spend the extra money and go with the Tele Vue. Much better mechanicals, as has been mentioned. Tolerances are better, too. The differences are well-worth the money in my not so humble opinion.

#5 csrlice12

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Posted 10 May 2013 - 10:40 AM

An ST80 with binoviewers? Please, Please, Please post a pic....and let us know how it works.

#6 DaveJ

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Posted 10 May 2013 - 11:24 AM

An ST80 with binoviewers? Please, Please, Please post a pic....and let us know how it works.


I use my Mark Vs in my wife's AT80EDTA all the time. Here's our grab-n-go set up for Hershel Wedge white-light solar viewing. The image is spectacularly detailed. Yeah, I know. I should be out mowing the grass. :grin:

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#7 mikey cee

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Posted 10 May 2013 - 12:06 PM

I have a 92% 2" GSO and if I actually thought anything was going to improve my views I would have traded it off by now. Put the savings to good use instead. ;) Mike

#8 csa/montana

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Posted 10 May 2013 - 01:35 PM

I have an AT on my 80mm scope & am very pleased with it.

#9 jhirsch

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Posted 10 May 2013 - 05:20 PM

I have the 1.25" AT and I'm currenly using am using the 2" GSO. I personally don't think you'll be disappointed in either. For the cost they're hard to beat.

#10 Don Taylor

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Posted 10 May 2013 - 08:27 PM

I use the AT dielectric which appears to be sourced from Long Perng (at
East the mechanicals appear to be). I also have an Orion 2" dielectric and it seems to come from the same source ( both marked Taiwan).

Finally, I have a 2" Baader cliklock (which is mechanically wonderful)

I have not been able to detect any optical difference between the three when used with the same eyepiece and scope.

I really prefer the Baader for its cliklock feature but again, no apparent optical advantage

#11 Eddgie

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Posted 11 May 2013 - 07:42 AM

I am going to recommend that you think hard about the potential binoviwer configuration.

Many refractors will not reach focus with binoviewers even with standard 1.25" diagonals.

This forces you to use some kind of magnifying lens (Barlow, GPC, or OCS), and when you do this, it limits you to relatively high powers.

Keeping the light path as short as possible allows you to avoid any extra magnificaiton.

The approach that I personally think is the most prodent with this future requirement in mind is to get the Baader T2 Prism diagonal.

You can buy this diagonal with the eyepeice holder in place, but when you want to later add binoviewers, you unscrew the eyepiece holder and then screw the Maxbright Binioviewer head directly tot the top of the diagonal.

This keeps the light path as short as possible, assuring that you are going to need as small an amount of magnification as possible.

I the MCT, it will also reduce your focal length, once again, giving you the lowest power possible.

These are very high quality diagonals, and very sturdy becuase they were designed with binoviewing applications in mind.

These are not inexpensive, but given the flexibility and the very short light path for binoviewing, I think it is worth spending the money up front with the idea of adding the binoviewers down the line.

Siebert also sells a diagonal that allows you to connect an pair of WO or similar binoviewers directly to the top of the diagonal, but I don't know if it includes the eyepeice holder. I believe he just sells the diagonal witht he dovetail ring setup, but you could ask him.

Do yourself a favor, and think ahead on the binoviewer requirement. Get a diagonal that allows for a short light path...

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#12 csa/montana

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Posted 11 May 2013 - 07:55 AM

You've brought up excellent points for the OP to consider; since he did mention binoviewers as a possibility! :bow:

#13 Eddgie

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Posted 11 May 2013 - 11:44 AM

Binoviewers are one of the most complex buying decisions one can make, and after starting off on the wrong foot, I became far more aware of the evils of light path length.

Someone anticipating binoviewers should dismiss all other charateristics of the diagonal (coatings, glass type, or whatever) and choose a good quality diagonal and binoviewer that offer the shortest possible light path (with the biggest prisms they can afford).

In this case, the OP can get a great diagonal with a 1.25" nose (though I highly recommend the two inch nose for binviewers) and even fit it with a Clicklock type eyepeice barrel.

The Siebert is also interesting because he now offers a connector to allow you to connect different clone viewers to it (WO, Celestron, and most others which seem to all be similar).

Siebert sady does not do a great job with his details.

He provides a 2" to 1.25" adapter that fits almost entirely into the focuser (good) so the diagonal can be used in 1.25" or 2" configurations (and again, I only recommend 2" nose configurations for binoviewers because they offer more grip against rotation).

What he doesn't say though is wheter the dovetail collar can be removed and replaced with a 1.25" eyepiece holder and if that is included in the price.

The Baader though is very well documented and offers a vast array of configuration options.

It is a more expensive way to go, but the quality is excellent, and you have consetllation (pun intended) of configuration options avaialble.

Here is the Siebert diagonal and pictures showing how it allows many scopes to function without GPCs...

Siebert short light path diagonal

The Baader system though is simply amazing.

And it works with Telvue binoviewrs (often available used for an "affordable" price), Maxbrights (my favorite inexpensive binoviewer), and Mark Vs.

The Sieberts work with the entry level binos though, and Siebert also offers a 25mm clear apeture bino that sits between the used Televue/Denks and the Maxbrights.

But that is a whole different can of worms, and I advise the OP to spend some time on the binoviewer forum.

But if he can't reach focus with a standard 1.25" diagonal and requires a GPC or Barlow, it really makes it impossible to get much true field out of even smaller telescopes.

#14 brokenwave

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Posted 11 May 2013 - 12:02 PM

I have a 2" OPT 99% diagonal ($119) a 2" Meade 5000 ($150), a 2" ES and have compared them all with a 2" Williams Optics ($139)and a 2" Baader click stop ($300)
We have seen zero difference between all 5. The Baader was very nice though. If you are worried about not having a Hi dollar diagonal. Make a sticker that say's Astro Physics and attach it, that will keep all the equipement snobs at bay. LOL

#15 cavefrog

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Posted 11 May 2013 - 07:46 PM

Eddgie, boy! you sure hit the nail on the head. the Baader T2 is what I have been looking at. I have been pondering the clicklock diagonal that is a little rich for a diagonal, and then I saw the T2 and its versatility. I have been wanting both a quality 1-1/4" diagonal, and I was thinking about a shorter focal distance for binos. and the T2 is what I found. but this is a mirror, isn't it? or do they make them both?
anyway, what is confusing me is that WO binos and Denks have a different output size and thread. how can one make both work in this diagonal? is there a different adapter for each? it seems there would have to be.

also, a 2" nose can be put on the T2 with a 2" clicklock eyepiece holder, basically making it a clicklock diagonal.
I haven't yet determined if this is a dielectric mirror though.

Theo

#16 cavefrog

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Posted 11 May 2013 - 08:37 PM

wow! and I thought the 2" clicklock was expensive.
they want $289.00 for just the base? another 100 for eyepiece holder, then who knows how much for the nosepiece?
we are talking about a $500.00 diagonal!!!

#17 spongebob@55

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Posted 11 May 2013 - 08:47 PM

very interesting.....love to have stuff with future possibilities. Already have a clicklock 2" diagonal.
Bob

#18 cavefrog

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Posted 11 May 2013 - 08:57 PM

ok, not a mirror. thought I read something about a mirror.
not the last mistake I'll make, I'm sure!

#19 Eddgie

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Posted 11 May 2013 - 09:32 PM

There are several Baader diagonals.

There is the T2 standard prism. This has the shortest light path (38mm I think).

Next is the Baader Ziess prism unit. Very expensive. It offers a few more millimeters of aperture but this is no real advantage because even the standard T2 has 32mm openings and none of the common binoveiwers require more than 28mm.

Then there is the Maxbright Mirror diagonal. This unit has I think 35mm openings. Once again, expensive and the bigger opening is not all that necessary.

However, this diagonal does have a 35mm mirror surface, so it could support up to a 35mm Panoptic in mono-vision mode.

For someone wanting to keep the light path short for monoviewing a C8, this might be a great option for both binoviewing and monoviewing.

I think this is the diagonal that now ships with the Mark V binoviewers when purchased from AP.

So, plenty of choices.

For binoviewing were the shortest possible light path is desired, it is hard to beat the standard prism.

As for adapters, of course the Maxbrights and the Televues can connect right up via the T2 threads.

The Mark V requires a dovetail.

There are adapters out there to connect the Denks.

Siebert might have adapters that could connect the others.

But what makes the Baader so good is that they make a huge range of mix and match components.

I love the T2 standard prism. Very high quality. Seems to be exactly the same performance as the Takahashi prism diagonal I used to own, and more robust to boot.






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