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Native binoviewing with an ED127 - so close....

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#26 Eddgie

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Posted 14 September 2019 - 01:38 PM

Note.  While standard eyepieces reached focus with the T2 diagonal and direct connected BV, the Baader zooms shown in the picture did not reach focus without some modification to the scope.  I was about 2mm short.  I bought a second visual back from ES and ground it down about 3mm so I could reach focus with the zooms.   When I sold the scope, I just put on the second visual back and tossed the one that I had ground down.

 

For the Arcturus though, because the light path of the BV is a lot shorter, even zooms would reach focus, so this would not be a problem for you if you decided to use zooms.

 

The Baader T2 diagonal with a T2 ready/modified binoviewer is the only way I know of that you will reach native focus without modifying the scope or using a different focuser.



#27 precaud

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Posted 14 September 2019 - 07:22 PM

I understand that some folks come into a thread and contribute without having read the whole thing. Here's why I am hesitant to just run out and buy another Baader diagonal.

 

4 or 5 years ago, after getting a Celestron CR-150 and sorting it's issues out (one of which was replacing the gawdawful 1.25" mirror diagonal it came with), reading and research led me to buy a Baader T2 with both nosepieces and the eyepiece holder with builtin helical focuser. No question, it was much better than the mirror it replaced. I assumed I had obtained a high-performance piece of kit.

 

Over the next year or so, two things happened that changed my opinion on that.

1. I got an ES ED127, which stomped the 6" achro in detail and contrast. I was shocked when, after remounting it, the ES's mirror diagonal easily outperformed the Baader prism in every respect.

2. I  got an 80mm reference flat and learned how to test diagonal mirrors and prisms using a contact flat. Then I could juxtapose my subjective impressions with some objective measurement.

 

And there it was, easy to see. The Baader diagonal is well-machined, but the prism was not high quality. See the photo: the fringe lines are curved, becoming wider and further apart from right to left, fanning out toward the top. According to the charts I have, this is a combination of astigmatism and "bent cone", with maybe some cylinder thrown in. No wonder the views were soft and contrast poor.

 

I bought used Orion and Vixen prism diagonals in the CN classifieds, and they both were superior.

 

So yes, I am definitely skeptical about running out and getting another Baader prism. You know the saying: "Burn me once..." Sure, there are many "good reports" on them, but I know from experience, subjective reports are relative to what one has and is accustomed to, and is subject to change in a flash. I haven't seen anyone else post a fringe test of their Baader diagonal.

 

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#28 Eddgie

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Posted 14 September 2019 - 07:33 PM

I am only trying to help you with your requirement, which was to be able to reach focus without a GPC.

 

If you don't like the solution for whatever reason, then simply don't do it. 

 

You might look at the Baader T2 mirror.  Light path is about 50mm and this might get you buy, but I have not used it on the 127ED and I don't know if it would work with your specific binoviewer.

 

Hope you are successful in your quest. 



#29 REC

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Posted 16 September 2019 - 11:22 AM

Thanks for weighing in, REC. I have read some of your posts re: using your BV's sans OCS with a C102. I have a C102 as well and was going to try it, but assumed that 4" was not going to be enough aperture and result in dim images. I guess you find otherwise?

 

Did the WO focuser give you more in-travel over the stock R&P (which appears to have a very long throw...) ?

The WO focuser was shorter than the stock one and I was able to have more back focus to get it to work. The 4" apertures works very well in the brighter objects. I use a pair of 16mm and for a larger exit pupils for DSO's, I use a pair of Meade 26mm SP.



#30 Kunama

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Posted 17 September 2019 - 01:14 AM

I understand that some folks come into a thread and contribute without having read the whole thing. Here's why I am hesitant to just run out and buy another Baader diagonal.

 

4 or 5 years ago, after getting a Celestron CR-150 and sorting it's issues out (one of which was replacing the gawdawful 1.25" mirror diagonal it came with), reading and research led me to buy a Baader T2 with both nosepieces and the eyepiece holder with builtin helical focuser. No question, it was much better than the mirror it replaced. I assumed I had obtained a high-performance piece of kit.

 

Over the next year or so, two things happened that changed my opinion on that.

1. I got an ES ED127, which stomped the 6" achro in detail and contrast. I was shocked when, after remounting it, the ES's mirror diagonal easily outperformed the Baader prism in every respect.

2. I  got an 80mm reference flat and learned how to test diagonal mirrors and prisms using a contact flat. Then I could juxtapose my subjective impressions with some objective measurement.

 

And there it was, easy to see. The Baader diagonal is well-machined, but the prism was not high quality. See the photo: the fringe lines are curved, becoming wider and further apart from right to left, fanning out toward the top. According to the charts I have, this is a combination of astigmatism and "bent cone", with maybe some cylinder thrown in. No wonder the views were soft and contrast poor.

 

I bought used Orion and Vixen prism diagonals in the CN classifieds, and they both were superior.

 

So yes, I am definitely skeptical about running out and getting another Baader prism. You know the saying: "Burn me once..." Sure, there are many "good reports" on them, but I know from experience, subjective reports are relative to what one has and is accustomed to, and is subject to change in a flash. I haven't seen anyone else post a fringe test of their Baader diagonal.

Which of the Baader T2 did you use. The T2 Zeiss spec prism is as good as any, the Maxbright is the one recommended by AstroPhysics with their MkV binoviewer kit. The very basic Baader prism is not at the same level as the others.....



#31 precaud

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Posted 18 September 2019 - 10:52 AM

Which of the Baader T2 did you use. The T2 Zeiss spec prism is as good as any, the Maxbright is the one recommended by AstroPhysics with their MkV binoviewer kit. The very basic Baader prism is not at the same level as the others.....

I had the standard one. I'm not going to be buying a Zeiss prism just to experiment with binoviewing...




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