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Can you use EP projection with binoviewers?

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#1 rwiederrich

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Posted 01 August 2019 - 12:23 PM

Letting this idea rattle around in my head, I was wondering if anyone had ever tried using an EP projection system prior to the binoviewer, instead of a barrlow?

 

Using a 2X barrlow prior to the binoviewer with say 10mm EP's will in essence double the magnification....what  effects(if any) would a 10mm projection EP have on another 10mm EP? Or any other EP for that matter?

 

Rob



#2 Astrojensen

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Posted 01 August 2019 - 12:46 PM

Yes, you can do that. I use it on telescopes that otherwise don't have enough back focus. 

 

The magnification can get pretty high. I use a 40mm projection eyepiece with T2 adapter (GSO made, sold under various names) from Teleskop-Service. The magnification factor is around 2.5x. Interestingly, the baffling is MUCH better than with a barlow!! Also noteworthy is that the image is suddenly right side up and correctly oriented (if you don't use a diagonal prism, such as on a newtonian). 

 

Image quality is very good, but there can be quite a lot of field curvature, depending on the telescope. The method seems to magnify the field curvature of the telescope and/or the eyepiece, plus it also seems to be quite f/ratio depending. It works really well with longer f/ratios. 

 

 

Clear skies!
Thomas, Denmark



#3 rwiederrich

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Posted 01 August 2019 - 03:59 PM

Yes, you can do that. I use it on telescopes that otherwise don't have enough back focus. 

 

The magnification can get pretty high. I use a 40mm projection eyepiece with T2 adapter (GSO made, sold under various names) from Teleskop-Service. The magnification factor is around 2.5x. Interestingly, the baffling is MUCH better than with a barlow!! Also noteworthy is that the image is suddenly right side up and correctly oriented (if you don't use a diagonal prism, such as on a newtonian). 

 

Image quality is very good, but there can be quite a lot of field curvature, depending on the telescope. The method seems to magnify the field curvature of the telescope and/or the eyepiece, plus it also seems to be quite f/ratio depending. It works really well with longer f/ratios. 

 

 

Clear skies!
Thomas, Denmark

I suspected such, but was uncertain.  I'm using a homemade 6"f/9 with loads of back focus.  I'll compare the images I get with the Barlow to what I get with the 10~12mm EP.  I might try a 24mm as well. I did notice slight vignetting  with the barlow...and some serious mag which induces greater CA as well.

This arrangement is for solar viewing mostly, though I do wish to use it for the young grandkids for lunar and planetary viewing.

 

Thanks for the advice and comment.

 

Rob




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