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Extenders vs Barlows

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#1 ScottW

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Posted 10 February 2021 - 08:19 PM

Hi,

 

I noticed that Tak offers extenders for its refractors. Is there any difference in use between extenders and barlow lenses?

 

Thanks,

Scott



#2 Spikey131

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Posted 10 February 2021 - 08:31 PM

They cost a lot more, for one thing.



#3 25585

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Posted 11 February 2021 - 05:27 PM

The Tak extenders are dedicated to those particular scopes they were designed to go with. Tak extenders fit between the focuser and diagonal, so are in effect an extension of the OTA in a straight line. 

 

For various sub-100mm aperture models, you can buy "Q" modules that fit before their focusers, making your scope a quadruplet long(er) FL, though Tak extenders on their 100mm & greater aperture models do the same, but look less elegant.

 

For any type, optically, Tak extenders are invisible. Fitting before a diagonal, they do not dictate diagonal or eyepiece size that can be used.  


Edited by 25585, 11 February 2021 - 05:29 PM.


#4 mikeDnight

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Posted 11 February 2021 - 06:03 PM

The Q actually turns a Sky 90 into a 90mm F8, a FC100DC /DF into F11.8, FC100DZ into an F12. 8. and a FC100DL into a F14.4. But that's not all. The 5 element 1.6X-Q corrects for any residual SA and CA.


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#5 laedco58

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Posted 11 February 2021 - 10:06 PM

Mike,

Did you use your previous DC with the extender Q? You posted a picture in another thread of your Extender Q and its the 1.25" version. I have used a 2" version in my DL several times with no degradation to the image quality as long as I didn't boost the magnification beyond what the seeing would support.

 

Larry 



#6 astromiester1

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Posted 04 April 2021 - 04:47 PM

I have a tak and extender but am trying to find another vendor like WO or someone that has an extender as well as a lens option for the refractor.. Anyone know if another company exists that does it?

 

Thanks

Dale



#7 photoracer18

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Posted 06 April 2021 - 07:08 PM

Extenders don't care where you put them in the optical train they still have the listed magnification. Barlows on the other hand give different magnification depending on whether they are in front or behind the diagonal. As an example a 1.5x Barlow is 1.5x behind the diagonal and about 2.25X in front of it.


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#8 25585

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Posted 07 April 2021 - 05:21 AM

The Q actually turns a Sky 90 into a 90mm F8, a FC100DC /DF into F11.8, FC100DZ into an F12. 8. and a FC100DL into a F14.4. But that's not all. The 5 element 1.6X-Q corrects for any residual SA and CA.

They are superb! I use the ED1.5x with my TSA-120, its as good as a Q 1.6x on my DL. No field curvature either, so its flattening the FoV too, not that the TSA has much anyway.

 

ES Barlow Extenders are a possibility, they may keep the same magnification wherever put in an optical train, anyone know?



#9 MartinPond

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Posted 07 April 2021 - 07:51 AM

They are superb! I use the ED1.5x with my TSA-120, its as good as a Q 1.6x on my DL. No field curvature either, so its flattening the FoV too, not that the TSA has much anyway.

 

ES Barlow Extenders are a possibility, they may keep the same magnification wherever put in an optical train, anyone know?

The ES Focal Extender is telecentric...

It is a 4-element Galilean, infinity-focused.  Magnification is not affected by position.

It is unfortunate that they call them "Focal Extender / Barlow"... 

I did double-check by putting a 6in extension after the 1.25//3X....image still clean and same (near as I can tell).. 


Edited by MartinPond, 07 April 2021 - 08:02 AM.



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