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TSA 120 vs FS 128

Optics
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#1 lwbehney

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Posted 31 July 2022 - 01:22 PM

Hello everyone. I found an interesting review of the TSA 120 from January 2010 detailing the differences between Takahashi’s old FS-128 line and the new TSA line.  The author included spot diagrams showing that the TSA 120 triplet had overall superior correction of chromatic aberration, but with careful scrutiny of the diagrams you find that for all wavelengths longer than  560 nm, the fluorite doubled has the tighter spot diagrams. 
Now I understand why I can see the red color of even dim Castor C and why carbon star color is so vivid compared to other telescopes I have had the fortune to look through. 
Unlike glass, fluorite  crystal lenses are not opaque to infrared or deep red and fluorite is transparent to photons with wavelengths from 100 to 100,000 angstroms 
I suggest we visualists beg for bigger aperture fluorite doublets than the 100 mm size than only Takahashi is making. 
Anyone else thinking along these lines?


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#2 CHASLX200

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Posted 31 July 2022 - 03:21 PM

This needs to be in the refractor section.  I would much rather have a 2 lens scope so the FS128 would be my pick.



#3 dweller25

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Posted 02 August 2022 - 09:35 AM

When I compared my TSA102 to my FS128 it was obvious that the TSA was better corrected either side of focus, but I preferred the warmer more vibrant tone of the FS.

 

And who observes either side of focus lol.gif


Edited by dweller25, 02 August 2022 - 11:38 AM.

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#4 donadani

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Posted 02 August 2022 - 11:10 AM

Had two FS-128 and two TSA-120 and stayed with a FS-128 in the end...

 

The FS cools quicker and the views are a bit brighter. I prefere its fixed dew cap, collimatable lenscell and manhole cover. All over that it has a fluorite lens :)

 

Love those FS scopes! so much that after all I bought a 102 on top when a good chance came up :)


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#5 25585

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Posted 03 August 2022 - 09:09 AM

Agema makes big fluorite doublets - 120, 130, 150, larger. The 130 is appealing.

 

I find it interesting that warmer rather than neutral is preferred by some. 

 

The FS128 has left an unfilled gap in Tak's range, the TOA130 is great but different. 



#6 SkyRanger

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Posted 03 August 2022 - 09:37 AM

I have a TSA 120.  I am completely happy with it—no complaints of any kind. (Visual astro only)

 

But I am also curious about the Agemas.  After a year of kicking the idea around I put down a deposit on the Agema 130.  If all goes well, I’ll have it late this year!

 

Gordon G


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