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Borg Fluorite Scopes: 71Fl, 72FL, 90FL, 106FL, 107FL, ...

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#26 Catalin81


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Posted 04 August 2020 - 04:33 PM

grin.gif I may have rushed into things a bit. Their correctors seem to be designed exclusively for photographic use judging by the schematics on the Tomytec site, as other members already stated. From an ‘astro’ point of view, I imagined the 1.4 extenders would be meant for visual use, but I now believe they are more about wildlife photography after all.


There is however a CN member (Ron Scarboro) that claims to having successfully used a 1.4 teleconverter with a diagonal on a 71fl with good results towards CA. There are also at least 2 other members with fuzzier stories, that claim to have used the extender visually but don’t give any details.

I do intend to get all 3 available correctors for the 90fl and play with them. I will post my results.

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#27 marcus_z



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Posted 05 August 2020 - 01:07 AM

Don't forget, 71FL and 90FL are different optics with totally different color correction. wink.gif  I don't notice false color in the 71FL, but I do in the 90FL.

#28 BGazing



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Posted 05 August 2020 - 04:29 AM

As for flatteners/reducers, there was a prototype built for FL by Siebert, but Ted's blog did not come back with the testing results after announcing that it was in its hands. You may draw the conclusions.

I think it is unfair to compare f/5.6 flourite doublets with triplets and doublets of longer f/ ratio. But 71 is immensely portable, you can take it, AzGti and carbon fiber tripod anywhere, irrespective of cabin luggage restrictions and exotic small planes with weird boarding rules in the middle of nowhere. You can, of course, have a 72ED for much less money. I am not magnification junkie, 71FL runs out of power probably around 115x-130x, not because it is fuzzy but because planets or the Moon become dark. 

Has anyone compared 89ED and 90FL head to head? 89ED is f/6.7, is it better or worse than fluorite at f/5.6?

To those who have 90FL, if used with FTF, how long is your 80 series tube? I know that 71FL and 89ED use the same 200mm length of the 80 series tube.

#29 Rich Caruana

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Posted 07 August 2020 - 07:20 PM

+1 for the AzGti + CF tripod as a lightweight travel mount for the 71FL and 90FL.  They work great together and the entire kit is easily packed in carry on bags.


@BGazing --- I use the 71FL and 90FL with the same 200mm series 80 tube and FTF.  No problems used visually.  Only issue I've run into so far is that there isn't enough back focus (in focus) when using the Baader 2" Herschel Wedge with the BHZ --- it's close but doesn't reach focus.  The Baader 2" Herschel has a long path length and I don't have problems with other 2" diagonals.  The 90FL and 200mm tubes work fine with a 1.25" Herschel diagonal, though the contrast appears to be better in the 2" Baader.


@Catalin81 --- would be great to hear about your experience with the 90FL and correctors when you get them.



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