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Equipment Discussions >> Refractors

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Tak FS60 vs Long Perng ED/"APO" new [Re: andysea]
      #6478269 - 04/20/14 11:38 PM

Not the FS60. But he offered the highest of praise for the TSA120. And some Zambuto mirror (he measured it at 99% Strehl). His results do seem to make sense, he really gave the hammer to William Optics (measured an FLT110 or was it 132 at about 0.44 Strehl).

I was reading his posts yesterday (using Google Translate). He's pretty much convinced me to go look for an LZOS triplet APO rather than continue to drool over an AP130GT. I certainly can spend $1800 much more easily than $6000 (there also was an SV152 LZOS on the mart recently for $4500, far far less than an AP155).

What I noticed from his tests is that his Strehl measurements track the LZOS interferometry reports quite well. So I am fairly confident that if you buy an LZOS APO with papers, you'll get what the paper says.

There's a local guy here in Singapore who tried to sell an LZOS 152 for $5500 USD in fact........ back in 2011. Maybe I should see if he's still selling it.

(I'm no fan of AP "appreciation" - yes they do seem to appreciate, but it's no investment given you can get higher returns elsewhere)


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rainycityastro
professor emeritus
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Reged: 03/29/10

Loc: Seattle, WA
Re: Tak FS60 vs Long Perng ED/"APO" new [Re: orlyandico]
      #6478370 - 04/21/14 01:18 AM

Re: Rohr's assessment of Borg scopes, AFAIK, he has only tested the 101ED and hasn't looked at the 71FL or the 77ED that have much better color correction.
Anyway, it is also important to look at spot size on the periphery of the image, not just the strehl number at the center of the image. For imaging, just that one number is limited in value. The 71FL Borg does really quite well overall.

The french site airylabs has pretty detailed interferometer reports of a bunch of scopes including the borg scopes. Unlike Rohr, they have provided spot size information for several scopes.
The strehl numbers are consistent with Rohr's data for all scopes. Tak comes out on top thanks to their dual FPL-53 and wide air spaces. Being in Singapore, you won't see any cooldown issues.
AP scopes are at a disadvantage, many of them being oil spaced and hence naturally harder to correct for spherochromatism. But Rolando himself has mentioned that in most real world comparisons, you won't see much difference between premium scopes that are properly cooled down.

http://www.airylab.fr/AirylabUS/index.php?option=com_content&view=article... has the tests mentioned earlier.

Regards,
--Ram


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rainycityastro
professor emeritus
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Reged: 03/29/10

Loc: Seattle, WA
Re: Tak FS60 vs Long Perng ED/"APO" new [Re: orlyandico]
      #6478375 - 04/21/14 01:21 AM

Quote:


(I'm no fan of AP "appreciation" - yes they do seem to appreciate, but it's no investment given you can get higher returns elsewhere)




Even as an owner of a nice AP scope, I agree fully with you. I never understood the idea of buying an expensive telescope as an investment. Buy it because it gives you enjoyment and doesnt drop too much in value, not because you think it is going to increase in price.


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Tak FS60 vs Long Perng ED/"APO" new [Re: rainycityastro]
      #6478387 - 04/21/14 01:37 AM

Thanks for that link Ram.. all the docs are in French and are PDF (so Google Translate in Chrome doesn't help).

But what stood out for me is that the LZOS 80mm blows away the Borg 71FL.. at least in polychromatic strehl. And the NP101 has a surprisingly mediocre Strehl. Looks like a good sample of a Skywatcher would beat it.. this kind of mirror's Rohr's results with a Genesis SDF.


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chboss
professor emeritus


Reged: 03/24/08

Loc: Zurich Switzerland
Re: Tak FS60 vs Long Perng ED/"APO" [Re: orlyandico]
      #6481712 - 04/22/14 05:33 PM

The newer Borg's seem to have better lens cells, that was one of the main problems on the old one that Wolfgang Rohr tested.
The FL types are ver similar in design to the TAK fluorite doublets, if not out of the same factory.

But the main point to consider Borg is the modular system that is ideal for photography or guiding.

best regards
Chris

Edited by chboss (04/22/14 05:35 PM)


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