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Tak FS60 vs Long Perng ED/"APO"

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#26 Kunama

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Posted 19 April 2014 - 04:30 AM

At that price and for that purpose it seems the logical way to go Orlando.

#27 Erik Bakker

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Posted 19 April 2014 - 07:09 AM

Stunning pair of Tak's Matt. Looks like a dream team to me :bow:

Look forward to your report on the FS128.

#28 Daniel Mounsey

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Posted 19 April 2014 - 08:35 AM

That's nice. I mounted the FC60.

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#29 Erik Bakker

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Posted 19 April 2014 - 10:34 AM

We may now also have 2 scopes that qualify as dreamteam-plus :jump:

#30 Mickey_C

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Posted 19 April 2014 - 11:42 AM

it's now time for me to bow out of this discussion :)

the $350 SV80ED is just impossible to resist, since it will live 95% of the time as a guide scope. I'll just tolerate the CA when I - rarely - use it as an imaging scope.


Find a used astrotech AT80 for less than that and you'll have a FLP-53 glass element - they're pretty close to color free, very similar to the tak doublets (I have owned several of those).

#31 orlyandico

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Posted 19 April 2014 - 12:45 PM

isn't the AT80 the achromat? there is an 80mm AT triplet but i seriously doubt it would be under $350... the SV non-Lomo triplet is usually around $500 to $600.. there also used to be a TMB upgrade lens for the AT80.. same as the WO Megrez 80 so yes, FPL-53. But they were never below $350, and are extremely rare...

#32 Mickey_C

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Posted 19 April 2014 - 03:53 PM

No sir, it's an Apochromatic Doublet. I found my AT80LE for $400 - the only difference being the carbon fiber tube. I just saw another sell for less, btw :(

http://www.manualsli...tro-Tech-At8...

Search astrobin images, you'll see what it can do.

#33 Mickey_C

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Posted 19 April 2014 - 03:57 PM

SORRY - I stand corrected. The AT80LE is an FPL-53 apo doublet, the regular AT80 apparently was not; I didn't know that.

Well, in any case, I still see the AT80LE for my price-point. I'm not THAT lucky.

#34 calypsob

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Posted 19 April 2014 - 10:35 PM

isn't the AT80 the achromat? there is an 80mm AT triplet but i seriously doubt it would be under $350... the SV non-Lomo triplet is usually around $500 to $600.. there also used to be a TMB upgrade lens for the AT80.. same as the WO Megrez 80 so yes, FPL-53. But they were never below $350, and are extremely rare...


Orly, If you want a cheap triplet check out the BM80, it is an FPL-51 triplet Barska Magnus 80mm It comes with a lifetime warranty for under $400. It optically will out perform a Tak doublet and any other doublet you can think of. The new focusers on these are much better than the old ones, you can see where they cut corners on finish in some areas but if you want a guilt free grab n go with a hard case, a free dielectric diagonal and some EP's check this scope out. there is a huge thread in this area about this scope. Sounds like it would be right up your alley. If you scroll down my flikr page a bit you can see alot of closeups of this refractor https://www.flickr.c...s/70374000@N08/

#35 Samir Kharusi

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Posted 19 April 2014 - 11:59 PM

Sounds like a very familiar desire. Mine: guide scope to serve as an imaging scope and also as a nice finder scope. Unfortunately what I found in my search was some incompatibility in the requirements:

Finder scope: Nice to be able to use 2" eyepieces for wide field visual observing when permanently mounted onto a C14. But it needs to be lightweight. Unfortunately most premium APOs are heavy, even at 60mm aperture.

Guide scope: my desired aperture is 70+mm. I found that 60mm involved searching for a bright enough guide star more often than I like. This ends up making its desirability as a lightweight finder scope even less.

Imaging scope: a flat enough image field over one's sensor is everything, all else is of secondary importance. I am happy to use a Canon APS-C camera, only occasionally full 35mm format. While I expect that manufacturers do not actually lie in their advertisements, one should be extremely suspicious if they do not brag and specify the flat diameter of the image field. Tak brags a lot about the large, designed-in, image field for their FSQ106. Do they do the same for the 60? If not, be very wary. As a corollary, I also found that some facility for adjusting orthogonality of a large sensor to the optical axis is essential unless extreme measures have been taken to assure the precision of the camera attachment system. Bayonet systems, like on camera lenses are well proven for that, and some scope manufacturers do provide something similar. A simple 2" eyepiece-type of attachment is often not precise enough, unless you have been very lucky with your sample or you use a "small" sensor by today's standards.

In brief, large sensor coverage (35mm format coverage is more rare than one expects initially. If the manufacturer does not brag about it then I expect that the scope will not deliver it; that simple to me) and orthogonality have disappointed me when I compared two TV imaging scopes to camera lenses. Mind you, both the scopes exhibit higher contrast and sharper stars centrally than the camera lenses, but overall the Canon tele-primes, IMHO, won out for imaging, on even an APS-C sensor, never mind on full 35mm format. Look for the bragging rights in the ads before forking out the $. I compared a TV140 (modified Petzval) to a Canon 600mm/4.0L IS and a TV60is (built-in flattener) to a Canon 400mm/5.6L. I suppose that's why many of us end up owning several toys :roflmao:

By the way, I have just been perusing the Tak website and I must compliment them for the way they present the specs for their scopes. If only other manufacturers were as honest and as clear as Tak! They give the diameter of the image circle with all configurations, etc. Beautifully laid out. You pays your money and take your pick. I also note that the Tak FS-60CB is NOT meant as an imaging OTA, but what a beaut that CCA-250 is! Only $17k...

#36 orlyandico

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Posted 20 April 2014 - 01:26 AM

calypsob, I have been eyeing that Barska Magnus with some suspicion over the past few days. $372 shipped from Amazon sounds like a steal, and it's a triplet.

But... all the stories of shoddy focusers have turned me off. I have had enough of mediocre mechanicals (and to be honest, I find the Long Perng 2" two-speed crayfords to be mediocre - I have extensive experience with these and they can't hold a DSLR-size sensor normal to the optical axis once you pile on the accessories e.g. OAG). Looks like you put a GSO on yours?

Just about the only stock focuser I've been happy with is the 2.7" R&P on my AT90EDT. Now that's an underrated scope.. It's just good enough that even though I have a Feathertouch on my newt, I feel no need to upgrade the AT90EDT's stock focuser.

In any case I cut a deal for the SV80ED so too late to back out now. It can't be that bad, I have experience with a Z70ED and in-focus it's good enough for wide field. And it seems to be a notch above the more generic Long Perngs in build quality and finish. We will see...

#37 calypsob

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Posted 20 April 2014 - 11:42 AM

calypsob, I have been eyeing that Barska Magnus with some suspicion over the past few days. $372 shipped from Amazon sounds like a steal, and it's a triplet.

But... all the stories of shoddy focusers have turned me off. I have had enough of mediocre mechanicals (and to be honest, I find the Long Perng 2" two-speed crayfords to be mediocre - I have extensive experience with these and they can't hold a DSLR-size sensor normal to the optical axis once you pile on the accessories e.g. OAG). Looks like you put a GSO on yours?

Just about the only stock focuser I've been happy with is the 2.7" R&P on my AT90EDT. Now that's an underrated scope.. It's just good enough that even though I have a Feathertouch on my newt, I feel no need to upgrade the AT90EDT's stock focuser.

In any case I cut a deal for the SV80ED so too late to back out now. It can't be that bad, I have experience with a Z70ED and in-focus it's good enough for wide field. And it seems to be a notch above the more generic Long Perngs in build quality and finish. We will see...


Hmm, I see where you are coming from there. I wish everything could always be perfect out of the box lol. They also make a 65mm triplet and jag just had a moonlight mounted to his. Yes, mine has a GSO and it requires an ED80 adapter flange to mount up. For $372, you could add a really nice focuser and still come in way less than $1,000. Because the ED80 is such a popular scope, everyone seems to have a focuser for that particular model, so the most effort would go into deciding what focuser you like the best. I personally like the GSO, it is fine for a dslr. The non linear bearing version is alot smoother than the more expensive linear bearing which I have on my RC8. Of course a feather touch blows a GSO out of the water. If I ever buy a CCD I will probably need to upgrade to a heavier lifting focuser. Food for thought.

#38 chboss

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Posted 20 April 2014 - 03:39 PM

If you want something light and adaptable you should also look at the Borg 60ED or the 71FL.

best regards
Chris

#39 orlyandico

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Posted 20 April 2014 - 10:05 PM

hi Chris,

as a German speaker I am sure you are familiar with the testing done by Wolfgang Rohr. His results are that most of the Borg ED's are actually only "halbapo" or not true APO's.

Given their high cost, I wouldn't consider them. Heck, he even considers the AP Traveler to be a half-APO.. (albeit with 95%+ strehl in the visual range). Now whether Rohr is the end-all of telescope testing or not, is a matter for debate. But he is quite systematic and in my opinion has provided a good service to the amateur community.

#40 andysea

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Posted 20 April 2014 - 10:13 PM

I wish I could read German....! Did he test the FS60?

#41 orlyandico

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Posted 20 April 2014 - 10:38 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)

#42 rainycityastro

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Posted 21 April 2014 - 12:18 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.f...view=article... has the tests mentioned earlier.

Regards,
--Ram

#43 rainycityastro

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Posted 21 April 2014 - 12:21 AM

(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.

#44 orlyandico

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Posted 21 April 2014 - 12:37 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.

#45 chboss

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Posted 22 April 2014 - 04:33 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

#46 orlyandico

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Posted 18 August 2014 - 10:23 PM

well.. in an unexpected turn of events a Lomo 80mm turned up and I now will have to get rid of that SV80ED doublet.. and look for a Borg 7887 since it seems to be the best flattener for the Lomo. Or maybe I'll just stick with m TRF2008 since I'm only using APS-C...








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