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FC100DF vs FC100DZ

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#1 gnowellsct

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Posted 20 October 2019 - 01:35 PM

Would like some education on the differences between these two scopes and why one would choose one or the other.  I see a slight difference in the focal length and one is two element fluorite and, in spite of what one would think, the DZ has one lens that is not fluorite (and is more expensive).

 

I'm assuming focusers and other hardware are the same.

 

thanks,

Greg N



#2 db2005

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Posted 20 October 2019 - 01:51 PM

The description here might shed some light on the differences: https://www.takahash...-refractor.html

 

According to this, a fluorite element is indeed being used; also it seems like color correction has been significantly improved over the current FC-100Ds; strehl ratio in the entire visible spectrum of more than 97.6%. Also has retractable dew shield, making it easier to travel with.



#3 25585

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Posted 20 October 2019 - 01:55 PM

https://www.ikarusim...e-apo-refractor

 

https://www.takahash...-refractor.html

 

DZ may be better for imaging. And it has a sliding dewshield. 



#4 Daniel Mounsey

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Posted 20 October 2019 - 02:25 PM

Would like some education on the differences between these two scopes and why one would choose one or the other.  I see a slight difference in the focal length and one is two element fluorite and, in spite of what one would think, the DZ has one lens that is not fluorite (and is more expensive).

 

I'm assuming focusers and other hardware are the same.

 

thanks,

Greg N

 

Anyone can answer this question by going to the extreme and compare the DF to a TSA102 which has virtually no false color at all just to remove all doubt. Pretty much what happens is when the DF is pushed or magnified on double and multiple stars to higher and higher magnifications, some observers can detect some trifling false color in the DF but for pretty much everything you look at including the Moon and planets where magnifications are typically less than those used on extreme doubles, there's really not much difference other than the fact the the TSA102 has an extremely neutral color fidelity. Stars are absolutely pure white in the TSA without a single trace of false color other than atmospheric dispersion effects.

 

I think it's nice that there's some buzz about the DZ because it will be a chance to have a doublet with color correction that's pretty much on par with a triplet for the most part. If you just don't even want to think about color, then maybe a DZ will be the way to go. For me, there's a point where I consider the color correction good enough and no further improvment needs to be made for practical observing at most magnifications. At this caliber of telescope level, I pay closer attention to optical figure. They're all great scopes but I usually have a tendency to gravitate towards optical figure where as most have a tendency to look at the marketing hype. It's obvious because most enthusiast considering any of these scopes hardly ever understand how to evaluate the optical figures anyway. 

 

For imaging, there's such an endless array of scope options and endless rebranding, who cares. Astrographs are a dime a dozen. You can have the worst spherical aberration and still take good astrophotos. Imagers are always obsessed with halos and aberrations at the corners. That has little to do with judging the actual optical figure of a telescope. Most just resort to specs but specs just don't do enough for me. 


Edited by Daniel Mounsey, 20 October 2019 - 02:40 PM.

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#5 Kunama

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Posted 20 October 2019 - 03:44 PM

Would like some education on the differences between these two scopes and why one would choose one or the other.  I see a slight difference in the focal length and one is two element fluorite and, in spite of what one would think, the DZ has one lens that is not fluorite (and is more expensive).

 

I'm assuming focusers and other hardware are the same.

 

thanks,

Greg N

Not sure if I am reading this correctly, seems to read that the DF has two CaF2 elements ..... which it does not 

 

Both the DF and DZ are the same configuration of a non-CaF2 lens at the front and a CaF2 element behind .... The lens spacing differs as well as their ROC... 

 

 

EDIT: When one reads Tak America's blurb of the DF one can get the wrong impression that the DF has 2 fluorite elements, the FC series are all the Steinheil design with a single CaF2 element in the doublet objective lens.

Though the site also have this paragraph that clears it up:

 

"The FC-100D series consists of an apochromatic fluorite Steinheil doublet with a 100 mm objective diameter.  Both telescopes in the series are 740 mm f/7.4 instruments.  The front element uses an eco-glass for maximum light transmission, with a coated fluorite rear element for superb color correction. "


Edited by Kunama, 20 October 2019 - 03:52 PM.

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#6 Hesiod

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Posted 21 October 2019 - 08:36 AM

I think that, with the release of the DZ, the DF will be phased out so the matter of picking one or the other will be only a matter of money (used/leftover DF vs new DZ) .

I think that they have optimized the objective design (from the barbaric translation seem to understand that the DZ will use a different matching glass, and probably different spacing) for their 4" doublets given the actually available materials; but the DF was already pretty good, since I notice minor faults in its CA correction only when using it side by side with the DL

#7 25585

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Posted 21 October 2019 - 09:29 AM

Look for a DL if a retractible dew shield & longer OTA is unimportant.


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#8 mikeDnight

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Posted 21 October 2019 - 02:23 PM

My DC is essentially colour free on the limb of the moon at 100X per inch, which is seriously impressive. I don't use wide angle eyepieces that introduce lateral colour. The only observable difference between my FC100DC and my friends FC100DL is that the DC offers a fractionally warmer image and the DL cooler. Neither show any trace of CA on the lunar limb even at high power and both are superlative planetary performers. I suspect the new DZ is primarily aimed at imagers, as they need to be more demanding with regard to CA than the visual observer, while needing a physically short scope.


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#9 barbie

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Posted 21 October 2019 - 05:05 PM

Agreed!!

#10 gnowellsct

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Posted 22 October 2019 - 05:45 PM

 

 

"The FC-100D series consists of an apochromatic fluorite Steinheil doublet with a 100 mm objective diameter.  Both telescopes in the series are 740 mm f/7.4 instruments.  The front element uses an eco-glass for maximum light transmission, with a coated fluorite rear element for superb color correction. "

:crazy: I thought one was f/8 and the other was f/7 ish.  I think that's on some of the net descriptions.  Definitely a case of bad advertising copy out there, I think.

 

Greg N



#11 Axunator

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Posted 23 October 2019 - 12:19 AM

:crazy: I thought one was f/8 and the other was f/7 ish. I think that's on some of the net descriptions. Definitely a case of bad advertising copy out there, I think

Greg N

Greg, DZ is f/8, DF (and DC) is f/7.4. And the limited run DL was f/9.

The quote in Matt’s post was related to DF and DC (and predates the release of DZ) which are optically identical and differ only in mechanics of the OTA (mainly focuser and length of the tube).

Edited by Axunator, 23 October 2019 - 12:21 AM.

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#12 25585

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Posted 23 October 2019 - 06:41 AM

DL v DZ v TSA102 for visual is a match I would like to see. 



#13 Axunator

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Posted 23 October 2019 - 07:48 AM

DL v DZ v TSA102 for visual is a match I would like to see. 

Albeit having never looked through any of the three (I have a DF), I'd expect any possible differences to be minuscule for visual observing, apart from the focal length differences  thinking1.gif

 

DF/DC vs DZ shootout might be more interesting and have more practical value, because one might actually detect some differences, at least in CA correction (which is already very, very good in focus in DF/DC, to be honest - just avoid the notorious 'dark tree branches against the bright sky' test at >250x tonofbricks.gif - which, to be accurate, is not really a specific test for in focus color correction, because branches showing purple are out of focus). I'd also think that current DF/DC owners are more likely to even consider "upgrading" to DZ than owners of DL's and TSA102's...


Edited by Axunator, 23 October 2019 - 09:00 AM.


#14 25585

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Posted 23 October 2019 - 08:44 AM

Albeit having never looked through any of the three (I have a DF), I'd expect any possible differences to be minuscule for visual observing, apart from the focal length differences  thinking1.gif

 

DF/DC vs DZ shootout might be more interesting and have more practical value, because one might actually detect some differences, at least in CA correction (which is already very, very good in focus in DF/DC, to be honest - just avoid the notorious 'dark tree branches against the bright sky' test at >250x tonofbricks.gif ). I'd also think that current DF/DC owners are more likely to even consider "upgrading" to DZ than owners of DL's and TSA102's...

My DL is going nowhere :)  Neither would a DC, DF or TSA had I got any. If I was looking to buy my first though, the retractable dewshield of a DZ might win me over, though price would be #1 consideration.


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#15 Axunator

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Posted 23 October 2019 - 08:53 AM

My DL is going nowhere smile.gif

That does not surprise me waytogo.gif

 

Neither would a DC, DF or TSA had I got any. If I was looking to buy my first though, the retractable dewshield of a DZ might win me over, though price would be #1 consideration.

I agree. Kind of... must resist the temptation, must resist... lol.gif



#16 StarDust1

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Posted 23 October 2019 - 11:56 AM

Haven't looked through the FC-100DZ yet, but loved the FC-100DF. The FC-100DZ looks nicer in my book, as it has longer focal length and the retractable dewshield is welcome. I wouldn't know why one would choose the DF over the DZ.



#17 Axunator

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Posted 23 October 2019 - 12:31 PM

I wouldn't know why one would choose the DF over the DZ.

Because of 500 €/$. It’s also somewhat lighter and in fact physically shorter once you screw the dew shield off (easy, no tools required job, but admittedly far from ideal solution for travel). But as others have contemplated, it is possible that DF will be phased out and only DZ will remain available.

Having said all that, if I were on the market for FC-100D now, DZ would be really hard to pass..

Edited by Axunator, 23 October 2019 - 12:37 PM.

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#18 Paul G

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Posted 23 October 2019 - 04:10 PM

Anyone can answer this question by going to the extreme and compare the DF to a TSA102 which has virtually no false color at all just to remove all doubt. Pretty much what happens is when the DF is pushed or magnified on double and multiple stars to higher and higher magnifications, some observers can detect some trifling false color in the DF but for pretty much everything you look at including the Moon and planets where magnifications are typically less than those used on extreme doubles, there's really not much difference other than the fact the the TSA102 has an extremely neutral color fidelity. Stars are absolutely pure white in the TSA without a single trace of false color other than atmospheric dispersion effects.

 

I think it's nice that there's some buzz about the DZ because it will be a chance to have a doublet with color correction that's pretty much on par with a triplet for the most part. If you just don't even want to think about color, then maybe a DZ will be the way to go. For me, there's a point where I consider the color correction good enough and no further improvment needs to be made for practical observing at most magnifications. At this caliber of telescope level, I pay closer attention to optical figure. They're all great scopes but I usually have a tendency to gravitate towards optical figure where as most have a tendency to look at the marketing hype. It's obvious because most enthusiast considering any of these scopes hardly ever understand how to evaluate the optical figures anyway. 

 

For imaging, there's such an endless array of scope options and endless rebranding, who cares. Astrographs are a dime a dozen. You can have the worst spherical aberration and still take good astrophotos. Imagers are always obsessed with halos and aberrations at the corners. That has little to do with judging the actual optical figure of a telescope. Most just resort to specs but specs just don't do enough for me. 

Daniel, any idea why Tak discontinued the TSA 102? It's one of the best scopes I've ever used.



#19 barbie

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Posted 23 October 2019 - 05:16 PM

I'm quite content with my DF and it's color correction at 250x and won't be getting a DZ anytime soon.
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#20 bobhen

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Posted 23 October 2019 - 05:16 PM

Daniel, any idea why Tak discontinued the TSA 102? It's one of the best scopes I've ever used.

I have absolutely no proof but my guess is that the TSA 120 was cannibalizing sales from the TSA 102. If one is going to spend north of 3k for 102mm, why not just pony-up another 1.5k for the TSA 120. You get more aperture and with basically no portability penalty. Pure imagers went for the FSQ 106 astrograph.

 

That also explains why Tak started producing lighter, less expensive doublets in the 100mm size. These scopes don’t compete with the TSA 120 or the 106 astrograph.

 

Market pressures can have unfortunate outcomes. The TSA optics (120 and 102) are killer.

 

Bob


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#21 YAOG

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Posted 23 October 2019 - 05:25 PM

Daniel, any idea why Tak discontinued the TSA 102? It's one of the best scopes I've ever used.

So they can sell more FC100DZ tubes? So they can sell an FOA-102? AFAIK nobody know the answer to this question except maybe Takahashi.   



#22 edif300

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Posted 23 October 2019 - 05:46 PM

The TSA-102 was available during 12 year.



#23 John Huntley

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Posted 23 October 2019 - 06:23 PM

I was pretty certain that the arrival of the DZ would mean no more production runs of the DL but I'm not so sure that both versions of the F/7.4 FC-100 would be axed as well ????

 

Apart from the retractable dew shield (nice feature) my reading of the DZ is that it delivers DL performance at a slightly faster focal ratio and, importantly for imagers, maintains it's composure better than the DL when the focal reducer is employed.

 

I don't image and I don't use my DL as a travel scope (other than here in the UK) I don't feel the need to move to a DZ but it's a nice progression of the series, thats for sure smile.gif


Edited by John Huntley, 23 October 2019 - 06:25 PM.

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#24 25585

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Posted 23 October 2019 - 07:51 PM

With much cheaper & increasing competition from China in triplets like SW Esprits, the 4 inch market was/is relatively saturated. Tak cater for imaging with their FSQ85 & 106 quadruplets.

 

It could be TSA120 is next to go. But that IMO depends on if a 125DZ doublet follows. Imagers have the TOA130 & 150, but have lost the FSQ130.

 

Vixen now only run up to a 115mm doublet and 100 tripet, Borg 107. Takahashi therefore have their home market in 120mm+ refractors to themselves? The TSA120 covers both visual and imaging, excelling in the former, but with own brand competition in the latter. A 120 fluorite doublet would sell, but maybe as one would be new, with the existing competition, would it hold up against the rest?

 

I can see light weight would be an asset. It may use a FC100 or TSA120 tube, 2.7" focuser, DL clamshell. So only the lenses and cel would be new parts.       




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