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Is the FC100DZ the best DOUBLET ever made?

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#1 mikeDnight

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Posted 27 January 2021 - 05:10 AM

Looking at the attached info and considering other great 4" refractors that are, or have been available, is there any doublet that's better than the DZ?

 

fc-100dz-strehlratio.jpg.jpg

 

fc-100dz-aberration.jpg.jpg

 


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#2 Marcus Roman

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Posted 27 January 2021 - 05:44 AM

Maybe, still nobody has a diagram for the '90s Takahashi FC100-N (fluorite doublet f10), nor for the Nikon ED100 (f12) or Pentax 105 SD f9,5.....and few tested them.

Would be lovely to make such a test against the DZ one day....I know the capability of FC100-N and the Pentax 105SD, though...


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#3 PETER DREW

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Posted 27 January 2021 - 06:12 AM

Don't believe what you see on paper, only believe what you see through the telescope.  smile.gif


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#4 junomike

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Posted 27 January 2021 - 07:38 AM

To Add to Peter's Posts.  IMO the question should be: "Is ---- the best independently tested theoretical Doublet (or Triplet) ever made".

 

And even then, how good does good need to be?



#5 25585

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Posted 27 January 2021 - 07:52 AM

I think the DL is, 'Z may be its equal though. cool.gif



#6 Erik Bakker

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Posted 27 January 2021 - 08:19 AM

The FC-100 DZ is likely the best compact 4" doublet ever made. Putting it up agains the (in comparison) massive classic Nikon 100ED and Takahashi FC-100 N doublets will probably give it a very hard time at high magnifications.


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#7 Marcus Roman

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Posted 27 January 2021 - 08:31 AM

The FC-100 DZ is likely the best compact 4" doublet ever made. Putting it up agains the (in comparison) massive classic Nikon 100ED and Takahashi FC-100 N doublets will probably give it a very hard time at high magnifications.

Someone did a comparison between a FC100DL and a FC100-N few years ago but don't find the article anymore...


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#8 mikeDnight

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Posted 27 January 2021 - 09:46 AM

Don't believe what you see on paper, only believe what you see through the telescope.  smile.gif

The trouble with that Peter, is that some don't believe what I see through the eyepiece. bigshock.gif


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#9 dweller25

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Posted 27 January 2021 - 09:56 AM

I believe the DZ is the optically best 4” doublet in the world.

 

At the moment ........


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#10 John Huntley

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Posted 27 January 2021 - 10:08 AM

How much difference can you see between what your DZ and the DC that you used to own show you Mike ?

 

What I've decided lately (with respect to others of course) is that it matters much more to me what I think of my scopes than what other people think of them grin.gif


Edited by John Huntley, 27 January 2021 - 10:22 AM.

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#11 mikeDnight

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Posted 27 January 2021 - 10:18 AM

I know the TSA is a triplet and so doesn't come under this discussion, but it is a world standard by which better doublet refractors could be measured by.  Also, how much credence should we give to data and graphs when assessing a scopes real life visual performance under the stars? I've used all these scopes over the years and feel that although the graphs look impressively different, the actual difference in performance is like splitting hairs.

2020-09-16 15.36.34.png

Screenshot_2021-01-27-14-50-47.png

2021-01-27 15.02.17.png


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#12 teashea

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Posted 27 January 2021 - 10:53 AM

I would not doubt that it is


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#13 noisejammer

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Posted 27 January 2021 - 11:25 AM

Hey gu's, when quoting something in a language other than English, please supply a translation.

 

In this case, Google does a mediocre job but after fixing really odd phonetics ...

 

"As a result, the Strehl intensity is 90% or more in the entire visible light region from 460 nm to 670 nm, and the Strehl ratio with visual intensity is 97.6%, which is higher than the f / 9 FC-100DL."

 

I'm sure a Japanese speaker can improve on this. :lol:


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#14 BillP

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Posted 27 January 2021 - 12:01 PM

I know the TSA is a triplet and so doesn't come under this discussion, but it is a world standard by which better doublet refractors could be measured by.  Also, how much credence should we give to data and graphs when assessing a scopes real life visual performance under the stars? I've used all these scopes over the years and feel that although the graphs look impressively different, the actual difference in performance is like splitting hairs.

I have the TSA-102 and have used the DL.  I did notice a difference, mostly tonal.  But then I did not push the DL optic to extremes.  Overall though, I think you are correct, that while things look different in the microscopic measures in the charts, visually it will more likely be inconsequential splitting of hairs.  That said, for 99% of observers will make no meaningful difference and likely never to be come across in their observations.  But there are always those folks who routinely push boundaries where some of those minuscule differences may play out in some way that may be insignificantly noticeable for the 99%, but for them meaningful in some way.  So there is always that, just need to practice care when reporting such things so as not to mislead that whatever is noticed is of any consequence to anything other than egos.


Edited by BillP, 27 January 2021 - 12:57 PM.

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#15 mikeDnight

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Posted 27 January 2021 - 12:46 PM

How much difference can you see between what your DZ and the DC that you used to own show you Mike ?

 

What I've decided lately (with respect to others of course) is that it matters much more to me what I think of my scopes than what other people think of them grin.gif

Unfortunately I had to sell my DC to fund the DZ John, so no direct comparison from me sadly. But you more than most,  know just how much I loved the DC. Apart from the DC giving a marginally warmer tone, I really can't see a difference. I've had the DZ upto 1000X on zeta Hercules and it was impressively sharp all things considered, though it was better at 500X. But the DC with its slightly shorter F ratio gave terrific views at 474X.  I really don't think there's very much in it between any of the Tak's, including the FS series. But then in the back of my mind, is the thought that the hairs breadth difference could mean the difference between seeing subtle detail and not seeing it. Looking at the graph's, there are differences between the Tak's, but to date, the best view I've ever had of Jupiter was through a friends DL. Im looking forward to the planets being high in our skies again!


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#16 25585

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Posted 27 January 2021 - 01:11 PM

Hey gu's, when quoting something in a language other than English, please supply a translation.

 

In this case, Google does a mediocre job but after fixing really odd phonetics ...

 

"As a result, the Strehl intensity is 90% or more in the entire visible light region from 460 nm to 670 nm, and the Strehl ratio with visual intensity is 97.6%, which is higher than the f / 9 FC-100DL."

 

I'm sure a Japanese speaker can improve on this. lol.gif

So what are the DL's figures in comparison then, anyone?



#17 Tyson M

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Posted 27 January 2021 - 05:12 PM

Unfortunately I had to sell my DC to fund the DZ John, so no direct comparison from me sadly. But you more than most,  know just how much I loved the DC. Apart from the DC giving a marginally warmer tone, I really can't see a difference. I've had the DZ upto 1000X on zeta Hercules and it was impressively sharp all things considered, though it was better at 500X. But the DC with its slightly shorter F ratio gave terrific views at 474X.  I really don't think there's very much in it between any of the Tak's, including the FS series. But then in the back of my mind, is the thought that the hairs breadth difference could mean the difference between seeing subtle detail and not seeing it. Looking at the graph's, there are differences between the Tak's, but to date, the best view I've ever had of Jupiter was through a friends DL. Im looking forward to the planets being high in our skies again!

I think seeing is the main arbiter over scopes of similar optical quality when it comes to planetary views. One of my best views of Jupiter was with a WO 98 FLT and that scope stinked at 180x mag or higher.  Had trouble on double stars.  Same scope gave me some of the best small aperture views of galaxies under extremely good transparency one summer, they were like glowing embers, easily picked out via starhopping everywhere.  An Orion 8" dob (the same night), showed me my first and only ever view of spiral arms in M51(or M101 I cant remember now).

 

I think the main thing is ease of use, so you can deploy these scopes at a moment's notice and catch these moments.  Quick cool down certainly helps too.


Edited by Tyson M, 27 January 2021 - 05:17 PM.

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#18 John Huntley

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Posted 27 January 2021 - 05:37 PM

So what are the DL's figures in comparison then, anyone?

Back in 2017 Google translated this from the Takahashi web site:

 

"In recent refractor telescopes, photo-visual short-focus apochromat is mainstream, but the long focus two-lens ball flow light apochromat telescope FC-100DL is different from these.

 

FC-100DL is FC type with Flow Light lens behind as its name suggests, it is suitable for long focus refraction of f / 9.0, high contrast image with little chromatic aberration and spherical aberration can be obtained.

 

Specifically, the halo of g line (purple) is reduced by about 40% compared to FC - 100 D of f / 7.3, and 97.5% of the Strehl ratio showing high magnification performance is increased by about 4% has been realized. (Data calculated value)

 

This aberration data is almost the same number as the triplet apochromat, and I think that you can understand that it is a telescope with high eye vision performance coupled with a stable image plane with zero coma."

 

I assume that "two-lens ball flow light" means a doublet flourite objective ?

 

It's probably not a lot of help !


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#19 tristan89

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Posted 28 January 2021 - 02:49 AM

If considering all doublet scopes, Foa-60 has better color correction according to the specification.


Sent from my iPhone using Tapatalk


Edited by tristan89, 28 January 2021 - 02:36 PM.

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#20 RedzoneMN

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Posted 28 January 2021 - 07:03 AM

The FC-100 DZ is likely the best compact 4" doublet ever made. Putting it up agains the (in comparison) massive classic Nikon 100ED and Takahashi FC-100 N doublets will probably give it a very hard time at high magnifications.

Is the current crop of FC 100 DZ designs different from the FC 100 N of yore?


Edited by RedzoneMN, 28 January 2021 - 07:08 AM.


#21 John Huntley

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Posted 28 January 2021 - 07:18 AM

Is the current crop of FC 100 DZ designs different from the FC 100 N of yore?

This Italian test compares the FC 100 DL with the FC 100 N - not quite what you are looking for but close !. There is an option to select the English language near the top of the page:

 

https://www.dark-sta...-n-vs-fc100-dl/


Edited by John Huntley, 28 January 2021 - 07:18 AM.

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#22 helpwanted

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Posted 28 January 2021 - 02:04 PM

I would say the DZ is the best available being made brand new, you can get into debates when asking about scopes no longer made, but off the shelf new, I say yes, the DZ is the best. 


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#23 teashea

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Posted 28 January 2021 - 02:17 PM

I have a DC, but when the DZ comes back into stock, I am going to purchase one.  From all I have read, it is a little bit better.  



#24 Marcus Roman

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Posted 28 January 2021 - 03:00 PM

Is the current crop of FC 100 DZ designs different from the FC 100 N of yore?

Just the focus, the FC100-N was an f/10 but they both are steinheil with fluorite glass in the back.

Coatings on the front flint are surely different and most probably the new DZ's are better as more modern.


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#25 helpwanted

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Posted 28 January 2021 - 04:43 PM

I have a DC, but when the DZ comes back into stock, I am going to purchase one.  From all I have read, it is a little bit better.  

Keep the DC long enough to do a side-by-side, but I bet it will be hard to see a difference. 


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