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Is the FC100DZ the best DOUBLET ever made?

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#26 25585

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Posted 29 January 2021 - 10:32 AM

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.  

Your TSA-120 will still be best!


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#27 lwbehney

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Posted 30 January 2021 - 12:28 AM

The Agema Optics fluorite doublets might be better. 

A shoot out is required.

-Larry


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#28 Steve Allison

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Posted 30 January 2021 - 12:41 AM

I would say that the object glasses made by Alvan Clark are the best doublets ever made- in crown and flint.

 

I don't know about these new-fangled fluorite doublets but discounting the glass types used, I don't think Alvan Clark et al have ever been surpassed with regard to optical figure.


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#29 balu01

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Posted 30 January 2021 - 12:43 AM

The Agema Optics fluorite doublets might be better. 

A shoot out is required.

-Larry

Is there a single one out there yet? To me those scopes are so magical they will never appear it looks like. 


Edited by balu01, 30 January 2021 - 12:43 AM.

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#30 donadani

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Posted 30 January 2021 - 12:59 AM

Is there a single one out there yet? To me those scopes are so magical they will never appear it looks like. 

At astroshop.de you can buy the 130 from stock...

https://www.astrosho.../m,Agema-Optics

 

It was tested in a paper magazine here too...

 

And here you find a test-report from a guy I know - so it´s valid for sure:

https://www.cloudyni...gema-130sd-apo/

 

 

...and btw. the best visual doublet - of course! and as we all know... is the good, old Tak FS-128 smile.gif

 

a1.jpg


Edited by donadani, 30 January 2021 - 01:04 AM.

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#31 RichA

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Posted 30 January 2021 - 02:09 AM

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.

I had a 4 inch f9 apo and a 120mm f8 achro side by side, looking at objects in Sagittarius.  The 120mm achro had a clear advantage owing to a relatively modest aperture advantage, you could see more nebulosity, dimmer stars.  However, the 4 inch images were "purer" to use a subjective term and the sky background was blacker, less defocused blue scattering from bright star fields.


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#32 teashea

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Posted 30 January 2021 - 02:04 PM

I would say that the object glasses made by Alvan Clark are the best doublets ever made- in crown and flint.

 

I don't know about these new-fangled fluorite doublets but discounting the glass types used, I don't think Alvan Clark et al have ever been surpassed with regard to optical figure.

Fluorite is not quite new-fangled.  


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#33 Steve Allison

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Posted 30 January 2021 - 03:10 PM

Tongue in cheek...


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#34 lwbehney

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Posted 30 January 2021 - 03:49 PM

At astroshop.de you can buy the 130 from stock...

https://www.astrosho.../m,Agema-Optics

 

It was tested in a paper magazine here too...

 

And here you find a test-report from a guy I know - so it´s valid for sure:

https://www.cloudyni...gema-130sd-apo/

 

 

...and btw. the best visual doublet - of course! and as we all know... is the good, old Tak FS-128 smile.gif

 

attachicon.gifa1.jpg

Thanks for these helpful links. I had not seen an actual field review of an Agema telescope until today. I really appreciate this type of comparison.

 

-Larry



#35 mikeDnight

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Posted 30 January 2021 - 05:19 PM

The Agema advert claims that the special front element protects the sensitive fluorite. Are they implying that the rear fluorite element is uncoated?  Or perhaps just perpetuating the myth that Fluorite elements are prone to deterioration? 


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#36 RedzoneMN

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Posted 30 January 2021 - 05:50 PM

The Agema 150 is a pricier doublet? than the TOA 150. 

 

 



#37 ullomat

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Posted 05 February 2021 - 07:55 AM

Hi,

the Agema SD 150 is 11.460 Euro in our Shop. German VAT (19%) included. In Germany, the comparable TOA-150 is at around 15.000 Euro, also incl. VAT.

For visual, I would vote for the Agema 150. I just tested the 130 in practice, but on our optical bench, the 150 performed really good. 

Why just for visual? Since there is no reducer/flattner available, there is no valid AP test possible. And for AP, the TOA is a proofen performer.

I would personally always prefer such a good flourite doublet over a triplet for visual applications. Every comparison I did until today, between high quality triplets and flourite doublets (the newer ones like Tak DZ, DL and Agema) for visual observations, convinced me here to go with a flourite doublet. Subtle difference, but it is there for me. Also for practical reasons like cooldown, weight. 

Btw, we had one Agema 150 in stock and it has been sold end of 2020. There may be a report from the buyer some time, but I do not know if he is a CN Member. 

cs,

Uli


Edited by ullomat, 05 February 2021 - 07:57 AM.

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#38 Daniel Mounsey

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Posted 05 February 2021 - 09:42 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.

attachicon.gif2020-09-16 15.36.34.png

attachicon.gifScreenshot_2021-01-27-14-50-47.png

attachicon.gif2021-01-27 15.02.17.png

 

Mike summarized this nicely here folks, he really did. IMO what he shared is important because most who read too deeply into these subjects are not being practical about these matters because the graphs tend to throw them off. Then when observers see the scopes side by side, they're like hhmmmm? BillP also brought up another subject which is what hits me probably the most that relates to slight tonal characteristics which is very subjective. I myself have been using an FC100DC which most consider to be the least favorable of the new high end doublets because of the mechanics. This is how most consider the lineup from favorable to least favorable. 

 

1. FC100DZ

2. FC100DL

3. FC100DF

4. FC100DC what I'm currently using at this time.

 

I could have any telescope I wanted and I'm extremely sensitive to false color. In reality, all these baby size fracs are awesome. Pick any one and you will be impressed with the views. If they weren't, I myself wouldn't be using the DC. I remember sitting in on a seminar in Pasadena CA at the PATS show some years ago learning about CCD sensors and we were looking at a PowerPoint presentation. One of the images was a super, magnified close-up of a CCD sensor. It looked like New York City with tiny, little square skyscrapers next to each other with different heights. I thought, Ohhhh..... this must be a bad sensor. What it was in reality though was a world class sensor for one of the most expensive cameras on the market! Then the gentleman doing the seminar zoomed out and the entire sensor looked like a flawless, perfectly flat landscape many miles across. All it was, was my perception because I had nothing else to compare it to. This is often what stats do to many onlookers investigating these matters. It's not because I hate stats. What I hate about stats is how people interpret them.

 

In their heads, they look at all these strehl's, spot diagrams, wavefronts, glass types etc and they think these figures are visible like the close up of the CCD. Often, they are put in place to illustrate to what the theoretical differences are on paper and they are real but they represent the differences of a small fraction. One of the things Peter Ceravolo taught me is that you have to look at the total, final wavefront and ultimately the final visual image. In the end, that's what you are really looking at. In the practical world, especially for most, you wouldn't see all those differences the way they appear on paper. This is why we take telescopes and compare them to each other side by side. That's what most would need to do to even see any differences and even then, most struggle. I'm not saying that's the case for every single observer, but for most, Mike's comments are quite true IMHO.

 

BTW, if anyone has a Takahashi sickness, it's me.  p55.https://www.cloudyni...takitis/page-55


Edited by Daniel Mounsey, 05 February 2021 - 10:13 AM.

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#39 peleuba

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Posted 05 February 2021 - 11:10 AM

I could have any telescope I wanted and I'm extremely sensitive to false color. In reality, all these baby size fracs are awesome. Pick any one and you will be impressed with the views. If they weren't, I myself wouldn't be using the DC. I remember sitting in on a seminar in Pasadena CA at the PATS show some years ago learning about CCD sensors and we were looking at a PowerPoint presentation. One of the images was a super, magnified close-up of a CCD sensor. It looked like New York City with tiny, little square skyscrapers next to each other with different heights. I thought, Ohhhh..... this must be a bad sensor. What it was in reality though was a world class sensor for one of the most expensive cameras on the market! Then the gentleman doing the seminar zoomed out and the entire sensor looked like a flawless, perfectly flat landscape many miles across. All it was, was my perception because I had nothing else to compare it to. This is often what stats do to many onlookers investigating these matters. It's not because I hate stats. What I hate about stats is how people interpret them.

 

 

Hi Daniel,  

 

I like my 100mm class APO's to be as small as possible, while delivering world-class views.  To this end, like you, I'd prefer the 100DC.  waytogo.gif  bow.gif

 

We all have opinions - some are more informed then others.  I judge the validity of the many opinions I read on CN on two things:  (1) Experience and (2) Perspective of the person espousing the particular opinion (or POV).   You touch on #2 quite well in your analogy of NYC sky scrapers and the CCD sensor.  Its similar to the old adage - sometimes one cannot see the forest for the trees.  

 

Although its not unique to Ceravolo, I agree - its the final wavefront that matters - not so much on how you get there.  In other words its the destination, not the journey.    I cringe when I read that some folks are strongly biased against any refractor not made up of FPLxx/Fluorite and not mated with Lanthanum.   Whatever.  Ignorance is bliss. 

 

Anyway, A really nice post that struck a chord and  made me think a little on this cold Friday morning.  I do regret that I cannot offer you a cure for the Takahashi addiction.


Edited by peleuba, 05 February 2021 - 11:55 AM.

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#40 donadani

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Posted 05 February 2021 - 12:35 PM

ok 4" doublets - hmm...

 

Vixen ED-102S sold

Vixen ED-102SS sold

Vixen FL-102S sold

Tak FC-100E sold

Tak FS-102N sold

Tak FS-102NSV sold

Tak FC-100DC sold

Tak FC-100DZ sold

 

Tak FC-100N left

TV-102 left

 

These are my two best ever made 4inch doublets smile.gif

 

The TV for day together with 2xSM90 and the Tak for night and everything 4inch can show.

 

If you ask for bigger doublets - definitely:

 

2.jpg

 

 

But I´m sure all of them reach not to the DL/DZ when it comes to color correction... but "overall best" for me is not cc only.


Edited by donadani, 05 February 2021 - 12:40 PM.

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#41 Daniel Mounsey

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Posted 05 February 2021 - 02:02 PM

Hi Daniel,  

 

I like my 100mm class APO's to be as small as possible, while delivering world-class views.  To this end, like you, I'd prefer the 100DC.  waytogo.gif  bow.gif

 

We all have opinions - some are more informed then others.  I judge the validity of the many opinions I read on CN on two things:  (1) Experience and (2) Perspective of the person espousing the particular opinion (or POV).   You touch on #2 quite well in your analogy of NYC sky scrapers and the CCD sensor.  Its similar to the old adage - sometimes one cannot see the forest for the trees.  

 

Although its not unique to Ceravolo, I agree - its the final wavefront that matters - not so much on how you get there.  In other words its the destination, not the journey.    I cringe when I read that some folks are strongly biased against any refractor not made up of FPLxx/Fluorite and not mated with Lanthanum.   Whatever.  Ignorance is bliss. 

 

Anyway, A really nice post that struck a chord and  made me think a little on this cold Friday morning.  I do regret that I cannot offer you a cure for the Takahashi addiction.

Well stated! bow.gif



#42 donadani

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Posted 05 February 2021 - 02:08 PM

maybe for interest...

 

1.jpg

1.jpg

3.jpg

2.jpg

 

 

...that DC was cute :)


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#43 Tyson M

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Posted 05 February 2021 - 02:39 PM

I too am extremely fond of the 100DC.  It is the lightest 100mm doublet I know of, for that, it serves an extremely useful purpose for grab and go on the smallest mounts.


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#44 helpwanted

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Posted 05 February 2021 - 02:43 PM

 

BTW, if anyone has a Takahashi sickness, it's me.  p55.https://www.cloudyni...takitis/page-55

Daniel,

have to traveled to Japan to take a factory tour? 



#45 Marcus Roman

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Posted 05 February 2021 - 03:13 PM

maybe for interest...

 

attachicon.gif1.jpg

attachicon.gif1.jpg

attachicon.gif3.jpg

attachicon.gif2.jpg

 

 

...that DC was cute smile.gif

Takahashi FC100N, fluorite steinhel doublet, f10, is amazing for being just 4”...only who tried it can understand....


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#46 teashea

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Posted 05 February 2021 - 06:50 PM

I would say that the object glasses made by Alvan Clark are the best doublets ever made- in crown and flint.

 

I don't know about these new-fangled fluorite doublets but discounting the glass types used, I don't think Alvan Clark et al have ever been surpassed with regard to optical figure.

That old fashion glass cannot compete in quality with new glass.  It is simple physics.


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#47 teashea

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Posted 05 February 2021 - 09:56 PM

The Agema advert claims that the special front element protects the sensitive fluorite. Are they implying that the rear fluorite element is uncoated?  Or perhaps just perpetuating the myth that Fluorite elements are prone to deterioration? 

I have a couple Takahashi telescopes with the Fluorite element behind the front element.  There has been discussion of that.  With modern lens coatings a Fluorite element is ok in front, but it does not have to be.  



#48 Steve Allison

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Posted 06 February 2021 - 12:42 AM

That old fashion glass cannot compete in quality with new glass.  It is simple physic

 

Do the crown and flint glasses produced today allow for a better optical figure? I wouldn't think so. But I am sure modern glasses are more homogenous and have fewer inclusions, such as bubbles and/or striae. And of course, modern glass types allow for better color correction.

 

My post was only with regard to the Clarks' skill in figuring an objective- with the materials that were available at the time.

 

Too bad we can't go back in time and give Alvan Clark, Sr. an 8 inch fluorite blank and suitable glass for the negative element...

 

Steve

 

P.S.- I can't remember if it was Roland Christen or if it was D&G optical that tested a particular Clark lens and found it to be better than 1/40th wave- and beyond the sensitivity of the equipment being used!

 

P.P.S.- If you have a "bad Clark lens" story, please don't post it and burst my bubble! smile.gif


Edited by Steve Allison, 06 February 2021 - 12:43 AM.

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#49 knight_parn

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Posted 06 February 2021 - 08:27 AM

At astroshop.de you can buy the 130 from stock...

https://www.astrosho.../m,Agema-Optics

 

It was tested in a paper magazine here too...

 

And here you find a test-report from a guy I know - so it´s valid for sure:

https://www.cloudyni...gema-130sd-apo/

 

 

...and btw. the best visual doublet - of course! and as we all know... is the good, old Tak FS-128 smile.gif

 

attachicon.gifa1.jpg

Just checked the price of these Agema's on astroshop.eu. Apparently the smallest SD120 being a doublet costs more than my LZOS 115 and is almost as much as a TSA-120 with the FTF3035 upgrade. These doublets must be extraordinarily good to go higher than other premium triplets.


Edited by knight_parn, 06 February 2021 - 08:29 AM.


#50 Daniel Mounsey

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Posted 06 February 2021 - 08:57 AM

Daniel,

have to traveled to Japan to take a factory tour? 

Not yet.

bawling.gif 


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