tell me the differences between FC100DZ, TS 115 TRIPLET, TS 125 DOUBLET LANT for visual use

[Fedele]

hi 

have any of you ever compared them directly?
What are the differences in the purely visual planetary use?  which guarantees the "wau" or "Ok" effect? the quality of the little one? the diameter of the large?
thank you

[Robindonne]

it's nice to read our collective thoughts back in sentences.  It's a psychological thing to always choose the middle one.  and in this case I suspect that it will again, provided that 115 triplet uses the best glass of the three options.  I'm only basing this on conjectures and read experiences.  But there is a catch.  There's a Tak in between that will throw all logical thinking upside down

[vlaiv]

Can't contribute much in terms of actual experience - I can only say that out of the three, I only really considered TS 115 as possible purchase.

[Chandra]

I have no real experience with any of the three apochromatics. At first glance these are three very similar instruments, medium focal length and multipurpose (visual/images), but judging by the cost and the proven optical quality of the brand, the first of them (the Taka), an F/8 doublet with a fluorite lens, should be the best for image quality.
At less than half its cost, the two TS are located. The TS 115 is an F/7 triplet with Ohara's FPL-51 and lanthanum crystal in two of its three elements (the composition of the third glass is not specified). The TS 125 at F/7.8 is a doublet with FPL-53 and lanthanum. Both have a good 2.5" R&P focuser with 360º of rotation. In this sense, the Takahashi's 2" R&P focuser is simpler, I'd say it doesn't rotate and is not double speed.
The high cost of the FC100DZ (about 3,200 euros) can put many observers off. TS alternative is not bad, as their products have a good build. In this case, I would lean towards the F/7.8 doublet, due to its larger aperture and, I presume, due to its better chromatic correction. https://takahashi-europe.com/catalog/refractors/doublets/fc-100dz/fc-100dz // 

http://www.mystarrynights.at/tst/TS 125-975 APO/

[vlaiv]

4 minutes ago, Chandra said:

, I would lean towards the F/7.8 doublet, due to its larger aperture and, I presume, due to its better chromatic correction.

Highly doubt that 125mm F/7.8 ED doublet will have as good color correction as triplet lens.

In reality, for visual - both will offer virtually color free image (that virtually is more meant for 125mm doublet, as triplet is really color free), but for imaging applications - triplet will simply pull ahead.

[michael.h.f.wilkinson]

In my experience (on other scopes), under good seeing conditions aperture is king for planets (imaging and observing). All three have pretty similar apertures, but unless there is something seriously wrong with the 125 mm doublet, it should have the edge in terms of resolution. The colour correction will theoretically be worse, but this will hardly be noticeable visually, and even in imaging I doubt the additional colour fringes could be spotted. Again, all lie in the 4-5" range, so changes won't be dramatic.

[vlaiv]

1 minute ago, michael.h.f.wilkinson said:

even in imaging I doubt the additional colour fringes could be spotted.

I was rather surprised to see how much CA there is in 125's little brother - 102 SD doublet (Altair Astro branded 102 ED-R).

 

[Chandra]

21 minutes ago, vlaiv said:

Dudo mucho que el doblete de 125 mm F / 7,8 ED tenga una corrección de color tan buena como la lente triple.

En realidad, para el aspecto visual, ambos ofrecerán una imagen virtualmente sin color (que virtualmente está más pensado para el doblete de 125 mm, ya que el triplete es realmente libre de color), pero para las aplicaciones de imágenes, el triplete simplemente avanzará.

I agree, both should have excellent color correction, but we often take for granted that triplets always guarantee better corrections than doublets, and from what I have read from experienced observers this is not always the case. Entering the old debate about low dispersion lenses is not the case, but an FPL-53 offers considerably less dispersion than an FPL-51, but it is true that the "apo" quality is usually given to triplets, not doublets. For my affirmation I am based on data published in another forum, where the color lines of the TS115 and the TS125 were compared. The comparison is not entirely accurate because the same lengths are not being measured, nor at the same pupillary point, but by extrapolation it might appear that the correction for the doublet is somewhat better than that for the triplet. But I could be wrong.

[Fedele]

So remain on the doublet. 
i go for the huge diameter or to te best quality

[johninderby]

Recently I chose the Tecnosky 125 over the 115 as it was for visual. Thought a very good doublet would be preferable. Has exceeded my expectations so far and better optics than any of the SW doublets I’ve used. Its ability to take very high magnification has particularly impressed me. Would rate it as a best buy considering what you get for the price.

Edited June 11, 2021 by johninderby

[Chandra]

The three tubes proposed are of high quality, although the Tak always play in 'another league', but an aperture of 6" will always exceed one of 4", even in more light captured and in a somewhat higher theoretical resolution, as michael.h.f.wilkinson said

[vlaiv]

37 minutes ago, Chandra said:

For my affirmation I am based on data published in another forum, where the color lines of the TS115 and the TS125 were compared. The comparison is not entirely accurate because the same lengths are not being measured, nor at the same pupillary point, but by extrapolation it might appear that the correction for the doublet is somewhat better than that for the triplet. But I could be wrong.

 

To be honest, I find it difficult to compare those two graphs. They used different wavelengths on those graphs - both in terms of color and in terms of wavelengths.

Triplet graph only uses three colors - Hb 486nm, Ha at 656 and some unspecified green at 588nm (which is technically not even green any more but rather orange).

While 125mm uses five colors - and again, colors are not matched to wavelength - yellow at 620nm, purple at 680nm and red at 546

In both cases - highly misleading.

I think both of those two graphs are more marketing than meaningful data.

What I know is that 100mm FPL-53 doublet needs to be around F/9 in order to be color free - that is SkyWatcher 100ED for example. As you move down in aperture, you can make it faster without having too much color issues - that is why SW 80ED is F/7.5

Above 125mm is pushing this with F/7.8 - it is too fast for ED doublet - for imaging anyway, it might be very good for visual.

On the other hand - there is very little difference in triplet based on FPL-51 glass and FPL-53.

In any case - I still do believe that 115mm is better corrected than 125mm, and yes - for visual - one might not even notice any difference. I think they are both great scopes of the money, and given my preferences - I'd still go for 115mm.

[CraigT82]

Haven't you already got an SW ED120?  I'm not sure the extra 5mm of the 125mm f7.8 is going to give you much more than what you get from that

Edited June 11, 2021 by CraigT82

[Louis D]

Having a 90mm FPL-53 triplet, I would probably err toward the 125 FPL-53 doublet just because cool down time will be much shorter than for a triplet.  It's pretty annoying having to wait 30 minutes or more to use high powers after taking the triplet outdoors while waiting for it to acclimate.  There will always be some color at high power with any refractor.  It just goes with the territory.  However the tightness of star points and their airy discs allows for easier viewing of tight doubles as compared to a reflector even with the minor residual color.

[michael.h.f.wilkinson]

1 hour ago, vlaiv said:

I was rather surprised to see how much CA there is in 125's little brother - 102 SD doublet (Altair Astro branded 102 ED-R).

 

CA in DSO seems to have a different impact than on planetary imaging, I find. As a rule, the centre is better corrected than the edges, and although you are working at higher resolution, you do not stretch the lower intensities as you do in DSOs, so the wings of the PSF aren't artificially boosted. This is because the dynamic range is much lower in planetary imaging

[Chandra]

28 minutes ago, vlaiv said:

Para ser honesto, me resulta difícil comparar esos dos gráficos. Utilizaron diferentes longitudes de onda en esos gráficos, tanto en términos de color como en términos de longitudes de onda.

El gráfico de triplete solo usa tres colores: Hb 486nm, Ha a 656 y algo de verde no especificado a 588 nm (que técnicamente ya ni siquiera es verde sino naranja).

Mientras que 125 mm usa cinco colores, y nuevamente, los colores no coinciden con la longitud de onda: amarillo a 620 nm, púrpura a 680 nm y rojo a 546

En ambos casos, muy engañoso.

Creo que ambos gráficos son más marketing que datos significativos.

Lo que sé es que el doblete FPL-53 de 100 mm debe estar alrededor de F / 9 para no tener color, eso es SkyWatcher 100ED, por ejemplo. A medida que se mueve hacia abajo en la apertura, puede hacerlo más rápido sin tener demasiados problemas de color; es por eso que SW 80ED es F / 7.5

Por encima de 125 mm está presionando esto con F / 7.8, es demasiado rápido para el doblete ED, para la imagen de todos modos, podría ser muy bueno para la vista.

Por otro lado, hay muy poca diferencia en el triplete basado en el vidrio FPL-51 y el FPL-53.

En cualquier caso, sigo creyendo que 115 mm se corrige mejor que 125 mm, y sí, por lo visual, es posible que ni siquiera note ninguna diferencia. Creo que ambos son grandes alcances del dinero y, dadas mis preferencias, seguiría apostando por 115 mm.

One of the advantages of the larger aberture is that there are more mask options. In the case of the TS125 it can become 115 or 100, as it suits us... Perhaps in planetary observation it is appropriate to convert it to a 100 and take advantage of the observation at high power colour free (we would be at F/9.7), while for DSO we remove the mask and enjoy its greater luminosity. Even accepting that it is more than very risky to affirm that the chromatic correction of the doublet is somewhat better than that of the triplet, in my opinion it is a little more versatile than its companion triplet.

[Fedele]

26 minutes ago, CraigT82 said:

Haven't you already got an SW ED120?  I'm not sure the extra 5mm of the 125mm f7.8 is going to give you much more than what you get from that

I need more quality in optics and mechanics

[Fedele]

Triplet is out now (if triplet i will buy the TSA120)

remain the Doublet. 

[dweller25]

This is easy - buy the TSA120 👍

[Robindonne]

I knew this question would turn in a sort of fight. And I’ve played with this question also sometimes. Maybe, like John already did, people like us, who own a sw120ed need to know why all these other mentioned scopes dont give that much of a Wow effect, like Fedele asks, compared to the 120ed. 
 

 

 

Edited June 11, 2021 by Robindonne

[johninderby]

A big WOW when I looked through the Tecnosky 125. Had an Equinox 120 and it just never impressed like the 125 does. Maybe the Equinox was a poor example?

I think when comparing scopes price is a big factor for most so getting the best within a buyers budget can be the decider.

Edited June 11, 2021 by johninderby

[KP82]

No direct experience with any of these 3 scopes. But if you were asking me to choose between Tak quality and more apertures purely for visual, I'd go for more aperture, in this case the TS 125.

I've looked through a Tak FC100DC and Vixen ED115 before so I'm aware of the high quality views these Japanese doublets can produce. But compared to my own Sharpstar made APM107, there is virtually no difference. Yes they cool down faster than my triplet, but only by a small margin.

[John]

My experience comes from owning a Tak FC100-DL, a Skywatcher ED120 and a TMB/LZOS 130 F/9.2 triplet and comparing them over the past 5 years. They are all excellent refractors

The Tak and TMB / LZOS have better mechanical build quality than the Skywatcher (unsurprising given the price difference between these scopes) but the ED120's optics hold up very well against the Takahashi and LZOS objectives.

When I bought the Tak and the TMB/LZOS I thought that I would be letting the ED120 got to a new home but that's not going to happen.

Whether you will find anyone who has actually compared the 3 scopes you are specifically interested in remains to be seen.

If you want one of the very best made in it's aperture then the Tak 100DZ will be the choice. If you can afford a TSA120 as well then you won't be asking what might have been in a larger aperture either.

One thing in the astronomy equipment game that I have learned is that buying the best quality you can rarely seems to lead to any regrets.

Have fun making the decision

 

 

 

 

Edited June 11, 2021 by John

[mikeDnight]

A 125mm ED will have a significant jump in planetary resolution over the 100mm, but the DZ is no slouch when it comes to delivering great lunar & planetary views. The 125 will give the 100mm DZ a run for its money I'm certain, but the level of colour correction and spherical correction of the Tak does give it a special place in the 4" line-up. Personally i think a good 5" refractor sits in a real sweet spot for planetary, however with a binoviewer, the 100mm can pull out some ultra fine detail that would be very close to that of the 5".

Edited June 13, 2021 by mikeDnight

[Robindonne]

I'm so glad we were able to help Fedele choose from the 3 options