Can a Takahashi 100 DZ Outperform a Non Premium 120-127mm ED Refractor

[mikeDnight]

2 hours ago, Mr Spock said:

Do you find there to be a difference in planetary performance between the two?

It's difficult to say for certain. When I first bought the BBHS I looked at a random stone wall a couple of miles away just to see if I could see any difference between the Tak and Baader prisms. The Baader definitely appeared sharper during the day when studying the toothed outline along the top of the wall, with the Tak being a little less well defined. It was a very subtle difference, so wether its a better prism, or the silver coating that made the difference I couldn't honestly say. So I'm inclined to say "yes" the Baader is better, but when looking at the Moon and planets, or stars and nebulae, I don't see any immediate difference. I suspect the Baader is marginally brighter,  and because of the wall comparison, sharper, but I think it's borderline. I've used both at very high magnification and both perform great on stars, but because of the helical micro focuser option of the BBHS, I tend to opt for that when observing double stars, and because I know its at least as good as the Tak. Hope this makes sense!

[vlaiv]

6 hours ago, Mr Spock said:

That sound a little odd as DZ users report the view is a bit cooler than other non Lanthanum Taks. As it's reported they both have the same level of correction and detail one wonders why the Lanthanum version is necessary for visual (it may reduce blue bloat for imaging).

Here are two quotes from said page:

Quote

Moreover, the scope description by some vendors uses the words "Lanthanum coatings" which, along with "new materials" indicates that a special kind of coating was used to cut out better part of the violet. Some materials, when doped with Lanthanum, can selectively absorb ultaviolet bands. For instance, LiNbO3 (Lithium niobate), doped with 5% Lanthanum, transmits only about 65% at 450nm, and less than 10% at 430nm, while transmitting over 90% of the longer wavelengths (undoped, it is near zero already at 450nm, but transmits only about 60% of the wavelengths over 500nm). With optimized transmission, light loss in the rest of wavelengths probably can be made negligible, with the absence of violet giving more abundance to the red hue - noticed in some reviews.

That is related to ED doublet with lanthanum glass.

On the matter of lanthanoids used with Tak100DZ, this is said:

Quote

Sometimes described as the "best doublet ever", this refractor is marketed as consisting of a rear fluorite element and a high-index/low-dispersion front element. The latter generally describes lanthanoid glasses. Fluoride is "privileged" vs. other SD (super-low dispersion) glasses in being higher on the RPD (relative partial dispersion) diagram, hance being able to use low Abbe# glasses - for a large Abbe# differential - without introducing secondary spectrum. Lanthanoids in general tend to be more or less loose in the violet; those that perform the best in that respect with fluorite are having refractive index of ~1.697 and ~55.5 dispersion (e-line). They include Schott N-Lak14, Hoya Lac14, CDGM H-Lak12 and Ohara S-Lal14. While not the best - differences are small - it is the Ohara glass that produces longitudinal aberration graph nearly identical to the one published (below).

This all emphasizes the point that proper mating of the elements is what is important and there are a lot of different glass types out there.

[John]

16 minutes ago, vlaiv said:

....This all emphasizes the point that proper mating of the elements is what is important and there are a lot of different glass types out there.

Very true and it's a point worth repeating often as well as the importance of figuring, polishing and mounting the elements.

As far as I know LZOS is the only glass manufacturer that makes the glass for both the ED/SD and the mating elements of it's objectives.

I think for the Takahashi objectives, the fluorite glass is made by Canon Optron, the mating element glass by Ohara (for the DZ at least perhaps ?) and the figuring, polishing and coating done by Canon Optron. I believe that the objective cell manufacture and the mounting of the elements within them is performed by Takahashi.

  

 

Edited November 22, 2023 by John

[bosun21]

34 minutes ago, vlaiv said:

Here are two quotes from said page:

That is related to ED doublet with lanthanum glass.

On the matter of lanthanoids used with Tak100DZ, this is said:

This all emphasizes the point that proper mating of the elements is what is important and there are a lot of different glass types out there.

How is Lanthanum coatings the same as Lanthanum glass?

[vlaiv]

3 minutes ago, bosun21 said:

How is Lanthanum coatings the same as Lanthanum glass?

They are not, but lanthanum glass is a material doped with lanthanum - which exhibits the same properties - absorption in violet part of spectrum - read the whole quote

[vlaiv]

@bosun21

Ok, there seems to be some confusion about the Lanthanum elements used and that's probably my fault. This is what I've gathered so far:

1. FPL53 is not the best match for lanthanum glass. Better matches are for example flourite glass like in Tak and FPL51 like in that fast doublet.

2. Lanthanum glass tends to create very high dispersion in Violet / UV part of spectrum, but can probably also absorb some light in this part (not sure about that part)

3. Lanthanum coatings are used to reduce impact of high dispersion in violet and control the color.

Quite possibly that 2 and 3 are often mixed by marketing teams, or even used together.

125mm F/7.8 doublet is thought to have above combination of glass and that it employs coatings to reduce issues:

Quote

In all, unless the TS Photoline uses some off-chart, custom lanthanum glass - which would be expensive - it is likely that it employs similar selective absorption coating as the one described under #10. The end result is a well performing telescope, and it is what matters.

 

[Elp]

TS also now do FPL55 in their triplets, probably similar to some other glass or another.

[John]

1 minute ago, Elp said:

TS also now do FPL55 in their triplets, probably similar to some other glass or another.

Somewhere between FPL-51 and FPL-53, rather oddly. Closer to FPL-53.

 

[bosun21]

The most important thing for me is that my Starfield with its FPL53 and Lanthanum glass lenses provides a CA free and good colour images. The rest of it I will leave to others.

[John]

I think lanthanum glass comes in many varieties. Some make excellent mating elements with certain ED/SD glass types and some are better suited to other purposes. 

There was a thread on this back in 2013 within which was this interesting post on lanthanum glass:

 

[johnturley]

Early last night (around 5pm), and before it clouded over, I looked at Jupiter for the first time with both the Tak 100 DZ and the ES 127 Refractor mounted on the AZ-EQ5 mount in AZ mode. I spent most of the time trying to get the two scopes, and their finders, aligned with each other, the secondary saddle on the AZ-EQ5 does have a fine adjustment in altitude, but not in azimuth, so the best I could achieve was the two scopes pointing within about a degree of each other (With my 14in Newtonian @Peter Drewmanufactured a device which enables a piggybacked scope to be exactly aligned with the main telescope).

Viewing conditions were not that good, which limited the optimum magnification to around 120x, plus the tracking on the AZ-EQ5 is not very good in AZ mode. At first I thought that the ES 127 had the advantage, delivering what I though was a brighter and more contrasty view, but this may have been due to the fact that I had put the ES127 out first and had cooled more, as the view through the 100DZ subsequently improved such that it was rivalling or possibly exceeding that through the ES 127.  I intend to carry out further comparisons including the moon in particular at the next couple of lunations.

As mentioned in another thread, I find it difficult to achieve sharp focus with the stock focuser on the Tak, and I intend to add on a high quality prism diagonal (Tak or Baader T2), and either a Micro Focuser or Baader Helical Focuser. 

Regardless of which scope performs best however, was the I find the 4kg Tak a doddle to carry out compared to the 9kg (with tube rings and diagonal) ES 127, which having had back problems, is one of the main reasons I decided to purchase the Tak. I may in the future also swap the AZ-EQ5 mount for something lighter to carry the Tak, such as the Skywatcher Star Adventurer GTi.

Edited December 7, 2023 by johnturley

[JeremyS]

All sounds very promising @johnturley 👍🏻

[Peter Drew]

It would be interesting to see whether a 4" Takahashi could outperform a 5" Takahashi.   Apples/apples.    🙂

[dweller25]

19 minutes ago, Peter Drew said:

It would be interesting to see whether a 4" Takahashi could outperform a 5" Takahashi.   Apples/apples.    🙂

Been there, done that - the answer is visually “no” , weight wise “yes”

Edited December 7, 2023 by dweller25

[josefk]

@Peter Drew as the owner of both ~3" and ~5" Tak OTAs i can promise you the 3" outperforms its bigger brother by quite a margin in the "carrying it up and down stairs" stakes! It may not be apples vs. apples - more like potato vs. sack of potatoes.

Edited December 7, 2023 by josefk

[Stu]

36 minutes ago, josefk said:

@Peter Drew as the owner of both ~3" and ~5" Tak OTAs i can promise you the 3" outperforms its bigger brother by quite a margin in the "carrying it up and down stairs" stakes! It may not be apples vs. apples - more like potato vs. sack of potatoes.

Touché 👍👍

[johnturley]

My original post was asking the question as to whether a Takahashi 100 DZ could outperform a Non Premium 120- 127 mm Refractor, such as my Explore Scientific 127mm FCD 100 Refractor, and based on the comparisons I have carried out so far, the answer appears to be one of ‘Yes, Maybe, but only Just’.

Last week (16th– 18th January), taking advantage of the cold clear conditions, I mounted both instruments on my Skywatcher AZ-EQ5 Mount in AZ mode (see photo), and compared the view of the Moon and Jupiter, through both scopes. It was not possible to get the two scopes exactly aligned to each other (the AZ-EQ5 has fine adjustments in altitude but not in azimuth), but managed it within a couple of degrees. I also on 16^th and 17^th January, compared the view with that through my Esprit 150, which is piggybacked on my 14in Newtonian in my observatory shed, and which can be seen to the right in the attached photo. In order to get the magnifications as close together as possible, I employed a 4.7mm ES 82 degree eyepiece in the Tak, a 5.5mm ES 62 degree eyepiece (which is a sharp little eyepiece) in ES 127, and a 7mm T6 Nagler in the Esprit 150, giving magnifications of 170x, 174x, and 150x respectively. I did try on one occasion a 3.5mm T6 Nagler giving 228x in the Tak, but viewing conditions weren’t good enough to support this magnification.

On 16 Jan in particular I compared visibility of craterlets within the Mare Crisium on the Moon, on 17 Jan the shadow transit of Europa on Jupiter, and on 18 January the Alpine Valley on the Moon. As expected, with its extra 27mm of aperture the ES 127 gave a brighter view, but the view through the 100 DZ appeared generally sharper, but only marginally so. One advantage maybe in the Tak's favour was that with it, I was using a Baader Zeiss Prism Diagonal, as opposed to a Baader 2in Dielectric Diagonal with the ES 127, and a 2in BBHS Diagonal with the Esprit. However the view through the Esprit 150, was significantly sharper and brighter than the other two instruments, I have compared the Esprit 150 with the ES127 on previous occasions, and thought that the advantage to the Esprit was greater than might be expected from just the extra 23mm of aperture.

Unfortunately I never got round to comparing my 9.25 CPC before I sold it with the Esprit 150, but I suspect that at least as far as sharpness was concerned, the advantage would have been with the Esprit, except perhaps under very good viewing conditions. The CPC however could give good planetary views, so I’m really surprised when @Mr Spockstated in another thread that his Tak 100DF consistently outperformed his C9.25 on Jupiter.

I haven’t so far done a comparison between 100DZ and the ES 127 when it comes to faint Deep Sky Objects, but with its extra 27 mm of aperture, I would expect the advantage to be ES 127

The outstanding thing about the Tak 100DZ however, is how light and portable it is compared to the ES127, and does pack good performance into a relatively small light package. One of the reasons I decided to purchase one, was that due to recent back problems I wanted a lighter and more portable scope, so as to reach areas of the sky which are obstructed from my observatory shed, and possibly also to take on holiday, so I don’t regret purchasing it. I may also consider a smaller lighter mount than my AZ-EQ5 (which was purchased to accommodate the ES 127), but it’s not too heavy to carry round, especially with just one counterweight, which is all that is needed with the 100 DZ

To summarise, based on my experience with my 100 DZ so far, Taks are optically very high quality scopes, but they do perform according to the Laws of Physics, and not the Laws of Magic, as some Tak enthusiasts suggest, permitting much higher magnifications (up to 100x or even 120x per inch of aperture) to be used compared to other scopes. I can’t see ever being able to use 400x to advantage on planets (maybe on double stars) through my 100DZ.

It would be interesting to compare the performance of a 100mm Tak with scopes such as the StellaMira 125mm ED Doublet, or Esprit 120 (similar price point). It may well be that the optical quality of Taks is more consistent than with most other makes, although Es Reid informed me that he has occasionally come across what he described as a Friday afternoon Tak, which is one reason why I went for the Zygo Test from Rother Valley Optics for my 100 DZ. I may be fortunate in so much as according to Es Reid, my Esprit was one of the best he had tested, he had in his workshop at the same time a Tak FS 152 for renovation, which he said my Esprit compared favorably to.

John

Edited January 21 by johnturley

[JeremyS]

That is a very interesting analysis, John. The Tak advantage is marginal, but if one seeks as close to perfection as is possible, then they do generally offer that. I wish I had realised this a few decades ago.

Regarding the Tak 100 vs C9.25 comparison, I join you in being a bit surprised by the claims you cite. I have an FC 100DZ and an FS 102, they are generally outperformed (visually) by my C9.25 in terms of Jupiter detail by quite a margin. The latter is a very fine instrument, without the diffraction spikes of my Mewlon 210, but it doesn’t have the “snap” focus of the smaller refractors. 

Edited January 21 by JeremyS

[johnturley]

1 hour ago, JeremyS said:

 

 I have an FC 100DZ and an FS 102, they are generally outperformed (visually) by my C9.25 in terms of Jupiter detail by quite a margin. The latter is a very fine instrument, without the diffraction spikes of my Mewlon 210, but it doesn’t have the “snap” focus of the smaller refractors. 

That's interesting as some observers regard Mewlons as being 'Planet Killers', however, especially since getting my Esprit 150, I've become more of a refractor enthusiast, and to me the ultimate Planet Killer if one could afford to buy and accommodate it, would be a TEC 200 or perhaps even a TEC 250. 

John 

[JeremyS]

1 minute ago, johnturley said:

That's interesting as some observers regard Mewlons as being 'Planet Killers', however, especially since getting my Esprit 150, I've become more of a refractor enthusiast, and to me the ultimate Planet Killer if one could afford to buy and accommodate it, would be a TEC 200 or perhaps even a TEC 250. 

John 

The M210 is indeed a planet killer. Superb views of Jupiter. But I have still not acclimated to the diffraction spikes. I still find them distracting. 

[Mr Spock]

With my 12" I use a variable polariser and don't see any diffraction spikes. The 210 has less light though and maybe too dark with a polariser?

My issue with the C9.25 was I found it very susceptible to seeing conditions. Quite often I would leave it out to cool (it was stored in a cold place) for quite a while, take a look through it, see how mushy it was, and put it away. Occasionally it would be good. I've had a few lunar sessions with it where it was sharp at x296, also split a 0.7" double with ease. But never saw any detail on Jupiter and never saw the GRS with it. 

[JeremyS]

4 minutes ago, Mr Spock said:

With my 12" I use a variable polariser and don't see any diffraction spikes. The 210 has less light though and maybe too dark with a polariser?

My issue with the C9.25 was I found it very susceptible to seeing conditions. Quite often I would leave it out to cool (it was stored in a cold place) for quite a while, take a look through it, see how mushy it was, and put it away. Occasionally it would be good. I've had a few lunar sessions with it where it was sharp at x296, also split a 0.7" double with ease. But never saw any detail on Jupiter and never saw the GRS with it. 

If I can locate my var polarising filter I can certainly try, Michael. Thanks.

[dweller25]

@JeremyS The issue with SCT’s is optical variability, it sounds like you have a very good one that works as a 9.25” should, perhaps @johnturley’s is not quite as good.

I can say with 100% confidence that the C9.25 I owned was the worst telescope I ever looked through - it really was a lemon that had gone rotten !

Stupidly I bought a C8 years later - it was a stunner ! 🙂

Edited January 21 by dweller25

[Deadlake]

The issue with the SCT is it needs a night of good seeing to use and also needs to acclimate to be usable. 

In the end I run out of time to use the C11, I just go for the APO as it's ready to use in thirty minutes.

The SCT has more image scale, however it's never as sharp or has the contrast of my APO.

The MTF of the APO I have just pulls away when looking at planets compared with the SCT.

Why do I have the C11, it's great on DSO, it just goes so deep on the stars I can see.

My back yard is SQM 21.

[dweller25]

1 minute ago, Deadlake said:

The issue with the SCT is it needs a night of good seeing to use and also needs to acclimate to be usable. 

In the end I run out of time to use the C11, I just go for the APO as it's ready to use in thirty minutes.

The SCT has more image scale, however it's never as sharp or has the contrast of my APO.

The MTF of the APO I have just pulls away when looking at planets compared with the SCT.

Why do I have the C11, it's great on DSO, it just goes so deep on the stars I can see.

My back yard is SQM 21.

Is your C11 reflectix wrapped ?