Worlds Best Doublet vs Best Triplet APO Refractor Telescope. Is the Triplet worth the extra cost???

Are you considering an APO refractor and not sure if you should get a doublet or triplet APO? This video features a Takahashi FS-128 and Astro Physics 130GT witch are widely considered as one of the best doublets and triplet APO's ever made to help you make the right choice!
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[@GarnettLeary]

Your reviews and comparisons are very valuable to the community. Your collection and experience with scopes is likely rivaled only by Ed Ting. This information is invaluable. People considering making a big investment in a scope should definitely come see your content. I recommend you often to folks in my circle. Thank you for your contributions.

[@AVTAstro]

Very kind of you to say that! Ed Ting certainly an inspiration! I remember reading his reviews for as long as I have been in the hobby👍

[@resottolamontagna904]

What a view man! You are living in a very beautiful place.

[@AVTAstro]

Thanks!

[@user-yd1zl1tv8x]

Great video! The opportunity to video review these two very special, very expensive refractors is a rare treat. Thanks for taking the time, effort and expense to do so. Great conclusions. Clear, concise, in all a great view. Thanks again. Kind regards!

[@AVTAstro]

Thanks for watching! I appreciate your feedback. Vlad.

[@elliotyip9844]

Binge watching both your channel and Ed's channel while doing my research into this hobby!

[@AVTAstro]

I'll take the privilege to say; welcome to the hobby! If you have any questions regarding gear or astro stuff in general feel free to reach out👍

[@jimpoop]

Revisiting this video as I now have several high-end refractors. Im honestly suprised that fs128 had that much CA.. I recently did a shoot out between my TSA120 and my Celestron c102f. And in focus I noticed very little in either scope. The Tak is slightly better, but only really because i see slightly more color out of focus in a star test in the C102.. but I think both are reeaally close. Even on very bright stars... at very high power, the Tak pulls away slightly on CA... but I think under most conditions, they are so close as to be essentially negligible. I love both.. I actually recently bought a moonlight focuser from you recently for my Celestron... now I really have a hard time deciding on what's my favorite.. it really made the 102 next level.

[@AVTAstro]

I think the big difference is people's sensitivity to blue light. It must vary as lots of people claim that they see no secondary color(usually blue). I easily see it even in the best of triplets at high power. And it's obviously there since as this video shows a CMOS camera easily captures it. I probably don't see quite as much as the camera but certainly an obvious amount. Congrats on the focuser, that will certainly give the Flourite Celestron the premium feel it deserves!

[@entropytango5348]

We should not forget that observing is something we learn. As you have looked through so many scopes, your ability to see things would be well in advance of your average amateur. Love these comparisons. I'd be interested to see the FS-128 comparing against the older AP-Star 12ED (not made with your standard ED I believe). Thanks for another fun vid.

[@AVTAstro]

Thats a good point about observing experience.

[@douweodh4146]

Stunning scenery where you live!

[@AVTAstro]

Thanks, it's certainly a privilege to live in such an area👍

[@GaryP747]

Nice work, thank you; I'm considering exactly this!

[@AVTAstro]

Glad it was helpful!

[@jimpoop]

Dang, looks like Ill need a triplet for sure for my next scope. I'd like to see a triplet comparison, like lower end, to high end. astrotech EDT, vs esprit, vs astrophysics/tak

[@AVTAstro]

Yeah that would be fun to do. Unfortunately I currently do not have an one of the more entry level triplets but I'll work on getting my hands on one👍

[@peter7624]

Surprising how little difference between the two images. I had a Vixen 4" achromat which was as good as my 4" apo. I realised a good doublet was better than a mediocre apo, but didn't think the top class achro and apo would compare visually. Great comparison by the way, very thorough, thanks for posting!

[@AVTAstro]

Glad you liked it! Thanks

[@jc4evur661]

Looking forward to your future review of the top-end quadruplet! 😁

[@AVTAstro]

Well I do own an FSQ-106;)

[@jc4evur661]

@@AVTAstro With all your equipment you must have an understanding wife. Lol

[@AVTAstro]

That would be a very true assessment. 😆

[@avt_astro206]

Great Overview Vlad!

[@AVTAstro]

Thanks!

[@slapastronomy8646]

Excellent video and two very nice scopes.

[@AVTAstro]

Glad you enjoyed it!

[@stephenpalmer7281]

Thanks for the excellent in depth comparison. My only refractor is a Skywatcher 120 ED doublet and optically for visual can’t imagine much better. Some day I may upgrade to a Tak. Be cool to see a comparison of a less expensive doublet like what I have compared to something like a tak fs-128. Opportunities for these comparisons are not in short supply 👍

[@AVTAstro]

I don't imagine you would be brown away by the difference you would see. I have had an SW 120ED in the past and it had nice optics. Have not done a direct comparison to a Take though.

[@Brian.001]

Is that the SKYWATCHER EVOSTAR 120ED DS PRO ??

[@johnadams9044]

If you like lots of color in your images, then you want a doublet. If you want serious color corrected optics with all light wavelengths focusing at a uniform point, go with the Triplet APO.

[@AVTAstro]

Well "lots of color" is a bit overstated in the case of a really good doublet like the FS-128. But in general yes a Triplet will have better color correction.

[@christiana8820]

Worlds best doublet is TeleVue TV85 refractor. Best quality build, view and portability. Also is perfect for dual use of day and night viewing(Considered one of the best birding scopes in the world.) It is the gold standard. Anyone that has owned one would agree. Good point on the weight balance issues. I do greatly enjoy your videos and enthusiasm for the hobby, however.

[@AVTAstro]

The TV-85 is a special scope to me. It was my first APO back in the early 2000's. I have many fond memories of observing with it and it showing mind bindingly good views for an 85mm scope. Years later I recently had another one. While yes the build quality is amazing on them I did not find the optics anything special(compared to all the other gear I own). Not saying its a bad scope at all, but its certainly not better then an FS-128.... See my review of it here: avt-astro.com/reviews/telescopes/televue-tv-85-apo-review/

[@christiana8820]

@@AVTAstro The FS 128 is a fine scope for sure. I use the green TV85 with HD-4 Gibraltar/Berlebach tripod, the full TeleVue Delos EP set, and TeleVue 35mm Panaoptic and 22mm Nagler Type4 EP. I only do visual and not astrophography. This set is functionally and visually a masterpiece. It is super easy to transport anywhere I go in the world, serves every function I could want visually, is an easy manually operated tool, draws an interested crowd that wants to take their first peek ever through a great scope - both day or night, and is something I could display in my den as a piece of functional art. I don't know anything else that even comes close to matching those qualities.... I can actually backpack this set (With a more mobile tripod) up mountains when I want. If I was looking to set up a home observatory I would obviously go another direction, but until then....

[@AVTAstro]

I can't disagree with you that it sounds like it's the perfect scope for you. And it is a great scope in general. But I guess your trying to make the point that since it's perfect for you it's somehow the best doublet out there. It's not optically witch is what the point of this video is. Best doublet vs best triplet. This is not even my opinion, the scopes in this video are widely considered by many to be the best.

[@Astronurd]

Great comparison Vlad. The difference in price is quite substantial between a doublet and a triplet though

[@AVTAstro]

Yup they are more expensive for sure!

[@Rich-hy2ey]

Thanks, nice on-site comparison. I've compared these kinds of scope extensively. With the AP triplet, you notice a purer white when viewing disks of something like Jupiter, the moon or Saturn, but having said that, for visual use both scope have extremely low-level colour. The fluorite-base Takahashi is as good as an apochromatic doublet gets. Neither gives up any detail on the moon or planets to chromatic aberration and on deep-sky objects, there is no difference between either.

[@AVTAstro]

Yup, both excellent scopes👍

[@rcpilot9963]

I have a TS 102 F11 ED doublet on FPL51 and I think it is almost perfect in correction of chromatic aberration, better than my past SW 100ED.

[@AVTAstro]

Yeah them f11's sound like a very cool scope. I'd like to take one for a spin. Maybe one day!

[@francescotoni26]

Very nice! Thanks

[@AVTAstro]

Thank you too!

[@markihde4381]

Vlad, I suspect you are correct that increasing magnification by adding a Barlow will increase the level of CA. But you have me interested in following up with my own experiment. What if magnification remains constant and I double the effective focal length with a Barlow? What I have in mind is pointing my 6", f/12 achromat at Vega with a 10mm eyepiece. (f = 1,800mm @ 180X). There should be a noticeable amount of CA. Then, insert a 2X Barlow with a 20mm eyepiece. (f = 3,600mm @ 180X @ f/24) Will there be a reduction in apparent CA?

[@AVTAstro]

With an eyepiece it's 100% going to have more CA. A lot of long eye relief eyepieces have a built in barlow. They do not somehow have less CA. There really is no magic cure to CA unfortunately.

[@AVTAstro]

And yes you will have a LOT of CA even with a f/12 on Vega. Most triplet APO's will show some color on Vega at 180x(or above).

[@exif6839]

I have the worlds best doublet APO: Kasei Nerius 102 SDP. A 102/f11 System with FPL53 Glass. The perfect APO with Polystrehl 0,99 from UV to IR.

[@AVTAstro]

Have not heard of it but at f/11 I'm sure it's a performer 👍

[@mikenofi281]

The amount of CA of a refractor is approximately determined by the f/ratio of the objective divided by the lens diameter in inches. CA = f#/D where f# is f/ratio or f-number, and D is the objective diameter in inches. You tested the same apertures, but if the f/#s are different you are not comparing apples with apples. What was the f/#s of each telescope? I belive the AP is a faster optical system. This may be why you were surprised by the amount of color in the AP short-tube triplet.

[@AVTAstro]

It's f/8 vs f/6.2. The formula you are using is probobly appropriate for comparing achromat. For APO's it will not apply as the the glass type and number of elements will greatly affect how well controlled the secondary color is. That's why even at f/6.2 the AP has better color correction.

[@mikenofi281]

@@AVTAstro Thanks for your response. You are correct, and the equation is in reference to an achromat. I realized this after I reread it. Good catch. From a design and fabrication perspective, it is harder to reduce the amount of CA in an f/6.2 triplet than in an f/7.5 triplet. Some form of the achromat equation still applies. I mention this because, in your video, you said you were surprised that the CA in the AP was as pronounced as it was. I was surprised by this as well. I surmised that the amount of color is likely the result of it being an f/6.2. That is fast for a 6-inch refractor! Some secondary color is likely to be present. BTW. I am also very sensitive to CA, and I have never viewed through any APO that doesn’t have a hint of CA present! My 80 mm f/6 Lomo is the best I have ever seen! Better than my SVs and TAKs. I enjoy your videos. You are an experienced observer, and your reviews are a step up compared to others. Please keep them coming.

[@AVTAstro]

I will agree with you 1000% on the Lomos!!! They are some of the best and underrated optics out there. I foolishly sold the ones I had, but will for sure own a keeper in the future👍 And thanks for the nice feedback!

[@astroblast9352]

Of course the size of the objective and focal ratio will impact the secondary color. Certain nights are better than others for seeing color I find. Worth trying on another more pristine sky.

[@AVTAstro]

I don't see how secondary color will be affected night-to-night. Even if it was the nice thing of doing a comparison side-by-side is that even if the seeing does affect the performance of one scope, it will do the same to the other.

[@astroblast9352]

@@AVTAstro just seems like my sky sometimes is hazy and all the light doesn't seem to come together perfectly . I try not to worry about what I'm seeing on those nights. But it could just be me haha. I've found my sky is pretty unique compared to other parts of the country. Especially impacts Night Vision astronomy performance.

[@AVTAstro]

Maybe water vapor can affect this. That's the only thing I can think of unless the object being observed is very low in the sky. Also NV is something I would love to try one day👍

[@danielchen4821]

My FC100DZ doesn’t show any color visually. Never tried AP though

[@AVTAstro]

And at what power and at what object is this on? I have also heard the same claims on the FS scopes... Different peoples eyes and experience in observing had a lot to do with what you can see both secondary color wise and detail in objects. Just food for thought as I know for a fact that the AP130gt is better color corrected then your DZ and even that shows secondary color on very bright stars at hight power s stated in the video!

[@markihde4381]

Would there be any value in putting a minus violet filter in front of the camera or in front of the eyepiece?

[@AVTAstro]

Not with these scopes unless your into imaging Vega. It's Lind of the ultimate tourcher test as it's bright and blue.

[@JamesAdams-ev6fc]

Nice 😊 discussion especially of the weight and cooling time differences that favor well-made doublets. That is not covered very often, and it is a point that Televue makes in favor of its TV85 scope. Filming with all those lights on must have been challenging 😰. Thanks for another great video. Everyone: subscribe you will not regret it!

[@AVTAstro]

Thanks for the nice feedback👍 Yeah shooting some footage certainly goes not help with preserving your night vision. Lol.

[@markihde4381]

Vlad, I've been thinking about this and am wondering how much effect there would be by adding a 2X Barlow to double the effective focal length. Since the triplet APO still shows some false color around bright objects like Vega, I'm wondering if using a method of increasing effective focal length to reduce chromatic aberration in doublet refractors might help. Raises the question for me, at least, about how apochromatic even the best APO telescopes are, and if increasing the effective focal length of a telescope is really the only means to mitigate this without ever completely eliminating false color in any refractor design.

[@AVTAstro]

I don't think you would get not less CA but more. Just like you get more CA by using higher powers visually. I honestly have no tried this though with a camera so you may be right. 🤷‍♂️

[@markihde4381]

@@AVTAstro Thanks, Vlad. I'm just a visual observer but it seems to me that the industry has not quantified a standard as to what "apochromatic" is. A $1,000 triplet "APO" refractor from one company probably isn't the same degree of apochromatic correction as an APO from Takahashi or Astro Physics. There should be a number next to any APO claim to quantify a level of color correction that can be measured. I've seen scopes with as many a five pieces of glass. That does not necessarily mean that those are more apochromatic than ones with better glass and only two or three elements.

[@gihanilangakoon]

Why not bring in a Stellarveu into the comparison?

[@AVTAstro]

They are nice. I just did not have one at the time.

[@area51xi]

What about quadruplets like the Tak FSQ 106EDXIV?

[@AVTAstro]

Well I have 2 FSQ 106ED's. They are awesome for wide field visual or for astrophotography. Its essentially a doublet with a built in filed flattener. Not ideal for high power work such as the planets.

[@area51xi]

@@AVTAstro I heard advice to wait on the FSQ106 because it doesn’t pair well with the new CMOS camera pixel size.

[@3dfxvoodoocards6]

How about achromat vs APO at the same price ?

[@AVTAstro]

Would be interesting to do. If I come across some that are in the same price range I'll be sure to make a video about it. Thanks!

[@3dfxvoodoocards6]

@@AVTAstro in my country an 80 mm APO costs just as much as a 127/1200 mm achromat. The difference in aperture is huge, I guess that in this case a 127/1200 mm achromat has to be better than a 80 mm APO. Unfortunately there are practically zero comparison videos on KZbin with the achromat vs APO at the same price range.

[@paulwood6729]

Another interesting video. I get why people hole AP & Tak as the most premium brands, do you know why people don't refer to Televue scopes as being on a par? Obviously TV are extremely good scopes but they're not referred to as being one of THE premium brands, that's what I mean.

[@AVTAstro]

If we where having this discussion 20 years ago there is no doubt that TeleVue would be considered one of the best refractor brands. In a way they still are especially when it comes to build quality. Optics wise most of their scopes(besides the NP's) are just an ED doublet that where amazing in the '90's but are no better than what the Chinese produce today. Its sad to say as the TV-85 was my first APO experience(witch was VERY positive at the time) back in early '00. Here is my blog post on this: avt-astro.com/reviews/telescopes/televue-tv-85-apo-review/

[@paulwood6729]

@@AVTAstroWow, I didn't expect that to be the answer! Thanks.

[@AVTAstro]

Paul just to be clear I'm not knocking on TeleVue, they make great products. The issue is that they have not done anything with their scopes optically since I had my TV-85 back in the day. These days they just cant compete optically with the amazing triplets that are out there both premium and not.

[@paulwood6729]

@@AVTAstro Thanks again. I had my eye on a TV NP127is as a retirement present but am thinking the NP127fli + 12" dob is a better way, with less compromise on both the visual & photo sides. I get that Taks are better, and cheaper in the c.5" range, but the TV is substantially faster and that appeals.

[@AVTAstro]

The NP models are an exception in the TV line they are a quadruplet and are indeed very fast. Can be used both visually and for AP. They are cool scopes. I actually had an NP-101 right after the TV-85 back in the day and it produced very nice wide FOV's. Was not too much of a fan of it for the planets though. This is going from memory from 20 years ago though so I'd really need to spend some time with an NP now to say how good one it after experiencing a number of premium APO's.

[@Nochift138]

What red dot finder site do you recommend?

[@AVTAstro]

I actually use this one on a lot of my scopes: amzn.to/33l1MGv Its honestly not the best quality and I have had a few fail over the years. This one is VERY nice but you do need a hex wrench to adjust it though: amzn.to/34EWO84

[@lornaz1975]

What would be the difference in the sharpness/clarity of a triplet vs a doublet?

[@AVTAstro]

Well I think I covered this in the video but if we are dealing with a very good Triplet and a very good doublet there is not much of a diffraction visually. For astrophotography you will for sure see a diffrance in clarity in that your images will have less secondary color especially around bright stars.

[@lornaz1975]

@@AVTAstro reason I asked is I complained a 100 mm Tak doublet to a William optics 120mm triplet. The triplet was considerable sharper. I just not sure what to make of this. I will have to do some research on it.

[@AVTAstro]

Well it is possible that you just had a bad sample of a Tak and an amazing sample of a WO. It's unlikely but could happen. There is sample variation with every scope, it's just that the premium brands have a consistently higher optical quality.

[@lornaz1975]

@@AVTAstro So I did some research on it all. As I understand being that the WO is a triplet it does increase contrast by better correcting the third wave length. Also, it is larger and would have some better resolution than a 4 inch. Lastly, it is taking in more light which would increase the contrast just by making it brighter. The target was the moon. At least that is my understanding. Like you said I doubt Tak screwed up. The 100dz is sharp. Maybe the WO is a good sample. I am able to use as high as 390x on the moon with it without much deteriation of the image and 7 bands on Jupiter. But as far as I know that might be normal for a scope like that.

[@AVTAstro]

Well you know at the end of the day if an owner of a scope is happy with its performance that's all that matters. The thing is that untill u own that ultra premium scope you will always be wondering what your missing. Once you own it you either realize you where not missing all that much(if you already had a good scope), or go on the web and tell everyone that does not have one that it's 1,000,000x better(depending on your persona)🤣🤣🤣🤣🤣🤣

[@bartekwitkowski7860]

Ciekawy film dzięki któremu można zauważyć różnicę między tymi dwoma refraktorami. Pytanie brzmi: Czy istnieją jakieś konkretne filtry, które są w stanie "wyciąć" niepożądane kolory? 😄😄👍 😄🤚.

[@AVTAstro]

Hi, yes they do make filters. Thats a band-aid on the issue though. In my opinion they do not solve the issue of the un-focused light at all. They just hide it.

[@bartekwitkowski7860]

@@AVTAstro OK. Dzięki za poświęcenie chwili czasu na odpowiedź. Twoja opinia jest dla mnie istotna ponieważ zauważyłem że masz doświadczenie związane ze sprzętem astronomicznym, a od dłuższego czasu zastanawiałem się czy filtr potrafi zredukować aberrację chromatyczną. Było by super gdybyś kiedyś zrobił film, który ukazuje różnice pomiędzy obrazem z filtrem a obrazem bez użycia filtra. Pozdrawiam serdecznie 😄🤚 🙂👍.

[@lornaz1975]

Vlad. What Tak do you have on the table and can you elaborate on the focuser being that its two speed?

[@AVTAstro]

Hey, that's a TSA-102mm. It has the stock Tak focuser with a Featertouch mechanics upgrade.

[@lornaz1975]

@@AVTAstro any opinion on the 100DZ for visual?

[@AVTAstro]

I have not used it personally but its the never doublet version of that TSA-102 you where asking about. The TSA-102 is no longer made but was a triplet with essentially perfect color correction(one of the best ever made). For visual use you will really not see much secondary color unless you are looking at VERY bright stars. It would make a very fine instrument. If you want to do astrophotography I would really look at some sort of triplet.

[@lornaz1975]

@@AVTAstro Yeah. TheTSA seems to be 120 and at this time I am not looking for something that large. Already got the WO 120 for that.Other than CA was just wondering how good the image would be for visual. Its F8 as appose to the F7.4

[@lornaz1975]

@@AVTAstro What is your opinion about Starlight Instruments - Micro Pinion vs the MEF-3 7:1 MicroEdge Focuser? I am thinking about adding one to mine eventually. The Starlight Instruments looks like the one you have on yours. Or should I consider the Feathertouch upgrade?

[@griffith500tvr]

Disappointing really, seems no money will buy a colour free scope (optical faults)

[@AVTAstro]

It will if you buy a non refractor. Lol. But in reality I test equipment to the limits. Most would just praise the bajeusus out of it and call it a great video🤣🤣🤣🤣

[@griffith500tvr]

@@AVTAstro What was the optically most fault free telescope you ever used? Have you any experience with Richi Chretien telescopes?

[@AVTAstro]

I actually have not as they are for astrophotography only. In my experience all telescopes have compromises. Unless I was really forced to live with one I would never settler for a one scope solution. It does not exist if you want to observe all the casmos has to offer😇

[@griffith500tvr]

@@AVTAstro Have you used any of the more unusual scopes like a Dall-Kirkham or similar?

[@nadirteymurov1]

Я болел за Так ((

[@AVTAstro]

Both are awesome scopes!

[@Michael_Franke]

Potentially interesting, but hardly understandable for a non-native speaker. Lots of incomprehensible mumbling. No offense. :-)

[@AVTAstro]

No offence taken. Maybe i can hire a translator at some point🤣🤣🤣

[@SamS-sn4uu]

I heard no mumbling, you're just not around other cultures. No Offense...