TheSkySearchers

Hi,

I want to know when buying a refractor, which is more important to have:

1. A triplet but with ED optics
2. A doublet but with Fluorite or FPL-53 optics

So if can't afford both or the type of scope i want can't be in both of above and only one of above, what will be the choice?

All scopes are well made and nice quality manufactured so no one will come to say that this build quality is better than the other one, so assume all are with excellent build quality.

This question always comes up , there are people more qualified then me on the topic for these two scopes.you'll have to hold on!

i'm just going on a hunch, i would assume that both are good quality scopes, then the triplet would be corrected better with colour ?.
i naturaly would budget on a purchase and pick the cheaper one ie probably the doublet and do narrowband imaging .and if i used a osc i would pick the tripplet .

are the scopes the same aperture and fl ?

yobbo89 wrote: ↑Wed Jan 27, 2021 12:49 pm This question always comes up , there are people more qualified then me on the topic for these two scopes.you'll have to hold on!

i'm just going on a hunch, i would assume that both are good quality scopes, then the triplet would be corrected better with colour ?.
i naturaly would budget on a purchase and pick the cheaper one ie probably the doublet and do narrowband imaging .and if i used a osc i would pick the tripplet .

are the scopes the same aperture and fl ?

Ok, i will give you 3 or 4 options or examples of scopes which are in mind or i am talking about

https://www.firstlightoptics.com/askar- ... graph.html

https://www.teleskop-express.de/shop/pr ... icate.html

https://agenaastro.com/sharpstar-61mm-f ... dphii.html

https://www.firstlightoptics.com/takaha ... actor.html

Each with either a flattener or a reducer, so what do you think? I could add more like doublets but i think one example with Fluorite instead of FPL-53 is the best option to include anyway

Both of your points are not that important actually.

FPL-53, FPL-51, FPL-55, FCD-1, FCD-100, FK-61 including Fluorite are all Extra Low Dispersion glasses (though Fluorite is a crystal).
They all have Fluorite in the glass formula.

A triplet does not necessarily give better colour correction than a doublet but a triplet will give you slightly more reach into the IR and the UV.

As long as the element is properly designed for the telescope they will all work well.

The purpose of using a Extra Low Dispersion element is the ability to make a shorter focal ratio telescope than one of similar colour correction in a achromat.

If you are worried about actual quality of the telescope then I would recommend you purchase the Takahashi.

Lady Fraktor wrote: ↑Wed Jan 27, 2021 6:58 pm Both of your points are not that important actually.

FPL-53, FPL-51, FPL-55, FCD-1, FCD-100, FK-61 including Fluorite are all Extra Low Dispersion glasses (though Fluorite is a crystal).
They all have Fluorite in the glass formula.

A triplet does not necessarily give better colour correction than a doublet but a triplet will give you slightly more reach into the IR and the UV.

As long as the element is properly designed for the telescope they will all work well.

The purpose of using a Extra Low Dispersion element is the ability to make a shorter focal ratio telescope than one of similar colour correction in a achromat.

If you are worried about actual quality of the telescope then I would recommend you purchase the Takahashi.

I care about having better colors with a scope at range of 280mm up to 320mm at most, do you know any scope at this range not expensive with nice colors corrected? I said 280mm not 250mm and 320mm not 360mm.

I can read, no need to repeat yourself.

The only one I can think of offhand is this: https://www.bresser.de/Astronomie/Teles ... L55ss.html

There are likely others available though.
If you just want colour correction then a doublet will work as well as a triplet unless you want the extra UV and IR ability.

Lady Fraktor wrote: ↑Wed Jan 27, 2021 7:51 pm I can read, no need to repeat yourself.

The only one I can think of offhand is this: https://www.bresser.de/Astronomie/Teles ... L55ss.html

There are likely others available though.
If you just want colour correction than a doublet will work as well as a triplet unless you want the extra UV and IR ability.

Ok, you also forgot reducers that can reduce the focal length to 270-320mm somehow with some scopes such as 60-70mm scopes maybe.

Is this scope highly recommended?

In another site same question it went far as one member only pointing about issues with any option i choose, so it is like there is no option of what i want, otherwise i have to accept any risk with issues then.

All what i want is a scope in this range between 280mm up to 320mm so i can use either Ha filter or Lum filter only with it, because i will use it in my dual imaging system which i will be using a 90mm F/6 triplet which also i am not sure about its quality and 0.65x reducer and future plan of color APS-C camera, i can't copy same this one again as each item is so expensive, so i won't buy APS-C twice or 0.65x twice, so definitely not 90mm F/6 if i want wider field with this combo, so i was thinking about 50-70mm options as long i will use only one filter or two anyway, they told me Ha isn't an issue and i know that, the issue is with Lum filter because it is exposed to all visible spectrum wavelength, so it will show issues from color in final processing even if i do colors in separate scope as triplet or even a reflector, so for that reason i try not get something not good enough with Lum filter then, i don't want to be forced with narrowbanbing only.

The Vixen is a popular telescope, more in EU than America but Vixen is better liked overall in EU.

You will have to decide on what compromises you need to make as there are not many refractors in this very short range.
I would avoid the Askar at least until actual reviews are posted, a triplet should not require a sub-aperture corrector and two different types of ED elements to get good colour correction.

Sharpstar has a good reputation if the 61mm will work for you.

Lady Fraktor wrote: ↑Wed Jan 27, 2021 8:23 pm The Vixen is a popular telescope, more in EU than America but Vixen is better liked overall in EU.

You will have to decide on what compromises you need to make as there are not many refractors in this very short range.
I would avoid the Askar at least until actual reviews are posted, a triplet should not require a sub-aperture corrector and two different types of ED elements to get good colour correction.

Sharpstar has a good reputation if the 61mm will work for you.

Good to know about Vixen, because when i look at my site astro reference mostly which is Astrobin, i really don't see much results from that Vixen scope, and i didn't see many results around, so that put it into suspicious status for me, but if you claim that is really popular in Eu then i don't mind, in fact i am not in Eu nor in USA, so it doesn't matter where is this scope or that is getting popular and more uses as long it is a good choice, so i will read more about it.

I did ask or included Takahahsi FS-60CB into questions around, but it sounds this scope isn't representing a high quality scope from many answers or votes, i just thought a Fluorite doublet from Takahashi should outperforms any FPL-53 doublet from China, but some claimed that they saw issues with it, it means i shouldn't put it as top vote then.

I looked at Askar and Sharpstar scopes, new tempting scopes, but i feel they are still unknown about their optics and its quality, i wanted Askar FRA400 more as i saw someone used this scope with 294 mono camera and amazing results, but even with those nice results when i show in the other site they managed to find issues, so for them all results are bad until it is free from issues [CA, halo, astigmatism, coma,....etc]

Sharpstar has been producing fine telescopes for decades, though I have not heard of Askar before and I have already said above why I would avoid it as a AP refractor.
Visually it would probably be fine.

Lady Fraktor wrote: ↑Thu Jan 28, 2021 5:12 am Sharpstar has been producing fine telescopes for decades, though I have not heard of Askar before and I have already said above why I would avoid it as a AP refractor.
Visually it would probably be fine.

The only Sharpstar scope in my mind is that 61EDPH II, sounds a great small wide field one as i want, but look at Askar FRA400 also, it is no less than this Askar, it is a quintuplet, but i feel like it became the war of who can make nicer look scope as there is also Radian Raptor 61, in the same league of Sharpstar and Askar, and that making it even more difficult to choose.

Can you judge a scope that is great amazing for narrowbanding to be used for broadbanding targets also?

TareqPhoto wrote: ↑Thu Jan 28, 2021 1:25 pm Can you judge a scope that is great amazing for narrowbanding to be used for broadbanding targets also?

Unfortunately I cannot tell something that specific.
I can look at a design and get an idea of how it should operate in general, this is why I have commented about the Askar as one to possibly take off of the list.

Lady Fraktor wrote: ↑Thu Jan 28, 2021 9:06 pm

TareqPhoto wrote: ↑Thu Jan 28, 2021 1:25 pm Can you judge a scope that is great amazing for narrowbanding to be used for broadbanding targets also?

Unfortunately I cannot tell something that specific.
I can look at a design and get an idea of how it should operate in general, this is why I have commented about the Askar as one to possibly take off of the list.

Funny thing is that in another forum or site and also on Facebook groups, Askar got high votes, so that means it is really a nice scope, even some pointed that they had issue or CA with Sharpstar 61 scope, so the new scope won and a scope that is out for a while didn't meet full expectation much, i won't get blind about it then.

TareqPhoto wrote: ↑Thu Jan 28, 2021 9:49 pm

Lady Fraktor wrote: ↑Thu Jan 28, 2021 9:06 pm

TareqPhoto wrote: ↑Thu Jan 28, 2021 1:25 pm Can you judge a scope that is great amazing for narrowbanding to be used for broadbanding targets also?

Unfortunately I cannot tell something that specific.
I can look at a design and get an idea of how it should operate in general, this is why I have commented about the Askar as one to possibly take off of the list.

Funny thing is that in another forum or site and also on Facebook groups, Askar got high votes, so that means it is really a nice scope, even some pointed that they had issue or CA with Sharpstar 61 scope, so the new scope won and a scope that is out for a while didn't meet full expectation much, i won't get blind about it then.

I think you are relying WAY too much on random reviews and votes by "who knows who?" rather than expert advice. The Takahashi and Vixen scopes mentioned up thread are examples how I would go as recommended. Also the title of the thread "design or optical quality" is problematic. You focus on the number of elements and glass types and TOTALLY neglect vitally important factors like the smoothness of the optical surface polish and scratch/dig specifications not to mention the design of the baffling system. Scattered light control is an important issue. So whether the design is well executed or not is going to be important. Vixen and Takahashi are well executed. I've looked through examples of both. I have no knowledge of Askar and could care less what a social media advertising campaign says.

But then, I know nothing. I'm just a retired physicist with a strong optics background who has built some optics and used some awfully fine examples. Go with the social media votes if you like. I hope that it works out for you.

notFritzArgelander wrote: ↑Thu Jan 28, 2021 10:11 pm

TareqPhoto wrote: ↑Thu Jan 28, 2021 9:49 pm

Lady Fraktor wrote: ↑Thu Jan 28, 2021 9:06 pm

Unfortunately I cannot tell something that specific.
I can look at a design and get an idea of how it should operate in general, this is why I have commented about the Askar as one to possibly take off of the list.

Funny thing is that in another forum or site and also on Facebook groups, Askar got high votes, so that means it is really a nice scope, even some pointed that they had issue or CA with Sharpstar 61 scope, so the new scope won and a scope that is out for a while didn't meet full expectation much, i won't get blind about it then.

I think you are relying WAY too much on random reviews and votes by "who knows who?" rather than expert advice. The Takahashi and Vixen scopes mentioned up thread are examples how I would go as recommended. Also the title of the thread "design or optical quality" is problematic. You focus on the number of elements and glass types and TOTALLY neglect vitally important factors like the smoothness of the optical surface polish and scratch/dig specifications not to mention the design of the baffling system. Scattered light control is an important issue. So whether the design is well executed or not is going to be important. Vixen and Takahashi are well executed. I've looked through examples of both. I have no knowledge of Askar and could care less what a social media advertising campaign says.

But then, I know nothing. I'm just a retired physicist with a strong optics background who has built some optics and used some awfully fine examples. Go with the social media votes if you like. I hope that it works out for you.

Please, don't put guilt on me also, i doubt that ALL social media people are dump and less knowledgeable, there are experts also, and there are who experimented, in fact the only Takahahsi scope i can afford and mentioned with my options is what someone just said that he had for 10 years and he saw CA with it, he care less with visual, but in imaging it bothers, so i can't throw away his 10 years of experience also, and also in groups or social media i didn't see much love to this Takahashi FS-60CB, so the name Takahashi is like not a bullet proof, not all scopes by them are well made, i could be wrong or they could be wrong, same goes to Vixen, in fact the only scope from Vixen which was voted for me was Vixen VSD 100mm F/3.8, that is not far price from Takahahsi or AP high end small scopes, means it is out of my reach.

I still can go for that Vixen FL55, didn't reject it all, but i also can't reject ALL other options just because they are new or they are popular among social media people or whatever, i have to see all options and wait and decide after enough time thinking, any scope can be good and can be bad also, i used my ST80 until now while it is still an achromatic used as a guide scope, almost 4 years and i am still holding it, so i won't buy something quick only because of the brand name reputation, because that is also fooled me and some said that it is not always the case, no need to always pay for the name although they do high quality designs, but sounds my requirement of a small wide field at 280mm-320mm range there aren't high end to choose or trust anyway, they make only for like 100mm up to 180mm, beyond that it is less demand for refractors.

There are no “bulletproof” options. Takahashi and Vixen are close enough for me.

notFritzArgelander wrote: ↑Fri Jan 29, 2021 12:25 am There are no “bulletproof” options. Takahashi and Vixen are close enough for me.

Actually my dream scope since 2018 was Takahahsi FSQ-106, now we are in 2021 and still it is a dream i couldn't afford, so if i have to wait it then it means years are gone, i might never get it, in fact it is the scope that i keep thinking about over all options i mentioned, but because i can't afford that so i try to find another one meeting my need at low reasonable prices.

TareqPhoto wrote: ↑Wed Jan 27, 2021 10:21 am Hi,

I want to know when buying a refractor, which is more important to have:

1. A triplet but with ED optics
2. A doublet but with Fluorite or FPL-53 optics

So if can't afford both or the type of scope i want can't be in both of above and only one of above, what will be the choice?

All scopes are well made and nice quality manufactured so no one will come to say that this build quality is better than the other one, so assume all are with excellent build quality.

You forgot quintuplet, surely 5 glass elements count for something.

I should say quality and design go together. If design has flows execution does not matter, and bad execution can trump a good design.

In selecting the right scope I would start with budget, after determining the right price range I would look at the application. For example for visual 60mm scope (and not just 60mm ) well executed doublet is all that you need.

Assume is that your scope is for photography, astro or terrestrial. In this case I will be of little help, but if you ask more specific questions you will get more productive answers. But, don't buy a scope just based on a type of glass.

I did a bit of reading on different refractors you listed, the Takahashi from every review I read rated it highly except for the R&P focuser.
It has a bit of slop that nobody could fully get rid of without replacing the focuser. Optically an excellent refractor.

The Askar seems to have a following but even the website says 'virtually eliminates almost all CA' wonderful marketing speak
If you are good with processing I would imagine it would not be hard to clean up the image if it is required.

Other than the Vixen 55mm I think you will have a hard time finding one that will fit into the focal length range you posted above.

Bigzmey wrote: ↑Fri Jan 29, 2021 2:42 am

TareqPhoto wrote: ↑Wed Jan 27, 2021 10:21 am Hi,

I want to know when buying a refractor, which is more important to have:

1. A triplet but with ED optics
2. A doublet but with Fluorite or FPL-53 optics

So if can't afford both or the type of scope i want can't be in both of above and only one of above, what will be the choice?

All scopes are well made and nice quality manufactured so no one will come to say that this build quality is better than the other one, so assume all are with excellent build quality.

You forgot quintuplet, surely 5 glass elements count for something.

I should say quality and design go together. If design has flows execution does not matter, and bad execution can trump a good design.

In selecting the right scope I would start with budget, after determining the right price range I would look at the application. For example for visual 60mm scope (and not just 60mm ) well executed doublet is all that you need.

Assume is that your scope is for photography, astro or terrestrial. In this case I will be of little help, but if you ask more specific questions you will get more productive answers. But, don't buy a scope just based on a type of glass.

It is only for astrophotography, visual is far away from my mind.

If i shouldn't buy the scope just based on a type of glass, then based on what exactly? Sometimes a budget is a factor, or it is a main factor.