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FLO

Prototype Sky-Watcher Evolux ED Refractors

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Posted (edited)

For sure it is not FPL53.

But what's important is if the glass is FPL53 "like" (FPL55, FC100) or if the glass is FPL51 "like" (FPL51, FC1, HK61).

I think a direct comparison (star test at high magnification) of the Evostar 80mm ED with this new Evolux should reveal the truth. The Evolux has almost the same diameter but it is a bit faster than the Evostar. If they are using an inferior glass (FP51 equivalent), chromatic aberration should be noticeable higher than CA in the Evostar 80ED.

Edited by Rick_It
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When a manufacturer chooses to omit specification on items that are important to performance, it puts me off buying.

This applies to any product, not just a scope.

If Skywatcher aren't telling, then either they have some wonderful new materials and methods they want to keep secret.
Or they want to leave the door open for future cost saving.
Or the product does not exist.

My suspicion would be that the first batch of new scopes would use good glass, stainless screws, metal tubes and brackets, etc.

Then later when are all blown away by the product and fighting to get stock....
Would they be tempted to put milk bottle glass in the end with push fittings to avoid screws in the plastic drainpipe tube?
OK an extreme example, but you get the idea.

We all have experienced or heard of products where certain years or marks or revisions are better.

In astronomy, I remember people asking for photos of Meade 4000 eyepieces before buying used.
This was to ascertain the quality. Some were known to be better than others.

In cars we all know about certain model years having a noisy engine fan, or missing vents, or other annoyances in different runs of the same model.

Just my two pennorth.

David.

 

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8 minutes ago, johninderby said:

That would have been my uneducated guess

Carbon Brush brings up an interesting point, by not specifying glass type there's nothing to stop Skywatcher changing over to different (poorer?) glass type at some point in the future which renders all the previous reviews and owners recommendations pretty much obsolete. 

At the moment if you buy any Skywatcher ED or triplet (bar the ED150) you at least have that guarantee of consistent material type 

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The issue with FPL-53 at one stage seemed to be its continuing availability - there were rumours that Ohara were going to reduce or phase out it's production. But since then I've seen quite a few new scopes coming into the market which specify at least one and sometimes more FPL-53 elements and some in quite large sizes so it seems that, for now, the future supply of FPL-53 is secure. Its price though will be of concern to the manufacturer of lower priced ED refractors - As of 2017, FPL53 glass cost around 20% more than FPL-55 and nearly 100% more than FPL-51.

 

 

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I've never looked through a FPL 55 refractor but if the numbers tell the full tale I'd be surprised if you could tell the difference, at least visually, in between that and FPL 53 scope (with the usual caveat of all other things being equal)

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I thought that FPL 55 glass was supposed to be superior to FPL 53 (although only marginally so), CFF state that their larger refractors use FPL 55, and give the impression that this is the case.

John 

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Posted (edited)
24 minutes ago, johnturley said:

I thought that FPL 55 glass was supposed to be superior to FPL 53 (although only marginally so), CFF state that their larger refractors use FPL 55, and give the impression that this is the case.

John 

The limited info I've seen on it is that 53 corrects CA slightly better than 55 has but that 55 has slightly better "polishing properties" whatever exactly that means 

 

I could be wrong though...

Edited by GazOC
Typo

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Perhaps Skywatcher are using Fluorite. Since Large deposits are available in China, why would they not exploit that, and encourage the Apo fraternity to their product.  

Heh Heh, perhaps I'm hallucinating.                                   Ron.

 

 

 

 

 

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I know that Yuri at TEC has moved from using fpl 53 glass to fluorite due to availability for the tec 140. 
 

At this price point I’d doubt it would be very high end fpl 53 or the like. 
 

That being said skywatcher still produces some fantastic refractors and I would certainly buy one again! 

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1 hour ago, barkis said:

Perhaps Skywatcher are using Fluorite. Since Large deposits are available in China, why would they not exploit that, and encourage the Apo fraternity to their product.  

Heh Heh, perhaps I'm hallucinating.                                   Ron.

 

 

 

 

 

Skywatcher don't advertise that any of their refractors utilise fluorite, and if this was the case I think that they would.

John  

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Thanks for the reply John, some good points made - I'd forgotten the blue ones came out first, it must have been an age thing 😃.

I agree with you that many (not all!) people are rather obsessed with specs, do listen to rumours and may be wary  of what they may see as a 'suspicious' lack of detail in specifications.

I would still say though that for me it's the view that does more talking than any spec (or reputation) does.  A better specification doesn't necessarily mean a better performance.  Over the years I have done quite a few side by side comparisons with telescopes (not necessarily my own) when the lesser specified and/or much cheaper scope has out performed what on paper would appear should have been much better performing scope.

I can easily think of a couple of cases I have witnessed when an owner of a highly specified (and expensive) scope has been somewhat aghast and amazed when their wonderfully expensive pride and joy has been easily defeated by a much humbler specified and much cheaper scope. The person has then gone on the sell their scope to replace it with the cheaper alternative. 

For me a side by side comparison in a real-life observing situation speaks volumes more than any spec sheets ever can do.  Specs can be an indication of potential performance of course, but they aren't the whole story.

 

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Posted (edited)

As you say Paul, in an ideal world we would be able to test our purchases before buying and then decide but, at least for me, it's just not an option  most cases

Pretty much all my astro purchases have had to be made on a spec sheet and word of mouth (which is notoriously risky where refractors are concerned, everyone seems to love THEIR refractor 😉

Edited by GazOC
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Posted (edited)

IMHO, when characteristics are not fully declared, it is a safe assumption to assume for the minimum / cheapest specifications. In this case, as the scope is still advertised as ED, I assume HK61 (chinese copy, and slightly worse, of FPL51).

Then, if someone tells me that CA is on par with the ED80 (FPL53), I will change my mind. But, if this is the case (and SW is using FPL55 or FC100), then this is really a crazy marketing strategy. If you are using a good glass, why don't you declare it?

Edited by Rick_It
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Posted (edited)

I don't think that the glass type matters as much as the overall performance (optical design, polish, F/ratio, etch) .

To put it in other words, how can anyone test if his fpl53 objective, is truly an fpl53??? 🤔

Edited by R26 oldtimer
Correct autocorrect
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On 08/01/2020 at 10:16, Rick_It said:

For sure it is not FPL53.

But what's important is if the glass is FPL53 "like" (FPL55, FC100) or if the glass is FPL51 "like" (FPL51, FC1, HK61).

I think a direct comparison (star test at high magnification) of the Evostar 80mm ED with this new Evolux should reveal the truth. The Evolux has almost the same diameter but it is a bit faster than the Evostar. If they are using an inferior glass (FP51 equivalent), chromatic aberration should be noticeable higher than CA in the Evostar 80ED.

Its almost certainly FPL55 or much more likely FCD100 as you say, this is a more premium scope than the EvoStar so I would be extremely shocked if they used a FPL51 class of glass in it, it would show up immediately and no one would buy a scope costing more than the EvoStar but with inferior performance. They just would not get away with it and I think they know that. 

I would personally be happy to take a change on the 62mm scope as a lead customer, skywatcher have a good reputation. 

Adam 

 

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Posted (edited)
20 hours ago, GazOC said:

The limited info I've seen on it is that 53 corrects CA slightly better than 55 has but that 55 has slightly better "polishing properties" whatever exactly that means 

 

I could be wrong though...

FPL55 and FCD100 are both harder than FPL53 and the increased hardness makes it easier to achieve a precise finish and shape. Also its not all about the Crown its about the flint too and although FCD100 is slightly more dispersing than FPL53 I have heard it said that the flint glass better matches its properties and so the combination of the two glass types may actually out perform FPL53 combinations. In theory the same may be true of FPL55 but my guess is FCD100 is being used here. 

Edited by Adam J
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1 hour ago, Adam J said:

FPL55 and FCD100 are both harder than FPL53 and the increased hardness makes it easier to achieve a precise finish and shape. Also its not all about the Crown its about the flint too and although FCD100 is slightly more dispersing than FPL53 I have heard it said that the flint glass better matches its properties and so the combination of the two glass types may actually out perform FPL53 combinations. In theory the same may be true of FPL55 but my guess is FCD100 is being used here. 

I believe Astro Physics have used FCD100 in their latest incarnation of the Stowaway triplet ?

 

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Posted (edited)

What will be the biggest frac in this range or has this not been confirmed 

I quite fancy a Evostar ED doublet after seeing one at IAS in November but thinking one of these maybe worth the wait. 

thanks.  John 

Edited by Telescope40

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8 hours ago, R26 oldtimer said:

I don't think that the glass type matters as much as the overall performance (optical design, polish, F/ratio, etch) .

To put it in other words, how can anyone test if his fpl53 objective, is truly an fpl53??? 🤔

Given a particular focal ratio, it is the glass types which determine the level of Chromatic Aberration correction that is possible, not the surface polish or accuracy of the surfaces of the lenses.

Regards.

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It would be interesting to find out what glass and crown is used in the ed72, as the correction seems very good. 

I wonder if someone like Es Reid would be able to tell if a scope was sent to him.

Nadeem

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You can derive the refractive index and the Abbe number of a glass, but this require dismantling the scope and testing the single lens using professional equipments.

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On ‎10‎/‎01‎/‎2020 at 09:44, Skyline said:

It would be interesting to find out what glass and crown is used in the ed72, as the correction seems very good. 

I wonder if someone like Es Reid would be able to tell if a scope was sent to him.

Nadeem

I agree with you Nadeem, I think the ED72 is excellent.

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I see SW Australia is listing the Evolux scopes on there site with other Australian retailers also listing them saying April-May release. 
https://skywatcheraustralia.com.au/product-category/otas/evolux/

Going by Google’s exchange rate and the price listed by SW Australia the 62ED is coming in at £352 and the 82 £704. There is an optional  0.9 FF/FR available to.  Not sure if there prices include tax/vat but I guess it’s a ballpark figure price wise. 

Edited by Danjc

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