Chinese now making ED glass!!

[GazOC]

Well it had to happen eventually......

http://www.azurephotonics.com/material/optical/introduction.htm

This is pretty big news, previous to this even the Chinese made Synta/ Revelation etc EDs had their FPL components made in Japan and shipped over to China for assembly. Now it looks like the Chinese are making their own (and a lot cheaper I believe), from this chart theres no FPL-53 counterpart yet just a FPL-51 but I'm sure a 53 will be on its way shortly. There should be some interesting scopes coming over the next year or so based on this development...large sized, 51 based apos are going to be a lot more affordable I reckon.

[Rob]

Oh... thats good news!

[SteelRat]

There should be some interesting scopes coming over the next year or so based on this development

SW Evostar 150 ED edition approaches then eh? :shock:

Good find Gaz.

[Zeffer]

I haven't even looked through the ED100 yet

Does this mean that soon there'll be 'glass made in Japan' on all the 2nd hand adverts whether or not it's better?

Affordable 6 inch apo. Look good on MartinB's Tak!

[lunator]

This could be the start of something good

A nice 8" F9 Apo for £500 would be fantastic

[SteelRat]

This could be the start of something good

A nice 8" F9 Apo for £500 would be fantastic

8)

[cygnusx1]

Hmmm we can dream....would the importers pass on the savings

[Ant]

I think (hope) that they would.

The chinese are very good at making stuff - beleive it or not they have trouble with good quality stainless steel! Japanese is much better!

So what you might find is that the cheaper APO's (I use the term loosely) made from chinese glass will be not quite be as good as the APO's made from glass from Japan - but still a significant step between an Achro and APO. Maybe 80% of the way there - but japanese is 99%...

But regardless exciting time ahead!

Ant

[cygnusx1]

Right, i make no claim to know much about refractors or APO's or Achro's, BUT

how does one really know what you getting?

I recently bought a Scopos classified as a APO, however i notice vignetting in the corners of my images and false colour in the stars.

Maybe im expecting too much, or perhaps its my setup, but my point being the quality could be anything from cheap achro plastic to super APO!!

P.S its really a nice little scope, make no mistake, was just expecting its imaging properties to be better

[Ant]

I think that this is the problem - there is no clear definition as to what an APO is...

My scope is an APO - it must be it says it on the lens cell - I have seen no false colour yet but I haven't images M45 yet, if you gonna get false colour it'll be on them...

I beleive that it is not possible to correct for false colour 100% (might be wrong), and that high and APO's get to something like 99%+, my scope has FPL51 glass so can maybe get to 97% (I'm now making the figures up as an example), FPL53 might get to 98%?

Achro's could be down to 60% maybe... But if you have glass that corrects to much better than Achro's but not as good as the FPL51 (maybe 95%) is it an APO?

If it is then what about glass that gets to 94%, if yes what about 93%.

I'm sure you can see where I'm going with this? The bounderies between Achro and APO are blurred.

Vignetting isn't anything to do with the quality of glass, more the size of the chip and the size of the hole.

Ant

[ianc]

Hi cygnusx1,

The only failsafe way is to buy a reputable brand on trust & if it does not perform as an APO should to their claims.

Stick it back where the sun don't shine!!

Cheers Ian

[Brass n glass]

there is no clear definition as to what an APO is

It used to be quite a bit clearer. I have a 1997 Vixen catalogue which makes a clear distinction between the "ED apo" version of a refractor (an element of extra-low dispersion glass in the objective) and the much more expensive "fluorite apo" version. These days the apo label gets stuck on just about anything that can claim that it isn't a plain old-fashioned achromatic - Hugh.

[lunator]

My view is that an APO should have 3 elements so that the three clours can be brought to correct focus.

Any 2 element refractor can achieve apo-like performance but isn't an APO.

This is just my opinion

Cheers

ian

[MartinB]

This is my idea of an apo - if the images through R, G and B filters are exactly par focal it's an apo!

[Brass n glass]

I've noticed that some companies add to the confusion by talking about semi apos - presumably that doesn't mean they slice the objective in half - Hugh

[John]

I have a 1997 Vixen catalogue which makes a clear distinction between the "ED apo" version of a refractor (an element of extra-low dispersion glass in the objective) and the much more expensive "fluorite apo" version.

Hugh,

Does that catalogue cover the Vixen ED102SS ? - if so, is there any chance you could scan the relevent page and e.mail a pic to me ? - I'm trying to find out more about my ED102SS you see.

Cheers,

John

[Brass n glass]

Scan? Is that something you do by turning a big brass handle? I'm afraid I'm not very technological; I've never had a goto mount, for example, and until I came onto SGL I thought Registax was something you had to do if the Vatman came after you. But I'm sure I can find someone with one of these scanner things. There's loads of stuff in the catalogue and I also have a French one from a few years later. The f9 telescope is called an ED102S (not SS).

You can certainly see what inspired the Skywatcher ED100. The 2000 catalogue from Medas, the French distributor, has the f6.5 version, which I think is the SS. Their price for the OTA was 14,148 francs, which from memory was quite a lot of money. There's a detailed review (in Italian I'm afraid, and why on earth did they scrub off the white paint?) at http://www.sidus.org/proveStrumenti/telescopi/vix102ss.html . They like it a lot - Hugh.

[Kaptain Klevtsov]

This is my idea of an apo - if the images through R, G and B filters are exactly par focal it's an apo!

Maybe you could get a set of RGB filters matched to an Achro. to make it parfocal with the specific filters?

Kaptain klevtsov

[GordonCopestake]

I've always thought if you had 3 pure RGB filters you could image happily through an achro, you just need to focus each time you change the filter. People do that with APO's too for some odd reason

[Kaptain Klevtsov]

I've done it Gordon, so if you use RGB filters, or better still narrowband filters, you can use any old lump of bottle bottom and get a nice image, so long as you refocus for each filter. My ST80 is ace with the Ha filter as there's NO out of focus halo stuff due to the monochromatic light getting through the filter.

What I was wondering is, if you got filters that were made so that you didn't need to refocus between filters, that would be ace.

In real life terms though, I wonder how my 120mm Evostar compares to an ED120 when using the RGB method?

Kaptain Klevstov

[GordonCopestake]

Theres a project for a rainy day.... oh no wait.... theres a project for a clear night