12 replies to this topic

[buckeyestargazer]

I've read in various places that OK4 glass (which LZOS uses) is similar to FPL-53 glass. first of all, is this true? Second, if this is true, then why does it seem like the price point of refractors that use FPL-53 is lower than refractors that use LZOS glass?

What are the advantages/disadvantages between these glass types, if any?

[Mike Clemens]

FPL-53 advantage - Ohara sells it to anyone who wants to make lenses from it.

OK4 disadvantage - LZOS keeps it all to themselves and makes their own lenses.

FPL53 disadvantage - I could buy some and fashion a *BLEEP* lens from it and tell you it's made from killer FPL53 glass.

OK4 advantage - LZOS makes truly killer lenses with their glass.

I see you are a 115 owner so you know the color correction of OK4 LZOS SD triplets is irreproachable.

[buckeyestargazer]

FPL-53 advantage - Ohara sells it to anyone who wants to make lenses from it.

OK4 disadvantage - LZOS keeps it all to themselves and makes their own lenses.

FPL53 disadvantage - I could buy some and fashion a *BLEEP* lens from it and tell you it's made from killer FPL53 glass.

OK4 advantage - LZOS makes truly killer lenses with their glass.

I see you are a 115 owner so you know the color correction of OK4 LZOS SD triplets is irreproachable.

Yes, my 115mm LZOS refractor is unbeatable and I love it. "Not everything on the internet is true..." but I was still surprised to read that some people consider OK4 and FPL-53 glass to be very similar. I used to have an Orion EON 80mm and it too had very good views and color correction, using FPL-53. Also, the highly regarded TMB130ss uses FPL-53.

Is there a difference in manufacturing and figuring of the lens that accounts for quality control of LZOS vs. anybody's FPL-53, or is there a qualitative difference between the two glass types?

Would a person be insane to trade a 115mm LZOS for a 130mm FPL-53?

[jrcrilly]

Would a person be insane to trade a 115mm LZOS for a 130mm FPL-53?

Certainly not if it's from TEC, Takahashi or Astro-Physics! As stated above, FPL-53 is used by lots of folks, from low-end Chinese stuff to the very top of the line. It's what they do with the glass that counts.

[peleuba]

Is there a difference in manufacturing and figuring of the lens that accounts for quality control of LZOS vs. anybody's FPL-53, or is there a qualitative difference between the two glass types?

Yes, absolutely. LZOS is the real deal. They along with AP and TEC grind, polish, and test their own lenses. And, in my first hand experience are really superb.

Would a person be insane to trade a 115mm LZOS for a 130mm FPL-53?

Not necessarily. I would want test each telescope individually on my bench then side-by-side in the field. Then, keep the best one. I value optical quality over aperture. If the smaller scope was higher in quality I'd keep it. Others, I am sure believe aperture is king and for some objects it is. But I prefer quality of over size.

[Scott Beith]

I have a SV102V which has a LOMO doublet made with OK4 and I have the TMB 130SS which uses FPL-53.

Both are simply outstanding.

In this situation as long as the manufacturer supplies a lens with an excellent figure - you are good to go.

What you NEED is the 115 AND the 130!

[buckeyestargazer]

What you NEED is the 115 AND the 130!

No, what I NEED is the 115 and an APM175 LZOS...but it ain't gonna happen.

[Fomalhaut]

I value optical quality over aperture. If the smaller scope was higher in quality I'd keep it. Others, I am sure believe aperture is king and for some objects it is. But I prefer quality of over size.

+1
For me also, it's quality over quantity. There are enough folks in my personal surroundings whose buckets bring a lot of photons more or less into average focus . Yes, it's nice to occasionally look through one of them on star-parties. However, when it comes down to covet a certain scope or not then I value quality above quantity. Because in my own scope I do not want to see "more" but want to see it more bautifully than in most of the others'. This gives me the best illusion looking through the porthole of a scpaceship.
Additionaly, since the best scope is the one that you use most, portability is my second most important quality focusing my interest on a certain instrument...
Chris

[orion69]

I value optical quality over aperture. If the smaller scope was higher in quality I'd keep it. Others, I am sure believe aperture is king and for some objects it is. But I prefer quality of over size.

Well, depends...
In few days I'll order new astrograph. I was deciding between APM 130/780 LZOS and TS 150/1000 and I opted for TS (both with Riccardi 0.75x FF/FR).
I know that LZOS has better optical quality but I expect TS to be fairly close which, in my opinion, more than compensate with aperture. Mechanically both scopes should be very close because I'm ordering TS APO with Feathertouch 3.5" focuser. And TS is few hundreds euro cheaper...

[buckeyestargazer]

Knez,
I'll be very interested to hear your impressions of the TS 150. Please do let us know when you receive it and have a chance to test it out.

[orion69]

Will do...

[Jared]

Would a person be insane to trade a 115mm LZOS for a 130mm FPL-53?

If they were trading to get the FPL-53, yes. If they were trading to get the 130mm aperture, maybe not.

The partial dispersion numbers for OK-4 and FPL-53 are not all that different, and LZOS makes a superb objective. I wouldn't switch because of the materials--there should be some other reason to make the change. As others have said, you can make a terrible telescope with first rate glass, and you can make a first rate telescope with either OK4 or FPL-53 (or even FPL-51, though not quite as fast a scope for a given color correction).

[jrbarnett]

OK4 is made by an optics manufacturer in Russia called LZOS, and is not generally made available to other optics makers. FPL-53 is a glass made not by an optics maker, but rather by one of the world's largest optical glass makers, Ohara. Ohara makes FPL-53 in a variety of quality levels and sells to optics makers the world over. Lower quality will tend to have more bubbles, occlusions and striae, and will cause the lenses that it ends up in to be not as good as they would have been had a higher grade of FPL-53 been used. You the consumer, though, will NEVER know what quality level of FPL-53 your manufacturer is using. The price difference between the best and worst grades of FPL-53 is enormous (4x+). We don't know much about OK4 quality levels since mostly it ends up in optics made by LZOS. LZOS optics, though, are among the finest available so likely they are reasonably selective in the glass quality criteria they apply to their refractor optics business.

Glass quality is an order of magnitude more important than glass type when it comes to refractor performance. Similarly, the quality and selection of mating glasses is every bit as important as the type of ED glass used. You can make an FPL-51 triplet with a much better figure and much better color correction than an FPL-53 triplet of the same aperture. How? By making more sensible mating glass choices on the former than the latter, and by extending the focal length of the instrument. Buying any scope based on the type of ED glass used, alone, is a fool's game. Only gullible and the uniformed fall for that one. Believing that FPL-53 in any way ensures a better telescope is akin to believing that the requirement for higher octane fuel ensures a better automobile.

A telescope is a system. The ED element in a refractor is just one small component of that system. To really know what you're buying, you need to understand the key elements of the entire system. Knowing partial data for just one element tells you nothing.

More musings on the topic of recognizing when you're being "sold to" by a manufacturer promoting a feature that is more or less irrelevant and uninformative:

http://tinyurl.com/aepzr6r

Regards,

Jim