[COLOR="Blue"]Dear Floyd,
the glass used is called OK4, produced by LZOS.
“Fluorite” was a bit of a loose term, which could be construed to include “synthetic fluorite” or fluorite glass, especially since glasses like FPL-53 or OK4 are mainly made of fluorite (to what proportion, I do not know, because I am not an expert on the subject). For more info, you can also contact Markus Ludes, from whom we source these LOMO lenses.
Check here below how it was used in the past (you can use google groups to search…). As to WO, we have since amended the terminology of our products; the scope is not called triplet fluorite but SUPER APO; we will only use “fluorite” for CaF2.
A few months ago, we have already run a thread on our yahoo group about this. You can check Apr. 2006 for more discussions.
At the end of the day, it should make little difference what is inside, as long as it performs as it should. Design and execution are way more important that the glass inside, also because it is not the fluorite that makes the difference, but the mating glasses and overall design. But this is my personal opinion only.
For more info, please do not hesitate to contact me. Enjoy your scope, it is capable of a GREAT performance, you will see!
Best wishes and keep up the good work on Astro Mart, I always read your posts!
Daniel
[/COLOR]
This is made even more confusing to me because of the explanation I received yesterday, but I can understand that the person that I talked with may have confused OK4 with FPL53. Still, this is not exactly clear. I guess the written response is the better one and I will accept it as the facts in this case.
Ok, I would like to post the references made to Fluorite and FPL53. I will not post who made these statements because I do not have his permission. But it is easily seen that there is some use of the term Fluorite and FPL53 together and it appears that the FPL53 is indeed a type or derivative of Fluorite.
It does not really matter who wrote this I guess, but it is a well respected optician. I only post this to help in our understanding of this situation and to show how this misinterpretation might have occurred.
[COLOR="Red"]Ohara FPL 53 and Fluorite, CaF2, have almost identical optical characteristics.
FPL 53 is made primarily of Fluorite. CaF2 is made of layers of crystal planes,
while FPL53 is an homogenous glass that can be more easily polished and can be
coated with a protective hard multi-layer anti-reflection coating.
CaF2 is normally left uncoated since the crystal planes that are exposed when
the blank is cut and polished will interfere with the coating adhesion.
Extraordinary procedures are required to coat a CaF2 optic - very expensive to
do in production.
There is also an equivalent material available from another Japanese glass
maker that is much less expensive than Ohara FPL53. Again, it has similar
properties to CaF2.[/COLOR]
[COLOR="Red"]The Term E.D. stands for extra low dispersion, and it applies to a variety
of glasses, INCLUDING Fluorite. Thus, Fluorite refractors are actually ED
apochromats. Some ED glasses barely qualify for this term, so that a lens
made with this material can have significant color error. It is entirely
up to the manufacturer which E.D. material to use, and if the competitive
pressures are on, the manufacturer will, of course, use the cheapest
material, thus compromising the color correction. The best ED glass
(FPL53) is every bit as good as Fluorite in correcting for color and other
aberrations. This ED glass is actually made from Fluorite and costs more.
The only difference is in the far U.V. transmission (3500A and below)
where fluorite is superior. [/COLOR]
[COLOR="Red"]will try to correct you. The "Fluorite-Glass" blend you refer to is Ohara
FPL53 which is superior to crystalline fluorite and costs a bundle more. It is
almost totally pure fluorite with certain additives to make it a glass instead
of crystal.
According to my sources in Japan, no one there uses the old crystalline
material anymore. They ALL use either FPL53 or the older FPL52 because of its
superior workability and stability during polishing. The labor time required
for finishing an FPL53 lens vs. a pure fluorite lens is 5 times less. Some
companies refer to this new material as fluorite, some call it fluorite-ED and
some call it SD. The only pure fluorite lenses now made come out of China where
the labor rate is still very low. I dont know of any telescope companies using
Chinese made fluorite lenses. [/COLOR]
Now, where does this leave us as far as understanding the use of the term Fluorite? I think it does make it a bit more clear that the terminology used for the materials in objectives is a bit loose at times and perhaps confusing even for those in the industry.
Perhaps William Optics was not so far off after all? :S
the glass used is called OK4, produced by LZOS.
“Fluorite” was a bit of a loose term, which could be construed to include “synthetic fluorite” or fluorite glass, especially since glasses like FPL-53 or OK4 are mainly made of fluorite (to what proportion, I do not know, because I am not an expert on the subject). For more info, you can also contact Markus Ludes, from whom we source these LOMO lenses.
Check here below how it was used in the past (you can use google groups to search…). As to WO, we have since amended the terminology of our products; the scope is not called triplet fluorite but SUPER APO; we will only use “fluorite” for CaF2.
A few months ago, we have already run a thread on our yahoo group about this. You can check Apr. 2006 for more discussions.
At the end of the day, it should make little difference what is inside, as long as it performs as it should. Design and execution are way more important that the glass inside, also because it is not the fluorite that makes the difference, but the mating glasses and overall design. But this is my personal opinion only.
For more info, please do not hesitate to contact me. Enjoy your scope, it is capable of a GREAT performance, you will see!
Best wishes and keep up the good work on Astro Mart, I always read your posts!
Daniel
[/COLOR]
This is made even more confusing to me because of the explanation I received yesterday, but I can understand that the person that I talked with may have confused OK4 with FPL53. Still, this is not exactly clear. I guess the written response is the better one and I will accept it as the facts in this case.
Ok, I would like to post the references made to Fluorite and FPL53. I will not post who made these statements because I do not have his permission. But it is easily seen that there is some use of the term Fluorite and FPL53 together and it appears that the FPL53 is indeed a type or derivative of Fluorite.
It does not really matter who wrote this I guess, but it is a well respected optician. I only post this to help in our understanding of this situation and to show how this misinterpretation might have occurred.
[COLOR="Red"]Ohara FPL 53 and Fluorite, CaF2, have almost identical optical characteristics.
FPL 53 is made primarily of Fluorite. CaF2 is made of layers of crystal planes,
while FPL53 is an homogenous glass that can be more easily polished and can be
coated with a protective hard multi-layer anti-reflection coating.
CaF2 is normally left uncoated since the crystal planes that are exposed when
the blank is cut and polished will interfere with the coating adhesion.
Extraordinary procedures are required to coat a CaF2 optic - very expensive to
do in production.
There is also an equivalent material available from another Japanese glass
maker that is much less expensive than Ohara FPL53. Again, it has similar
properties to CaF2.[/COLOR]
[COLOR="Red"]The Term E.D. stands for extra low dispersion, and it applies to a variety
of glasses, INCLUDING Fluorite. Thus, Fluorite refractors are actually ED
apochromats. Some ED glasses barely qualify for this term, so that a lens
made with this material can have significant color error. It is entirely
up to the manufacturer which E.D. material to use, and if the competitive
pressures are on, the manufacturer will, of course, use the cheapest
material, thus compromising the color correction. The best ED glass
(FPL53) is every bit as good as Fluorite in correcting for color and other
aberrations. This ED glass is actually made from Fluorite and costs more.
The only difference is in the far U.V. transmission (3500A and below)
where fluorite is superior. [/COLOR]
[COLOR="Red"]will try to correct you. The "Fluorite-Glass" blend you refer to is Ohara
FPL53 which is superior to crystalline fluorite and costs a bundle more. It is
almost totally pure fluorite with certain additives to make it a glass instead
of crystal.
According to my sources in Japan, no one there uses the old crystalline
material anymore. They ALL use either FPL53 or the older FPL52 because of its
superior workability and stability during polishing. The labor time required
for finishing an FPL53 lens vs. a pure fluorite lens is 5 times less. Some
companies refer to this new material as fluorite, some call it fluorite-ED and
some call it SD. The only pure fluorite lenses now made come out of China where
the labor rate is still very low. I dont know of any telescope companies using
Chinese made fluorite lenses. [/COLOR]
Now, where does this leave us as far as understanding the use of the term Fluorite? I think it does make it a bit more clear that the terminology used for the materials in objectives is a bit loose at times and perhaps confusing even for those in the industry.
Perhaps William Optics was not so far off after all? :S
[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue
Amateur Imager
