so called new approach to design doublet APOs. ;>)

From: "tmboptical" TMBoptical@a...
Date: Thu Nov 18, 2004 10:11 am
Subject: Optical Details on the Burgess 92mm Fluorite Apo


With Tom Davis' excellent review of the Burgess 92mm fluorite
apochromat, and for a doublet, its color free performance, I
thought it is the right time to explain why this telescope
is so special.

All current doublet ED and fluorite doublets that are on the
market today are not true apochromats. You may want to read
the correct definition of what a true apochromat is on my web
site at:

http://www.tmboptical.com/itemsGrid.asp?cat_id=32

The ED and fluorite doublets refractors (even the highest
quality), do not have three color crossings, where three
widely spaced colors come to the same focus. They also all
have a significant amount of out of focus violet. This may
not be apparent at first, but when you compare, say a Tak
doublet fluorite to a true triplet apochromat (TMB, AP),
or a Newtonian, on a bright object, you then can easily
notice the yellowish coloration, and the violet halo
around stars like Vega or a planet (in a dark sky) like
Venus, at high power.

This is because all ED and fluorite designs use a matching
flint glass, such as KF-3, KzF-2, and other flints that are
at the same general point in the partial dispersion area on
the glass charts. The partial dispersions of these flints do
not match up well in the violet and very deep red, to the ED
or fluorite elements, and the result is visible color.

Now you might ask, how is it that the Burgess fluorite
doublet can have so much better color correction, so much
so that there is no color in focus at all, and only the
smallest trace of out of focus color on a star like Vega,
and that assumes that you have good color vision, and know
how to look for very small color errors.

The secret is that the Burgess fluorite doublet uses a
special crown element with the fluorite. Again, on the
partial dispersion glass chart, you can see that this
special crown glass has almost a perfect partial match
to fluorite, and thus, the one element cancels the color
of the other element to an exceedingly high degree. So much
that it has the color correction of a triplet lens, and
like a high quality triplet apo, has three color crossings
too.

This is the ultimate way to make a production fluorite
doublet. I have designs on my computer using the same
fluorite/crown glass at larger apertures, that have the
same or better color correction, at only a small increase
in focal ratio. Or, in other words, this lens scales up
nicely, and can give the same color free performance in
larger apertures.

This is truly a new level of performance in the fluorite
and ED doublet market. We are very proud that we can bring
this product out to the marketplace, and at a price that is
more than competitive.

Thomas Back
TMB Optical

================================================== ===============

Dear Mr. Back,

Sure, your self-confidence has no limits. And as one, well known
in optical design and manufacturing, person said, someday your head
will explode due to your unlimited self-confidence.

I should mention specially for your instance, that ARIES 7" F/8
Fluorite
objective you saw at one StarParty (AstroFest?) which was with
cracked fluorite element has the design, which is essentialy the same,
as you called "truly a new level of performance in the fluorite
and ED doublet market". Also, I should to note, that these ARIES
objectives were designed and made about 7 years ago. The largest one
was 12" F/9. And right now we making tubes for a serie of 6 such 7"
F/8
Fluorite doublets.
It will be useful to note also, that these doublets has color
correction,
that in 430nm-656nm range, is same good as LZOS made TMB 6" F/8 Super
SD TRIPLET. And, of course, such objectives has better contrast, that
these
triplets (include 175mm ones) because they have two surfaces less,
shorter
lightpass in the glasses. These doublets also have significantly
shorter
colldown time. Objectives have lesser mass and a telescope has better
balance.

Of course, I am not a first person, who know this approach to APO
doublets
design and manufacturing. So, this approach to design can't be called
as
"truly new level". Please, note this specially for yourself.


VD

"ValeryD" wrote in message
om...
Dear Mr. Back,

Sure, your self-confidence has no limits. And as one, well known
in optical design and manufacturing, person said, someday your head
will explode due to your unlimited self-confidence.

I should mention specially for your instance, that ARIES 7" F/8
Fluorite
objective you saw at one StarParty (AstroFest?) which was with
cracked fluorite element has the design, which is essentialy the same,
as you called "truly a new level of performance in the fluorite
and ED doublet market". Also, I should to note, that these ARIES
objectives were designed and made about 7 years ago. The largest one
was 12" F/9. And right now we making tubes for a serie of 6 such 7"
F/8
Fluorite doublets.
It will be useful to note also, that these doublets has color
correction,
that in 430nm-656nm range, is same good as LZOS made TMB 6" F/8 Super
SD TRIPLET. And, of course, such objectives has better contrast, that
these
triplets (include 175mm ones) because they have two surfaces less,
shorter
lightpass in the glasses. These doublets also have significantly
shorter
colldown time. Objectives have lesser mass and a telescope has better
balance.

Of course, I am not a first person, who know this approach to APO
doublets
design and manufacturing. So, this approach to design can't be called
as
"truly new level". Please, note this specially for yourself.


VD

Valery,

I think a bit of clarification is needed here. This lens is not a TMB
design,
it is one of the Chinese manufacturer. What is amazing here is that they
are doing this to a high quality level at such a low price. In this
respect,
it is a truly new level, as it brings high performance optics down to a
price point many more will be able to afford. This is the sort of thing
you have attempted to accomplish with the Chromacor.

What this scope represents is the first true APO design from China. I
own an Orion 80ED along with the new Burgess fluorite, and have
done enough side-by-side comparison of these two scopes to know
the fluorite is better corrected in every way. I can detect zero color
on this scope on any object in-focus, and only the barest traces of
color in the rings outside of focus on Sirius, and that is so subtle as
to be almost non-existent. Besides that, the star images are clearly
tighter than the 80ED, and contrast is noticeably better as well.
It takes Chinese optics to the next level.

I've seen way too many personal attacks between optical manufacturers
of late. As I had experienced with the Chromacor, I have been taking
the brunt of the bashing over this product as well. I have been willing
to do so because I believe it is a product that others will really be
pleased
to own an use, and I wanted its merits to become known before others
managed to make it disappear, or worse yet, someone like Meade or
Orion snatched it up and charged twice the price for it.

As for your designs and their capabilities, I have a great deal of respect
for them. I have no doubts you came up with a similar design well before
this. Again, the real point to this is that other than high-end optical
manufacturers like yourself or Roland (who has also come up with some
fine doublet designs in the past), none of the more common manufacturers
are using this type of design. To make this design available at such a
low price point is the real innovation here. I applaud Bill and Thomas for
passing the cost savings on to the rest of us rather than profit gouging
as is the common practice in business today (in general, forget optics
here).

Thanks, Tom Davis

"Tom Davis" wrote in message

Valery,

I think a bit of clarification is needed here. This lens is not a TMB
design,
it is one of the Chinese manufacturer. What is amazing here is that they
are doing this to a high quality level at such a low price.

What is the price? Is there a place to see/buy this scope or is it "in the
planning stage"?

Ed T.

What is amazing here is that they
are doing this to a high quality level at such a low price

What is the price going to be?

Roland Christen

"Chris1011" wrote in message
...
What is amazing here is that they
are doing this to a high quality level at such a low price

What is the price going to be?

Roland Christen

Roland,

I'm not entirely sure on this. I'm fairly sure that they will start out
under
$1000. What I think may affect this is the level of content that will
be packaged with the scope. The early quoted prices were for a scope
with lesser mechanics and I do not believe included the WO dialectric
diagonal (rather a less expensive enhanced aluminum unit). Also, I
believe which eyepieces will ship with it have not been decided. Since
I bought essentially a stripped unit (one-off WO case with no provision
for accessories), no diagonal or eyepieces, I can't really peg a price
based on my experience. At best I can ballpark it somewhere under
$1000. This is still quite a price for the quality of the optics and the
level of content. Since production has already started, I'm sure Bill
will put out a post soon with the final content of the package and the
final price to customers. I think my guess is fairly close, though.

Thanks, Tom Davis

Aaaaaaah Soo! Charlie Chan was right!

Mark



Tom Davis wrote:

"ValeryD" wrote in message
om...
Dear Mr. Back,

Sure, your self-confidence has no limits. And as one, well known
in optical design and manufacturing, person said, someday your head
will explode due to your unlimited self-confidence.

I should mention specially for your instance, that ARIES 7" F/8
Fluorite
objective you saw at one StarParty (AstroFest?) which was with
cracked fluorite element has the design, which is essentialy the same,
as you called "truly a new level of performance in the fluorite
and ED doublet market". Also, I should to note, that these ARIES
objectives were designed and made about 7 years ago. The largest one
was 12" F/9. And right now we making tubes for a serie of 6 such 7"
F/8
Fluorite doublets.
It will be useful to note also, that these doublets has color
correction,
that in 430nm-656nm range, is same good as LZOS made TMB 6" F/8 Super
SD TRIPLET. And, of course, such objectives has better contrast, that
these
triplets (include 175mm ones) because they have two surfaces less,
shorter
lightpass in the glasses. These doublets also have significantly
shorter
colldown time. Objectives have lesser mass and a telescope has better
balance.

Of course, I am not a first person, who know this approach to APO
doublets
design and manufacturing. So, this approach to design can't be called
as
"truly new level". Please, note this specially for yourself.


VD

Valery,

I think a bit of clarification is needed here. This lens is not a TMB
design,
it is one of the Chinese manufacturer. What is amazing here is that they
are doing this to a high quality level at such a low price. In this
respect,
it is a truly new level, as it brings high performance optics down to a
price point many more will be able to afford. This is the sort of thing
you have attempted to accomplish with the Chromacor.

What this scope represents is the first true APO design from China. I
own an Orion 80ED along with the new Burgess fluorite, and have
done enough side-by-side comparison of these two scopes to know
the fluorite is better corrected in every way. I can detect zero color
on this scope on any object in-focus, and only the barest traces of
color in the rings outside of focus on Sirius, and that is so subtle as
to be almost non-existent. Besides that, the star images are clearly
tighter than the 80ED, and contrast is noticeably better as well.
It takes Chinese optics to the next level.

I've seen way too many personal attacks between optical manufacturers
of late. As I had experienced with the Chromacor, I have been taking
the brunt of the bashing over this product as well. I have been willing
to do so because I believe it is a product that others will really be
pleased
to own an use, and I wanted its merits to become known before others
managed to make it disappear, or worse yet, someone like Meade or
Orion snatched it up and charged twice the price for it.

As for your designs and their capabilities, I have a great deal of respect
for them. I have no doubts you came up with a similar design well before
this. Again, the real point to this is that other than high-end optical
manufacturers like yourself or Roland (who has also come up with some
fine doublet designs in the past), none of the more common manufacturers
are using this type of design. To make this design available at such a
low price point is the real innovation here. I applaud Bill and Thomas for
passing the cost savings on to the rest of us rather than profit gouging
as is the common practice in business today (in general, forget optics
here).

Thanks, Tom Davis

"Tom Davis" wrote in message m...
Valery,

I think a bit of clarification is needed here. This lens is not a
TMB
design,
it is one of the Chinese manufacturer. What is amazing here is that they
are doing this to a high quality level at such a low price. In this
respect,
it is a truly new level, as it brings high performance optics down to a
price point many more will be able to afford. This is the sort of thing
you have attempted to accomplish with the Chromacor.

What this scope represents is the first true APO design from China. I
own an Orion 80ED along with the new Burgess fluorite, and have
done enough side-by-side comparison of these two scopes to know
the fluorite is better corrected in every way. I can detect zero color
on this scope on any object in-focus, and only the barest traces of
color in the rings outside of focus on Sirius, and that is so subtle as
to be almost non-existent. Besides that, the star images are clearly
tighter than the 80ED, and contrast is noticeably better as well.
It takes Chinese optics to the next level.

I've seen way too many personal attacks between optical manufacturers
of late. As I had experienced with the Chromacor, I have been taking
the brunt of the bashing over this product as well. I have been willing
to do so because I believe it is a product that others will really be
pleased
to own an use, and I wanted its merits to become known before others
managed to make it disappear, or worse yet, someone like Meade or
Orion snatched it up and charged twice the price for it.

As for your designs and their capabilities, I have a great deal of respect
for them. I have no doubts you came up with a similar design well before
this. Again, the real point to this is that other than high-end optical
manufacturers like yourself or Roland (who has also come up with some
fine doublet designs in the past), none of the more common manufacturers
are using this type of design. To make this design available at such a
low price point is the real innovation here. I applaud Bill and Thomas for
passing the cost savings on to the rest of us rather than profit gouging
as is the common practice in business today (in general, forget optics
here).

Thanks, Tom Davis

Tom,

The problem is that Mr.Back tried to create an impression, that ALL
doublets
on the market were not true apochromats. And this is not true.

Such designs as KzFSN2+CaF2, FPL53+ZKN7, LaK8+CaF2 etc, etc has zero
secondary
spectrum within entire visual spectrum. These designs were well know
far
before Mr.Back began to play with his Zemax version. Some of them were
MADE
serially by Roland Christen in size 5" and 6".
Our first doublets of 7" (!) were MADE just a year or two after
Mr.Back has began his Zemax learning curve. And they have 3 crossings
and show zero color
in focus on any celestial and terrestial light sources.
We also can easily remind, that former Celestron's 4" F/9 Fluorite
doublets
were completely free of secondary color in focus.

So, these BO objectives are not a new level in design/performance in
APO
manufacturing. In fact, they are old enough in design and just tiny vs
some other doublets made many years ago. The only "innovation" is very
low price - this is not Tom's or Bill's achievement, just a chinese
reality.
Tom should be more modest and honest in his claims.


I think a bit of clarification is needed here. This lens is not a TMB
design, it is one of the Chinese manufacturer.

???? How about this statement from Tom's speaker?

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From: "Norman L. Rubenstein" nlr@r...
Date: Fri Nov 19, 2004 8:38 pm
Subject: NEW INFORMATION RE THE 92mm FLOURITE APO


Dear List Members:

TMB asked me to post the following additional information for you all
concerning the new 92mm Flourite Apo scopes:

The Burgess 92mm doublet fluorite uses a crown glass as the second
element
that has an exceptional Abbe separation from the fluorite element,
much more
in fact than the ZKN-7 that was used in Roland's 130mm f/8 and 155mm
f/9 ED
doublets. We also are using longer focal ratios, the combination
lowering
sphero-chromatism to quite low levels. This is shown by the low RMS
wavefront values from g to h (violet to deep red).
----------------------------------------------------------------------------

The key phrase is: "We also are using longer focal ratios".


Such marketing approach does not make Bill's and Tom's products
better.
They both many times said, that their products will speak for
theirselves.
Nobody saw these products so far, but quite a few peoples have heard
such
a marketing hype.
Let Bill and Tom follow their own promises.


VD

Such marketing approach does not make Bill's and Tom's products
better.
They both many times said, that their products will speak for
theirselves.
Nobody saw these products so far, but quite a few peoples have heard
such
a marketing hype.
Let Bill and Tom follow their own promises.


VD

Valery

when I going to see your new douplet Apo's ? Can we fight with your
scope against this chinese revolution , pricewise or quality wise ?

Markus




--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

On Mon, 22 Nov 2004 19:10:36 +0000 (UTC), "Markus Ludes"
wrote:

Such marketing approach does not make Bill's and Tom's products
better.
They both many times said, that their products will speak for
theirselves.
Nobody saw these products so far, but quite a few peoples have heard
such
a marketing hype.
Let Bill and Tom follow their own promises.


VD

Valery

when I going to see your new douplet Apo's ? Can we fight with your
scope against this chinese revolution , pricewise or quality wise ?

Markus

I've got a question. Meade makes their little (90mm-125mm) Maks on
a machine, no hand work. They seem to achieve very good surfaces
with it. Why can't spherical apo elements be made
in the same way, or can they? Would this help control costs or is the
glass cost the overwhelming factor?

"RichA" wrote in message
...

I've got a question. Meade makes their little (90mm-125mm) Maks on
a machine, no hand work. They seem to achieve very good surfaces
with it. Why can't spherical apo elements be made
in the same way, or can they? Would this help control costs or is the
glass cost the overwhelming factor?

I suspect all the optics in China is being made on expensive machines, and
go directly from the final polish into the coating lab. I doubt very much
they have opticians on the payroll carefully handfiguring anything. (And I
am sure someone will jump in if I'm wrong.)

Clear skies, Alan