A Brief History of Astro-Physics Lenses
edwski
OUTSTANDING post!!!
thanks for the info.
ed
TMBack wrote in message <19990504222219...@ng34.aol.com>...
>A Brief History of Astro-Physics Lenses
> I guess this wasn't so brief after all!
>
>Sincerely,
>
>Thomas Back
>
>
>
Anthony Ayiomamitis
> A Brief History of Astro-Physics Lenses
>
Thomas, this is an awesome review. Also, thank you for including the pricing
during the evolution of these scopes.
Anthony.
TMBack
I hope the following history of the Apochromatic lens designs
made by Roland Christen of Astro-Physics is of some interest to
the readers of s.a.a. I do not claim complete accuracy. If anyone
has more information, or any corrections, please feel free to post
them.
The first ad that I am aware of was in Sky and Telescope
magazine, December 1981. Two lenses were offered: A 6" f/11
magnesium fluoride coated oil triplet for $1800, and a 8" f/11 for
$3600, both in cell. These lenses proceeded Roland's article in
Sky and Telescope, October 1981, page 376, "An Apochromatic
Triplet Objective." This was a groundbreaking article, and was
the beginning of the new age of Apochromatic refractors. The
prototype was a 5" f/12, and was shown at the Riverside
Telescope Making Conference. The images of Jupiter impressed
the attendees beyond any telescope on the field, and won the
prize for the most innovative optical design.
Roland was very fortunate to find a large supply of an abnormal
dispersion flint, similar to Schott KzFS-1, but even better in its
color correcting properties. In fact, it was ordered by NASA, but
was never used. When Roland found that the supply was available
for sale, he gladly bought it up. By-the-way, this "NASA" flint glass
was the ultimate in short KZ flint glass. No manufacture supplies
a flint glass that can match its abnormal dispersion properties
today.
The next ad was for two new apochromatic scopes. A 5" f/6 for
$950, and 5"f/12 Super Planetary for $975 (what a deal, what does
a 5" apo cost today!). These were complete scopes. They used a
design of BK-7/KzFS-1(NASA)/BaF-10 or BaK-1/KzFS-1/BaFN-10
glass.
Then came the infamous 6-inch f/9 NASA triplet, which only (it is
said) 24 were made. The scope was advertised in the July 1984
issue of Sky and Telescope, and priced at a slightly rich $1695, for
that time. For another $1300, you could have a complete mount and
custom tripod.
Astro-Physics then expanded their line to a 4"f/6 ($795) and 5" f/6
($995). This 5" model was the worst Astro-Physics refractor ever
produced, from a standpoint of optical correction. It was simply too
large and fast before the advent of ED glasses. The last model in the
line was a replacement for 6-inch f/9 NASA triplet, the 6" f/8 ($1295),
which used KzFSN-4 as the abnormal dispersion flint element.The
color and spherochromatism of this model was slightly less well
corrected than the older 6-inch f/9, but was $400 cheaper. Interesting
that the stated quality was 1/56 wave RMS, virtually the same as
today.
At this point, Roland's success made for a big life decision. Quit a
safe, well paying job, or go full time into telescope making. The
choice was made, and Roland went into the full time telescope
making business. More ads were taken out in the astro magazines,
and a new, more complete line of apochromatic refractors were
introduced. The August 1986 issue of Sky and Telescope might have
been the most impressive ad for its time. Seven apochromatic
refractors were listed, and the most impressive was the 6" f/12 Super
Planetary for $1540. The ad read: "Our new long focus refractors are
designed for the most discriminating Lunar/Planetary observer who
does not want any compromise in performance... The Lunar limb and
the disks of the planets are sharply outlined against black sky,
resembling charcoal drawings." Well, I can tell you that got my
interest! I placed an order for one, and at the next AstroFest Telescope
Convention, I viewed Jupiter with a 6"f/12 with the one and only Robert
Cox, and we were both staggered with the amount of planetary detail.
Robert's own words: "The planet presented a clear, sharp edge with a
high contrast view of the surface features." I might add that at this
same AstroFest, Roland and Marj bought a custom 8" f/14 triplet, that
was giving views of Jupiter at 300x that reminded everyone of the
Voyager pictures (just ask Marj), as around 11:00 PM the first night,
the seeing was near perfect.
The other scopes in the line were a 4"f/6 ($895); 5"f/6 ($1195); 4"f/10
($895); 5"F/8 ($1195); 6"F/8 ($1440), and the 5" F/12 ($1225). This
last scope was Terence Dickinson's first AP purchase and was so
impressed with. Roland was also taking orders for larger, custom lenses.
A 8" was purchased by Sue and Alan French, and they took this scope
to many star parties. All these scope were based on a similar design,
crown glass (BK-7 or BaK-1), abnormal dispersion flint (KzFS-1 or
KzFSN-4) and Barium flints (BaF-10, BaFN-10). To learn more about
this type of apochromatic lens design, see Telescope Making issue 28,
page 20. A little known fact about the early 6" f/12 Super Planetary
scopes is that they also use the "NASA" glass. The later models
(I presume the NASA flint glass ran out) used K-7 crown and KzFSN-4
flint glass.
Roland correctly perceived that the market wanted faster apo-
chromats, that were extremely well suited for photography. Thus the
"StarFire" line. The first ad was very craftily placed right in the
famous article by John Gregory and his 8" f/15 doublet apochromatic
in the June 1985 issue, page 662, the ad, page 665. If it was place
there by chance or otherwise, it couldn't have been in a better place
in the magazine.
This design used the same flint as the older Astro-Physics scopes,
but to increase color correction, two abnormal dispersion flints were
used. I can't tell you what the two other flints are (as a designer, they
are too good for me to let the publicknow, and to keep Roland's design
proprietary), but it is sufficient to say that the violet correction was as
much as 5x times better in the new StarFire design. There was a 4"f/8
($1195); 5" f/8 ($1660); 5.7" f/7 ($1850); 6"f/9 ($2395) and the king of
production StarFires, the 7" f/9 at only $3600! In the last production
runs of the larger non-ED StarFires, he airspaced the design and also
allowed the six different radii to vary on each surface. These last
production StarFires' were almost the match of the current ED Astro-
Physics scopes, and the final price was $4495.
In a letter dated February 16, 1989, I received information on a 8" f/15
airspaced StarFire, coated in cell for $7985. I believe one or two were
sold. I'm sure the owner of such a lens is very happy with its planetary
performance.
Then the new era began. It was AstroFest 1990, and Roland brought
his ultimate line of ED EDT triplets. I had my 6"f/12 setup next to the
new 6.1" f/9 EDT, and at first cast glance on Saturn, I knew it was all
over. This scope was a knockout, and in color correction and contrast,
clearly beat my 6" f/12 Super Planetary. This was a prototype, was
airspaced and not even coated! I asked Roland if he was considering
a 7.1" version, and he said possibly. When I got the news from Astro-
Physics that indeed a 180mm f/9 EDT was to be made, I said GREAT!
I sent in my deposit and patiently waited for my dream scope. The
EDT design used ZKN-7 crown glass and FPL-52 ED glass. The last
runs of the smaller EDT models used the same crown glass but
FPL-53 ED glass. They were even better corrected for monochromatic
and poly-chromatic aberrations. Prices for the EDTs: 105mm f/5.8
($1725); 130mm f/8 ($2450); 155 f/9 ($3195) 180mm f/9 ($4595).
There was also a very small run of 130mm f/8 ($1795) and 155mm f/9
($2595) doublets, but Roland discontinued these because the demand
for the EDT triplets far exceeded the ED doublets.
I left out the first ED Astro-Physics scope, the Star12 ED. At $1585,
it was a steal, and I know some very happy owners of this scope. While
not having the color correction of the EDT triplets, they were nevertheless
very sharp. My friend Gordon Garica (expert Solar photographer) took
some 1 arc second shots of the Sun with this scope, and his work can
be seen in Astronomy, Sky and Telescope, ALPO, and the book "Solar
Astronomy Handbook." He currently uses an AP 130mm f/8 EDT.
Roland then set out to make the ultimate astrograph, and he did. It
was the first "EDF." It used the StarFire design, but with FPL-51 with
an airspace. With a 4-inch field corrector and focuser, it took some of
the most impressive widefield astrophotos ever taken. The 152mm
f/7.5 EDF ($6400) was the first apochomatic telescope that I had ever
seen that was completely color free -- even out of focus. I know of no
other lens design that was put into production that was better than this
design. There were a few 206mm f/7.9 EDFs ($12500), and as most of
you know, they sell for twice as much now.
FPL-53 was the next step, and the 180mm f/7 EDF was born. At
$8200, they sold instantly. Tony Hallas has used his extensively for
wonderful deep-sky imaging. Once again, when they ever hit the used
market, the going price is much higher than the retail was. A few 9-inch
and 10-inch apochromats were sold to Colleges and rich individuals,
the design details being kept secret.
The final evolution in the design of Astro-Physics lenses were in the
latest EDT and EDF designs. Roland found that by combining FPL-53
(the best ED glass) with two different crown glasses, he could reduce
spherochromatism even further, and keep the design diffraction limited
out to 10000A in the near infrared. This is important for CCD imaging,
as CCDs still have sensitivity at those wavelengths. He also instituted
the use of a vertical interferometer, Opticam CNC glass surface profiler
and his latest toy, a UofR polishing machine.
The latest Astro-Physics lenses have outstanding optical qualities
and unit to unit consistency. The tube assemblies and matched
accessories are just as outstanding. These telescopes are a joy to
use.
Starvick
Regards, Jeff V.
>
>A Brief History of Astro-Physics Lenses
>
e-mail, remove QQQ
Dennis Simmons
A very useful historical and technical perspective - thanks.
I am relatively new to astronomy, (historically challenged) and also live
way on upside-down-under, (geographically challenged), so the rich tapestry
of product evolution that you wove on the web, proved highly informative
and provided very pleasant reading. I now have some insight into what makes
these instruments such an energetic topic of discussion. Once again, many
thanks for the post.
Best regards
Dennis Simmons.
Robert
Thanks once again for enlightening the group, excellent!
Rob
TMBack wrote:
> (snip)
Jay Reynolds Freeman
guide so that we can tell one from another...
--
Jay Reynolds Freeman -- freeman at netcom dot com -- I speak only for myself.
BKuperinsk
Thomas
Bob Kuperinsky
Richard DeLuca
(TMBack) wrote:
> A Brief History of Astro-Physics Lenses
>
> I hope the following history of the Apochromatic lens designs
> made by Roland Christen of Astro-Physics is of some interest to
> the readers of s.a.a. I do not claim complete accuracy. If anyone
> has more information, or any corrections, please feel free to post
> them.
>
_HUGE SNIP_
> The latest Astro-Physics lenses have outstanding optical qualities
> and unit to unit consistency. The tube assemblies and matched
> accessories are just as outstanding. These telescopes are a joy to
> use.
>
> I guess this wasn't so brief after all!
>
Thomas,
Thank you for the wonderful chronology of AP lenses. Some of this
information is new to me.
I happen to own one of Roland's last 6" f/9 Starfires on an 800 mount. I
almost opted for the 7" f/9 instead, but I wasn't sure the 800 mount would
be stable enough for photography. Interestingly enough, I've never done
any photography with this particular instrument. Delivery was in December
'89 as I recall, and I was pleased beyond my expectations. This scope (in
a roll-off) has provided ten years of outstanding and trouble-free
service.
At the time, I didn't believe a better refractor would ever be produced. Then
I got a side-by-side comparison with a friend's (Joe Bergeron) 6" f/9 EDT
during the Jupiter-comet impacts. The slightly increased contrast and
correction was immediately apparent, and if Roland decides to again
produce a 6" or 7" in longer focal lengths, I'll probably be back on the
list.......:)
Starry Skies,
Richard DeLuca
TMBack
I want to apologize to my friend Gordon, as I misspelled
his name -- it is Gordon Garcia.
Thanks again,
Thomas Back
JaePbond
Thank YOU!!
Tom,
I guess the one scope that was left out although it was not sold as an AP, may
be the 94mm f/7 Brandon which used the AP made lenses.
Perhaps you could verify my understanding of it's history. I think it first
made its appearance in S & T ads in '86 or so as a white tube 92mm under the
Vernonscope name ? Later changed to 94mm (same lens but different lens
holder?) with a blue tube with double rings and lastly a blue tube with a
single ring. I thought it was sold until early 90's during the same period
as the first 4" f/8 Starfires so would it be safe to assume that it was the
same Starfire design? The color correction would have been a bit less versus
the 4" f/8 due to it's shorter f/7 design?
Jae P
Richard DeLuca
ody...@spectra.net (Richard DeLuca) wrote:
>
> At the time, I didn't believe a better refractor would ever be
produced. Then
> I got a side-by-side comparison with a friend's (Joe Bergeron) 6" f/9 EDT
> during the Jupiter-comet impacts.
OOPS! Excuse me. That should be 'JOEY' Bergeron.............8*}
WHALEN44
Great post! You sure keep up with your AP's!
Richard Whalen
whal...@aol.com
Time spent observing the heavens is not deducted from your lifespan
Ratboy99
rat
~( );>
Sue and Alan
According to notes I made long ago, the first ad for the 94mm Brandon was in
the June, 1987 issue of Sky & Telescope. Vernonscope had previously been
selling an 80mm "APO". That was the one with the infamous 1800 power ad
(Mar thru May, 1985).
Clear skies, Alan
JaePbond wrote in message <19990505132803...@ng-fw1.aol.com>...
JosephB41
cotton-picking know-nothing AP neophyte newbieuberweenie!
Oh well, I still enjoyed the post.
Joe Bergeron (JABer...@aol.com)
JosephB41
I got a side-by-side comparison with a friend's (Joe Bergeron) 6" f/9 EDT
correction was immediately apparent,
8>O
And my EDT predates the interferometric testing! Perhaps it is only 1/8 wave!
Perhaps the current scopes are minutely better! Whatever shall I do?
Doug Bell
Anyone have an idea where the they fit in?
Thanks,
Doug Bell
TMBack wrote:
> Thanks guys, I'm happy that you took the time to read it!
TMBack
>I guess the one scope that was left out although it was not
>sold as an AP, may be the 94mm f/7 Brandon which used
>the AP made lenses.
Glad you brought that up, I forgot about the Astro-Physics
Brandon lenses. The 94mm f/7 and 5-inch f/8 Brandon, both
in Unitron tube assemblies.
>Perhaps you could verify my understanding of it's history.
>I think it first made its appearance in S & T ads in '86 or so
>as a white tube 92mm under the Vernonscope name? Later
>changed to 94mm (same lens but different lens holder?) with
>a blue tube with double rings and lastly a blue tube with a
>single ring.
That's right, the first Brandon apochromat was a 92mm f/7,
in a white Unitron tube assembly. As you say, Don opened up
the cell diameter to 94mm and changed the color to blue. Then
to cheapen it up, he junked the fine push-pull cell to an un-
adjustable one. I believe the first ad was in the June 1987 issue
of Sky and Telescope, page 658. This was the best issue of
Sky and Telescope ever, in my opinion, because of the
revolutionary products such as the TeleVue ad for the 20mm
Nagler, the introduction of the Astro-Physics StarFire series, the
92mm Brandon apo, the Uranometria 2000.0 article, the review
of the books "Advanced Telescope Making Techniques, Vol. I
and II," Scotty Houston's great Deep Sky Wonders column (we
all miss him), the Gregory apochromat design, the finest earth
based photo of Mars ever taken by Jean Dragesco, with the
Pic-du-Midi 43-inch and the wonderful Viking color image of
Mars' Valles Marineris image. What an issue!
>I thought it was sold until early 90's during the same period as the
>first 4" f/8 Starfires so would it be safe to assume that it was the
>same Starfire design? The color correction would have been a bit
>less versus the 4" f/8 due to it's shorter f/7 design?
No, the Brandon 94mm used the same design as the older 5"f/8
and 6"/f8 Astro-Physics lenses. The 94mm Brandon showed a
bit more color than the StarFire lenses. The 5-inch Brandon,
however, did use the 5-inch "StarFire" design. I'm not sure
on the Brandon prices. I think the 92mm was first offered at
$999.
Another Astro-Physics telescope I forgot to mention was a
limited production (1990) of a Super Planetary 6" f/12 StarFire
($2995). It was billed as the ultimate in planetary images for its
size.
Thomas Back
Richard DeLuca
jose...@aol.com (JosephB41) wrote:
> Gee, Thomas! You showed me up with your post! You made me look like a
> cotton-picking know-nothing AP neophyte newbieuberweenie!
>
Joe,
You really gotta start getting out with people more often.......8*}
Paul Rest
Well, maybe I'll be able to afford one someday, siggghhhhh..........
Clear skies.
-Paul
Er451
Excellent post! Really enjoyed reading it.
I agree with you, these scopes are a joy to use.
Clear Skies,
Eric Jamison
AndersonRM
(JosephB41) writes:
>And my EDT predates the interferometric testing! Perhaps it is only 1/8 wave!
>Perhaps the current scopes are minutely better! Whatever shall I do?
Then again, it may be 1/20th wave. If the residual error were confined
to spherical over or under correction, you could measure it using a flat
and a micrometer eyepiece.
-Rich
MaxWebhead
very nice,, Rolands scopes are mint,, too bad im 50,000 down on the waiting
list.,, but ill wait
I got the patiance of an astronomer
~ Buddy from N.Y ~ "Serenity is just a level of Insanity thats pleasurable"
AndersonRM
that was featured in Photonics magazine that can produce
aspheric surfaces for a fraction of the previous cost to hand-work
aspherics? Do you know if the University kept ownership of the
patent for the machine?
Thanks
-Rich
JaePbond
Thomas,
>No, the Brandon 94mm used the same design as the older 5"f/8
>and 6"/f8 Astro-Physics lenses. The 94mm Brandon showed a
>bit more color than the StarFire lenses. The 5-inch Brandon,
>however, did use the 5-inch "StarFire" design. I'm not sure
>on the Brandon prices. I think the 92mm was first offered at
>$999.
Thanks for the clarification. I'll have to dig up the June 1987 issue from
the attic.
Jae P
R. Kantrowitz
original price was $795 with a price increase to $895 as of April 1, 1986.
I beat the price increase and purchased it for $795. So the $795 and $895
scopes are one and the same. The delivery time on the 4-inch in 1986 was
one year.
When the Brandon 94mm came out, I purchased one of these also. There wasn't
much of a difference in the optics, but the color correction in the 4-inch
made the stars more blue white and the focuser was a giant 2.75 inches.
Naturally I kept the 4-inch and sold the Brandon.
The Starfire 5-inch that I purchased in 1987 took a mere 6 months to arrive.
The color correction of the 5-inch Starfire was definitely better than that
of the 4 inch, but using an Astrophysics 2-inch barlow and Vernonscope
diagonal still keeps the images in the 4 inch beyond those in longer focal
length 4-inch achromats.
Ralph K.