People's eyes versus the interferometer

Hi John,

With the size of those short focal length eyepieces, I'm not sure what he
expects an interferometer to show. I'm not sure if he doesn't think these
things through or if it is intentional trolling. I guess either way, the
result is the same...

Well, with the recent no-respond-to-trolls pledge, should we ignore him in
the future? I'm not sure if this is innocent ignorance or deliberate troll.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
Lunar Picture of the Day http://www.lpod.org/
************************************

"John Steinberg" wrote in message
...
CLT wrote:

(That just does not parse well)

Take a look at what it costs to get an interferometer report with a
scope.
Figure the cost of testing each eyepiece.

I won't pretend to speak for Rich, but if the past is a reliable
indicator of the future, he may well argue that volume amortization
would decrease the costs such that it would be economically feasible.

See any of his posts over the last 5 years on CCDs for further
edification.

He may also hold to the belief that AP telescopes would be less costly
and more plentiful if Roland simply skipped lunch 5 days a week.

While increased volume can have a material impact on production costs,
that dog just won't hunt in this particular case.

Voodoo economics, it ain't just for US right-wingers, kids!

--
-John Steinberg
email: lid

-= I link therefore I'm spammed =-

And then... they'd have to pass on the costs of these tests to the consumer.
No thanks. I'll take my chances(and read some reviews ;^) and if something
doesn't work the way I want it to for the equipment I use, fine, I'll just
sell it on Astromart.(or, give it away)

Best regards,
Bill



I can't speak to the original poster, but I, myself, was thinking more of the
possibility of having representative samples of the eyepieces (of each specific
type and focal length, of course) tested rather than every single eyepiece
tested and just assume (yes, I know what assumptions can bring you) that the
individual eyepieces from the premium manufacturers wouldn't vary much from
eyepiece to eyepiece. Do a full battery of whatever types of tests are most
relevant for eyepieces at various telescope focal ratios to give some objective
results to compare. Of course, I would gather a fair amount of this is already
done during the design phase of a "new" eyepiece... but how available is the
data? For most people, though, (myself included) the results wouldn't be too
meaningful, but it would still be to some. Part of me still says the more
objective information available, the better... and the relevance of the tests
can always be learned if it's important enough to someone. For those who don't
fully understand what the results say or how significant slight differences
are, they could still give some bragging rights, just as some do now ("My
Strehl ratio is bigger than _your_ Strehl ratio!"). Isn't that what it's all
about, anyway? hehe

"Richard" wrote in message
om...
Can people's eyes reveal more about optics than an interferometer used
properly? Of course not. Which begs the question; If telescopes are
routinely tested on interferometers for quality instead of relying on
subjective human eye tests, why aren't eyepieces (some of which cost more
than medium sized scopes) tested as well by any mfgs?
-Rich

Why, in heaven's name, would anyone want to test an eyepiece with an
interferometer, and how would you do it?

People obsess far too much about eyepieces. The size and quality of the
telescope is by far more important than the eyepiece, and any quality
eyepiece is almost certain to be diffraction limited on-axis. For the
maximum contrast, and a subtle gain over lesser eyepieces, you need to pay
careful attention to glass selection, a good polish, proper coatings, and
clean surfaces - which are not what you look at with an interferometer.

Clear skies, Alan

"John Steinberg" wrote in message
...
Chuck wrote:

Well, with the recent no-respond-to-trolls pledge, should we ignore him
in
the future? I'm not sure if this is innocent ignorance or deliberate
troll.

There are times when words fail me and only an image can articulate my
feelings properly, Chuck.

http://isthatspam.0catch.com/mri.html

As always, pop-up, pop-under, and every other kind of ad blocker highly
recommended.

I love it!

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
Lunar Picture of the Day http://www.lpod.org/
************************************



-
-John Steinberg
email: lid

-= I link therefore I'm spammed =-

(ValeryD) wrote in message om...
(Richard) wrote in message . com...
Can people's eyes reveal more about optics than an interferometer used
properly? Of course not. Which begs the question; If telescopes are
routinely tested on interferometers for quality instead of relying on
subjective human eye tests, why aren't eyepieces (some of which cost more
than medium sized scopes) tested as well by any mfgs?
-Rich

Hi Rich,

Good question, but...

1. Do you have any idea how to test interferometrically 5mm eyepiece?

Have you seen those handheld industrial spectroscopes? They could make
"mini-interferometers to test eyepieces!.


2. Do you know the price for interferometrical test with processed data?

Not really. I think someone mentioned about $1500 plus the reference lens.
But if it was done for one eyepiece, subsequent tests shouldn't be
expensive...I think.


I can tell you, that the price of such labor volume is about the same as
good medium price eyepiece cost.
Do you need increasing prices of eyepieces in about 3x (because of restricted
eyepieces and the test itself)?

If that's the case, then how do optical firms guarantee lens elements
to be a specific wavelength and scratch and dig, lenses that may only
cost $50 or less?


3. Do you think it is necessary to do such a test for eyepieces?

Honestly, I'm not sure for all of them, but a eyepiece whose whole field
lens is illuminated when used on scope might be worth testing.
-Rich


LOL

V.D.

Honestly, I'm not sure for all of them, but a eyepiece whose whole field
lens is illuminated when used on scope might be worth testing.
-Rich

This shows that you lack an understanding of the light paths and geometry of
the rays in eyepieces. Interferometry will not buy you anything with this kind
of optic.

As far as surface quality, the surfaces of small lenses are tested using test
plates, which is a type of surface interferometry. A test of this type tales
about 3 seconds.

Scratch and dig is not something that can be measured in this manner in any
case. This is done with microscopic examination of the lens surface. If you
think that surfaces of cheap imported eyepieces are tested for scratch and dig
individually, you are dreaming.

RC

RC

"Alan French" wrote in message . ..
"Richard" wrote in message
om...
Can people's eyes reveal more about optics than an interferometer used
properly? Of course not. Which begs the question; If telescopes are
routinely tested on interferometers for quality instead of relying on
subjective human eye tests, why aren't eyepieces (some of which cost more
than medium sized scopes) tested as well by any mfgs?
-Rich

Why, in heaven's name, would anyone want to test an eyepiece with an
interferometer, and how would you do it?

People obsess far too much about eyepieces. The size and quality of the
telescope is by far more important than the eyepiece, and any quality
eyepiece is almost certain to be diffraction limited on-axis. For the
maximum contrast, and a subtle gain over lesser eyepieces, you need to pay
careful attention to glass selection, a good polish, proper coatings, and
clean surfaces - which are not what you look at with an interferometer.

Clear skies, Alan

Good polish? Can't interferometers test for that as well as the quality
of the glass, etc?
-Rich

"CLT" not@thisaddress wrote in message ...
Hi Rich,

Take a look at what it costs to get an interferometer report with a scope.
Figure the cost of testing each eyepiece. Add that to the cost of each
eyepiece. I believe you'll also have some trouble testing short focal length
eyepieces.

At the end, you discover you have added a good deal of cost with little
gain.

It must be different in other areas of optics where small lenses are
always sold with a specification? I guess intecepting the beam from
a telescope must be "special" compared with using small lenses in
things like laser optics, microscopy, interferometry, eye test
equipment, high end
binoculars, electro-optics, electro-lithography, etc, etc.
-Rich

Good polish? Can't interferometers test for that as well as the quality
of the glass, etc?

It is one of the nastier secrets of optics that infernaltometers can indeed
test all that stuff and more. Infernaltometers have now reached the stage
where each optical surface in complex optics can be tested independently in
one automated pass. Although the initial purchase of the test equipment is
expensive, sufficient volume would easily bring it down to a cost of under a
dollar for each system tested.

This of course raises the question as to why this isn't done. And the answer
obviously lies within the sinister Optics Equipment Mafia (aka OEM or just
"the Mafia" for short). Some of the more prominent heads of stateside mafia
families include individuals such as Uncle Al (The Nag Father). You may
notice that Al Nagler and Al Capone both have the same first name. This is
not a coincidence. Al Nagler's grandfather ran bootleg whiskey for Al Capone
during the prohibition and Al Nagler is named for his early optics
benefactor. You see, the early Televue eyepieces were made of melted down
prohibition whiskey bottles donated to Al Nagler by Capone's grandson. Small
drops of the now very-aged whiskey survived and were absorbed when the glass
was remelted and annealed. This explain the mellow smoothness of those early
eyepieces.

Roland "Machine-Gun Polish" Christen heads another family prominent US-based
family. He is of course an import, having expanded the Canadian (Geese)
branch of the mafia into new territory. Rival opticians who did not buy
"protection" from him found their cars dive-bombed into submission by the
Canadian geese. However, more recently this has backfired on him as the
geese branch of the family went independent. They are currently trying to
extort flouride glass from him to use in their toothpaste racket.

Of course, Canada is not the only country whose OEM is trying to muscle in
on US turf. The Misiuk family was heavily involved in Russian/USSR optics
mafia wars for nearly a century. Dmitri (The MakFather) forced them out of
their earlier territories, and one branch of the family headed to the US.
This family is headed by another Al. Again we see the connection with Al
Capone. Why else do you think so many people use alcohol to clean those
filters?

More recently Valary (The ChromaFather) has also been expanding his
operation, competing with the Ludes family in Germany as well as taking over
the color numbers racket. Obviously he would not want to see cheap
Infernaltometers readouts on eyepieces, and is working hard to suppress
those who would do so. He was recently seen giving the kiss of death to a
Zeiss optician who had double-crossed him. The optician was then taken to a
remote site and decollimated.

The mafia wars are fierce, with no eyepiece given or taken. The Lumicon
family was recently put "out-of-business" in a brutal massacre, though
another OEM family is trying to move into their area and take over by using
the Lumicon name and connections/runners.

Most of these families are gearing up for more intense wars, hitting the
mattresses to battle additional Russian OEMafia families moving in as well
as the Chinese Tong headed by the Synta family. Inexpensive Infernaltometers
are obviously something they all want to avoid. They have thrown their
muscle into keeping the secrets from the public, threatening to vignette
anyone who infernaltometers an eyepiece.

Unfortunately, the Focal Back Institute (FBI) has been unable to infiltrate
these secret societies and mafia families. It was hoped the new terrorism
laws would help here, but they have so far been unable to make congress see
that diffraction limiting is a threat to the national security. At this time
we need every astronomer to write to his or her congressperson and warn them
of this grave danger.

Clear (Infernaltometered) Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
Lunar Picture of the Day http://www.lpod.org/
************************************

It must be different in other areas of optics where small lenses are
always sold with a specification? I guess intecepting the beam from
a telescope must be "special" compared with using small lenses in
things like laser optics, microscopy, interferometry, eye test
equipment, high end
binoculars, electro-optics,electro-lithography, etc, etc.
-Rich

Rich:

I would avoid this sort of defensive offense. It lets the rest of the dumbies
here know that you are one of us...

jon