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Re: [tmboptical] Re: Interferometry (was: 130 TMB & TEC 140 (was TMB 130)

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  • Mike C
    ... Thanks for the update, Kurt. My point is mostly about the inclusion or exclusion of abberations like astigmatism, coma, tilt, etc. If you present fantastic
    Message 1 of 22 , Mar 2, 2004
      > >
      > > http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-
      > > 8&threadm=20040110140005.14218.00003213%40mb-
      > > m28.aol.com&rnum=1&prev=/groups%3Fq%3Dg:thl2624612743d%26dq%3D%26hl%
      > > 3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26selm%
      > > 3D20040110140005.14218.00003213%2540mb-m28.aol.com
      > >
      > >
      > > Regards,
      > > Kurt
      >
      > Darn Yahoo always messes up long links. Try:
      >
      > http://makeashorterlink.com/?D2A815797
      >
      > Kurt
      >


      Thanks for the update, Kurt. My point is mostly about the
      inclusion or exclusion of abberations like astigmatism, coma, tilt, etc.
      If you present fantastic strehl results, but dont tell how you arrived at
      them, then what is it worth? For example, the "apo1" lens on that
      PCS forum I mentioned earlier shows 99% Strehl, but astig is shown
      as subtracted, etc. Is it 99% strehl? Who knows.

      Mike
    • Mike C
      ... LZOS uses a Twyman-Green interferometer. Does Zygo really play into it? I dont know. Here is another post from that great thread that Kurt Milhaco linked
      Message 2 of 22 , Mar 2, 2004
        >
        > One has to ask is that strehl measurement made with a certified Zygo
        > interferometer and how many data points are used. Also, is the test
        > done with the lenses in the cell or setup on a test bench? I don't
        > know how TEC does it but LZOS tests with a certified Zygo
        > interferometer using thousands of data points across the lense
        > surface.
        >

        LZOS uses a Twyman-Green interferometer. Does Zygo really play into it?
        I dont know.

        Here is another post from that great thread that Kurt Milhaco linked to.
        It has this quote from Roland:

        (quote)
        The other thing that is really stupid of them was to test the fluorite and the
        other refractor with a Zygo. This commercial interferometer sends a beam of red
        laser light through the telescope. To get the true P-V wavefront error of a
        refractor one MUST use a green light source (Zygo does not provide this in
        their product line).
        (/quote)

        I don't know if that is still a fact since you hear about Zygo interferometry all
        the time. Maybe Zygo has become a generic term on the web for interferometer.

        Mike
      • mihalco
        ... Maybe Zygo has become a generic term on the web for interferometer. ... Zygo has made interferometers for a long time, but I don t think they are
        Message 3 of 22 , Mar 2, 2004
          --- In tmboptical@yahoogroups.com, "Mike C" <mike@e...> wrote:
          Maybe Zygo has become a generic term on the web for interferometer.
          >
          > Mike

          Zygo has made interferometers for a long time, but I don't think they
          are considered a *generic* term for an interferometer. There are a
          number of interferometer types that can be configured for telescope
          optic testing. Fizeau and Tywman Green are typical. They are not
          complete unto themselves. They need additional optics (reference
          elements, flats, etc) in order to test telescope optics. These all
          have to be made to an extremely high accuracy, (1/10-1/20+ wave).
          Mounts and environment are also critical. Most optical folks would
          probably agree that any non-phase shifting interferometer (Zygo
          included) is capable at best of measuring down to 1/20 wave. Many
          optical shops build their own test interferometer, and buy commercial
          software to evaluate the interferograms. Properly used, their
          results can be as good as any commercial interferometer. Zygo's
          aren't magically certified, but as a commercial product, they have
          been well characterized, have lots of support optics available, and
          have a long product evolution that has made them reliable, usable,
          etc. They also cost a lot :>) They also have lot's of good stuff on
          their web site. Look at the GPI family:
          http://www.zygo.com/gpi/gpifam.htm
          It can be configured for visual fringe analysis (i.e. your eyeball)
          all the way through computer based phase shifting measurement. Also,
          Roland's statement on SAA about Zygo's not offering green laser
          support is dated. This is available as an option now.

          Regards,
          Kurt
        • Tube Tim
          ... Your right, it is Twyman-Green at 532 nm. ... It does when you read the wrong test report. When I said Zygo I was thinking of a test report on a mirror
          Message 4 of 22 , Mar 2, 2004
            >--- In tmboptical@yahoogroups.com, "Mike C" <mike@e...> wrote:
            >
            > LZOS uses a Twyman-Green interferometer.

            Your right, it is Twyman-Green at 532 nm.


            > Does Zygo really play into it?

            It does when you read the wrong test report. When I said Zygo I was
            thinking of a test report on a mirror flat I have. My bad.

            > I dont know.
            >
            > Here is another post from that great thread that Kurt Milhaco linked
            > to. It has this quote from Roland:

            Who? Never heard of him.

            >
            > (quote)
            > The other thing that is really stupid of them was to test the
            fluorite and the
            > other refractor with a Zygo. This commercial interferometer sends a
            beam of red
            > laser light through the telescope. To get the true P-V wavefront
            error of a
            > refractor one MUST use a green light source (Zygo does not provide
            this in
            > their product line).
            > (/quote)

            I always wondered about this. If you test at 633nm and find a 1/10
            wave optic can you declare it is:

            = 1/10 * (633 nm / 532 nm )

            or a 1 / 8.4 optic at 532nm? If not why not?

            >
            > I don't know if that is still a fact since you hear about Zygo
            > interferometry all the time. Maybe Zygo has become a generic term on
            > the web for interferometer.
            >

            Perhaps, but it's not accurate.

            > Mike


            Tim
          • APM_Telescopes
            The TEC show strehl of 99% only in its Zemax calculation, ask TMB and you will see that the TMB offer in the zemax calculation even higher strehl than 99% 99%
            Message 5 of 22 , Mar 2, 2004
              The TEC show strehl of 99% only in its Zemax calculation, ask TMB and you
              will see that the TMB offer in the zemax calculation even higher strehl than
              99%

              99% strehl is about 1/60 RMS and thats not what TEC warrantee for his scopes

              best wishes
              Markus
              ----- Original Message -----
              From: "Michael Frias" <aaronslandscape@...>
              To: <tmboptical@yahoogroups.com>
              Sent: Tuesday, March 02, 2004 5:39 PM
              Subject: [tmboptical] Re: 130 TMB & TEC 140 (was TMB 130)


              > Mario,
              > That is a good question. The TEC shows a very high strehl of 0.99. Is this
              all
              > that really matters? It'll be nice to hear some comparison notes on the
              two
              > scopes.
              > Michael
              >
              >
              >
              >
              > --- In tmboptical@yahoogroups.com, "Mario" <mauriel@o...> wrote:
              > > Hello.
              > >
              > > Desire to buy a 130 TMB F:6 but before desire indicates to me if its
              > > quality is parallel to the price. Other that I like is TEC 140 APO.
              > >
              > > As will be better?
              > >
              > > Thanks,
              > >
              > > Mario Muriel - Spain.
              >
              >
              >
              >
              > Yahoo! Groups Links
              >
              >
              >
              >
              >
            • APM_Telescopes
              ... Lens testings must include coma, astigmatism , only defocuse and tilt from set up need to be removed and thats the way how LZOS doing it. If the fringes
              Message 6 of 22 , Mar 2, 2004
                >
                > The TMB reports are interesting but don't include the fringes or the
                > decisions made by whoever was producing the results. (Were tilt,
                > defocus, astigmatism, coma subtracted from the results? Or were they
                > included in the presented results?) I don't know.

                Lens testings must include coma, astigmatism , only defocuse and tilt from
                set up need to be removed and thats the way how LZOS doing it.



                If the fringes were
                > included then I guess you could throw it into an analysis package
                > and have it spit out the same results for you.
                >
                > Roland posted some quickfringe results to the PCS forums a while
                > back. See here:
                > http://www.pcsincnet.com:16080/forum/viewforum.php?f=2


                Roland shows 8 lines, this is already to much and makes lines to straight,
                usual 3-4 lines shall be used as high power scale to see all small deffects

                best wishes
                Markus

                > They include fringes in all cases, but they all vary in the abberations
                > which were subtracted when calculating the Strehl. For example the
                > "apo1" high quality APO with fringes sent by another manufacturer
                > shows 99% strehl but astigmatism and coma have been subtracted
                > from those results. That can certainly improve the strehl on the report,
                > right?
                >
                > Also, like you mention, cell or no cell? Lens orientation as well can
                > change everything. As far as I'm concerned.. IMHO.. YMMV... etc.
                > Interferometry can't be well compared from manufacturer to manufacturer.
                > Maybe if we had an independant lab testing them all and trying to
                > maintain total objectivity and sharing the full process of analysis.
                >
                > Mike
                >
                >
                >
                >
                >
                > Yahoo! Groups Links
                >
                >
                >
                >
                >
              • APM_Telescopes
                LZOS use green Twymann Interferometer for final testreport best wishes Markus ... From: mihalco To: Sent:
                Message 7 of 22 , Mar 2, 2004
                  LZOS use green Twymann Interferometer for final testreport

                  best wishes
                  Markus
                  ----- Original Message -----
                  From: "mihalco" <mihalco@...>
                  To: <tmboptical@yahoogroups.com>
                  Sent: Tuesday, March 02, 2004 11:34 PM
                  Subject: [tmboptical] Interferometry (was: 130 TMB & TEC 140 (was TMB 130)


                  > Hi Mike,
                  > It turns out that there are two ways to utilize the fringe data to
                  > arrive at the surface profile. Programs like QuickFringe trace
                  > fringe centers, and use these data points to fit a set of polynomials
                  > (that represent the various abberations) to these data points. The
                  > number of data points is limited to those placed on fringe centers.
                  > Newer ZGYO's (and others) can do what is called phase shifting
                  > interferometry. This is done by taking multiple images of the fringe
                  > pattern (typically 4 or 5), with the reference beam phase shifted 90
                  > deg between each image. Visually, it appears as though the fringe
                  > pattern visibly scrolls (in steps) across the surface. The first and
                  > fifth images *should* be darn near identical, if everything is in
                  > good calibration (5 images at 0, 90, 180, 270, 360 deg phase. 0 =
                  > 360). Using per pixel irradiance values from this series of images,
                  > the phase (and Optical Path Difference) can be extracted for each
                  > pixel. Each pixel effectively becomes a data point to which the
                  > polynomials are fit to, giving a complete coverage of the optic
                  > surface, as well as a more accurate representation of the surface
                  > figure. Note that a number of companies offer retrofit phase
                  > shifters and software that work with older ZYGO's that just did
                  > static fringe analysis. I have no idea what setup LZOS uses. In any
                  > case, properly done testing on an interferometer should yield
                  > repeatable results, independent of which interferometer was used.
                  > This doesn't that every interferometer is capable of the same
                  > accuracy and repeatability - this depends on a number of factors. A
                  > good discussion of this is at:
                  > http://www.opticalmechanics.com/interferometric_test_results.htm
                  > Hope this helps,
                  > Regards,
                  > Kurt Mihalco
                  >
                  > --- In tmboptical@yahoogroups.com, "Mike C" <mike@e...> wrote:
                  > > > One has to ask is that strehl measurement made with a certified
                  > Zygo
                  > > > interferometer and how many data points are used. Also, is the
                  > test
                  > > > done with the lenses in the cell or setup on a test bench? I
                  > don't
                  > > > know how TEC does it but LZOS tests with a certified Zygo
                  > > > interferometer using thousands of data points across the lense
                  > > > surface. Testing the lens in the cell will yield a lower strehl
                  > from
                  > > > one meaured while setup in an ideal lab environment. In cell is
                  > what
                  > > > counts as that's the way you use it.
                  > >
                  > >
                  > > Hi Tim
                  > >
                  > > Please help me sort out interferometry. Someone in-the-know needs to
                  > > post a treatise on interferometry on Cloudy Nights. Hopefully it
                  > wont
                  > > land in the new "laboratory reports" area...
                  > >
                  > > Aren't interferometry results interpreted by a computers
                  > measurements
                  > > of interference fringes? So it's not actually putting thousands of
                  > data
                  > > points across the lens surface right? It's putting "X" amount of
                  > points
                  > > up and down the fringe pattern and then making judgements on that?
                  > > I wonder if changing the quantity of points in the fringe pattern
                  > has that
                  > > much effect. I have heard only conflicting reports about what
                  > changing
                  > > the quantity of measurement points within the fringe pattern does.
                  > >
                  > > The TMB reports are interesting but don't include the fringes or
                  > the
                  > > decisions made by whoever was producing the results. (Were tilt,
                  > > defocus, astigmatism, coma subtracted from the results? Or were they
                  > > included in the presented results?) I don't know. If the fringes
                  > were
                  > > included then I guess you could throw it into an analysis package
                  > > and have it spit out the same results for you.
                  > >
                  > > Roland posted some quickfringe results to the PCS forums a while
                  > > back. See here:
                  > > http://www.pcsincnet.com:16080/forum/viewforum.php?f=2
                  > > They include fringes in all cases, but they all vary in the
                  > abberations
                  > > which were subtracted when calculating the Strehl. For example the
                  > > "apo1" high quality APO with fringes sent by another manufacturer
                  > > shows 99% strehl but astigmatism and coma have been subtracted
                  > > from those results. That can certainly improve the strehl on the
                  > report,
                  > > right?
                  > >
                  > > Also, like you mention, cell or no cell? Lens orientation as well
                  > can
                  > > change everything. As far as I'm concerned.. IMHO.. YMMV... etc.
                  > > Interferometry can't be well compared from manufacturer to
                  > manufacturer.
                  > > Maybe if we had an independant lab testing them all and trying to
                  > > maintain total objectivity and sharing the full process of analysis.
                  > >
                  > > Mike
                  >
                  >
                  >
                  >
                  > Yahoo! Groups Links
                  >
                  >
                  >
                  >
                  >
                • APM_Telescopes
                  ... above is exclusiv valid for raw mirror telescopes like newtonians with no lens or corrector includet. Achromats, Apos, and Maks cannot be rated straight
                  Message 8 of 22 , Mar 3, 2004
                    >
                    > I always wondered about this. If you test at 633nm and find a 1/10
                    > wave optic can you declare it is:
                    >
                    > = 1/10 * (633 nm / 532 nm )
                    >
                    > or a 1 / 8.4 optic at 532nm? If not why not?
                    >
                    >
                    above is exclusiv valid for raw mirror telescopes like newtonians with no
                    lens or corrector includet. Achromats, Apos, and Maks cannot be rated
                    straight this way, because the optic can be nulled at red, it can also be
                    over or undercorrected at red. Only if a optic is perfect designed with null
                    at green and 100% made correspondance to the design ( non optic in the world
                    is done this way, due manufactor and glas errors ).

                    so you can have a apo at red with 1/10 wave, who can be at green 1/4 wave
                    but can also be 1/15 wave at green, depends how the manufactoring came out.

                    best wishes

                    Markus
                  • Tube Tim
                    ... wrote: Got it; thanks Markus. Tim ... with no ... also be ... with null ... the world ... wave ... came out.
                    Message 9 of 22 , Mar 3, 2004
                      --- In tmboptical@yahoogroups.com, "APM_Telescopes"
                      <apm_telescopes@w...> wrote:


                      Got it; thanks Markus.


                      Tim


                      > >
                      > > I always wondered about this. If you test at 633nm and find a 1/10
                      > > wave optic can you declare it is:
                      > >
                      > > = 1/10 * (633 nm / 532 nm )
                      > >
                      > > or a 1 / 8.4 optic at 532nm? If not why not?
                      > >
                      > >
                      > above is exclusiv valid for raw mirror telescopes like newtonians
                      with no
                      > lens or corrector includet. Achromats, Apos, and Maks cannot be rated
                      > straight this way, because the optic can be nulled at red, it can
                      also be
                      > over or undercorrected at red. Only if a optic is perfect designed
                      with null
                      > at green and 100% made correspondance to the design ( non optic in
                      the world
                      > is done this way, due manufactor and glas errors ).
                      >
                      > so you can have a apo at red with 1/10 wave, who can be at green 1/4
                      wave
                      > but can also be 1/15 wave at green, depends how the manufactoring
                      came out.
                      >
                      > best wishes
                      >
                      > Markus
                    • Michael Frias
                      So what does all this mean? As quoted from the TEC specifications, Design: Aplanatic oiled triplet APO, ED glass with two other ones. Optimized for e-line
                      Message 10 of 22 , Mar 3, 2004
                        So what does all this mean? As quoted from the TEC specifications, "Design:
                        Aplanatic oiled triplet APO, ED glass with two other ones. Optimized for e-line
                        546nm - Strehl 0.99, PV 1/20 (calculated)".
                        What is the e-line? What does this show? Anything?




                        --- In tmboptical@yahoogroups.com, "APM_Telescopes" <
                        apm_telescopes@w...> wrote:
                        > LZOS use green Twymann Interferometer for final testreport
                        >
                        > best wishes
                        > Markus
                      • APM_Telescopes
                        here you see the TMB designed Strehl for the 6 F/8 Apo a.. Wave front and Strehl Ratios OPD Wave front (P-V) Strehl Ratio Spot Size Radius (microns) 4358A
                        Message 11 of 22 , Mar 3, 2004
                          here you see the TMB designed Strehl for the 6"F/8 Apo
                          a.. Wave front and Strehl Ratios

                          OPD Wave front (P-V) Strehl Ratio Spot Size Radius (microns)
                          4358A 0.1972 waves 0.8490 5.66
                          4800A 0.1362 waves 0.9353 3.27
                          4861A 0.1261 waves 0.9426 3.06
                          5461A 0.0416 waves 0.9916 1.96
                          5876A 0.0899 waves 0.9874 1.90
                          6439A 0.1847 waves 0.9283 2.32



                          and here for the TMB 80/600 triplet
                          Wave front and Strehl Ratios


                          OPD Wave front (P-V) Strehl Ratio
                          4358A 0.2635 waves 0.8299
                          4861A 0.1684 waves 0.9157
                          5100A 0.0998 waves 0.9707
                          5300A 0.0492 waves 0.9938
                          5461A 0.0177 waves 0.9990
                          5550A 0.0185 waves 0.9984
                          5876A 0.0582 waves 0.9866
                          6100A 0.0741 waves 0.9793
                          6563A 0.0847 waves 0.9775
                          7065A 0.0712 waves 0.9853


                          now ask Yuri for his design and I am willing to do a bit bet, that his
                          strehl at the other wavelenghtes will not be at this high level, otherwise I
                          could not explain, why I can see a high power startest some spherochromatism

                          thanks
                          Markus

                          ----- Original Message -----
                          From: "Michael Frias" <aaronslandscape@...>
                          To: <tmboptical@yahoogroups.com>
                          Sent: Wednesday, March 03, 2004 5:05 PM
                          Subject: [tmboptical] Re: Interferometry (was: 130 TMB & TEC 140 (was TMB
                          130)


                          > So what does all this mean? As quoted from the TEC specifications,
                          "Design:
                          > Aplanatic oiled triplet APO, ED glass with two other ones. Optimized for
                          e-line
                          > 546nm - Strehl 0.99, PV 1/20 (calculated)".
                          > What is the e-line? What does this show? Anything?
                          >
                          >
                          >
                          >
                          > --- In tmboptical@yahoogroups.com, "APM_Telescopes" <
                          > apm_telescopes@w...> wrote:
                          > > LZOS use green Twymann Interferometer for final testreport
                          > >
                          > > best wishes
                          > > Markus
                          >
                          >
                          >
                          >
                          >
                          >
                          > Yahoo! Groups Links
                          >
                          >
                          >
                          >
                          >
                        • Mike C
                          ... Yuri previously mentioned the TEC140 is calculated 1/2 wave at 436 nm. Here is a quote: Also no problem on deep sky, but with slight violet halo around
                          Message 12 of 22 , Mar 3, 2004
                            > here you see the TMB designed Strehl for the 6"F/8 Apo
                            > a.. Wave front and Strehl Ratios
                            >
                            > OPD Wave front (P-V) Strehl Ratio Spot Size Radius (microns)
                            > 4358A 0.1972 waves 0.8490 5.66
                            > 4800A 0.1362 waves 0.9353 3.27
                            > 4861A 0.1261 waves 0.9426 3.06
                            > 5461A 0.0416 waves 0.9916 1.96
                            > 5876A 0.0899 waves 0.9874 1.90
                            > 6439A 0.1847 waves 0.9283 2.32
                            >

                            > now ask Yuri for his design and I am willing to do a bit bet, that his
                            > strehl at the other wavelenghtes will not be at this high level, otherwise I
                            > could not explain, why I can see a high power startest some spherochromatism
                            >
                            > thanks
                            > Markus
                            >


                            Yuri previously mentioned the TEC140 is calculated 1/2 wave at
                            436 nm. Here is a quote: "Also no problem on deep sky, but with
                            slight violet halo around bright white-blue stars like Vega (see Vega's
                            intensity diagramm in the same file), Deneb, that radiate most of their
                            energy in 300-400nm range - for which our design is less corrected
                            (1/2 wave for 436nm)."

                            Here is another Yuri quote about the TEC140:
                            "the wave aberrations do not exceed 1/4 wave for:
                            C-line (656nm - red)
                            e-line (546nm - green)
                            F-line (480nm - blue)
                            and 1/2 for g-line (436nm - violet) and corrected for coma (aplanat)."


                            As I understand things, the TMB152 abberations do not exceed
                            1/4 wave from 448nm to 780nm.

                            Mike
                          • Tube Tim
                            ... Who? Never heard of him. ... It looks better than that, about 1/7 th wave: From the APM site: 4358A 0.1972 waves 0.8490 5.66 4800A 0.1362 waves
                            Message 13 of 22 , Mar 3, 2004
                              >--- In tmboptical@yahoogroups.com, "Mike C" <mike@e...> wrote:>
                              >
                              >
                              > Yuri previously mentioned the TEC140 is calculated 1/2 wave at

                              Who? Never heard of him.

                              > 436 nm. Here is a quote: "Also no problem on deep sky, but with
                              > slight violet halo around bright white-blue stars like Vega (see
                              > Vega's intensity diagramm in the same file), Deneb, that radiate
                              > most of their energy in 300-400nm range - for which our design is
                              > less corrected (1/2 wave for 436nm)."
                              >
                              > Here is another Yuri quote about the TEC140:
                              > "the wave aberrations do not exceed 1/4 wave for:
                              > C-line (656nm - red)
                              > e-line (546nm - green)
                              > F-line (480nm - blue)
                              > and 1/2 for g-line (436nm - violet) and corrected for coma (aplanat)."
                              >
                              >
                              > As I understand things, the TMB152 abberations do not exceed
                              > 1/4 wave from 448nm to 780nm.
                              >

                              It looks better than that, about 1/7'th wave:

                              From the APM site:

                              4358A 0.1972 waves 0.8490 5.66
                              4800A 0.1362 waves 0.9353 3.27
                              4861A 0.1261 waves 0.9426 3.06
                              5461A 0.0416 waves 0.9916 1.96
                              5876A 0.0899 waves 0.9874 1.90
                              6439A 0.1847 waves 0.9283 2.32

                              > Mike


                              Tim
                            • Mario
                              Hello. Desire that informs to me on the 130 TMB F:6. That so it is compared with COMPLEXION 140? In photography, notices the field curvature? What other good
                              Message 14 of 22 , Mar 6, 2004
                                Hello.

                                Desire that informs to me on the 130 TMB F:6.

                                That so it is compared with COMPLEXION 140?
                                In photography, notices the field curvature?
                                What other good options exist?

                                Thanks and a greeting.
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