How did Skylab's electrographic camera work?











up vote
3
down vote

favorite












This answer links to history.nasa.gov's SP-404 Skylab's Astronomy and Space Sciences. In what looks like chapter 2, page 14 there is mention of Skylab's electrographic camera, shown below.



In the image I see what looks like a Cassegrain optical telescope except that there are also electron trajectories shown and a magnetic field.



Question: How did Skylab's electrographic camera work? How does the magnetic field contribute to the operation, and why is that curved surface that looks just like a Cassegrain hyperbolic secondary mirror actually curved?



Skylab electrographic camera










share|improve this question


















  • 3




    The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
    – Uwe
    Dec 1 at 23:10










  • Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
    – uhoh
    Dec 1 at 23:16












  • The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
    – Uwe
    Dec 2 at 0:09










  • @Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
    – uhoh
    Dec 2 at 0:19










  • Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
    – Uwe
    Dec 2 at 15:15















up vote
3
down vote

favorite












This answer links to history.nasa.gov's SP-404 Skylab's Astronomy and Space Sciences. In what looks like chapter 2, page 14 there is mention of Skylab's electrographic camera, shown below.



In the image I see what looks like a Cassegrain optical telescope except that there are also electron trajectories shown and a magnetic field.



Question: How did Skylab's electrographic camera work? How does the magnetic field contribute to the operation, and why is that curved surface that looks just like a Cassegrain hyperbolic secondary mirror actually curved?



Skylab electrographic camera










share|improve this question


















  • 3




    The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
    – Uwe
    Dec 1 at 23:10










  • Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
    – uhoh
    Dec 1 at 23:16












  • The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
    – Uwe
    Dec 2 at 0:09










  • @Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
    – uhoh
    Dec 2 at 0:19










  • Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
    – Uwe
    Dec 2 at 15:15













up vote
3
down vote

favorite









up vote
3
down vote

favorite











This answer links to history.nasa.gov's SP-404 Skylab's Astronomy and Space Sciences. In what looks like chapter 2, page 14 there is mention of Skylab's electrographic camera, shown below.



In the image I see what looks like a Cassegrain optical telescope except that there are also electron trajectories shown and a magnetic field.



Question: How did Skylab's electrographic camera work? How does the magnetic field contribute to the operation, and why is that curved surface that looks just like a Cassegrain hyperbolic secondary mirror actually curved?



Skylab electrographic camera










share|improve this question













This answer links to history.nasa.gov's SP-404 Skylab's Astronomy and Space Sciences. In what looks like chapter 2, page 14 there is mention of Skylab's electrographic camera, shown below.



In the image I see what looks like a Cassegrain optical telescope except that there are also electron trajectories shown and a magnetic field.



Question: How did Skylab's electrographic camera work? How does the magnetic field contribute to the operation, and why is that curved surface that looks just like a Cassegrain hyperbolic secondary mirror actually curved?



Skylab electrographic camera







imaging observation telescope skylab






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Dec 1 at 22:49









uhoh

34.2k17117421




34.2k17117421








  • 3




    The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
    – Uwe
    Dec 1 at 23:10










  • Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
    – uhoh
    Dec 1 at 23:16












  • The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
    – Uwe
    Dec 2 at 0:09










  • @Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
    – uhoh
    Dec 2 at 0:19










  • Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
    – Uwe
    Dec 2 at 15:15














  • 3




    The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
    – Uwe
    Dec 1 at 23:10










  • Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
    – uhoh
    Dec 1 at 23:16












  • The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
    – Uwe
    Dec 2 at 0:09










  • @Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
    – uhoh
    Dec 2 at 0:19










  • Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
    – Uwe
    Dec 2 at 15:15








3




3




The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
– Uwe
Dec 1 at 23:10




The answer is there in the link to chapter 2 page 14. The magnetic field is used as a lens for the electrons to build an image of electrons on the film as it is done in an electron microscope. The UV light is translated into electrons by a photocathode on the second smaler mirror.
– Uwe
Dec 1 at 23:10












Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
– uhoh
Dec 1 at 23:16






Is the photocathode in front of the secondary, or on it? Why is there a secondary mirror at all? There is a puzzle here. Magnetic lenses have strong chromatic aberration, how does the system achieve good electron image quality in this case?
– uhoh
Dec 1 at 23:16














The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
– Uwe
Dec 2 at 0:09




The photocathode should be on the secondary mirror, the UV photons are absorbed in the photocathode and the electrons are emitted. The vertical arrow is only to indicate the optical or electron image. Poor quality of the magnetic lens is compensated by the very short wavelength of the electrons.
– Uwe
Dec 2 at 0:09












@Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
– uhoh
Dec 2 at 0:19




@Uwe there is no such compensation, that doesn't make sense. Electron microscopes work extremely hard to fight the huge chromatic aberration inherent in magnetic lenses.
– uhoh
Dec 2 at 0:19












Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
– Uwe
Dec 2 at 15:15




Okay, I am wrong about compensation. But chromatic aberration requires different electron wavelengths or energies. If the acceleration voltage is constant and the UV wavelength bandwidth is small, the electrons wavelength variation is small and thus chromatic aberration too.
– Uwe
Dec 2 at 15:15










1 Answer
1






active

oldest

votes

















up vote
8
down vote



accepted










Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt bias, which allows them to be focused with good resolution onto a film surface using the magnetic field.



"Electrographic cameras for the vacuum ultraviolet" by Carruthers, G. R. in "Electrography and astronomical applications; Proceedings of the Conference", Austin, Tex., March 11, 12, 1974. (A75-23926 09-89) Austin, University of Texas, 1974, p. 93-113; Discussion, p. 114-116.



Citing the article:




[...] we have been developing a series of magnetically focused electrographic cameras utilizing front-surface alkali-halide photocathode [...] In these devices, the photocathode is mounted at the focus of an optical system which is partially contained within the imaging device.



diagram of an electrographic Schmidt camera




So, apparently, the secondary mirror does not actually work as a mirror (the optical path ends here) and its shape only corrects the field curvature. See Schmidt camera.






share|improve this answer























    Your Answer





    StackExchange.ifUsing("editor", function () {
    return StackExchange.using("mathjaxEditing", function () {
    StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
    StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
    });
    });
    }, "mathjax-editing");

    StackExchange.ready(function() {
    var channelOptions = {
    tags: "".split(" "),
    id: "508"
    };
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function() {
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled) {
    StackExchange.using("snippets", function() {
    createEditor();
    });
    }
    else {
    createEditor();
    }
    });

    function createEditor() {
    StackExchange.prepareEditor({
    heartbeatType: 'answer',
    convertImagesToLinks: false,
    noModals: true,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: null,
    bindNavPrevention: true,
    postfix: "",
    imageUploader: {
    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
    allowUrls: true
    },
    noCode: true, onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    });


    }
    });














    draft saved

    draft discarded


















    StackExchange.ready(
    function () {
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fspace.stackexchange.com%2fquestions%2f32497%2fhow-did-skylabs-electrographic-camera-work%23new-answer', 'question_page');
    }
    );

    Post as a guest















    Required, but never shown

























    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    8
    down vote



    accepted










    Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt bias, which allows them to be focused with good resolution onto a film surface using the magnetic field.



    "Electrographic cameras for the vacuum ultraviolet" by Carruthers, G. R. in "Electrography and astronomical applications; Proceedings of the Conference", Austin, Tex., March 11, 12, 1974. (A75-23926 09-89) Austin, University of Texas, 1974, p. 93-113; Discussion, p. 114-116.



    Citing the article:




    [...] we have been developing a series of magnetically focused electrographic cameras utilizing front-surface alkali-halide photocathode [...] In these devices, the photocathode is mounted at the focus of an optical system which is partially contained within the imaging device.



    diagram of an electrographic Schmidt camera




    So, apparently, the secondary mirror does not actually work as a mirror (the optical path ends here) and its shape only corrects the field curvature. See Schmidt camera.






    share|improve this answer



























      up vote
      8
      down vote



      accepted










      Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt bias, which allows them to be focused with good resolution onto a film surface using the magnetic field.



      "Electrographic cameras for the vacuum ultraviolet" by Carruthers, G. R. in "Electrography and astronomical applications; Proceedings of the Conference", Austin, Tex., March 11, 12, 1974. (A75-23926 09-89) Austin, University of Texas, 1974, p. 93-113; Discussion, p. 114-116.



      Citing the article:




      [...] we have been developing a series of magnetically focused electrographic cameras utilizing front-surface alkali-halide photocathode [...] In these devices, the photocathode is mounted at the focus of an optical system which is partially contained within the imaging device.



      diagram of an electrographic Schmidt camera




      So, apparently, the secondary mirror does not actually work as a mirror (the optical path ends here) and its shape only corrects the field curvature. See Schmidt camera.






      share|improve this answer

























        up vote
        8
        down vote



        accepted







        up vote
        8
        down vote



        accepted






        Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt bias, which allows them to be focused with good resolution onto a film surface using the magnetic field.



        "Electrographic cameras for the vacuum ultraviolet" by Carruthers, G. R. in "Electrography and astronomical applications; Proceedings of the Conference", Austin, Tex., March 11, 12, 1974. (A75-23926 09-89) Austin, University of Texas, 1974, p. 93-113; Discussion, p. 114-116.



        Citing the article:




        [...] we have been developing a series of magnetically focused electrographic cameras utilizing front-surface alkali-halide photocathode [...] In these devices, the photocathode is mounted at the focus of an optical system which is partially contained within the imaging device.



        diagram of an electrographic Schmidt camera




        So, apparently, the secondary mirror does not actually work as a mirror (the optical path ends here) and its shape only corrects the field curvature. See Schmidt camera.






        share|improve this answer














        Similarly to night vision devices, the light sensitive part is the photocathode, which releases electrons when hit by photons. The electrons at the photocathode are accelerated by the -25 kilovolt bias, which allows them to be focused with good resolution onto a film surface using the magnetic field.



        "Electrographic cameras for the vacuum ultraviolet" by Carruthers, G. R. in "Electrography and astronomical applications; Proceedings of the Conference", Austin, Tex., March 11, 12, 1974. (A75-23926 09-89) Austin, University of Texas, 1974, p. 93-113; Discussion, p. 114-116.



        Citing the article:




        [...] we have been developing a series of magnetically focused electrographic cameras utilizing front-surface alkali-halide photocathode [...] In these devices, the photocathode is mounted at the focus of an optical system which is partially contained within the imaging device.



        diagram of an electrographic Schmidt camera




        So, apparently, the secondary mirror does not actually work as a mirror (the optical path ends here) and its shape only corrects the field curvature. See Schmidt camera.







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Dec 2 at 0:35









        uhoh

        34.2k17117421




        34.2k17117421










        answered Dec 1 at 23:08









        szulat

        63569




        63569






























            draft saved

            draft discarded




















































            Thanks for contributing an answer to Space Exploration Stack Exchange!


            • Please be sure to answer the question. Provide details and share your research!

            But avoid



            • Asking for help, clarification, or responding to other answers.

            • Making statements based on opinion; back them up with references or personal experience.


            Use MathJax to format equations. MathJax reference.


            To learn more, see our tips on writing great answers.





            Some of your past answers have not been well-received, and you're in danger of being blocked from answering.


            Please pay close attention to the following guidance:


            • Please be sure to answer the question. Provide details and share your research!

            But avoid



            • Asking for help, clarification, or responding to other answers.

            • Making statements based on opinion; back them up with references or personal experience.


            To learn more, see our tips on writing great answers.




            draft saved


            draft discarded














            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fspace.stackexchange.com%2fquestions%2f32497%2fhow-did-skylabs-electrographic-camera-work%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown





















































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown

































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown







            Popular posts from this blog

            Ellipse (mathématiques)

            Quarter-circle Tiles

            Mont Emei