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Re: [spectro-l] Stage OHP ce n'est qu'un debut

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  • Robin Leadbeater
    Hi Tom, That is an interesting arrangement. Is the grating you use blazed? If so at what first order wavelength? How does the efficiency using the higher
    Message 1 of 15 , Sep 6, 2008
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      Hi Tom,
       
      That is an interesting arrangement. Is the grating you use blazed? If so at what first order wavelength?  How does the efficiency using the higher orders compare with using first order for all wavelengths?
       
      Robin
       
      ---- Original Message ----
      From: Tom Buchanan
      To: spectro-l@yahoogroups.com
      Sent: Saturday, September 06, 2008 3:26 AM
      Subject: Re: [spectro-l] Stage OHP ce n'est qu'un debut

      >
      Bonjour Jean-Pierre,
      >
      > Great work on your interesting
      spectrograph!
      >
      > My spectrograph has a transmittance diffraction
      grating with 600
      > grooves/mm.
      > The camera and attached filter
      holder pivots about the center of the
      > diffraction grating and can be
      fastened in seven possible positions.
      > Reference is made to Kodak
      Publication No. B-3, "Kodak Filters for
      > Scientific and Technical Uses."
      > I have tried various filters for the second- and third-order
      spectra
      > of the sun,
      > Venus, Mars, and Jupiter, in order to avoid
      overlapping the orders.
      >
      > I use specific Wratten filters for the
      section of spectrum that I
      > want to record.
      > The first position
      records first order from 3800 to 6900 angstroms
      > and requires no filter.
      > The second position records first order infrared from 6700 to
      the
      > upper limit of detection and requires a Wratten filter #22 .
      > The second position records second order from 3800 to 5400
      angstroms
      > and requires no filter.
      > The third position records
      second order from 5100 to 6900 angstroms
      > and requires a Wratten
      filter  #8 .
      > The third position records third order from 3800 to
      4600 angstroms
      > and requires a Wratten filter #34 .
      > The fourth
      position records second order infrared from 6700 to 8100
      > angstroms or to
      the upper limit of detection and requires a Wratten
      > filter #22 . 
      > The fourth positiion records third order from 4400 to 5400
      angstroms
      > and requires Wratten filters both #'s 2B and 38A.
      > The
      fifth position records third order from 5300 to 6000 angstroms
      > and
      requires a Wratten filter #12.
      > The sixth position records third order
      from 5900 to 6400 angstroms
      > and requires a Wratten filter #12.
      >
      The seventh position records third order from 6350 to 6700 angstroms
      > and
      requires a Wratten filter #22.
      >
      > For digital cameras, an
      infrared-blocking filter is normally
      > necessary for recording the visible
      parts of the spectrum, except in
      > first order. 
      >
      > I
      hope this information helps.
      >
      > Cordialement,
      >
      > Tom
      Buchanan
      >
      >
    • Tom Buchanan
      ... From: Tom Buchanan To: spectro-l@yahoogroups.com Sent: Saturday, September 06, 2008 4:16 PM Subject: Re: [spectro-l] Stage OHP ce n est qu un debut Hi
      Message 2 of 15 , Sep 6, 2008
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        ----- Original Message -----
        Sent: Saturday, September 06, 2008 4:16 PM
        Subject: Re: [spectro-l] Stage OHP ce n'est qu'un debut

        Hi Robin,
         
        Yes, my Bausch & Lomb grating is blazed at 4800 angstroms in first order for an original efficiency of 57%. 
        The best resolution with a slit is about 2500 in first order, 6000 in second order, and 10000 in third order. 
        For slitless operation, the resolution is about half of these values. 
        For first trials of exposure above first order, I add three stops for second order,
        add six stops for third order, and add an additional stop for each filter used in the optical train. 
         
        In 1982 I built this versatile spectrograph by using only one grating that cost $600 then.
         
        To correct a couple of mistakes in my previous table:
        The third position records third order from 3800 to 4600 angstroms and requires Wratten filters both #'s 34 and 38A.
        The fourth position records third order from 4400 to 5400 angstroms and requires Wratten filter #38A.
         
        These recommendations might change as I experiment further. 
         
        Tom Buchanan
         
         
         
         
        ----- Original Message -----
        Sent: Saturday, September 06, 2008 8:41 AM
        Subject: Re: [spectro-l] Stage OHP ce n'est qu'un debut

        Hi Tom,
         
        That is an interesting arrangement. Is the grating you use blazed? If so at what first order wavelength?  How does the efficiency using the higher orders compare with using first order for all wavelengths?
         
        Robin
         
        ---- Original Message ----
        From: Tom Buchanan
        To: spectro-l@yahoogrou ps.com
        Sent: Saturday, September 06, 2008 3:26 AM
        Subject: Re: [spectro-l] Stage OHP ce n'est qu'un debut

        > Bonjour Jean-Pierre,
        >
        > Great work on your interesting spectrograph!
        >
        > My spectrograph has a transmittance diffraction grating with 600
        > grooves/mm.
        > The camera and attached filter holder pivots about the center of the
        > diffraction grating and can be fastened in seven possible positions.
        > Reference is made to Kodak Publication No. B-3, "Kodak Filters for
        > Scientific and Technical Uses."
        > I have tried various filters for the second- and third-order spectra
        > of the sun,
        > Venus, Mars, and Jupiter, in order to avoid overlapping the orders.
        >
        > I use specific Wratten filters for the section of spectrum that I
        > want to record.
        > The first position records first order from 3800 to 6900 angstroms
        > and requires no filter.
        > The second position records first order infrared from 6700 to the
        > upper limit of detection and requires a Wratten filter #22 .
        > The second position records second order from 3800 to 5400 angstroms
        > and requires no filter.
        > The third position records second order from 5100 to 6900 angstroms
        > and requires a Wratten filter  #8 .
        > The third position records third order from 3800 to 4600 angstroms
        > and requires a Wratten filter #34 .
        > The fourth position records second order infrared from 6700 to 8100
        > angstroms or to the upper limit of detection and requires a Wratten
        > filter #22 . 
        > The fourth positiion records third order from 4400 to 5400 angstroms
        > and requires Wratten filters both #'s 2B and 38A.
        > The fifth position records third order from 5300 to 6000 angstroms
        > and requires a Wratten filter #12.
        > The sixth position records third order from 5900 to 6400 angstroms
        > and requires a Wratten filter #12.
        > The seventh position records third order from 6350 to 6700 angstroms
        > and requires a Wratten filter #22.
        >
        > For digital cameras, an infrared-blocking filter is normally
        > necessary for recording the visible parts of the spectrum, except in
        > first order. 
        >
        > I hope this information helps.
        >
        > Cordialement,
        >
        > Tom Buchanan
        >
        >

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