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Re: New version 0.8x reducer - more vignetting?

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  • digidodi
    Yes, I know, i am preparing a review of the FLT110 including EOS 5D photography and it is clear T2 on its own is a limiting factor (we knew that since the film
    Message 1 of 12 , Jan 2, 2007
      Yes, I know, i am preparing a review of the FLT110 including EOS 5D
      photography and it is clear T2 on its own is a limiting factor (we
      knew that since the film era ;) ). But it shouldn't be at all for APS
      size format. Something else is going on here...

      Dodi


      --- In William-Optics@yahoogroups.com, Ciobotas <ciobota@...> wrote:
      >
      > There is indeed vignetting, as Andrew and I have discussed it in
      another
      > forum. Bear in mind though, those pics are stretched, the raws
      don't show
      > nearly as bad (although still very pronounced). Once I rebuild my
      pc I'll
      > post some flats I took with it and a few scopes, like the 66SD and m90.
      >
      > The kicker though is that the lens elements cover the diameter of the t
      > thread and the sct thread on the other side. In other words, the
      vignetting
      > should be no worse than the meade unit (indeed, less, since the
      reduction is
      > less). Check out the link to the reducer and see for yourself:
      >
      > http://www.optcorp.com/product.aspx?pid=9180&kw=focal%20reducer&st=2
      >
      > That is the reducer that is sold now, and it shows the 2" nosepiece as
      > well. I am totally baffled as to the source of the vignetting, this
      > particular reducer should show no more vignetting than any other reducer
      > with a t thread adapter.
      >
      > Btw, t thread adapters have long been recognized as barely
      sufficient for
      > 35mm film, especially for fast scopes. If you take 35mm film width
      and 55mm
      > distance from film to adapter plane, you can see that 42mm width at the
      > adapter gives you a pretty small cone angle. So I would suspect
      that all
      > 35mm digital cameras will suffer from some vignetting with any fast
      scope,
      > worse with a reducer.
      >
      > Just my thoughts.
      >
      > Daniel
      >
      >
      >
      >
      > On 1/2/07, digidodi <ddierick@...> wrote:
      > >
      > > Ouch, indeed, that is TERRIBLE vignetting at this format of sensor. It
      > > is more like a peephole :(
      > >
      > > You could try with flats, but ok, that always gives quality loss in
      > > the vignetted areas. There is no magic with flats.
      > >
      > > I would ask WO support if this is supposed to be behaviour of this
      > > reducer.
      > >
      > > Dodi
      > >
      > >
      > > --- In William-Optics@yahoogroups.com, "candtuk" <candtuk@> wrote:
      > > >
      > > > --- In William-Optics@yahoogroups.com, "Timm Bottoni" <t.bottoni@>
      > > > wrote:
      > > > >
      > > > > Hi,
      > > > >
      > > > > Doh! Never mind - I see from the new pictures it attached
      directly
      > > > > to the T-Ring - what was I thinking???
      > > > >
      > > > > If you can post a pic of the daytime sky, it should be easy to see
      > > > > any vignetting
      > > > >
      > > > > Timm
      > > >
      > > > Here you go - not a daytime sky, but a nightime stretched image. It
      > > > was a high moon and only 30s shots hence the lack of stars and
      bright
      > > > background. The blown up area is the rop right of each frame, so you
      > > > can see there are stars there, but they are difficult to see in the
      > > > vignetted area as its so dark...
      > > >
      > > > I again used 3 spacings between the reducer and t-mount of the
      300D -
      > > > no spacing (55 mm), 0.5mm (55.5mm) and 1mm (56 mm) - the extra space
      > > > is needed to get to ~56mm, which is the recommended distance...
      > > >
      > > > http://www.ag-images.co.uk/download/0mmspacing.jpg
      > > > http://www.ag-images.co.uk/download/0.5mmspacing.jpg
      > > > http://www.ag-images.co.uk/download/1mmspacing.jpg
      > > >
      > > > I'm quite disappointed in the vignetting - I can't imagine what it
      > > > would be like on a bigger chip...
      > > >
      > > > AndrewG
      > > > http://
      > > >
      > >
      > >
      > >
      > >
      > > www.william-optics.com
      > > Yahoo! Groups Links
      > >
      > >
      > >
      > >
      >
    • Timm Bottoni
      Calling Scott Walker - ring... ring.... I am not familiar at all with the Orion ED80 enough to know what else could be causing the vignetting, so I would
      Message 2 of 12 , Jan 2, 2007
        Calling Scott Walker - ring... ring....

        I am not familiar at all with the Orion ED80 enough to know what else
        could be causing the vignetting, so I would assume it's the WO
        reducer/ff, but Scott knows a fair amount about these things.

        Another idea... could the focuser tube be causing it?

        Timm

        --- In William-Optics@yahoogroups.com, Ciobotas <ciobota@...> wrote:
        >
        > There is indeed vignetting, as Andrew and I have discussed it in
        another
        > forum. Bear in mind though, those pics are stretched, the raws
        don't show
        > nearly as bad (although still very pronounced). Once I rebuild my
        pc I'll
        > post some flats I took with it and a few scopes, like the 66SD and
        m90.
        >
        > The kicker though is that the lens elements cover the diameter of
        the t
        > thread and the sct thread on the other side. In other words, the
        vignetting
        > should be no worse than the meade unit (indeed, less, since the
        reduction is
        > less). Check out the link to the reducer and see for yourself:
        >
        > http://www.optcorp.com/product.aspx?pid=9180&kw=focal%20reducer&st=2
        >
        > That is the reducer that is sold now, and it shows the 2"
        nosepiece as
        > well. I am totally baffled as to the source of the vignetting, this
        > particular reducer should show no more vignetting than any other
        reducer
        > with a t thread adapter.
        >
        > Btw, t thread adapters have long been recognized as barely
        sufficient for
        > 35mm film, especially for fast scopes. If you take 35mm film width
        and 55mm
        > distance from film to adapter plane, you can see that 42mm width at
        the
        > adapter gives you a pretty small cone angle. So I would suspect
        that all
        > 35mm digital cameras will suffer from some vignetting with any fast
        scope,
        > worse with a reducer.
        >
        > Just my thoughts.
        >
        > Daniel
        >
        >
        >
        >
        > On 1/2/07, digidodi <ddierick@...> wrote:
        > >
        > > Ouch, indeed, that is TERRIBLE vignetting at this format of
        sensor. It
        > > is more like a peephole :(
        > >
        > > You could try with flats, but ok, that always gives quality loss
        in
        > > the vignetted areas. There is no magic with flats.
        > >
        > > I would ask WO support if this is supposed to be behaviour of this
        > > reducer.
        > >
        > > Dodi
        > >
        > >
        > > --- In William-Optics@yahoogroups.com, "candtuk" <candtuk@> wrote:
        > > >
        > > > --- In William-Optics@yahoogroups.com, "Timm Bottoni"
        <t.bottoni@>
        > > > wrote:
        > > > >
        > > > > Hi,
        > > > >
        > > > > Doh! Never mind - I see from the new pictures it attached
        directly
        > > > > to the T-Ring - what was I thinking???
        > > > >
        > > > > If you can post a pic of the daytime sky, it should be easy
        to see
        > > > > any vignetting
        > > > >
        > > > > Timm
        > > >
        > > > Here you go - not a daytime sky, but a nightime stretched
        image. It
        > > > was a high moon and only 30s shots hence the lack of stars and
        bright
        > > > background. The blown up area is the rop right of each frame,
        so you
        > > > can see there are stars there, but they are difficult to see in
        the
        > > > vignetted area as its so dark...
        > > >
        > > > I again used 3 spacings between the reducer and t-mount of the
        300D -
        > > > no spacing (55 mm), 0.5mm (55.5mm) and 1mm (56 mm) - the extra
        space
        > > > is needed to get to ~56mm, which is the recommended distance...
        > > >
        > > > http://www.ag-images.co.uk/download/0mmspacing.jpg
        > > > http://www.ag-images.co.uk/download/0.5mmspacing.jpg
        > > > http://www.ag-images.co.uk/download/1mmspacing.jpg
        > > >
        > > > I'm quite disappointed in the vignetting - I can't imagine what
        it
        > > > would be like on a bigger chip...
        > > >
        > > > AndrewG
        > > > http://
        > > >
        > >
        > >
        > >
        > >
        > > www.william-optics.com
        > > Yahoo! Groups Links
        > >
        > >
        > >
        > >
        >
      • Scott Walker
        The new FF does not use the full aperture of the T-thread. The rear aperture is about 32 mm. The T-thread limit is about 38.5mm. The real limit in the new FF
        Message 3 of 12 , Jan 2, 2007
          The new FF does not use the full aperture of the T-thread. The rear aperture is about 32 mm. The T-thread limit is about 38.5mm. The real limit in the new FF is in the front lens which has is about a 30mm aperture. It is this small aperture which is causing the vignette.
           
          Scott Walker
          ----- Original Message -----
          From: Ciobotas
          Sent: Tuesday, January 02, 2007 3:41 PM
          Subject: Re: [William-Optics] Re: New version 0.8x reducer - more vignetting?

           There is indeed vignetting, as Andrew and I have discussed it in another forum.  Bear in mind though, those pics are stretched, the raws don't show nearly as bad (although still very pronounced).  Once I rebuild my pc I'll post some flats I took with it and a few scopes, like the 66SD and m90.
           
           The kicker though is that the lens elements cover the diameter of the t thread and the sct thread on the other side.  In other words, the vignetting should be no worse than the meade unit (indeed, less, since the reduction is less).  Check out the link to the reducer and see for yourself:
           
           
           That is the reducer that is sold now, and it shows the 2" nosepiece as well.  I am totally baffled as to the source of the vignetting, this particular reducer should show no more vignetting than any other reducer with a t thread adapter.
           
           Btw, t thread adapters have long been recognized as barely sufficient for 35mm film, especially for fast scopes.  If you take 35mm film width and 55mm distance from film to adapter plane, you can see that 42mm width at the adapter gives you a pretty small cone angle.  So I would suspect that all 35mm digital cameras will suffer from some vignetting with any fast scope, worse with a reducer.
           
          Just my thoughts.
           
          Daniel
           
           

           
          On 1/2/07, digidodi <ddierick@hotmail. com> wrote:
          Ouch, indeed, that is TERRIBLE vignetting at this format of sensor. It
          is more like a peephole :(

          You could try with flats, but ok, that always gives quality loss in
          the vignetted areas. There is no magic with flats.

          I would ask WO support if this is supposed to be behaviour of this
          reducer.

          Dodi


          --- In William-Optics@ yahoogroups. com, "candtuk" <candtuk@...> wrote:
          >
          > --- In William-Optics@ yahoogroups. com , "Timm Bottoni" <t.bottoni@>
          > wrote:
          > >
          > > Hi,
          > >
          > > Doh!  Never mind - I see from the new pictures it attached directly
          > > to the T-Ring - what was I thinking???
          > >
          > > If you can post a pic of the daytime sky, it should be easy to see
          > > any vignetting
          > >
          > > Timm
          >
          > Here you go - not a daytime sky, but a nightime stretched image. It
          > was a high moon and only 30s shots hence the lack of stars and bright
          > background. The blown up area is the rop right of each frame, so you
          > can see there are stars there, but they are difficult to see in the
          > vignetted area as its so dark...
          >
          > I again used 3 spacings between the reducer and t-mount of the 300D -
          > no spacing (55 mm), 0.5mm (55.5mm) and 1mm (56 mm) - the extra space
          > is needed to get to ~56mm, which is the recommended distance...
          >
          > http://www.ag- images.co. uk/download/ 0mmspacing. jpg
          > http://www.ag- images.co. uk/download/ 0.5mmspacing. jpg
          > http://www.ag- images.co. uk/download/ 1mmspacing. jpg
          >
          > I'm quite disappointed in the vignetting - I can't imagine what it
          > would be like on a bigger chip...
          >
          > AndrewG
          > http://
          >




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        • Scott Walker
          Timm here is a response I made to a previous posting. The new FF does not use the full aperture of the T-thread. The rear aperture is about 32 mm. The T-thread
          Message 4 of 12 , Jan 2, 2007
            Timm here is a response I made to a previous posting.
             
            The new FF does not use the full aperture of the T-thread. The rear aperture is about 32 mm. The T-thread limit is about 38.5mm. The real limit in the new FF is in the front lens which has is about a 30mm aperture. It is this small aperture which is causing the vignette.
             
            Scott Walker
            ----- Original Message -----
            Sent: Tuesday, January 02, 2007 7:42 PM
            Subject: [William-Optics] Re: New version 0.8x reducer - more vignetting?

            Calling Scott Walker - ring... ring....

            I am not familiar at all with the Orion ED80 enough to know what else
            could be causing the vignetting, so I would assume it's the WO
            reducer/ff, but Scott knows a fair amount about these things.

            Another idea... could the focuser tube be causing it?

            Timm

            --- In William-Optics@ yahoogroups. com, Ciobotas <ciobota@... > wrote:
            >
            > There is indeed vignetting, as Andrew and I have discussed it in
            another
            > forum. Bear in mind though, those pics are stretched, the raws
            don't show
            > nearly as bad (although still very pronounced). Once I rebuild my
            pc I'll
            > post some flats I took with it and a few scopes, like the 66SD and
            m90.
            >
            > The kicker though is that the lens elements cover the diameter of
            the t
            > thread and the sct thread on the other side. In other words, the
            vignetting
            > should be no worse than the meade unit (indeed, less, since the
            reduction is
            > less). Check out the link to the reducer and see for yourself:
            >
            > http://www.optcorp. com/product. aspx?pid= 9180&kw=focal% 20reducer& st=2
            >
            > That is the reducer that is sold now, and it shows the 2"
            nosepiece as
            > well. I am totally baffled as to the source of the vignetting, this
            > particular reducer should show no more vignetting than any other
            reducer
            > with a t thread adapter.
            >
            > Btw, t thread adapters have long been recognized as barely
            sufficient for
            > 35mm film, especially for fast scopes. If you take 35mm film width
            and 55mm
            > distance from film to adapter plane, you can see that 42mm width at
            the
            > adapter gives you a pretty small cone angle. So I would suspect
            that all
            > 35mm digital cameras will suffer from some vignetting with any fast
            scope,
            > worse with a reducer.
            >
            > Just my thoughts.
            >
            > Daniel
            >
            >
            >
            >
            > On 1/2/07, digidodi <ddierick@.. .> wrote:
            > >
            > > Ouch, indeed, that is TERRIBLE vignetting at this format of
            sensor. It
            > > is more like a peephole :(
            > >
            > > You could try with flats, but ok, that always gives quality loss
            in
            > > the vignetted areas. There is no magic with flats.
            > >
            > > I would ask WO support if this is supposed to be behaviour of this
            > > reducer.
            > >
            > > Dodi
            > >
            > >
            > > --- In William-Optics@ yahoogroups. com, "candtuk" <candtuk@> wrote:
            > > >
            > > > --- In William-Optics@ yahoogroups. com, "Timm Bottoni"
            <t.bottoni@>
            > > > wrote:
            > > > >
            > > > > Hi,
            > > > >
            > > > > Doh! Never mind - I see from the new pictures it attached
            directly
            > > > > to the T-Ring - what was I thinking???
            > > > >
            > > > > If you can post a pic of the daytime sky, it should be easy
            to see
            > > > > any vignetting
            > > > >
            > > > > Timm
            > > >
            > > > Here you go - not a daytime sky, but a nightime stretched
            image. It
            > > > was a high moon and only 30s shots hence the lack of stars and
            bright
            > > > background. The blown up area is the rop right of each frame,
            so you
            > > > can see there are stars there, but they are difficult to see in
            the
            > > > vignetted area as its so dark...
            > > >
            > > > I again used 3 spacings between the reducer and t-mount of the
            300D -
            > > > no spacing (55 mm), 0.5mm (55.5mm) and 1mm (56 mm) - the extra
            space
            > > > is needed to get to ~56mm, which is the recommended distance...
            > > >
            > > > http://www.ag- images.co. uk/download/ 0mmspacing. jpg
            > > > http://www.ag- images.co. uk/download/ 0.5mmspacing. jpg
            > > > http://www.ag- images.co. uk/download/ 1mmspacing. jpg
            > > >
            > > > I'm quite disappointed in the vignetting - I can't imagine what
            it
            > > > would be like on a bigger chip...
            > > >
            > > > AndrewG
            > > > http://
            > > >
            > >
            > >
            > >
            > >
            > > www.william- optics.com
            > > Yahoo! Groups Links
            > >
            > >
            > >
            > >
            >

          • CandT
            Thanks Scott - so how come its supposed to be for APS sized chips? the Rebel chip is the smallest of the Canon s DSLR isn t it? Does the problem now show up as
            Message 5 of 12 , Jan 2, 2007
              Thanks Scott - so how come its supposed to be for APS sized chips? the Rebel chip is the smallest of the Canon's DSLR isn't it? Does the problem now show up as much with the 66mm scopes?
               
              Using this online focal reducer calculator - if the values you are saying are 30mm front diameter, 56mm to CCD, and a focal length of 260mm, then the unvignetted field is only 20.48mm. (The 300D is ~22mm x ~15mm) - meaning it will always vignette for DSLR chips...
               
               
              As Daniel rightly pointed out though - my image was stretched a fair bit, and maybe it won't be as apparent with properly processed shots, so I'll reserve my final assessment until my next clear sky outing - which at UK rates is likely to be sometime in late 2009....
               
              AndrewG


              From: William-Optics@yahoogroups.com [mailto:William-Optics@yahoogroups.com] On Behalf Of Scott Walker
              Sent: 03 January 2007 04:25
              To: William-Optics@yahoogroups.com
              Subject: Re: [William-Optics] Re: New version 0.8x reducer - more vignetting?

              The new FF does not use the full aperture of the T-thread. The rear aperture is about 32 mm. The T-thread limit is about 38.5mm. The real limit in the new FF is in the front lens which has is about a 30mm aperture. It is this small aperture which is causing the vignette.
               
              Scott Walker
              .

            • Timm Bottoni
              Thanks Scott for this info. I understand what you mean now. I wonder why it was designed that way. Maybe Daniel or William can let us know if they get a
              Message 6 of 12 , Jan 3, 2007
                Thanks Scott for this info. I understand what you mean now.

                I wonder why it was designed that way. Maybe Daniel or William can
                let us know if they get a chance.

                Timm

                --- In William-Optics@yahoogroups.com, "Scott Walker" <sdwalker@...>
                wrote:
                >
                > Timm here is a response I made to a previous posting.
                >
                > The new FF does not use the full aperture of the T-thread. The rear
                aperture is about 32 mm. The T-thread limit is about 38.5mm. The real
                limit in the new FF is in the front lens which has is about a 30mm
                aperture. It is this small aperture which is causing the vignette.
                >
                > Scott Walker
                > ----- Original Message -----
                > From: Timm Bottoni
                > To: William-Optics@yahoogroups.com
                > Sent: Tuesday, January 02, 2007 7:42 PM
                > Subject: [William-Optics] Re: New version 0.8x reducer - more
                vignetting?
                >
                >
                > Calling Scott Walker - ring... ring....
                >
                > I am not familiar at all with the Orion ED80 enough to know what
                else
                > could be causing the vignetting, so I would assume it's the WO
                > reducer/ff, but Scott knows a fair amount about these things.
                >
                > Another idea... could the focuser tube be causing it?
                >
                > Timm
                >
                > --- In William-Optics@yahoogroups.com, Ciobotas <ciobota@> wrote:
                > >
                > > There is indeed vignetting, as Andrew and I have discussed it
                in
                > another
                > > forum. Bear in mind though, those pics are stretched, the raws
                > don't show
                > > nearly as bad (although still very pronounced). Once I rebuild
                my
                > pc I'll
                > > post some flats I took with it and a few scopes, like the 66SD
                and
                > m90.
                > >
                > > The kicker though is that the lens elements cover the diameter
                of
                > the t
                > > thread and the sct thread on the other side. In other words,
                the
                > vignetting
                > > should be no worse than the meade unit (indeed, less, since the
                > reduction is
                > > less). Check out the link to the reducer and see for yourself:
                > >
                > > http://www.optcorp.com/product.aspx?pid=9180&kw=focal%
                20reducer&st=2
                > >
                > > That is the reducer that is sold now, and it shows the 2"
                > nosepiece as
                > > well. I am totally baffled as to the source of the vignetting,
                this
                > > particular reducer should show no more vignetting than any
                other
                > reducer
                > > with a t thread adapter.
                > >
                > > Btw, t thread adapters have long been recognized as barely
                > sufficient for
                > > 35mm film, especially for fast scopes. If you take 35mm film
                width
                > and 55mm
                > > distance from film to adapter plane, you can see that 42mm
                width at
                > the
                > > adapter gives you a pretty small cone angle. So I would suspect
                > that all
                > > 35mm digital cameras will suffer from some vignetting with any
                fast
                > scope,
                > > worse with a reducer.
                > >
                > > Just my thoughts.
                > >
                > > Daniel
                > >
                > >
                > >
                > >
                > > On 1/2/07, digidodi <ddierick@> wrote:
                > > >
                > > > Ouch, indeed, that is TERRIBLE vignetting at this format of
                > sensor. It
                > > > is more like a peephole :(
                > > >
                > > > You could try with flats, but ok, that always gives quality
                loss
                > in
                > > > the vignetted areas. There is no magic with flats.
                > > >
                > > > I would ask WO support if this is supposed to be behaviour of
                this
                > > > reducer.
                > > >
                > > > Dodi
                > > >
                > > >
                > > > --- In William-Optics@yahoogroups.com, "candtuk" <candtuk@>
                wrote:
                > > > >
                > > > > --- In William-Optics@yahoogroups.com, "Timm Bottoni"
                > <t.bottoni@>
                > > > > wrote:
                > > > > >
                > > > > > Hi,
                > > > > >
                > > > > > Doh! Never mind - I see from the new pictures it attached
                > directly
                > > > > > to the T-Ring - what was I thinking???
                > > > > >
                > > > > > If you can post a pic of the daytime sky, it should be
                easy
                > to see
                > > > > > any vignetting
                > > > > >
                > > > > > Timm
                > > > >
                > > > > Here you go - not a daytime sky, but a nightime stretched
                > image. It
                > > > > was a high moon and only 30s shots hence the lack of stars
                and
                > bright
                > > > > background. The blown up area is the rop right of each
                frame,
                > so you
                > > > > can see there are stars there, but they are difficult to
                see in
                > the
                > > > > vignetted area as its so dark...
                > > > >
                > > > > I again used 3 spacings between the reducer and t-mount of
                the
                > 300D -
                > > > > no spacing (55 mm), 0.5mm (55.5mm) and 1mm (56 mm) - the
                extra
                > space
                > > > > is needed to get to ~56mm, which is the recommended
                distance...
                > > > >
                > > > > http://www.ag-images.co.uk/download/0mmspacing.jpg
                > > > > http://www.ag-images.co.uk/download/0.5mmspacing.jpg
                > > > > http://www.ag-images.co.uk/download/1mmspacing.jpg
                > > > >
                > > > > I'm quite disappointed in the vignetting - I can't imagine
                what
                > it
                > > > > would be like on a bigger chip...
                > > > >
                > > > > AndrewG
                > > > > http://
                > > > >
                > > >
                > > >
                > > >
                > > >
                > > > www.william-optics.com
                > > > Yahoo! Groups Links
                > > >
                > > >
                > > >
                > > >
                > >
                >
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