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Re: TEC 110 F/5.6

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  • AndreasBraun
    ... Yuri, thanks for the info. This will result in 0.8mm inwards curvature at 19.4mm off axis (one half of the UWAN28 s field stop diameter of 38.8mm) and in
    Message 1 of 25 , Mar 1, 2010
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      --- In tec-scopes@yahoogroups.com, "Yuri" <tec@...> wrote:
      >
      >
      >
      > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
      > ...
      > My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
      > >
      > > best,
      > >
      > > JimP
      > >
      > Jim, the APO110 F5.6 has radius of curvature of the field 235 mm. Being F5.6 the scope be more critical for the choice of the eyepieces, but the FF is still not needed for visual observing.
      > Best regards, Yuri
      >

      Yuri, thanks for the info.

      This will result in 0.8mm inwards curvature at 19.4mm off axis (one half of the UWAN28's field stop diameter of 38.8mm) and in 0.7mm inwards curvature at 18.1mm off axis (one half of the Ethos21's field stop diameter of 36.2mm).

      For the UWAN28 there will be an inwards defocusing of only 0.3mm neccessary (0.8mm minus the intrinsic FC of the UWAN28 of 0.5mm). This will translate into just 0.4 diopters accommodation power neccessary.

      For the Ethos21 (assuming a flat field for this eyepiece) there will be an inwards defocusing of 0.7mm neccessary. This will translate into 1.8 diopters accommodation power neccessary (0.7mm defocus in combination with the focal length of 21mm).

      Andreas
    • Jason
      Andreas, your info is interesting. Can you show how you derived it? How do you find out FC for eyepieces? I ve only seen FC diagrams for one ep line - the
      Message 2 of 25 , Mar 1, 2010
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        Andreas, your info is interesting. Can you show how you derived it? How
        do you find out FC for eyepieces? I've only seen FC diagrams for one ep
        line - the Pentax XW's (I don't recall, however, any numbers given for
        FC for the XW's on that site).

        I'm curious how you know FC for eps. It would be very nice to know in
        advance before buying eps. That way we might optimize a set for a
        certain scope. This could be very important for a short focus refractor
        like the TEC110FL.

        I would also, just out of curiosity, like to know how you calculated the
        diopters of refocusing necessary in your examples.

        Thank you,
        -Jason

        > -------- Original Message --------
        > Subject: [tec-scopes] Re: TEC 110 F/5.6
        > From: "AndreasBraun" <andydj5xp@...>
        > Date: Mon, March 01, 2010 3:30 am
        > To: tec-scopes@yahoogroups.com
        >
        >
        > --- In tec-scopes@yahoogroups.com, "Yuri" <tec@...> wrote:
        > >
        > >
        > >
        > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
        > > ...
        > > My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
        > > >
        > > > best,
        > > >
        > > > JimP
        > > >
        > > Jim, the APO110 F5.6 has radius of curvature of the field 235 mm. Being F5.6 the scope be more critical for the choice of the eyepieces, but the FF is still not needed for visual observing.
        > > Best regards, Yuri
        > >
        >
        > Yuri, thanks for the info.
        >
        > This will result in 0.8mm inwards curvature at 19.4mm off axis (one half of the UWAN28's field stop diameter of 38.8mm) and in 0.7mm inwards curvature at 18.1mm off axis (one half of the Ethos21's field stop diameter of 36.2mm).
        >
        > For the UWAN28 there will be an inwards defocusing of only 0.3mm neccessary (0.8mm minus the intrinsic FC of the UWAN28 of 0.5mm). This will translate into just 0.4 diopters accommodation power neccessary.
        >
        > For the Ethos21 (assuming a flat field for this eyepiece) there will be an inwards defocusing of 0.7mm neccessary. This will translate into 1.8 diopters accommodation power neccessary (0.7mm defocus in combination with the focal length of 21mm).
        >
        > Andreas
      • scott1702
        It s not the field curvature from the lens that will bother you, it s the eyepiece performance at f/5.6. A 35mm Panoptic will look absolutely great, they are
        Message 3 of 25 , Mar 1, 2010
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          It's not the field curvature from the lens that will bother you, it's the eyepiece performance at f/5.6. A 35mm Panoptic will look absolutely great, they are designed to work in f/5 dobs.

          Most eyepieces without built-in barlow will not look so great at the edge. However, the 110 is only one 1.7x Barcon away from a more comfortable f/9.5.

          -Scott


          --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@...> wrote:
          >
          > Please help me with what that means when I look into the FOV. Will the outer 1/3, 1/4 or what be out of focus when the center is in focus? Field flattener??
          >
          > JimP
          >
          > --- In tec-scopes@yahoogroups.com, "mihalco" <mihalco@> wrote:
          > >
          > > Hi Jim,
          > > IIRC, the field curvature for a refractor (non-Petzval) is approximately 1/3 the focal length, so for a 110mm f5.6 (616mm fl), it would be a radius of approx 205mm.
          > > Regards,
          > > Kurt
          > >
          > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
          > > >
          > > > Hello,
          > > > I was just reading the review of a 90mm doublet on Astromart and the discussion of flat field intrigued me. I know some high end apo manufacturers are primarily interested in producing a scope for wide field astrophotography and that is perfectly fine. The fact that they perform exceedingly well visually is a bonus. As I have spent the Vast majority of viewing through my refractors on axis, i.e., planets, double stars and specific craters etc., on the Moon I have not done a lot of wide field viewing and am not an expert on which scopes produce flat fields for visual observing. I understand the Petzel 4-element design does this (?). My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
          > > >
          > > > best,
          > > >
          > > > JimP
          > > >
          > >
          >
        • AndreasBraun
          Jason, the FC of the UWAN28 has been evaluated simply by discovering that together with the TEC140 there is no refocusing neccessary between the center and the
          Message 4 of 25 , Mar 1, 2010
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            Jason,

            the FC of the UWAN28 has been evaluated simply by discovering that together with the TEC140 there is no refocusing neccessary between the center and the edge of field. According to Yuri the TEC140 has a radius of curvature of about -380mm which in turn means that the UWAN28 apparently has the same FC (accurate within the depth of focus of 0.05mm for this f/7 scope).

            I don't know of any other source to know about FC of eyepieces. They are not published (besides the mentioned Pentax XWs).


            Translating a focus shift into accommodation diopters is simple:

            The 28mm (0.028m) focal length of the UWAN translates into 35.7 diopter (1/(0.028m)). The remaining 0.3mm focus shift equal 1.07% of 28mm, and the same 1.07% of 35.7 diopter equal 0.38 diopter. They now have to be compensated for either by accomodation power of the eye or by refocusing between center and edge of field.

            Andreas


            --- In tec-scopes@yahoogroups.com, "Jason" <jason@...> wrote:
            >
            > Andreas, your info is interesting. Can you show how you derived it? How
            > do you find out FC for eyepieces? I've only seen FC diagrams for one ep
            > line - the Pentax XW's (I don't recall, however, any numbers given for
            > FC for the XW's on that site).
            >
            > I'm curious how you know FC for eps. It would be very nice to know in
            > advance before buying eps. That way we might optimize a set for a
            > certain scope. This could be very important for a short focus refractor
            > like the TEC110FL.
            >
            > I would also, just out of curiosity, like to know how you calculated the
            > diopters of refocusing necessary in your examples.
            >
            > Thank you,
            > -Jason
            >
            > > -------- Original Message --------
            > > Subject: [tec-scopes] Re: TEC 110 F/5.6
            > > From: "AndreasBraun" <andydj5xp@...>
            > > Date: Mon, March 01, 2010 3:30 am
            > > To: tec-scopes@yahoogroups.com
            > >
            > >
            > > --- In tec-scopes@yahoogroups.com, "Yuri" <tec@> wrote:
            > > >
            > > >
            > > >
            > > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
            > > > ...
            > > > My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
            > > > >
            > > > > best,
            > > > >
            > > > > JimP
            > > > >
            > > > Jim, the APO110 F5.6 has radius of curvature of the field 235 mm. Being F5.6 the scope be more critical for the choice of the eyepieces, but the FF is still not needed for visual observing.
            > > > Best regards, Yuri
            > > >
            > >
            > > Yuri, thanks for the info.
            > >
            > > This will result in 0.8mm inwards curvature at 19.4mm off axis (one half of the UWAN28's field stop diameter of 38.8mm) and in 0.7mm inwards curvature at 18.1mm off axis (one half of the Ethos21's field stop diameter of 36.2mm).
            > >
            > > For the UWAN28 there will be an inwards defocusing of only 0.3mm neccessary (0.8mm minus the intrinsic FC of the UWAN28 of 0.5mm). This will translate into just 0.4 diopters accommodation power neccessary.
            > >
            > > For the Ethos21 (assuming a flat field for this eyepiece) there will be an inwards defocusing of 0.7mm neccessary. This will translate into 1.8 diopters accommodation power neccessary (0.7mm defocus in combination with the focal length of 21mm).
            > >
            > > Andreas
            >
          • BobH
            ... Hi Scott, With all due respect, I disagree. Yes the eyepiece performance is important at f/5.6, but so is field flatness! There are some of us who enjoy
            Message 5 of 25 , Mar 6, 2010
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              > It's not the field curvature from the lens that will bother you, it's the eyepiece performance at f/5.6. > -Scott
              >
              Hi Scott,

              With all due respect, I disagree. Yes the eyepiece performance is important at f/5.6, but so is field flatness! There are some of us who enjoy using wide field eyepieces and like having them deliver tack sharp edge to edge sharpness.

              I am another person who would like to know if there is some kind of field flattener solution that would work well for visual observers. I like your question and hope that you get an answer that is helpful.

              The only good solution to your particular query is a different telescope. The TeleVue NP-101 f/5.4 and the NP-127 f5.2 will give you fabulous flat field performance with wide field eyepieces. These telescopes and lightweight and perform beautifully.

              Maybe this will be of some help.

              Sincerely,

              Bob



              > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
              > >
              > > Please help me with what that means when I look into the FOV. Will the outer 1/3, 1/4 or what be out of focus when the center is in focus? Field flattener??
              > >
              > > JimP
              > >
              > > --- In tec-scopes@yahoogroups.com, "mihalco" <mihalco@> wrote:
              > > >
              > > > Hi Jim,
              > > > IIRC, the field curvature for a refractor (non-Petzval) is approximately 1/3 the focal length, so for a 110mm f5.6 (616mm fl), it would be a radius of approx 205mm.
              > > > Regards,
              > > > Kurt
              > > >
              > > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
              > > > >
              > > > > Hello,
              > > > > I was just reading the review of a 90mm doublet on Astromart and the discussion of flat field intrigued me. I know some high end apo manufacturers are primarily interested in producing a scope for wide field astrophotography and that is perfectly fine. The fact that they perform exceedingly well visually is a bonus. As I have spent the Vast majority of viewing through my refractors on axis, i.e., planets, double stars and specific craters etc., on the Moon I have not done a lot of wide field viewing and am not an expert on which scopes produce flat fields for visual observing. I understand the Petzel 4-element design does this (?). My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
              > > > >
              > > > > best,
              > > > >
              > > > > JimP
              > > > >
              > > >
              > >
              >
            • scott1702
              Bob - I think the answer you seek was already given - some kind of flattener is the optional TEC field flattener for the scope. It will correct the field
              Message 6 of 25 , Mar 8, 2010
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                Bob - I think the answer you seek was already given - "some kind of flattener" is the optional TEC field flattener for the scope. It will correct the field curvature, whether for camera or eye. It is the same thing that AP and Tak offer for all their refractors.

                So the answer is "yes", there's a field flattener, but will it "work well" for visual users? instead of marketing these as a visual accessory, TEC and AP state that they're not necessary for visual use:

                >>>Jim, the APO110 F5.6 has radius of curvature of the filed 235 mm. Being F5.6 the scope be more critical for the choice of the eyepieces, but the FF is still not needed for visual observing.
                Best regards, Yuri>>

                Do you have a 35mm Panoptic? I used mine in a f/5.8 Traveler and it worked very well at the edge-of-field. I expect it will do the same in the 110mm. It costs a lot less than the field flattener. I don't see much difference, if any, when I'm using this eyepiece in f/9 refractors vs. f/5.8 ones.


                --- In tec-scopes@yahoogroups.com, "BobH" <bdphanson@...> wrote:
                >
                >
                >
                > > It's not the field curvature from the lens that will bother you, it's the eyepiece performance at f/5.6. > -Scott
                > >
                > Hi Scott,
                >
                > With all due respect, I disagree. Yes the eyepiece performance is important at f/5.6, but so is field flatness! There are some of us who enjoy using wide field eyepieces and like having them deliver tack sharp edge to edge sharpness.
                >
                > I am another person who would like to know if there is some kind of field flattener solution that would work well for visual observers. I like your question and hope that you get an answer that is helpful.
                >
                > The only good solution to your particular query is a different telescope. The TeleVue NP-101 f/5.4 and the NP-127 f5.2 will give you fabulous flat field performance with wide field eyepieces. These telescopes and lightweight and perform beautifully.
                >
                > Maybe this will be of some help.
                >
                > Sincerely,
                >
                > Bob
                >
                >
                >
                > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
                > > >
                > > > Please help me with what that means when I look into the FOV. Will the outer 1/3, 1/4 or what be out of focus when the center is in focus? Field flattener??
                > > >
                > > > JimP
                > > >
                > > > --- In tec-scopes@yahoogroups.com, "mihalco" <mihalco@> wrote:
                > > > >
                > > > > Hi Jim,
                > > > > IIRC, the field curvature for a refractor (non-Petzval) is approximately 1/3 the focal length, so for a 110mm f5.6 (616mm fl), it would be a radius of approx 205mm.
                > > > > Regards,
                > > > > Kurt
                > > > >
                > > > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
                > > > > >
                > > > > > Hello,
                > > > > > I was just reading the review of a 90mm doublet on Astromart and the discussion of flat field intrigued me. I know some high end apo manufacturers are primarily interested in producing a scope for wide field astrophotography and that is perfectly fine. The fact that they perform exceedingly well visually is a bonus. As I have spent the Vast majority of viewing through my refractors on axis, i.e., planets, double stars and specific craters etc., on the Moon I have not done a lot of wide field viewing and am not an expert on which scopes produce flat fields for visual observing. I understand the Petzel 4-element design does this (?). My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
                > > > > >
                > > > > > best,
                > > > > >
                > > > > > JimP
                > > > > >
                > > > >
                > > >
                > >
                >
              • Yuri
                It could be bad marketing , but we will not offer FF for visual observations, it is designed and needed only for photo or imaging, and if sensor size diagonal
                Message 7 of 25 , Mar 9, 2010
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                  It could be "bad marketing", but we will not offer FF for visual observations, it is designed and needed only for photo or imaging, and if sensor size diagonal is larger than ~15mm.

                  I have tested the APO110 at day time today (no stars here until weekend) with following eyepieces:
                  Pentax XW 30mm, 20mm, 5mm
                  Pentax XF 12mm
                  Nikon WF 8mm
                  TAK LE 7.5mm, 5mm
                  Zeiss 16mm, 10mm, 6mm
                  1.8X Barlow
                  All above eyepieces were performed well with APO110FL. Counting that my eye accommodation is not perfect anymore, I still was able to see sharp image at center and edge of FOV without re-focusing.
                  Best regards,
                  Yuri


                  --- In tec-scopes@yahoogroups.com, "scott1702" <samortimer@...> wrote:
                  >
                  > Bob - I think the answer you seek was already given - "some kind of flattener" is the optional TEC field flattener for the scope. It will correct the field curvature, whether for camera or eye. It is the same thing that AP and Tak offer for all their refractors.
                  >
                  > So the answer is "yes", there's a field flattener, but will it "work well" for visual users? instead of marketing these as a visual accessory, TEC and AP state that they're not necessary for visual use:
                  >
                  > >>>Jim, the APO110 F5.6 has radius of curvature of the filed 235 mm. Being F5.6 the scope be more critical for the choice of the eyepieces, but the FF is still not needed for visual observing.
                  > Best regards, Yuri>>
                  >
                  > Do you have a 35mm Panoptic? I used mine in a f/5.8 Traveler and it worked very well at the edge-of-field. I expect it will do the same in the 110mm. It costs a lot less than the field flattener. I don't see much difference, if any, when I'm using this eyepiece in f/9 refractors vs. f/5.8 ones.
                  >
                  >
                  > --- In tec-scopes@yahoogroups.com, "BobH" <bdphanson@> wrote:
                  > >
                  > >
                  > >
                  > > > It's not the field curvature from the lens that will bother you, it's the eyepiece performance at f/5.6. > -Scott
                  > > >
                  > > Hi Scott,
                  > >
                  > > With all due respect, I disagree. Yes the eyepiece performance is important at f/5.6, but so is field flatness! There are some of us who enjoy using wide field eyepieces and like having them deliver tack sharp edge to edge sharpness.
                  > >
                  > > I am another person who would like to know if there is some kind of field flattener solution that would work well for visual observers. I like your question and hope that you get an answer that is helpful.
                  > >
                  > > The only good solution to your particular query is a different telescope. The TeleVue NP-101 f/5.4 and the NP-127 f5.2 will give you fabulous flat field performance with wide field eyepieces. These telescopes and lightweight and perform beautifully.
                  > >
                  > > Maybe this will be of some help.
                  > >
                  > > Sincerely,
                  > >
                  > > Bob
                  > >
                  > >
                  > >
                  > > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
                  > > > >
                  > > > > Please help me with what that means when I look into the FOV. Will the outer 1/3, 1/4 or what be out of focus when the center is in focus? Field flattener??
                  > > > >
                  > > > > JimP
                  > > > >
                  > > > > --- In tec-scopes@yahoogroups.com, "mihalco" <mihalco@> wrote:
                  > > > > >
                  > > > > > Hi Jim,
                  > > > > > IIRC, the field curvature for a refractor (non-Petzval) is approximately 1/3 the focal length, so for a 110mm f5.6 (616mm fl), it would be a radius of approx 205mm.
                  > > > > > Regards,
                  > > > > > Kurt
                  > > > > >
                  > > > > > --- In tec-scopes@yahoogroups.com, "jimhp29401us" <thefamily90@> wrote:
                  > > > > > >
                  > > > > > > Hello,
                  > > > > > > I was just reading the review of a 90mm doublet on Astromart and the discussion of flat field intrigued me. I know some high end apo manufacturers are primarily interested in producing a scope for wide field astrophotography and that is perfectly fine. The fact that they perform exceedingly well visually is a bonus. As I have spent the Vast majority of viewing through my refractors on axis, i.e., planets, double stars and specific craters etc., on the Moon I have not done a lot of wide field viewing and am not an expert on which scopes produce flat fields for visual observing. I understand the Petzel 4-element design does this (?). My questions are as follows. What will the field curvature be like in the TEC 100 F/5.6 for the visual observer? Can you use a field flattener for visual observations and if so how does that effect the FOV (F ratio?)?
                  > > > > > >
                  > > > > > > best,
                  > > > > > >
                  > > > > > > JimP
                  > > > > > >
                  > > > > >
                  > > > >
                  > > >
                  > >
                  >
                • elbugs@aol.com
                  How you tested the scope with the Nagler 31 & the Ethos eyepieces ? Thank You
                  Message 8 of 25 , Mar 9, 2010
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                    How you tested the scope with the Nagler 31 & the Ethos eyepieces ?
                     
                    Thank You
                  • mrgrytt
                    ... I think your only concern will be with the simple eyepiece designs that are generally regarded to be best when used with slower f/ratio scopes. The only
                    Message 9 of 25 , Mar 9, 2010
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                      --- In tec-scopes@yahoogroups.com, elbugs@... wrote:
                      >
                      > How you tested the scope with the Nagler 31 & the Ethos eyepieces ?
                      >
                      > Thank You


                      I think your only concern will be with the simple eyepiece designs that are generally regarded to be best when used with slower f/ratio scopes.

                      The only somewhat comparable scope I have is a TMB 105/650 (f/6.2) and it gives excellent performance with both the 31mm Nagler and the Ethos eyepieces. I wouldn't think there would be much difference with the slightly faster TEC 110FL. I do have some eyepieces that I keep away from the faster 105/650 but they simply aren't designed to give edge to edge performance with that fast of a scope. Close to on axis they also perform well.

                      Harvey
                    • Yuri
                      ... Do not have this brand, will you loan them for test? (-: Regards, Yuri
                      Message 10 of 25 , Mar 9, 2010
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                        --- In tec-scopes@yahoogroups.com, elbugs@... wrote:
                        >
                        > How you tested the scope with the Nagler 31 & the Ethos eyepieces ?
                        >
                        > Thank You
                        >
                        Do not have this brand,
                        will you loan them for test? (-:
                        Regards, Yuri
                      • wilcoxmilton
                        ... My final thoughts on this: I do have the 31T5 and was worried about the same issue several years ago when Yuri changed the 160FL design from f/8 to f/7.
                        Message 11 of 25 , Mar 11, 2010
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                          --- In tec-scopes@yahoogroups.com, elbugs@... wrote:
                          >
                          > How you tested the scope with the Nagler 31
                          > & the Ethos eyepieces ?
                          >

                          My final thoughts on this:

                          I do have the 31T5 and was worried about the same issue several years ago when Yuri changed the 160FL design from f/8 to f/7. It turned out to be a non-issue.

                          Consider that the 31T5 in the 110FL is going to yield a bit less than 20x. At that low a magnification observers will be hard pressed to notice any difference in edge stars unless they are obsessed with finding it. I predict most will be so blown away by the 4° field they will forget to even check.

                          IMO what buyers should be worried about is how well this scope will perform at 220x, not 20x. Achieving a tenth wave figure in f/5.6 optics is not easy, but given Yuri's interferometry and master opticians I'm confident he can do it. Note that Roland's 105mm f/5.8 Traveler (with similar field curvature) cost $3,480.00 8 years ago, so I feel that Yuri's price for the 110FL is extremely fair.

                          Lastly, it was mentioned that if you want a perfectly flat field buy a Petzval. What wasn't mentioned is that the scope will be longer and heavier and probably not as good on-axis as the 110FL or Traveler.

                          And I still think Yuri should call the new scope "Eclipse" before Roland takes the name... :-D

                          Clear skies,
                          Milt
                        • Yuri
                          ... Milt, I rather call it Ex-pedition . As per flat field in Pet-zvals - does anybody know how flat is that flat? Classical Pet-zval has better chromatic
                          Message 12 of 25 , Mar 11, 2010
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                            --- In tec-scopes@yahoogroups.com, "wilcoxmilton" <wilcoxmilton@...> wrote:
                            >
                            > --- In tec-scopes@yahoogroups.com, elbugs@ wrote:
                            > >
                            > > How you tested the scope with the Nagler 31
                            > > & the Ethos eyepieces ?
                            > >
                            >
                            > My final thoughts on this:
                            >
                            > I do have the 31T5 and was worried about the same issue several years ago when Yuri changed the 160FL design from f/8 to f/7. It turned out to be a non-issue.
                            >
                            > Consider that the 31T5 in the 110FL is going to yield a bit less than 20x. At that low a magnification observers will be hard pressed to notice any difference in edge stars unless they are obsessed with finding it. I predict most will be so blown away by the 4° field they will forget to even check.
                            >
                            > IMO what buyers should be worried about is how well this scope will perform at 220x, not 20x. Achieving a tenth wave figure in f/5.6 optics is not easy, but given Yuri's interferometry and master opticians I'm confident he can do it. Note that Roland's 105mm f/5.8 Traveler (with similar field curvature) cost $3,480.00 8 years ago, so I feel that Yuri's price for the 110FL is extremely fair.
                            >
                            > Lastly, it was mentioned that if you want a perfectly flat field buy a Petzval. What wasn't mentioned is that the scope will be longer and heavier and probably not as good on-axis as the 110FL or Traveler.
                            >
                            > And I still think Yuri should call the new scope "Eclipse" before Roland takes the name... :-D
                            >
                            > Clear skies,
                            > Milt
                            >

                            Milt, I rather call it "Ex-pedition".
                            As per flat field in Pet-zvals - does anybody know how flat is that flat?
                            Classical Pet-zval has better chromatic correction comparing to usual objective for the price of increased length, but it's field is more curved...
                            Does anyone has design data or optical scheme at least of the given Pet-zval or should I call Al?

                            Best regards, Yuri
                          • wilcoxmilton
                            Yuri, My layman s understanding is that in Televue s Nagler-Petzval the back doublet also serves as a field flattener. Of course both doublets are also
                            Message 13 of 25 , Mar 11, 2010
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                              Yuri,

                              My layman's understanding is that in Televue's "Nagler-Petzval" the back doublet also serves as a field flattener. Of course both doublets are also slower but I don't know if this helps since the net f/ratio is still fast. In any case, imagers use them without any additional FF.

                              Milt

                              --- In tec-scopes@yahoogroups.com, "Yuri" <tec@...> wrote:
                              >
                              > should I call Al?
                              >
                            • Ron Hranac
                              If you had your choice of any of the current crop of available Tele Vue eyepieces that Yuri should check in the 110, what would be your preferences? Ron ...
                              Message 14 of 25 , Mar 11, 2010
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                                If you had your choice of any of the current crop of available Tele Vue eyepieces that Yuri should check in the 110, what would be your preferences?

                                Ron

                                --- On Thu, 3/11/10, Yuri <tec@...> wrote:

                                From: Yuri <tec@...>
                                Subject: [tec-scopes] Re: TEC 110 F/5.6
                                To: tec-scopes@yahoogroups.com
                                Date: Thursday, March 11, 2010, 1:06 PM

                                 



                                --- In tec-scopes@yahoogro ups.com, "wilcoxmilton" <wilcoxmilton@ ...> wrote:
                                >
                                > --- In tec-scopes@yahoogro ups.com, elbugs@ wrote:
                                > >
                                > > How you tested the scope with the Nagler 31
                                > > & the Ethos eyepieces ?
                                > >
                                >
                                > My final thoughts on this:
                                >
                                > I do have the 31T5 and was worried about the same issue several years ago when Yuri changed the 160FL design from f/8 to f/7. It turned out to be a non-issue.
                                >
                                > Consider that the 31T5 in the 110FL is going to yield a bit less than 20x. At that low a magnification observers will be hard pressed to notice any difference in edge stars unless they are obsessed with finding it. I predict most will be so blown away by the 4° field they will forget to even check.
                                >
                                > IMO what buyers should be worried about is how well this scope will perform at 220x, not 20x. Achieving a tenth wave figure in f/5.6 optics is not easy, but given Yuri's interferometry and master opticians I'm confident he can do it. Note that Roland's 105mm f/5.8 Traveler (with similar field curvature) cost $3,480.00 8 years ago, so I feel that Yuri's price for the 110FL is extremely fair.
                                >
                                > Lastly, it was mentioned that if you want a perfectly flat field buy a Petzval. What wasn't mentioned is that the scope will be longer and heavier and probably not as good on-axis as the 110FL or Traveler.
                                >
                                > And I still think Yuri should call the new scope "Eclipse" before Roland takes the name... :-D
                                >
                                > Clear skies,
                                > Milt
                                >

                                Milt, I rather call it "Ex-pedition" .
                                As per flat field in Pet-zvals - does anybody know how flat is that flat?
                                Classical Pet-zval has better chromatic correction comparing to usual objective for the price of increased length, but it's field is more curved...
                                Does anyone has design data or optical scheme at least of the given Pet-zval or should I call Al?

                                Best regards, Yuri


                              • wilcoxmilton
                                ... None; I m not worried. Milt
                                Message 15 of 25 , Mar 11, 2010
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                                  >
                                  > If you had your choice of any of the current crop of
                                  > available Tele Vue eyepieces that Yuri should check
                                  > in the 110, what would be your preferences?
                                  >

                                  None; I'm not worried.

                                  Milt
                                • scott1702
                                  ... interesting discussion - I think there will be many volunteer eyepiece testers after they start shipping!! it would appear that some petzvals do indeed
                                  Message 16 of 25 , Mar 12, 2010
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                                    --- In tec-scopes@yahoogroups.com, Ron Hranac <rjhranac@...> wrote:
                                    >
                                    > If you had your choice of any of the current crop of available Tele Vue eyepieces that Yuri should check in the 110, what would be your preferences?
                                    >
                                    > Ron
                                    >

                                    interesting discussion - I think there will be many volunteer eyepiece testers after they start shipping!!

                                    it would appear that some petzvals do indeed need a flattener w/ large ccd chips...

                                    http://www.televue.com/engine/page.asp?ID=350
                                  • Yuri
                                    We had a visitor today that came with two cases filled with real treasure - a few dozen TV eyepieces!!! I choose 4 for testing them with APO110FL: Nagler Type
                                    Message 17 of 25 , Mar 12, 2010
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                                      We had a visitor today that came with two cases filled with real treasure - a few dozen TV eyepieces!!! I choose 4 for testing them with APO110FL:
                                      Nagler Type 5 31mm (X)
                                      Panoptic 24mm
                                      Ethos 13mm
                                      Ethos 6mm
                                      I had also a few our own eyepieces that were used for previous tests:
                                      Pentax XW 30mm (X), 20mm, 5mm
                                      Nikon WF 8mm
                                      TAK LE 7.5mm, 5mm

                                      The weather was cooperating tonight and I was able to test almost all
                                      above eyepieces except 2"-s: Nagler 31mm and Pentax 30mm that I marked as untested (X) since forgot 2" diagonal at shop... will do additional test tomorrow.

                                      Only one eyepiece from all tested tonight required slight re-focusing - Pentax 20mm*, all other were fine. Test performed on: Pleyades, M42 and random fields of stars.
                                      Most memorable were:
                                      Ethos 13mm, Ethos 6mm, Nikon WF 8mm and Pentax XW 5mm - all with pin-point stars from center to the edge of FOW!
                                      Al Nagler did great work in designing 100 degrees eyepieces and they will be performing perfectly for our new APO110FL.

                                      Pentax 20 was very good at the day time - Pentax XW line has much smaller distortion comparing to TVs eyepieces and could be recommended for those who will use the APo110 scope for daytime observations.

                                      I want to thank Ron Hranac who spent time to come and loaned us part of his TV treasure for tests!

                                      Best regards, Yuri














                                      --- In tec-scopes@yahoogroups.com, "Yuri" <tec@...> wrote:
                                      >
                                      > It could be "bad marketing", but we will not offer FF for visual observations, it is designed and needed only for photo or imaging, and if sensor size diagonal is larger than ~15mm.
                                      >
                                      > I have tested the APO110 at day time today (no stars here until weekend) with following eyepieces:
                                      > Pentax XW 30mm, 20mm, 5mm
                                      > Pentax XF 12mm
                                      > Nikon WF 8mm
                                      > TAK LE 7.5mm, 5mm
                                      > Zeiss 16mm, 10mm, 6mm
                                      > 1.8X Barlow
                                      > All above eyepieces were performed well with APO110FL. Counting that my eye accommodation is not perfect anymore, I still was able to see sharp image at center and edge of FOV without re-focusing.
                                      > Best regards,
                                      > Yuri
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