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Re: [Stellarvue] SV102 Apo owners ... false color on Jupiter?

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  • Darren Hennig
    Mike: What are you using for EPs? Any Barlows used last night? Cheaper Barlows can often be a culprit. Bear in mind that there is a phenomenon of atmospheric
    Message 1 of 13 , May 1, 2005
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      Mike:

      What are you using for EPs? Any Barlows used last night? Cheaper Barlows can often be a culprit. Bear in mind that there is a phenomenon of "atmospheric refraction" that may also contribute to a slight "pseudo chroma" being present on Jupiter and Venus under the right combination of conditions. I am not saying that what you saw is not chroma, but just offering some possible causes.

      Darren.
      __________________________________________

      "Every star is a grain of sand in God's playground..."


      [Non-text portions of this message have been removed]
    • James Braddy
      I ve noticed this over 200X as well, I got the same thing, but it was even worse in the FS-102 I used to own. Possible cause might be my Everbright diagonal,
      Message 2 of 13 , May 1, 2005
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        I've noticed this over 200X as well, I got the same thing, but it
        was even worse in the FS-102 I used to own. Possible cause might be
        my Everbright diagonal, wich I used with both scopes, or maybe it's
        just the limitations of a Doublet design. I don't really consider it
        a problem though. However if you currently have all three 4" scopes,
        where I you, I'd consider selling them all and upgrading to the SV-
        130 triplett, or a TEC-140!
        At least that's my two cents worth.
        JDBraddy

        --- In Stellarvue@yahoogroups.com, "ciscochrist"
        <mike.corrieri@c...> wrote:
        > Does anybody else see a tinge of false color while viewing Jupiter?
        >
        > I have a small faint cloud of purple light in a halo around the
        > planet. I didn't notice it until I looked for it.
        >
        > I tried to push up the power last night to 200x, and it was there -

        > also the seeing was not good enough to really support it. On a
        clear
        > night I will see how high I can push it, and if it becomes
        problematic
        > on using high power on very bright objects.
        >
        > For what it's worth there was a bit of false color in my Takahashi
        > FS102 (just a tiny bit less than the SV), though none whatsoever
        in my
        > FC100.
        >
        > The figure on the lens is VERY good though - it has razor sharp
        images.
        >
        > All in all, I am pretty satisfied with the first light. If I can
        > stabilize the mount a little more, I'll be in good shape.
        >
        > Mike C.
      • David Owen
        I haven t really noticed any up to 200x on mine but I rarely go above 180x (5mm eyepiece). David O. ... clear ... problematic ... in my ... images.
        Message 3 of 13 , May 1, 2005
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          I haven't really noticed any up to 200x on mine but I rarely go
          above 180x (5mm eyepiece).

          David O.

          --- In Stellarvue@yahoogroups.com, "ciscochrist"
          <mike.corrieri@c...> wrote:
          > Does anybody else see a tinge of false color while viewing Jupiter?
          >
          > I have a small faint cloud of purple light in a halo around the
          > planet. I didn't notice it until I looked for it.
          >
          > I tried to push up the power last night to 200x, and it was there -

          > also the seeing was not good enough to really support it. On a
          clear
          > night I will see how high I can push it, and if it becomes
          problematic
          > on using high power on very bright objects.
          >
          > For what it's worth there was a bit of false color in my Takahashi
          > FS102 (just a tiny bit less than the SV), though none whatsoever
          in my
          > FC100.
          >
          > The figure on the lens is VERY good though - it has razor sharp
          images.
          >
          > All in all, I am pretty satisfied with the first light. If I can
          > stabilize the mount a little more, I'll be in good shape.
          >
          > Mike C.
        • Ricky Richey
          Mike I get a slight amount of false color with my Sv 102 apo on Sirius and Vega - the amount varies with atmospheric conditions and level of power used - on
          Message 4 of 13 , May 1, 2005
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            Mike

            I get a slight amount of false color with my Sv 102 apo on Sirius and Vega - the amount varies with atmospheric conditions and level of power used - on exceptionally good nights there is virtually none on anything at any power. I have never seen any on Jupiter, Saturn, or the moon no matter how much power or how bad the condtions. I have seen some on Venus. As I said the CA I see is directly related to atmospheric condtions and power levels used but is never obtrusive. Like your scope, mine is very sharp.

            CDS
            RJR
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          • ciscochrist
            Hmmm... Are you seeing false color, or atmospheric refraction? That may exhibit itself as blue on the limb of the planet, or divided, with blue on one side and
            Message 5 of 13 , May 1, 2005
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              Hmmm...

              Are you seeing false color, or atmospheric refraction? That may
              exhibit itself as blue on the limb of the planet, or divided, with
              blue on one side and red on the other. As such, depending on seeing
              conditions, and the proximity of the object to zenith, it could
              completely disappear. I noticed some of this last night while
              Jupiter was ascending. I also wonder if this may be partly exposed
              by the coatings of the Pentax line - I certainly see it far less in
              the Naglers. The Pentax are definitely more glare prone.

              False color on the other hand, is symptomatic of the focal length of
              the blue wavelength being slightly off from the red and green
              wavelengths. Atmospheric conditions will neither exacerbate or
              diminish this effect; it's a function of the design.

              Look at a very bright object, like Jupiter, and examine the halo of
              light around the planet. Does it have a purplish-tint? In my SV102A
              it is so slight I had to really look for it.

              The FC100 was an exceptional hand figured flourite refractor, no
              longer manufactured (the market value would not support its price
              today). The FS102 is a great Flourite refractor, but once again, it
              exhibits false color as well. I no longer have either, so I cannot
              do a head to head comparison, though I remember them both well.

              I think the SV102 is not exhibiting more false color than should be
              expected of a finely made ED doublet, perhaps on par, or very close
              to, a well made flourite. As for the image quality(sharpness,
              contrast, and ability to "snap" into focus), it's very good,
              definitely on par with the FC100.

              I wish I would have the opportunity to compare it to the SV triplet!

              MC
            • Ricky Richey
              MC You re right about CA being a function of the design, but false color levels and performance are effected by atmospheric conditions even in achromats (wedge
              Message 6 of 13 , May 1, 2005
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                MC

                You're right about CA being a function of the design, but false color levels and performance are effected by atmospheric conditions even in achromats (wedge spectrum aside). False color and its abverse observation effects can seem to dramaticlly increase with bad obseving conditions - while those instrument that have no false color will hold up better under adverse contions. I've seen this on many telescopes over the years. I once had a SV 102 ED triplet achro that was excetionlly sharp and detailed when the atmosphere was good - I mean exceptional - but when it got bad it would not hold up to a TAK FS 78 that I had at the same time.

                CDS
                RJR
                ----- Original Message -----
                From: ciscochrist
                To: Stellarvue@yahoogroups.com
                Sent: Sunday, May 01, 2005 12:39 PM
                Subject: [Stellarvue] Re: SV102 Apo owners ... false color on Jupiter?


                Hmmm...

                Are you seeing false color, or atmospheric refraction? That may
                exhibit itself as blue on the limb of the planet, or divided, with
                blue on one side and red on the other. As such, depending on seeing
                conditions, and the proximity of the object to zenith, it could
                completely disappear. I noticed some of this last night while
                Jupiter was ascending. I also wonder if this may be partly exposed
                by the coatings of the Pentax line - I certainly see it far less in
                the Naglers. The Pentax are definitely more glare prone.

                False color on the other hand, is symptomatic of the focal length of
                the blue wavelength being slightly off from the red and green
                wavelengths. Atmospheric conditions will neither exacerbate or
                diminish this effect; it's a function of the design.

                Look at a very bright object, like Jupiter, and examine the halo of
                light around the planet. Does it have a purplish-tint? In my SV102A
                it is so slight I had to really look for it.

                The FC100 was an exceptional hand figured flourite refractor, no
                longer manufactured (the market value would not support its price
                today). The FS102 is a great Flourite refractor, but once again, it
                exhibits false color as well. I no longer have either, so I cannot
                do a head to head comparison, though I remember them both well.

                I think the SV102 is not exhibiting more false color than should be
                expected of a finely made ED doublet, perhaps on par, or very close
                to, a well made flourite. As for the image quality(sharpness,
                contrast, and ability to "snap" into focus), it's very good,
                definitely on par with the FC100.

                I wish I would have the opportunity to compare it to the SV triplet!

                MC





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              • ciscochrist
                I agree that false color could increase, but it s hard to imagine it disappearing entirely, under any seeing conditions, when nothing is there that is going to
                Message 7 of 13 , May 1, 2005
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                  I agree that false color could increase, but it's hard to imagine it
                  disappearing entirely, under any seeing conditions, when nothing is
                  there that is going to bring blue back into focus.

                  I'll have to investigate that one more thoroughly! Thanks for the
                  info.

                  Mike

                  --- In Stellarvue@yahoogroups.com, "Ricky Richey" <s7t7a7r7@n...>
                  wrote:
                  > MC
                  >
                  > You're right about CA being a function of the design, but false
                  color levels and performance are effected by atmospheric conditions
                  even in achromats (wedge spectrum aside). False color and its
                  abverse observation effects can seem to dramaticlly increase with
                  bad obseving conditions - while those instrument that have no false
                  color will hold up better under adverse contions. I've seen this on
                  many telescopes over the years. I once had a SV 102 ED triplet
                  achro that was excetionlly sharp and detailed when the atmosphere
                  was good - I mean exceptional - but when it got bad it would not
                  hold up to a TAK FS 78 that I had at the same time.
                  >
                  > CDS
                  > RJR
                  message have been removed]
                • Ricky J. Richey
                  Mike There is some CA seen in my Sv 102apo, say on Sirius, on the best of nights - it is just very slight and you have to look for it. While on those bad
                  Message 8 of 13 , May 1, 2005
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                    Mike

                    There is some CA seen in my Sv 102apo, say on Sirius, on the best of
                    nights - it is just very slight and you have to look for it. While on
                    those bad nights, its very obviuos and seems to dramatically
                    increase. I haven't really done an analysis as to exactly what would
                    be ALL the causes for the increase - it would be an interesting
                    subject though. I hope I haven't been confusing with any of this.

                    CDS
                    RJR
                  • k75jim@aol.com
                    Mike, I have a SV102V APO and notice no color on any object. However, I am 63 and my eyes are not what they once were. The 102 APO s are moderate f/l
                    Message 9 of 13 , May 1, 2005
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                      Mike,

                      I have a SV102V APO and notice no color on any object. However, I am 63 and
                      my eyes are not what they once were. The 102 APO's are moderate f/l
                      doublets so it is possible that some sharp eyed individual might see a very, very
                      slight touch of color on very bright objects. (Any APO doublet is subject to
                      this. If you went for a high quality triplet APO there would be zero color
                      period -- or at least that's the way it should be.) In my local astro club
                      perhaps one in twenty might squint and say he/she maybe saw a tiny bit of c
                      olor.

                      Enjoy your 102 APO. When at a dark site you can pull some remarkably faint
                      objects with it.

                      Clear, dark skies,

                      Jim S.
                      Redlands, CA




                      [Non-text portions of this message have been removed]
                    • Walt Kramel
                      Hi Folks, I have been following the discussions of: false color & CA. Like all of the posts by members of the SV group, very interesting and informative. My
                      Message 10 of 13 , May 1, 2005
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                        Hi Folks,

                        I have been following the discussions of: false color & CA. Like all
                        of the posts by members of the SV group, very interesting and
                        informative. My thanks to all who have contributed to these edifying
                        discussions!

                        A few quick questions for the group to help me clarify something in my
                        thinking:

                        a.) it is my understanding that an achromatic refractor brings (2)
                        colors (wavelengths) of light into focus at the focal point. Are these
                        (2) colors red/green, or red/blue?

                        b.) an apochromatic refractor brings (3) colors into focus at the
                        focal point. Are these colors red/green/blue?

                        c.) do all manufacturers who use the terminology "achromatic" &
                        "apochromatic" agree upon the exact same wavelengths of light, so there
                        is consistency "across the board" form one manufacturer to another?

                        Thanks in advance to all who reply.

                        Br,

                        Walt K.

                        (the following previous posts have been heavily edited for brevity)



                        Ricky Richey wrote:

                        > MC
                        >
                        > You're right about CA being a function of the design, but false color
                        > levels and performance are effected by atmospheric conditions even in
                        > achromats .. time.
                        >
                        > CDS
                        > RJR


                        > Subject: [Stellarvue] Re: SV102 Apo owners ... false color on Jupiter?
                        >
                        >
                        > Hmmm...
                        >
                        > Are you seeing false color, or atmospheric refraction? ...
                        >
                        >
                        > False color on the other hand, is symptomatic of the focal length of
                        > the blue wavelength being slightly off from the red and green
                        > wavelengths....
                        >
                        >
                        > I think the SV102 is not exhibiting more false color than should be
                        > expected of a finely made ED doublet,....
                        >
                        > I wish I would have the opportunity to compare it to the SV triplet!
                        >
                        > MC
                        >
                        >
                      • stellarvue1
                        Mike: I also wish this and some day when time permits I will do that. Thus far, every time I have tested the 102T I did not have an 102A to test against it.
                        Message 11 of 13 , May 1, 2005
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                          Mike:

                          I also wish this and some day when time permits I will do that. Thus
                          far, every time I have tested the 102T I did not have an 102A to
                          test against it. But the 102T has absolutely stunning performance
                          and mirror like color correction. Super apos do that. But I promised
                          and so, one day I will deliver on that promise to do a direct
                          comparison.

                          Right now Gary Hand has a 102T in a binoviewing version telescope in
                          Midnight Stardust. What a gem it is. I am not sure if he also has a
                          102A in stock but if he does, people could do such a comparison.
                          Looking in daylight at the edge of a white sign against a dark blue
                          background is about the toughest test of color correction. It would
                          be interesting to compare these.

                          Eyepieces make a big difference in the amount of color one will see
                          of course. Zeiss orthos, Takahashi LE's and the like show much less
                          CA in our telescopes than conventional Plossls and even some highly
                          touted and more expensive eyepieces.

                          I found it interesting that you felt the Tak has slightly less and
                          James Braddy felt his has slightly more false color. Such is the
                          critical nature of this test and the extremes we push our telescopes
                          to. What we may be seeing here is the variation that exists from one
                          model to the next. All very slight but noticeable when we take
                          glass, pass the light of Sirius through it and hope to see zero
                          false color. If only I had an apo when I was growing up! ;-)

                          Enjoy the telescope

                          Vic Maris
                        • ciscochrist
                          Vic, Ahhhh, Sirius! Indeed, the FS102 had obvious false color on Sirius. Glad you mentioned that, I had entirely forgotten about it. Sirius seems to be a good
                          Message 12 of 13 , May 1, 2005
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                            Vic,

                            Ahhhh, Sirius! Indeed, the FS102 had obvious false color on Sirius.
                            Glad you mentioned that, I had entirely forgotten about it. Sirius
                            seems to be a good Super-Apo litmus test.

                            Mike
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