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And now, for something completely different :)

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  • ed_turco
    I ve been looking at this group for awhile now and what I see is a lot of mirrors with similar problems and annoyances, with pictures to substantiate their
    Message 1 of 5 , Sep 1, 2009
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      I've been looking at this group for awhile now and what I see is a lot of mirrors with similar problems and annoyances, with pictures to substantiate their makers' distress. What I'd like to do is discuss is methods to avoid these problems, rather than try to offer advice to individuals in our group. After a while, getting so much advice from ten different people can be confusing at best.

      My two pet problems which can be avoided are the use of too fast f/ratios in Newtonians and turned edges. I'd like to see a discussion of this so that people in the group can see how to avoid getting to the point of a almost finished mirror and then wondering what to do.

      I do not intend to disparage anyone's work or technique, but a discussion or study of what to do makes for better, more easily finished mirrors.

      So stay tuned...


      Ed Turco
    • Mel Bartels
      Hmm, my experience with students in my mirror making classes over the years is that small slow mirrors (6 f/8) are harder than big fast mirrors (10 f/5 to
      Message 2 of 5 , Sep 1, 2009
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        Hmm, my experience with students in my mirror making classes over the years
        is that small slow mirrors (6" f/8) are harder than big fast mirrors (10"
        f/5 to 16" f/4).

        Turned edges are not an issue with my students. They quickly learn that
        avoiding the edge often results in turning it.

        What I see as closer to root cause is too much advice, no inspection of how
        the mirror is being ground, polished and figured, and lack of follow through
        by the mirror maker.

        Also prevalent is this attitude that it's about getting the mirror done.
        Actually, the journey is very important, and making mistakes and learning
        from this is part of the deal. People are impatient and not willing to make
        mistakes in order to learn.

        Joining the local club and signing up for a mirror making class or taking
        pointers from an experienced amateur is key. One can learn to make mirrors
        with no direct advice, but this requires a student devoted to studying the
        reference works.

        Otherwise we all might be better off if the student pairs up with a mentor,
        someone who volunteers from the discussion group and commits to following
        through, with the rest of us staying relatively quiet. That's what I do:
        avoid from offering conflicting advice if it looks like someone is taking
        the lead in helping.

        Mel Bartels




        -----Original Message-----
        From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
        Of ed_turco
        Sent: Tuesday, September 01, 2009 4:44 PM
        To: atm_free@yahoogroups.com
        Subject: [atm_free] And now, for something completely different :)

        I've been looking at this group for awhile now and what I see is a lot of
        mirrors with similar problems and annoyances, with pictures to substantiate
        their makers' distress. What I'd like to do is discuss is methods to avoid
        these problems, rather than try to offer advice to individuals in our group.
        After a while, getting so much advice from ten different people can be
        confusing at best.

        My two pet problems which can be avoided are the use of too fast f/ratios in
        Newtonians and turned edges. I'd like to see a discussion of this so that
        people in the group can see how to avoid getting to the point of a almost
        finished mirror and then wondering what to do.

        I do not intend to disparage anyone's work or technique, but a discussion or
        study of what to do makes for better, more easily finished mirrors.

        So stay tuned...


        Ed Turco



        ------------------------------------

        Yahoo! Groups Links
      • zway2bisfancyfree
        ... Hi Mel, I agree your advice below is good and I for one have been able to make a handful of good mirrors solo with only remote hand holding. It was my
        Message 3 of 5 , Sep 1, 2009
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          --- In atm_free@yahoogroups.com, "Mel Bartels" <mbartels@...> wrote:
          >

          Hi Mel, I agree your advice below is good and I for one have been able to make a handful of good mirrors solo with only remote hand holding. It was my mistakes that really cemented the concepts into my head. I'm interested why you think fast mirrors are easier than slow. Is this because the focault and Ronchi data is easier to discern?

          Just interested. I had a much easier time with my 10 inch F4.9 than my pair of 6 inch F10's but I assumed it was because the 6's came first.

          Thanks Dave H.






          > Hmm, my experience with students in my mirror making classes over the years
          > is that small slow mirrors (6" f/8) are harder than big fast mirrors (10"
          > f/5 to 16" f/4).
          >
          > Turned edges are not an issue with my students. They quickly learn that
          > avoiding the edge often results in turning it.
          >
          > What I see as closer to root cause is too much advice, no inspection of how
          > the mirror is being ground, polished and figured, and lack of follow through
          > by the mirror maker.
          >
          > Also prevalent is this attitude that it's about getting the mirror done.
          > Actually, the journey is very important, and making mistakes and learning
          > from this is part of the deal. People are impatient and not willing to make
          > mistakes in order to learn.
          >
          > Joining the local club and signing up for a mirror making class or taking
          > pointers from an experienced amateur is key. One can learn to make mirrors
          > with no direct advice, but this requires a student devoted to studying the
          > reference works.
          >
          > Otherwise we all might be better off if the student pairs up with a mentor,
          > someone who volunteers from the discussion group and commits to following
          > through, with the rest of us staying relatively quiet. That's what I do:
          > avoid from offering conflicting advice if it looks like someone is taking
          > the lead in helping.
          >
          > Mel Bartels
          >
          >
          >
          >
          > -----Original Message-----
          > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
          > Of ed_turco
          > Sent: Tuesday, September 01, 2009 4:44 PM
          > To: atm_free@yahoogroups.com
          > Subject: [atm_free] And now, for something completely different :)
          >
          > I've been looking at this group for awhile now and what I see is a lot of
          > mirrors with similar problems and annoyances, with pictures to substantiate
          > their makers' distress. What I'd like to do is discuss is methods to avoid
          > these problems, rather than try to offer advice to individuals in our group.
          > After a while, getting so much advice from ten different people can be
          > confusing at best.
          >
          > My two pet problems which can be avoided are the use of too fast f/ratios in
          > Newtonians and turned edges. I'd like to see a discussion of this so that
          > people in the group can see how to avoid getting to the point of a almost
          > finished mirror and then wondering what to do.
          >
          > I do not intend to disparage anyone's work or technique, but a discussion or
          > study of what to do makes for better, more easily finished mirrors.
          >
          > So stay tuned...
          >
          >
          > Ed Turco
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
        • Mel Bartels
          Most guys hands are too big for 6 inch and smaller blanks. Consequently they over stroke and over power the figuring. Additionally, slow mirrors are touchy
          Message 4 of 5 , Sep 1, 2009
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            Most guys' hands are too big for 6 inch and smaller blanks. Consequently
            they over stroke and over power the figuring. Additionally, slow mirrors
            are touchy affairs, harder to see the slight parabolization and easier to
            overshoot back and forth. Faster mirrors have an uphill battle to get the
            parabolization into the mirror, so no back and forth. They are actually
            easier! I'm sure analogies comes to mind.

            My experience is that success is not strongly correlated with number of
            mirrors made. For instance, invariably in my mirror making class, a first
            timer will get a 16 inch f/4 parabolized just right in the first 20 minutes
            of figuring (that just happened, twice, no less!). That guy doing the 6"
            f/8 will struggle night after night. I don't see that second made mirrors
            are that much better than first time mirrors.

            My guess is that there are too many mistakes to be made before someone
            becomes skilled at mirror making, and that it takes several mirrors to run
            into a good portion of the mistakes. I don't see that fewer mistakes are
            necessarily made with 6 inch f/8 mirrors compared to 10 inch f/5.

            People wanted to hear where I thought there were unsubstantiated beliefs in
            amateur astronomy/telescope making. Well, until someone can convince me,
            this seems to be one of these beliefs.

            Mel Bartels




            -----Original Message-----
            From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
            Of zway2bisfancyfree
            Sent: Tuesday, September 01, 2009 7:06 PM
            To: atm_free@yahoogroups.com
            Subject: [atm_free] Re: And now, for something completely different :)

            --- In atm_free@yahoogroups.com, "Mel Bartels" <mbartels@...> wrote:
            >

            Hi Mel, I agree your advice below is good and I for one have been able to
            make a handful of good mirrors solo with only remote hand holding. It was
            my mistakes that really cemented the concepts into my head. I'm interested
            why you think fast mirrors are easier than slow. Is this because the
            focault and Ronchi data is easier to discern?

            Just interested. I had a much easier time with my 10 inch F4.9 than my pair
            of 6 inch F10's but I assumed it was because the 6's came first.

            Thanks Dave H.






            > Hmm, my experience with students in my mirror making classes over the
            years
            > is that small slow mirrors (6" f/8) are harder than big fast mirrors (10"
            > f/5 to 16" f/4).
            >
            > Turned edges are not an issue with my students. They quickly learn that
            > avoiding the edge often results in turning it.
            >
            > What I see as closer to root cause is too much advice, no inspection of
            how
            > the mirror is being ground, polished and figured, and lack of follow
            through
            > by the mirror maker.
            >
            > Also prevalent is this attitude that it's about getting the mirror done.
            > Actually, the journey is very important, and making mistakes and learning
            > from this is part of the deal. People are impatient and not willing to
            make
            > mistakes in order to learn.
            >
            > Joining the local club and signing up for a mirror making class or taking
            > pointers from an experienced amateur is key. One can learn to make
            mirrors
            > with no direct advice, but this requires a student devoted to studying the
            > reference works.
            >
            > Otherwise we all might be better off if the student pairs up with a
            mentor,
            > someone who volunteers from the discussion group and commits to following
            > through, with the rest of us staying relatively quiet. That's what I do:
            > avoid from offering conflicting advice if it looks like someone is taking
            > the lead in helping.
            >
            > Mel Bartels
            >
            >
            >
            >
            > -----Original Message-----
            > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
            > Of ed_turco
            > Sent: Tuesday, September 01, 2009 4:44 PM
            > To: atm_free@yahoogroups.com
            > Subject: [atm_free] And now, for something completely different :)
            >
            > I've been looking at this group for awhile now and what I see is a lot of
            > mirrors with similar problems and annoyances, with pictures to
            substantiate
            > their makers' distress. What I'd like to do is discuss is methods to
            avoid
            > these problems, rather than try to offer advice to individuals in our
            group.
            > After a while, getting so much advice from ten different people can be
            > confusing at best.
            >
            > My two pet problems which can be avoided are the use of too fast f/ratios
            in
            > Newtonians and turned edges. I'd like to see a discussion of this so that
            > people in the group can see how to avoid getting to the point of a almost
            > finished mirror and then wondering what to do.
            >
            > I do not intend to disparage anyone's work or technique, but a discussion
            or
            > study of what to do makes for better, more easily finished mirrors.
            >
            > So stay tuned...
            >
            >
            > Ed Turco
            >
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >




            ------------------------------------

            Yahoo! Groups Links
          • Mark Whitaker
            I agree with the statement about the 6 being difficult due to the size of the blank. I would suggest that an 8 mirror is a better choice for a first mirror
            Message 5 of 5 , Sep 2, 2009
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              I agree with the statement about the 6" being difficult due to the size of the blank.  I would suggest that an 8" mirror is a better choice for a first mirror as it is just easier on the hands to work with.

              I have not made any long mirrors but my experience is that mirrors of f/5 to f/6 were easier to complete than faster mirrors.

              I've only made 5 mirrors so far (all f/6 to f/4.3).  Each successive mirror was an order of magnitude better than the previous mirror.  I do agree that there are many mistakes that can be made and typically, not all of them will be made on the first mirror.  Every mirror I have made has offered surprises that I did not see experience earlier mirrors.

              A mirror made in a class under the tutelage of an experienced mirror maker is likely to be a much different experience than the amateur working in a vacuum.  My first mirror attempt was in a total vacuum (no internet in those days) and I had Texereau's book as a guide.  Subsequent mirrors had remote support but even when questions were asked, more often or not there were all types of different responses (some helpful, some not).  In such an environment, you take risks and learn what works and what doesn't.

              It is also my opinion that mirror making is like riding a bicycle.  Some of us have great difficulty in learning while others hop on and take off.  But once learned, it is never forgotten.  Mirror making books make it sound easy and indeed it is, once you learn how and have gained confidence.  Like riding a bicycle, it takes determination, perseverance and the willingness to fall down a time or two.

              Mark




              From: Mel Bartels <mbartels@...>
              To: atm_free@yahoogroups.com
              Sent: Tuesday, September 1, 2009 9:32:24 PM
              Subject: RE: [atm_free] Re: And now, for something completely different :)

               

              Most guys' hands are too big for 6 inch and smaller blanks. Consequently
              they over stroke and over power the figuring. Additionally, slow mirrors
              are touchy affairs, harder to see the slight parabolization and easier to
              overshoot back and forth. Faster mirrors have an uphill battle to get the
              parabolization into the mirror, so no back and forth. They are actually
              easier! I'm sure analogies comes to mind.

              My experience is that success is not strongly correlated with number of
              mirrors made. For instance, invariably in my mirror making class, a first
              timer will get a 16 inch f/4 parabolized just right in the first 20 minutes
              of figuring (that just happened, twice, no less!). That guy doing the 6"
              f/8 will struggle night after night. I don't see that second made mirrors
              are that much better than first time mirrors.

              My guess is that there are too many mistakes to be made before someone
              becomes skilled at mirror making, and that it takes several mirrors to run
              into a good portion of the mistakes. I don't see that fewer mistakes are
              necessarily made with 6 inch f/8 mirrors compared to 10 inch f/5.

              People wanted to hear where I thought there were unsubstantiated beliefs in
              amateur astronomy/telescope making. Well, until someone can convince me,
              this seems to be one of these beliefs.

              Mel Bartels

              -----Original Message-----
              From: atm_free@yahoogroup s.com [mailto:atm_free@yahoogroup s.com] On Behalf
              Of zway2bisfancyfree
              Sent: Tuesday, September 01, 2009 7:06 PM
              To: atm_free@yahoogroup s.com
              Subject: [atm_free] Re: And now, for something completely different :)

              --- In atm_free@yahoogroup s.com, "Mel Bartels" <mbartels@.. .> wrote:
              >

              Hi Mel, I agree your advice below is good and I for one have been able to
              make a handful of good mirrors solo with only remote hand holding. It was
              my mistakes that really cemented the concepts into my head. I'm interested
              why you think fast mirrors are easier than slow. Is this because the
              focault and Ronchi data is easier to discern?

              Just interested. I had a much easier time with my 10 inch F4.9 than my pair
              of 6 inch F10's but I assumed it was because the 6's came first.

              Thanks Dave H.

              > Hmm, my experience with students in my mirror making classes over the
              years
              > is that small slow mirrors (6" f/8) are harder than big fast mirrors (10"
              > f/5 to 16" f/4).
              >
              > Turned edges are not an issue with my students. They quickly learn that
              > avoiding the edge often results in turning it.
              >
              > What I see as closer to root cause is too much advice, no inspection of
              how
              > the mirror is being ground, polished and figured, and lack of follow
              through
              > by the mirror maker.
              >
              > Also prevalent is this attitude that it's about getting the mirror done.
              > Actually, the journey is very important, and making mistakes and learning
              > from this is part of the deal. People are impatient and not willing to
              make
              > mistakes in order to learn.
              >
              > Joining the local club and signing up for a mirror making class or taking
              > pointers from an experienced amateur is key. One can learn to make
              mirrors
              > with no direct advice, but this requires a student devoted to studying the
              > reference works.
              >
              > Otherwise we all might be better off if the student pairs up with a
              mentor,
              > someone who volunteers from the discussion group and commits to following
              > through, with the rest of us staying relatively quiet. That's what I do:
              > avoid from offering conflicting advice if it looks like someone is taking
              > the lead in helping.
              >
              > Mel Bartels
              >
              >
              >
              >
              > -----Original Message-----
              > From: atm_free@yahoogroup s.com [mailto:atm_free@yahoogroup s.com] On Behalf
              > Of ed_turco
              > Sent: Tuesday, September 01, 2009 4:44 PM
              > To: atm_free@yahoogroup s.com
              > Subject: [atm_free] And now, for something completely different :)
              >
              > I've been looking at this group for awhile now and what I see is a lot of
              > mirrors with similar problems and annoyances, with pictures to
              substantiate
              > their makers' distress. What I'd like to do is discuss is methods to
              avoid
              > these problems, rather than try to offer advice to individuals in our
              group.
              > After a while, getting so much advice from ten different people can be
              > confusing at best.
              >
              > My two pet problems which can be avoided are the use of too fast f/ratios
              in
              > Newtonians and turned edges. I'd like to see a discussion of this so that
              > people in the group can see how to avoid getting to the point of a almost
              > finished mirror and then wondering what to do.
              >
              > I do not intend to disparage anyone's work or technique, but a discussion
              or
              > study of what to do makes for better, more easily finished mirrors.
              >
              > So stay tuned...
              >
              >
              > Ed Turco
              >
              >
              >
              > ------------ --------- --------- ------
              >
              > Yahoo! Groups Links
              >

              ------------ --------- --------- ------

              Yahoo! Groups Links


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