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Re: [bigdob] 36 Inch Mirror Blank

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  • William Schwittek
    I m guessing that blank will weigh much more than 100 pounds. The volume of the mirror is pi * r * r * h where r (radius) is 18 inches, and h (height) is 2.5
    Message 1 of 16 , Jan 1, 2007
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      I'm guessing that blank will weigh much more than 100 pounds.

      The volume of the mirror is pi * r * r * h where r (radius) is 18
      inches, and h (height) is 2.5 inches. That means 2543 cubic inches of
      glass or 1.47 cubic feet. I'm just guessing the specific gravity of
      glass is about 3 so we have about 275 pounds. Of course, I am ignoring
      the glass that is removed for the actual figure of the mirror but I'd
      think this mirror would be well over 100 pounds.

      - Bill

      |
      ________________________________________________________________________
      |
      | 1. 36 Inch Mirror Blank
      | Posted by: "ghb959" ghberry@... ghb959
      | Date: Sun Dec 31, 2006 8:55 am ((PST))
      |
      | Hi; I am a new member that just join. And I have work out a big mirror
      | blank design. The mirror blank will be of a fuse glass design. 2 1/2
      | inches thick and 36 inches in diameter. The weight should be around a
      | 100 pounds or less. The top glass will be slump to the F Ratio you
      | want and the bottom will be flat making it easier to grind and make
      | the mirror cell. I need at least four more people that would want to
      | buy a mirror blank for my project to go ahead. Late summer would be
      | the time to received the blanks. Thank You Gordon Berry
      |
    • Gordon & Sherri Berry
      Hi Bill; I do not have the total weight figure out but it the total mass of glass weight less then 150 pounds I will still be happy. I do not have a cost on
      Message 2 of 16 , Jan 1, 2007
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        Hi Bill;
        I do not have the total weight figure out but it the total mass of glass
        weight less then
        150 pounds I will still be happy.
        I do not have a cost on the material at this time?
        Everything will be made out of BVC glass. The top and bottom pieces will be
        a 1/2 thick glass.
        The top piece of glass will be ground flat and slump to the F Ratio.
        There will be eight ribs 1 1/2 wide by 1/2 inch thick cut to the F Ratio.
        The left over material will be cut and use to fill up the edge.
        Then the glass will be put in a oven and fuse.
        I have a 12 inch mirror out of BVC glass and it is nice to work with. It
        take half the time to grind and polish then Pyrex take.
        I got the ideal from looking in a old Sky and Telescope magazine. But the
        one problem in fusing the glass is everything was stack and fuse and slump
        with the F Ratio at the same time. Making the bottom also slump and hard to
        work.
        All the material use will be precut.
        http://www.ajstelescopeworkshop.ca/ AJ told me he would work up a price for
        me in January but I would need at least four more orders. He told me my
        design would work.
        He does outstanding work. The reason I went with the fuse concept was the
        great savings on weight. A 32 inch 2 1/4 thick mirror blank out of BVC glass
        weight around 175 pounds.
        I hoped I answer most of your question this design will work and the total
        weight of the scope should also come down.
        This has been a goal of mine for over ten years and I filling very good
        about completing it.
        I am hoping that if five or more of us buy a blank that the price will come
        down.
        Thank You
        Gordon Berry


        Two each mirror blanks is a 1/2 inch thick.
        Eight ribs space apart is 4.5 inches on center.
        ----- Original Message -----
        From: "William Schwittek" <syzygy@...>
        To: "MAIL LIST: Bigdob" <bigdob@yahoogroups.com>
        Sent: Monday, January 01, 2007 8:46 AM
        Subject: Re: [bigdob] 36 Inch Mirror Blank


        > I'm guessing that blank will weigh much more than 100 pounds.
        >
        > The volume of the mirror is pi * r * r * h where r (radius) is 18
        > inches, and h (height) is 2.5 inches. That means 2543 cubic inches of
        > glass or 1.47 cubic feet. I'm just guessing the specific gravity of
        > glass is about 3 so we have about 275 pounds. Of course, I am ignoring
        > the glass that is removed for the actual figure of the mirror but I'd
        > think this mirror would be well over 100 pounds.
        >
        > - Bill
        >
        > |
        > ________________________________________________________________________
        > |
        > | 1. 36 Inch Mirror Blank
        > | Posted by: "ghb959" ghberry@... ghb959
        > | Date: Sun Dec 31, 2006 8:55 am ((PST))
        > |
        > | Hi; I am a new member that just join. And I have work out a big mirror
        > | blank design. The mirror blank will be of a fuse glass design. 2 1/2
        > | inches thick and 36 inches in diameter. The weight should be around a
        > | 100 pounds or less. The top glass will be slump to the F Ratio you
        > | want and the bottom will be flat making it easier to grind and make
        > | the mirror cell. I need at least four more people that would want to
        > | buy a mirror blank for my project to go ahead. Late summer would be
        > | the time to received the blanks. Thank You Gordon Berry
        > |
        >
        >
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
        >
        >
        > --
        > No virus found in this incoming message.
        > Checked by AVG Free Edition.
        > Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date: 12/29/2006
        >
        >
      • Gregg
        Some ribbed blanks that are fused together suffer from print-through of the pattern into the front surface. This may be true even if the mirror has been
        Message 3 of 16 , Jan 1, 2007
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          Some ribbed blanks that are fused together suffer from "print-through"
          of the pattern into the front surface. This may be true even if the
          mirror has been fine annealed, ground and polished. When it goes
          through a temperature adjustment (as all mirrors do when used out of
          doors) there may be a noticable change in the quality of the figure
          that was tested under closely-controlled indoor temperature. There is
          a backup Hubble main mirror of 97.5"x13" of zero-expansion glass that
          is a sandwich of front and rear plates and a central honeycomb,
          avoiding 80% of the weight of a solid disk. It was polished and
          figured at the approximate operating temperature it could experience
          in the Space Telescope in orbit. It has shown no structural problems.
          Mirror structures made from a higher coefficient of expansion material
          will have higher stresses on the joints than ones of more stable
          glasses. This may be true with BVC glass vs. Pyrex or Zerodur.
          A 16 inch Pyrex ribbed mirror that was used in a friend's
          Newtonian/Cassegrain fell apart when he lifted it out of the cell for
          cleaning. He lost 1/3 of the front part. I think a few years of
          desert hot days and cold nights did that mirror in.

          --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
          wrote:
          >
          > Hi Bill;
          > I do not have the total weight figure out but it the total mass of
          glass
          > weight less then
          > 150 pounds I will still be happy.
          > I do not have a cost on the material at this time?
          > Everything will be made out of BVC glass. The top and bottom pieces
          will be
          > a 1/2 thick glass.
          > The top piece of glass will be ground flat and slump to the F Ratio.
          > There will be eight ribs 1 1/2 wide by 1/2 inch thick cut to the F
          Ratio.
          > The left over material will be cut and use to fill up the edge.
          > Then the glass will be put in a oven and fuse.
          > I have a 12 inch mirror out of BVC glass and it is nice to work with. It
          > take half the time to grind and polish then Pyrex take.
          > I got the ideal from looking in a old Sky and Telescope magazine.
          But the
          > one problem in fusing the glass is everything was stack and fuse and
          slump
          > with the F Ratio at the same time. Making the bottom also slump and
          hard to
          > work.
          > All the material use will be precut.
          > http://www.ajstelescopeworkshop.ca/ AJ told me he would work up a
          price for
          > me in January but I would need at least four more orders. He told me my
          > design would work.
          > He does outstanding work. The reason I went with the fuse concept
          was the
          > great savings on weight. A 32 inch 2 1/4 thick mirror blank out of
          BVC glass
          > weight around 175 pounds.
          > I hoped I answer most of your question this design will work and the
          total
          > weight of the scope should also come down.
          > This has been a goal of mine for over ten years and I filling very good
          > about completing it.
          > I am hoping that if five or more of us buy a blank that the price
          will come
          > down.
          > Thank You
          > Gordon Berry
          >
          >
          > Two each mirror blanks is a 1/2 inch thick.
          > Eight ribs space apart is 4.5 inches on center.
          > ----- Original Message -----
          > From: "William Schwittek" <syzygy@...>
          > To: "MAIL LIST: Bigdob" <bigdob@yahoogroups.com>
          > Sent: Monday, January 01, 2007 8:46 AM
          > Subject: Re: [bigdob] 36 Inch Mirror Blank
          >
          >
          > > I'm guessing that blank will weigh much more than 100 pounds.
          > >
          > > The volume of the mirror is pi * r * r * h where r (radius) is 18
          > > inches, and h (height) is 2.5 inches. That means 2543 cubic inches of
          > > glass or 1.47 cubic feet. I'm just guessing the specific gravity of
          > > glass is about 3 so we have about 275 pounds. Of course, I am
          ignoring
          > > the glass that is removed for the actual figure of the mirror but I'd
          > > think this mirror would be well over 100 pounds.
          > >
          > > - Bill
          > >
          > > |
          > >
          ________________________________________________________________________
          > > |
          > > | 1. 36 Inch Mirror Blank
          > > | Posted by: "ghb959" ghberry@... ghb959
          > > | Date: Sun Dec 31, 2006 8:55 am ((PST))
          > > |
          > > | Hi; I am a new member that just join. And I have work out a big
          mirror
          > > | blank design. The mirror blank will be of a fuse glass design. 2 1/2
          > > | inches thick and 36 inches in diameter. The weight should be
          around a
          > > | 100 pounds or less. The top glass will be slump to the F Ratio you
          > > | want and the bottom will be flat making it easier to grind and make
          > > | the mirror cell. I need at least four more people that would want to
          > > | buy a mirror blank for my project to go ahead. Late summer would be
          > > | the time to received the blanks. Thank You Gordon Berry
          > > |
          > >
          > >
          > >
          > >
          > > Yahoo! Groups Links
          > >
          > >
          > >
          > >
          > >
          > > --
          > > No virus found in this incoming message.
          > > Checked by AVG Free Edition.
          > > Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date:
          12/29/2006
          > >
          > >
          >
        • Gordon & Sherri Berry
          Hi Gregg; This is still in the planning stage I will check into it. I do not known all the mechanical properties of BVC glass. Here is the web site for A.J.
          Message 4 of 16 , Jan 1, 2007
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            Hi Gregg;
            This is still in the planning stage I will check into it. I do not known all the mechanical properties of BVC glass.
            Here is the web site for A.J. shop in Canada
            www.ajstelescopeworkshop.ca he does have charts on all the properties of the glass. If you want to check it out.
            Thank you for your input and hopefully I will have more information to pass on this project as it comes available. If any one out there thinks that there needs to be more support in the middle between the ribs please let me known. Or any other ideals on how to tackle this problem please let me known.
            Thank You
            Gordon Berry

            ----- Original Message -----
            From: Gregg
            To: bigdob@yahoogroups.com
            Sent: Monday, January 01, 2007 8:04 PM
            Subject: [bigdob] Re: 36 Inch Mirror Blank


            Some ribbed blanks that are fused together suffer from "print-through"
            of the pattern into the front surface. This may be true even if the
            mirror has been fine annealed, ground and polished. When it goes
            through a temperature adjustment (as all mirrors do when used out of
            doors) there may be a noticable change in the quality of the figure
            that was tested under closely-controlled indoor temperature. There is
            a backup Hubble main mirror of 97.5"x13" of zero-expansion glass that
            is a sandwich of front and rear plates and a central honeycomb,
            avoiding 80% of the weight of a solid disk. It was polished and
            figured at the approximate operating temperature it could experience
            in the Space Telescope in orbit. It has shown no structural problems.
            Mirror structures made from a higher coefficient of expansion material
            will have higher stresses on the joints than ones of more stable
            glasses. This may be true with BVC glass vs. Pyrex or Zerodur.
            A 16 inch Pyrex ribbed mirror that was used in a friend's
            Newtonian/Cassegrain fell apart when he lifted it out of the cell for
            cleaning. He lost 1/3 of the front part. I think a few years of
            desert hot days and cold nights did that mirror in.

            --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
            wrote:
            >
            > Hi Bill;
            > I do not have the total weight figure out but it the total mass of
            glass
            > weight less then
            > 150 pounds I will still be happy.
            > I do not have a cost on the material at this time?
            > Everything will be made out of BVC glass. The top and bottom pieces
            will be
            > a 1/2 thick glass.
            > The top piece of glass will be ground flat and slump to the F Ratio.
            > There will be eight ribs 1 1/2 wide by 1/2 inch thick cut to the F
            Ratio.
            > The left over material will be cut and use to fill up the edge.
            > Then the glass will be put in a oven and fuse.
            > I have a 12 inch mirror out of BVC glass and it is nice to work with. It
            > take half the time to grind and polish then Pyrex take.
            > I got the ideal from looking in a old Sky and Telescope magazine.
            But the
            > one problem in fusing the glass is everything was stack and fuse and
            slump
            > with the F Ratio at the same time. Making the bottom also slump and
            hard to
            > work.
            > All the material use will be precut.
            > http://www.ajstelescopeworkshop.ca/ AJ told me he would work up a
            price for
            > me in January but I would need at least four more orders. He told me my
            > design would work.
            > He does outstanding work. The reason I went with the fuse concept
            was the
            > great savings on weight. A 32 inch 2 1/4 thick mirror blank out of
            BVC glass
            > weight around 175 pounds.
            > I hoped I answer most of your question this design will work and the
            total
            > weight of the scope should also come down.
            > This has been a goal of mine for over ten years and I filling very good
            > about completing it.
            > I am hoping that if five or more of us buy a blank that the price
            will come
            > down.
            > Thank You
            > Gordon Berry
            >
            >
            > Two each mirror blanks is a 1/2 inch thick.
            > Eight ribs space apart is 4.5 inches on center.
            > ----- Original Message -----
            > From: "William Schwittek" <syzygy@...>
            > To: "MAIL LIST: Bigdob" <bigdob@yahoogroups.com>
            > Sent: Monday, January 01, 2007 8:46 AM
            > Subject: Re: [bigdob] 36 Inch Mirror Blank
            >
            >
            > > I'm guessing that blank will weigh much more than 100 pounds.
            > >
            > > The volume of the mirror is pi * r * r * h where r (radius) is 18
            > > inches, and h (height) is 2.5 inches. That means 2543 cubic inches of
            > > glass or 1.47 cubic feet. I'm just guessing the specific gravity of
            > > glass is about 3 so we have about 275 pounds. Of course, I am
            ignoring
            > > the glass that is removed for the actual figure of the mirror but I'd
            > > think this mirror would be well over 100 pounds.
            > >
            > > - Bill
            > >
            > > |
            > >
            __________________________________________________________
            > > |
            > > | 1. 36 Inch Mirror Blank
            > > | Posted by: "ghb959" ghberry@... ghb959
            > > | Date: Sun Dec 31, 2006 8:55 am ((PST))
            > > |
            > > | Hi; I am a new member that just join. And I have work out a big
            mirror
            > > | blank design. The mirror blank will be of a fuse glass design. 2 1/2
            > > | inches thick and 36 inches in diameter. The weight should be
            around a
            > > | 100 pounds or less. The top glass will be slump to the F Ratio you
            > > | want and the bottom will be flat making it easier to grind and make
            > > | the mirror cell. I need at least four more people that would want to
            > > | buy a mirror blank for my project to go ahead. Late summer would be
            > > | the time to received the blanks. Thank You Gordon Berry
            > > |
            > >
            > >
            > >
            > >
            > > Yahoo! Groups Links
            > >
            > >
            > >
            > >
            > >
            > > --
            > > No virus found in this incoming message.
            > > Checked by AVG Free Edition.
            > > Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date:
            12/29/2006
            > >
            > >
            >






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


            No virus found in this incoming message.
            Checked by AVG Free Edition.
            Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date: 12/29/2006


            [Non-text portions of this message have been removed]
          • Gregg
            I read on a webpage (http://www.oldham-optical.co.uk/Glass.htm) where BVC has a TCoE of 2.4-2.8 while Pyrex or equivalent is 3.2 and fused silica is 0.55, and
            Message 5 of 16 , Jan 1, 2007
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              I read on a webpage (http://www.oldham-optical.co.uk/Glass.htm) where
              BVC has a TCoE of 2.4-2.8 while Pyrex or equivalent is 3.2 and fused
              silica is 0.55, and Zerodur or ULE is 0.05 or less. BVC also has
              slightly stiffer resistance to flexure. It may be less expensive than
              other choices in sizes larger than 16".
              BVC is known to be softer than plate, which is softer than Pyrex. It
              might be easier to work, also easier to go too deep when polishing and
              figuring. An extra-smooth surface polish may be difficult.

              --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
              wrote:
              >
              > Hi Gregg;
              > This is still in the planning stage I will check into it. I do not
              known all the mechanical properties of BVC glass.
              > Here is the web site for A.J. shop in Canada
              > www.ajstelescopeworkshop.ca he does have charts on all the
              properties of the glass. If you want to check it out.
              > Thank you for your input and hopefully I will have more information
              to pass on this project as it comes available. If any one out there
              thinks that there needs to be more support in the middle between the
              ribs please let me known. Or any other ideals on how to tackle this
              problem please let me known.
              > Thank You
              > Gordon Berry
              >
              > ----- Original Message -----
              > From: Gregg
              > To: bigdob@yahoogroups.com
              > Sent: Monday, January 01, 2007 8:04 PM
              > Subject: [bigdob] Re: 36 Inch Mirror Blank
              >
              >
              > Some ribbed blanks that are fused together suffer from "print-through"
              > of the pattern into the front surface. This may be true even if the
              > mirror has been fine annealed, ground and polished. When it goes
              > through a temperature adjustment (as all mirrors do when used out of
              > doors) there may be a noticable change in the quality of the figure
              > that was tested under closely-controlled indoor temperature. There is
              > a backup Hubble main mirror of 97.5"x13" of zero-expansion glass that
              > is a sandwich of front and rear plates and a central honeycomb,
              > avoiding 80% of the weight of a solid disk. It was polished and
              > figured at the approximate operating temperature it could experience
              > in the Space Telescope in orbit. It has shown no structural problems.
              > Mirror structures made from a higher coefficient of expansion material
              > will have higher stresses on the joints than ones of more stable
              > glasses. This may be true with BVC glass vs. Pyrex or Zerodur.
              > A 16 inch Pyrex ribbed mirror that was used in a friend's
              > Newtonian/Cassegrain fell apart when he lifted it out of the cell for
              > cleaning. He lost 1/3 of the front part. I think a few years of
              > desert hot days and cold nights did that mirror in.
              >
              > --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@>
              > wrote:
              > >
              > > Hi Bill;
              > > I do not have the total weight figure out but it the total mass of
              > glass
              > > weight less then
              > > 150 pounds I will still be happy.
              > > I do not have a cost on the material at this time?
              > > Everything will be made out of BVC glass. The top and bottom pieces
              > will be
              > > a 1/2 thick glass.
              > > The top piece of glass will be ground flat and slump to the F Ratio.
              > > There will be eight ribs 1 1/2 wide by 1/2 inch thick cut to the F
              > Ratio.
              > > The left over material will be cut and use to fill up the edge.
              > > Then the glass will be put in a oven and fuse.
              > > I have a 12 inch mirror out of BVC glass and it is nice to work
              with. It
              > > take half the time to grind and polish then Pyrex take.
              > > I got the ideal from looking in a old Sky and Telescope magazine.
              > But the
              > > one problem in fusing the glass is everything was stack and fuse and
              > slump
              > > with the F Ratio at the same time. Making the bottom also slump and
              > hard to
              > > work.
              > > All the material use will be precut.
              > > http://www.ajstelescopeworkshop.ca/ AJ told me he would work up a
              > price for
              > > me in January but I would need at least four more orders. He
              told me my
              > > design would work.
              > > He does outstanding work. The reason I went with the fuse concept
              > was the
              > > great savings on weight. A 32 inch 2 1/4 thick mirror blank out of
              > BVC glass
              > > weight around 175 pounds.
              > > I hoped I answer most of your question this design will work and the
              > total
              > > weight of the scope should also come down.
              > > This has been a goal of mine for over ten years and I filling
              very good
              > > about completing it.
              > > I am hoping that if five or more of us buy a blank that the price
              > will come
              > > down.
              > > Thank You
              > > Gordon Berry
              > >
              > >
              > > Two each mirror blanks is a 1/2 inch thick.
              > > Eight ribs space apart is 4.5 inches on center.
              > > ----- Original Message -----
              > > From: "William Schwittek" <syzygy@>
              > > To: "MAIL LIST: Bigdob" <bigdob@yahoogroups.com>
              > > Sent: Monday, January 01, 2007 8:46 AM
              > > Subject: Re: [bigdob] 36 Inch Mirror Blank
              > >
              > >
              > > > I'm guessing that blank will weigh much more than 100 pounds.
              > > >
              > > > The volume of the mirror is pi * r * r * h where r (radius) is 18
              > > > inches, and h (height) is 2.5 inches. That means 2543 cubic
              inches of
              > > > glass or 1.47 cubic feet. I'm just guessing the specific
              gravity of
              > > > glass is about 3 so we have about 275 pounds. Of course, I am
              > ignoring
              > > > the glass that is removed for the actual figure of the mirror
              but I'd
              > > > think this mirror would be well over 100 pounds.
              > > >
              > > > - Bill
              > > >
              > > > |
              > > >
              > __________________________________________________________
              > > > |
              > > > | 1. 36 Inch Mirror Blank
              > > > | Posted by: "ghb959" ghberry@ ghb959
              > > > | Date: Sun Dec 31, 2006 8:55 am ((PST))
              > > > |
              > > > | Hi; I am a new member that just join. And I have work out a big
              > mirror
              > > > | blank design. The mirror blank will be of a fuse glass
              design. 2 1/2
              > > > | inches thick and 36 inches in diameter. The weight should be
              > around a
              > > > | 100 pounds or less. The top glass will be slump to the F
              Ratio you
              > > > | want and the bottom will be flat making it easier to grind
              and make
              > > > | the mirror cell. I need at least four more people that would
              want to
              > > > | buy a mirror blank for my project to go ahead. Late summer
              would be
              > > > | the time to received the blanks. Thank You Gordon Berry
              > > > |
              > > >
              > > >
              > > >
              > > >
              > > > Yahoo! Groups Links
              > > >
              > > >
              > > >
              > > >
              > > >
              > > > --
              > > > No virus found in this incoming message.
              > > > Checked by AVG Free Edition.
              > > > Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date:
              > 12/29/2006
              > > >
              > > >
              > >
              >
              >
              >
              >
              >
              >
              >
              ------------------------------------------------------------------------------
              >
              >
              > No virus found in this incoming message.
              > Checked by AVG Free Edition.
              > Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date:
              12/29/2006
              >
              >
              > [Non-text portions of this message have been removed]
              >
            • burgman1
              Hi, I think the first step would be to find a mirror maker that will handle the BVC glass. I have a 18.5 BVC mirror and my mirror maker went through a lot of
              Message 6 of 16 , Jan 2, 2007
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                Hi,

                I think the first step would be to find a mirror maker that will handle
                the BVC glass. I have a 18.5" BVC mirror and my mirror maker went
                through a lot of time and effort to get mine completed. BVC glass is
                not the easiest glass to figure. If you are planning on making the
                mirror yourself I would re-think the BVC glass unless you have had
                several large mirrors under your belt.

                Dave
                18.5 f4.5 BVC DOB
              • Ric Rokosz
                ... But the ... slump ... Being the person who wrote that S&T article,having the blank evenly curved is far stiffer than one having a flat bottom.I never found
                Message 7 of 16 , Jan 2, 2007
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                  --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
                  wrote:
                  >I have a 12 inch mirror out of BVC glass and it is nice to work with. It
                  > take half the time to grind and polish then Pyrex take.
                  > I got the ideal from looking in a old Sky and Telescope magazine.
                  But the
                  > one problem in fusing the glass is everything was stack and fuse and
                  slump
                  > with the F Ratio at the same time. Making the bottom also slump and
                  >hard to
                  > work.

                  Being the person who wrote that S&T article,having the blank evenly
                  curved is far stiffer than one having a flat bottom.I never found it
                  to be a problem when working any of my fused blanks.


                  > All the material use will be precut.
                  > http://www.ajstelescopeworkshop.ca/ AJ told me he would work up a
                  price for
                  > me in January but I would need at least four more orders. He told me my
                  > design would work.
                  > He does outstanding work. The reason I went with the fuse concept
                  was the
                  > great savings on weight. A 32 inch 2 1/4 thick mirror blank out of
                  BVC glass
                  > weight around 175 pounds.
                  > I hoped I answer most of your question this design will work and the
                  total
                  > weight of the scope should also come down.

                  You might consider a plate glass or pyrex, fused cellular blank made
                  by Jean_Guy Moreau in Quebec.One of his 36 incher is being done by
                  Norm Fullman. Jean Moreau has worked on his cellular glass designs for
                  many years.He can be found on the atm list (http://www.atmlist.net)
                  and the yahoo group:atm_free.He does sell a few every year and does
                  place ads on Astromart and you can order just one at a time from 12 to
                  36 incher.Tell Jean Ric sent you.

                  > This has been a goal of mine for over ten years and I filling very good
                  > about completing it.

                  Sooner than you think,

                  Ric Rokosz
                • Ric Rokosz
                  ... Do you know who made that mirror? I did a 14 inch fused cellular of pyrex written up in S&T,back in 1983, that when finished was stored in a metal garden
                  Message 8 of 16 , Jan 2, 2007
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                    --- In bigdob@yahoogroups.com, "Gregg" <starryskyn@...> wrote:

                    > A 16 inch Pyrex ribbed mirror that was used in a friend's
                    > Newtonian/Cassegrain fell apart when he lifted it out of the cell for
                    > cleaning. He lost 1/3 of the front part. I think a few years of
                    > desert hot days and cold nights did that mirror in.
                    >

                    Do you know who made that mirror?

                    I did a 14 inch fused cellular of pyrex written up in S&T,back in
                    1983, that when finished was stored in a metal garden shed for 12
                    years.The temp varied from -20 to over 40 deg C over the year and the
                    mirror still holds it's figure to this day.The problem your friend's
                    mirror had was in the manufacturing process,not the idea of fused
                    celluars.Any cast/fused mirror will have a printthrough problem to
                    some degree,the pro's make allownaces for this.There is a trade off
                    between lightweight/stiffness and figure quality.The pro's get around
                    this my either ion milling the blank,(no pressure on the faceplate
                    really) or using a counter air pressure to stop the slight sag between
                    cells.Fused cellulars can be made with no printthrough,just a problem
                    of technique.

                    Ric
                  • Polaraligned
                    Mike Lockwood did a 32 BVC recently: http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html He does nice work. He did a 8.25 Minor
                    Message 9 of 16 , Jan 2, 2007
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                      Mike Lockwood did a 32" BVC recently:
                      http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html

                      He does nice work. He did a 8.25" Minor axis diagonal
                      for my 32" and he did a fantastic job on it.


                      Scott




                      --- In bigdob@yahoogroups.com, "burgman1" <burgman1@...> wrote:
                      >
                      > Hi,
                      >
                      > I think the first step would be to find a mirror maker that will handle
                      > the BVC glass. I have a 18.5" BVC mirror and my mirror maker went
                      > through a lot of time and effort to get mine completed. BVC glass is
                      > not the easiest glass to figure. If you are planning on making the
                      > mirror yourself I would re-think the BVC glass unless you have had
                      > several large mirrors under your belt.
                      >
                      > Dave
                      > 18.5 f4.5 BVC DOB
                      >
                    • Gordon & Sherri Berry
                      Hi Dave; The only problem so far with the glass I found is you have to be careful when you are fine grinding at 5 micron because the glass and the tool if
                      Message 10 of 16 , Jan 2, 2007
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                        Hi Dave;
                        The only problem so far with the glass I found is you have to be careful when you are fine grinding at 5 micron because the glass and the tool if allow to dry out as you are grinding want to stick and will scratch easy. But the scratch that did happen to me polish out.
                        The next time I do another mirror I am going to try to add a little soap to the mix during fine grinding.
                        And I also have found out when figuring. Is not to go around the glass more three time. That is enough to effect a change.
                        My friend is also doing a 12 inch BVC mirror
                        and he also love the glass. It is so easy to work.
                        Gordon
                        ----- Original Message -----
                        From: burgman1
                        To: bigdob@yahoogroups.com
                        Sent: Tuesday, January 02, 2007 8:38 AM
                        Subject: [bigdob] Re: 36 Inch Mirror Blank


                        Hi,

                        I think the first step would be to find a mirror maker that will handle
                        the BVC glass. I have a 18.5" BVC mirror and my mirror maker went
                        through a lot of time and effort to get mine completed. BVC glass is
                        not the easiest glass to figure. If you are planning on making the
                        mirror yourself I would re-think the BVC glass unless you have had
                        several large mirrors under your belt.

                        Dave
                        18.5 f4.5 BVC DOB






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                      • Gordon & Sherri Berry
                        Hi Scott; This what I trying to get to!!! And I did find a book at our local library. And it is call Warm Glass: A complete guide to forming techniques fusing,
                        Message 11 of 16 , Jan 2, 2007
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                          Hi Scott;
                          This what I trying to get to!!!
                          And I did find a book at our local library.
                          And it is call Warm Glass: A complete guide to forming techniques fusing, slumping and casting.
                          I thank everyone for there input on this. I think going to read up more on this subject and hopefully I will have a big mirror or one expensive tabletop piece to talk about.
                          Gordon
                          ----- Original Message -----
                          From: Polaraligned
                          To: bigdob@yahoogroups.com
                          Sent: Tuesday, January 02, 2007 5:53 PM
                          Subject: [bigdob] Re: 36 Inch Mirror Blank


                          Mike Lockwood did a 32" BVC recently:
                          http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html

                          He does nice work. He did a 8.25" Minor axis diagonal
                          for my 32" and he did a fantastic job on it.

                          Scott

                          --- In bigdob@yahoogroups.com, "burgman1" <burgman1@...> wrote:
                          >
                          > Hi,
                          >
                          > I think the first step would be to find a mirror maker that will handle
                          > the BVC glass. I have a 18.5" BVC mirror and my mirror maker went
                          > through a lot of time and effort to get mine completed. BVC glass is
                          > not the easiest glass to figure. If you are planning on making the
                          > mirror yourself I would re-think the BVC glass unless you have had
                          > several large mirrors under your belt.
                          >
                          > Dave
                          > 18.5 f4.5 BVC DOB
                          >






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                          [Non-text portions of this message have been removed]
                        • Mike Lockwood
                          Hi, ... http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html ... Thanks, Scott. My current machine could probably be configured to
                          Message 12 of 16 , Jan 3, 2007
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                            Hi,

                            --- In bigdob@yahoogroups.com, "Polaraligned" <polaraligned@...> wrote:
                            > Mike Lockwood did a 32" BVC recently:
                            http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html
                            > He does nice work. He did a 8.25" Minor axis diagonal
                            > for my 32" and he did a fantastic job on it.

                            Thanks, Scott.

                            My current machine could probably be configured to handle a 36" blank,
                            but I am planning a larger machine, too. 36" shouldn't be a problem.

                            I can email you privately if you wish.

                            Mike Lockwood
                            http://bi-staff.beckman.uiuc.edu/~melockwo/index.html
                          • Gordon & Sherri Berry
                            Hi Mike; Please email at ghberry@earthlink.net I need a diagonal mirror this spring. Thank You Gordon Berry ... From: Mike Lockwood To: bigdob@yahoogroups.com
                            Message 13 of 16 , Jan 4, 2007
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                              Hi Mike;
                              Please email at ghberry@... I need a diagonal mirror this spring.
                              Thank You
                              Gordon Berry

                              ----- Original Message -----
                              From: Mike Lockwood
                              To: bigdob@yahoogroups.com
                              Sent: Wednesday, January 03, 2007 5:39 PM
                              Subject: [bigdob] Re: 36 Inch Mirror Blank


                              Hi,

                              --- In bigdob@yahoogroups.com, "Polaraligned" <polaraligned@...> wrote:
                              > Mike Lockwood did a 32" BVC recently:
                              http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html
                              > He does nice work. He did a 8.25" Minor axis diagonal
                              > for my 32" and he did a fantastic job on it.

                              Thanks, Scott.

                              My current machine could probably be configured to handle a 36" blank,
                              but I am planning a larger machine, too. 36" shouldn't be a problem.

                              I can email you privately if you wish.

                              Mike Lockwood
                              http://bi-staff.beckman.uiuc.edu/~melockwo/index.html






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                              Checked by AVG Free Edition.
                              Version: 7.1.409 / Virus Database: 268.16.0/609 - Release Date: 12/29/2006


                              [Non-text portions of this message have been removed]
                            • Mike Lockwood
                              Gordon, ... Somehow the last part of your email got chopped off. You can try to post it again or you can find my private email address by searching through
                              Message 14 of 16 , Jan 5, 2007
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                                Gordon,

                                --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
                                wrote:
                                > Please email at ghberry@... I need a diagonal mirror this spring.
                                > Thank You
                                > Gordon Berry

                                Somehow the last part of your email got chopped off. You can try to
                                post it again or you can find my private email address by searching
                                through the ATM archives for messages I've posted.

                                Sorry to clutter up the group with this.

                                Mike Lockwood
                              • John Mahony
                                Yahoo deletes email addresses after the @ sign if you re reading messages on the group page. Gordon s email was ghberry(at)earthlink.net. -John ...
                                Message 15 of 16 , Jan 5, 2007
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                                  Yahoo deletes email addresses after the @ sign if you're reading messages on
                                  the group page. Gordon's email was ghberry(at)earthlink.net.

                                  -John


                                  --- Mike Lockwood <parabola30@...> wrote:

                                  > Gordon,
                                  >
                                  > --- In bigdob@yahoogroups.com, "Gordon & Sherri Berry" <ghberry@...>
                                  > wrote:
                                  > > Please email at ghberry@... I need a diagonal mirror this spring.
                                  > > Thank You
                                  > > Gordon Berry
                                  >
                                  > Somehow the last part of your email got chopped off. You can try to
                                  > post it again or you can find my private email address by searching
                                  > through the ATM archives for messages I've posted.
                                  >
                                  > Sorry to clutter up the group with this.
                                  >
                                  > Mike Lockwood
                                  >
                                  >
                                  >
                                  >
                                  > Yahoo! Groups Links
                                  >
                                  >
                                  >
                                  >


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