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Light materials for telescope tube?

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  • davidgr1200
    I have a 6 Newtonian reflector which I built about 30 years ago. The garden where I live is not very suitable for astronomy (Lots of tall trees around it) but
    Message 1 of 26 , Aug 1 1:56 AM
      I have a 6" Newtonian reflector which I built about 30 years ago. The
      garden where I live is not very suitable for astronomy (Lots of tall
      trees around it) but there is a football field about 500 yards away
      which would be better. However my telesope weighs too much to be able
      to carry it that far.
      The tube is square and made of wood. Does anyone have any suggestions
      as to what material I could use to rebuild the tube so that it is
      much lighter? The tube is about four foot long.

      Thanks

      David Griffin
      (Sweden)
    • Hugues.Laroche@ses-astra.com
      ... ... Ah you too? A bit later than you I made my first 10 . It was so heavy that two persons were needed to move it around. Since then, it has been
      Message 2 of 26 , Aug 1 2:22 AM
        >I have a 6" Newtonian reflector which I built about 30 years ago.
        <snip>
        >However my telesope weighs too much to be able to carry it that far.
        >The tube is about four foot long.

        Ah you too? A bit later than you I made my first 10". It was
        so heavy that two persons were needed to move it around.
        Since then, it has been rebuilt as a truss tube dobsonian,
        with light plywood and off-the-shelf aluminum 16 mm truss tubes.
        It could easily be made even lighter.

        I can literally imagine a dozen way to rebuild a 6" so that
        it is lightweight. You even can get away without a
        complete truss. I have no image to propose you, but
        I am sure some on the list have good URLs.

        Keep on it, you will see how you will be relieved to have
        your scope as good as before, but with the possibility
        to be operational only a few seconds after having
        decided so... Good luck!

        Hugues




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      • Vladimir Galogaza
        David, You did not mention what kind of mount you have. Dobson or else. If you will consider truss design there will be considerable weight saving and 6 truss
        Message 3 of 26 , Aug 1 3:06 AM
          David,

          You did not mention what kind of mount you have. Dobson or else.
          If you will consider truss design there will be considerable weight
          saving and 6" truss telescope can be made in collapsible manner to help
          transportation.

          Regards
          Vladimir.
        • davidgr1200
          Vladimir, It has an altazimuth mount (all built in wood). If I can rebuild the (square) tube in another, lighter, material and can still connect it to the
          Message 4 of 26 , Aug 1 3:58 AM
            Vladimir,
            It has an altazimuth mount (all built in wood). If I can
            rebuild the (square) tube in another, lighter, material and can still
            connect it to the other parts then I can also remove some of the
            counterweights making it even lighter (I shall not be using it in a
            storm!). I want to retain a complete tube if I can and just replace
            the wooden (or even some of the wooden) parts of the tube with a
            lighter material. As thirty years have gone by I feel sure there must
            be something lighter than wood which is just as easy to work with
            (but probably more expensive!). I want to be able to carry it
            complete without having to assemble it every time.

            David Griffin
            (Sweden)
            --- In atm_free@yahoogroups.com, "Vladimir Galogaza"
            <vladimir.galogaza@z...> wrote:
            > David,
            >
            > You did not mention what kind of mount you have. Dobson or else.
            > If you will consider truss design there will be considerable weight
            > saving and 6" truss telescope can be made in collapsible manner to
            help
            > transportation.
            >
            > Regards
            > Vladimir.
          • planetmanwest
            ... Hello David, Use Sonotube . It is one brand name of a thick-walled cardboard material usually used as a form to pour concrete pillars. In the US it is
            Message 5 of 26 , Aug 1 4:50 AM
              --- In atm_free@yahoogroups.com, "davidgr1200" <Davidgr@b...> wrote:
              > I have a 6" Newtonian...
              > The tube is square and made of wood...
              > as to what material...
              > much lighter?

              Hello David,
              Use "Sonotube". It is one brand name of a thick-walled cardboard
              material usually used as a form to pour concrete pillars. In the US
              it is available at any building materials supplier or hardware store.
              It is stiff, light, easy to cut, and very inexpensive. A four
              foot section of 8 inch diameter tube should cost no more than 10 USD
              (probably closer to 5 USD).
              Stiffen it a little more with a plywood ring at the spider and
              seal it well against moisture with oil-based enamel paint.
              Perhaps you can use a section of your existing square tube as an
              adapter to fit the round tube to your existing alt-az mount.

              - Jim
            • davidgr1200
              Hi Jim, How does Sonotube cope with moisture? I am not intending to leave it out in the rain but it is often left outside under a roof. Presumably I would
              Message 6 of 26 , Aug 1 4:59 AM
                Hi Jim,
                How does "Sonotube" cope with moisture? I am not intending to
                leave it out in the rain but it is often left outside under a roof.
                Presumably I would need to paint it both inside (matt black) and out.
                Hmm, sounds like a good idea, if I can find the right diameter.

                Thanks for the suggestion

                David

                --- In atm_free@yahoogroups.com, "planetmanwest" <jsstars@w...>
                wrote:
                > Hello David,
                > Use "Sonotube". It is one brand name of a thick-walled
                cardboard
                > material usually used as a form to pour concrete pillars. In the US
                > it is available at any building materials supplier or hardware
                store.
                > It is stiff, light, easy to cut, and very inexpensive. A four
                > foot section of 8 inch diameter tube should cost no more than 10
                USD
                ...
                > - Jim
              • Hugues.Laroche@ses-astra.com
                ... I have not this experience, but I would fear that in this environment the sonotube will give problems. A waterproof recipee is to build a fiberglass+epoxy
                Message 7 of 26 , Aug 1 5:15 AM
                  >How does "Sonotube" cope with moisture? I am not intending to
                  >leave it out in the rain but it is often left outside under a roof.

                  I have not this experience, but I would fear that in this
                  environment the sonotube will give problems.

                  A waterproof recipee is to build a fiberglass+epoxy tube.
                  Very light, quite strong and does not fear humidity.
                  The making-of will maybe give you problems but that's
                  only once, huh? My experiences with fiberglass and
                  polyester resin are so far not too good, but I think that's
                  mainly me.

                  Hugues




                  --
                  DISCLAIMER:
                  This e-mail contains proprietary information some or all of which may be
                  legally privileged. It is for the intended recipient only. If an addressing
                  or transmission error has misdirected this e-mail, please notify the author
                  by replying to this e-mail. If you are not the intended recipient you must
                  not use, disclose, distribute, copy, print, or rely on this e-mail.
                • scopebuilder.1@juno.com
                  have you considered adding wheels? John On Fri, 01 Aug 2003 08:56:46 -0000 davidgr1200 ...
                  Message 8 of 26 , Aug 1 5:47 AM
                    have you considered adding wheels?

                    John

                    On Fri, 01 Aug 2003 08:56:46 -0000 "davidgr1200" <Davidgr@...>
                    writes:
                    > I have a 6" Newtonian reflector which I built about 30 years ago. The
                    >
                    > garden where I live is not very suitable for astronomy (Lots of tall
                    >
                    > trees around it) but there is a football field about 500 yards away
                    > which would be better. However my telesope weighs too much to be
                    > able
                    > to carry it that far.
                    > The tube is square and made of wood. Does anyone have any
                    > suggestions
                    > as to what material I could use to rebuild the tube so that it is
                    > much lighter? The tube is about four foot long.
                    >
                    > Thanks
                    >
                    > David Griffin
                    > (Sweden)
                    >
                    >
                    >
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                  • Michael Lindner
                    ... Wood. An 8 square tube made of 1/8 plywood with inside corner molding at the corners, and a few 1/4 plywood baffles to stiffen it shouldn t weigh in
                    Message 9 of 26 , Aug 1 6:25 AM
                      On Friday 01 August 2003 04:56 am, davidgr1200 wrote:
                      > The tube is square and made of wood. Does anyone have any suggestions
                      > as to what material I could use to rebuild the tube so that it is
                      > much lighter? The tube is about four foot long.

                      Wood. An 8" square tube made of 1/8" plywood with inside corner molding at the
                      corners, and a few 1/4" plywood baffles to stiffen it shouldn't weigh in more
                      than 5-10 pounds, if that. A concrete form tube should be in about the same
                      weight class. You can get more exotic...

                      A traditional truss scope probably will be heavier than a well built enclosed
                      tube, but you can make an "Alice" scope like
                      http://www.atmsite.org/contrib/Ravneberg/alice/ if you want to get fancy.

                      --
                      Michael Lindner
                      http://www.starastronomy.org
                      http://home.att.net/~mikel http://www.atmsite.org
                      http://home.attbi.com/~dcass/atmfaq/atm-faq.htm
                    • davidgr1200
                      No! I live in a northerly climate which means that snow is on the ground a large part of the winter (which is the time when I can observe objects other than
                      Message 10 of 26 , Aug 1 7:01 AM
                        No! I live in a northerly climate which means that snow is on the
                        ground a large part of the winter (which is the time when I can
                        observe objects other than the sun). Perhaps skis might be an idea?
                        Nice bit of lateral thinking though.

                        David Griffin
                        (Sweden)
                        --- In atm_free@yahoogroups.com, scopebuilder.1@j... wrote:
                        > have you considered adding wheels?
                        >
                        > John
                        >
                        > On Fri, 01 Aug 2003 08:56:46 -0000 "davidgr1200" <Davidgr@b...>
                        > writes:
                        > > I have a 6" Newtonian reflector which I built about 30 years ago.
                        The
                        > >
                        > > garden where I live is not very suitable for astronomy (Lots of
                        tall
                        > >
                        > > trees around it) but there is a football field about 500 yards
                        away
                        > > which would be better. However my telesope weighs too much to be
                        > > able
                        > > to carry it that far.
                        > > The tube is square and made of wood. Does anyone have any
                        > > suggestions
                        > > as to what material I could use to rebuild the tube so that it is
                        > > much lighter? The tube is about four foot long.
                        > >
                        > > Thanks
                        > >
                        > > David Griffin
                        > > (Sweden)
                      • davidgr1200
                        Michael, Thin plywood was one of my first thoughts but I was worried about the risk of it warping. Perhaps I could make one of the four side out of plywood?
                        Message 11 of 26 , Aug 1 7:03 AM
                          Michael,
                          Thin plywood was one of my first thoughts but I was worried
                          about the risk of it warping. Perhaps I could make one of the four
                          side out of plywood? That would save me some weight.

                          David Griffin
                          (Sweden)

                          --- In atm_free@yahoogroups.com, Michael Lindner <mikell@o...> wrote:
                          > On Friday 01 August 2003 04:56 am, davidgr1200 wrote:
                          > > The tube is square and made of wood. Does anyone have any
                          suggestions
                          > > as to what material I could use to rebuild the tube so that it is
                          > > much lighter? The tube is about four foot long.
                          >
                          > Wood. An 8" square tube made of 1/8" plywood with inside corner
                          molding at the
                          > corners, and a few 1/4" plywood baffles to stiffen it shouldn't
                          weigh in more
                          > than 5-10 pounds, if that. A concrete form tube should be in about
                          the same
                          > weight class. You can get more exotic...
                          >
                          > A traditional truss scope probably will be heavier than a well
                          built enclosed
                          > tube, but you can make an "Alice" scope like
                          > http://www.atmsite.org/contrib/Ravneberg/alice/ if you want to get
                          fancy.
                          >
                          > --
                          > Michael Lindner
                          > http://www.starastronomy.org
                          > http://home.att.net/~mikel http://www.atmsite.org
                          > http://home.attbi.com/~dcass/atmfaq/atm-faq.htm
                        • Richard Schwartz
                          Concrete sewage pipe is commonly available and is immune to moisture. In fact, it is FREE if you don t mind doing messy work. (You have to dig up the street
                          Message 12 of 26 , Aug 1 7:30 AM
                            Concrete sewage pipe is commonly available and is immune to moisture. In
                            fact, it is FREE if you don't mind doing messy work. (You have to dig up
                            the street to get it.) While you are digging up the street, be sure to
                            save the asphalt for your next pitch lap. Also, save the dirt and
                            elutriate it for abrasives if it is high in silica and low in limestone.
                            Don't let the police catch you!

                            . . . Richard

                            ----- Original Message -----
                            From: <Hugues.Laroche@...>
                            To: <atm_free@yahoogroups.com>
                            Sent: Friday, August 01, 2003 5:15 AM
                            Subject: Re: [atm_free] Re: Light materials for telescope tube?


                            >
                            >
                            > >How does "Sonotube" cope with moisture? I am not intending to
                            > >leave it out in the rain but it is often left outside under a roof.
                            >
                            > I have not this experience, but I would fear that in this
                            > environment the sonotube will give problems.
                            >
                            > A waterproof recipee is to build a fiberglass+epoxy tube.
                            > Very light, quite strong and does not fear humidity.
                            > The making-of will maybe give you problems but that's
                            > only once, huh? My experiences with fiberglass and
                            > polyester resin are so far not too good, but I think that's
                            > mainly me.
                            >
                            > Hugues
                            >
                            >
                            >
                            >
                            > --
                            > DISCLAIMER:
                            > This e-mail contains proprietary information some or all of which may be
                            > legally privileged. It is for the intended recipient only. If an
                            addressing
                            > or transmission error has misdirected this e-mail, please notify the
                            author
                            > by replying to this e-mail. If you are not the intended recipient you must
                            > not use, disclose, distribute, copy, print, or rely on this e-mail.
                            >
                            >
                            >
                            >
                            > To unsubscribe from this group, send an email to:
                            > atm_free-unsubscribe@yahoogroups.com
                            >
                            >
                            >
                            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                            >
                            >
                            >
                          • Richard Schwartz
                            There is a thinner version of plywood here called door skin that would make an excellent light weight tube. It is imported to California from our former
                            Message 13 of 26 , Aug 1 8:24 AM
                              There is a thinner version of plywood here called "door skin" that would make an excellent light weight tube.   It is imported to California from our former Communst Russian enemy!  (Actually, some of those Russian girls look pretty good, almost as blonde, beautiful, and perfect as Nordic!  Why were they the "enemy"?  Many are now moving into certain neighborhoods of Los Angeles.) 
                               
                              --Doorskiin is easy to cut with cheap hand tools
                               
                              --finish the edges with a large sheet of sandpaper  glued to a flat board.  Edges must be flat.
                               
                              --assemble it with water-based white glue (which is sometimes yellow).   Use two coats of glue.   The first coat is thinned with water so that it penetrated the edge of the plywood.   After it is dry, sand again, and use the glue undiluted for assembly.
                               
                              --You can seal doorskin against moisture with marine spar varnish.    It will not warp. 
                               
                              --Wood has an inherent natural beauty that must be covered with flat black paint.   I have a special finish that greatly reduces radar reflections, if that matters to your telescope. 
                               
                              Here is an example of my harmonica case made from doorskin.   
                               
                              Harmonica Case
                               
                              Too bad  this picture will be deleted from the archives.  
                               
                              I had hopes of making aircraft parts of doorskin, inspired by  the murderous Nazis with their futurisitic Me-232 and H-9.  By this time in the war, their aluminum industry was wrecked by American bombing and the approaching enemy, but they had plenty of trees, cows (the glue is made from milk), and slave labor.  When the Horten brothers relocated to Argentina, they found it even worse: the glue and wood were of poor quality. 
                               
                              A square tube is OK, but a five-sided tube with a 36 degree offset mounting saddle gives you ten possible positions for the eyepiece and contributes to viewing comfort.  (This only works if you can flip the declination axis 180 degrees.)
                               
                              Richard
                               
                              ----- Original Message -----
                              From: "davidgr1200" <Davidgr@...>
                              Sent: Friday, August 01, 2003 7:03 AM
                              Subject: [atm_free] Re: Light materials for telescope tube?

                              > Michael,
                              >         Thin
                              plywood was one of my first thoughts but I was worried
                              > about the risk
                              of it warping. Perhaps I could make one of the four
                              > side out of
                              plywood? That would save me some weight.
                              >
                              > David Griffin
                              >
                              (Sweden)
                            • Michael Lindner
                              ... I believe plywood is no more likely to warp than solid wood. You are more likely have problems using both products together, as they will have different
                              Message 14 of 26 , Aug 1 10:25 AM
                                On Friday 01 August 2003 10:03 am, davidgr1200 wrote:
                                > Thin plywood was one of my first thoughts but I was worried
                                > about the risk of it warping. Perhaps I could make one of the four
                                > side out of plywood?

                                I believe plywood is no more likely to warp than solid wood. You are more
                                likely have problems using both products together, as they will have
                                different rates of expansion. Three to five coats of a good polyurethane
                                varnish inside and out will keep the plywood fairly water resistant. Also be
                                sure to use an exterior grade plywood.

                                Richard Berry has instructions for making a square plywood tube in his book
                                "Build Your Own Telescope".

                                Clear skies.
                                --
                                Michael Lindner
                                http://www.starastronomy.org
                                http://home.att.net/~mikel http://www.atmsite.org
                                http://home.attbi.com/~dcass/atmfaq/atm-faq.htm
                              • planetmanwest
                                ... Hello David, If sealed well with some good paint it will give many years of service. I have uploaded three photos of the most recent scope I made with
                                Message 15 of 26 , Aug 1 2:55 PM
                                  --- In atm_free@yahoogroups.com, "davidgr1200" <Davidgr@b...> wrote:
                                  > Hi Jim,
                                  > How does "Sonotube" cope with moisture?

                                  Hello David,
                                  If sealed well with some good paint it will give many years of
                                  service. I have uploaded three photos of the most recent scope I made
                                  with cardboard tube to the atm_free Yahoo site photo albums. Look in
                                  the "J&S" album. I built this telescope during the two weeks
                                  preceding Christmas 1996 or 1997 for my daughter, and it has seen
                                  many many nights of dewing and frosting. Sometimes the frost is so
                                  thick the tube is white instead of green. When the sunlight hits it
                                  the next morning the frost melts and runs off. Now, 6 years later it
                                  looks as good as the first time out and is just as firm and strong
                                  (and light weight) as the day it was made.
                                  The first and third photos show the way the tube is put together
                                  with an internal skeleton of plywood rings and wooden dowels. The
                                  third photo is a view down the tube illuminated by sunlight. Look
                                  closely to see one of the three dowels. The second photo is a closeup
                                  of the azimuth circle. You can see one of the three 1/2 inch thick
                                  pie-shaped teflon pads under the azimuth disk by reflection.
                                  Make your skeleton of plywood rings such that there is one flush
                                  with the skyward end, another near it by the spider, a couple more
                                  mear where the tube will be clamped, and another down near the mirror
                                  cell. Use at least three 1/4 inch hardwood dowels through holes in
                                  the rings to hold them together and glue it to make it strong.
                                  When the glue dries, shove the skeleton down into the tube with
                                  plenty of wood glue to make the skeleton a permanent part of the tube.
                                  This will make the tube very stiff but still quite light in weight.
                                  Paint the tube inside and out with oil-based house primer, then
                                  when dry, finish coat it with 3 or 5 coats of good oil based enamel.
                                  When holes are drilled into the tube (prior to painting of
                                  course), clean off the excess paper burrs with a razor blade, then
                                  seal the holes with wood glue using a match stick to ensure that the
                                  material exposed by the drill is sealed well against moisture. Let it
                                  soak up as much wood glue as it can. Keep all points of access to the
                                  cardboard sealed against moisture and the tube will last many years.
                                  With care, the tube should last decades.
                                  But then again, the cardboard tubing is very inexpensive, so if
                                  you don't want to do all that work, just leave it plain and replace
                                  it when it wears out. Most brands of the stuff have a wax or thin
                                  plastic coating that helps to seal the major surfaces by default.
                                  I built a Cassegrain using this tubing in the late 1970's and
                                  didn't bother to paint it at all. I just had some rubber sheet
                                  wrapped around the outside held in place with upholstery tacks. It
                                  lasted about three years before moisture eventually made the tube
                                  weak.
                                  Check it out. The stuff should be available almost anywhere in
                                  the world that concrete is sold...

                                  - Jim S.
                                • Richard Schwartz
                                  In sealing wood or sonotube with white glue, dilute the glue with water about 1 part glue to 2 parts water, so that it will penetrate better. Do let it dry
                                  Message 16 of 26 , Aug 3 6:35 PM
                                    In sealing wood or sonotube with white glue, dilute the glue with water
                                    about 1 part glue to 2 parts water, so that it will penetrate better. Do
                                    let it dry an extra day.


                                    ----- Original Message -----
                                    From: "planetmanwest" <jsstars@...>
                                    To: <atm_free@yahoogroups.com>
                                    Sent: Friday, August 01, 2003 2:55 PM
                                    Subject: [atm_free] Re: Light materials for telescope tube?


                                    > --- In atm_free@yahoogroups.com, "davidgr1200" <Davidgr@b...> wrote:
                                    > > Hi Jim,
                                    > > How does "Sonotube" cope with moisture?
                                    >
                                    > Hello David,
                                    > If sealed well with some good paint it will give many years of
                                    > service. I have uploaded three photos of the most recent scope I made
                                    > with cardboard tube to the atm_free Yahoo site photo albums. Look in
                                    > the "J&S" album. I built this telescope during the two weeks
                                    > preceding Christmas 1996 or 1997 for my daughter, and it has seen
                                    > many many nights of dewing and frosting. Sometimes the frost is so
                                    > thick the tube is white instead of green. When the sunlight hits it
                                    > the next morning the frost melts and runs off. Now, 6 years later it
                                    > looks as good as the first time out and is just as firm and strong
                                    > (and light weight) as the day it was made.
                                    > The first and third photos show the way the tube is put together
                                    > with an internal skeleton of plywood rings and wooden dowels. The
                                    > third photo is a view down the tube illuminated by sunlight. Look
                                    > closely to see one of the three dowels. The second photo is a closeup
                                    > of the azimuth circle. You can see one of the three 1/2 inch thick
                                    > pie-shaped teflon pads under the azimuth disk by reflection.
                                    > Make your skeleton of plywood rings such that there is one flush
                                    > with the skyward end, another near it by the spider, a couple more
                                    > mear where the tube will be clamped, and another down near the mirror
                                    > cell. Use at least three 1/4 inch hardwood dowels through holes in
                                    > the rings to hold them together and glue it to make it strong.
                                    > When the glue dries, shove the skeleton down into the tube with
                                    > plenty of wood glue to make the skeleton a permanent part of the tube.
                                    > This will make the tube very stiff but still quite light in weight.
                                    > Paint the tube inside and out with oil-based house primer, then
                                    > when dry, finish coat it with 3 or 5 coats of good oil based enamel.
                                    > When holes are drilled into the tube (prior to painting of
                                    > course), clean off the excess paper burrs with a razor blade, then
                                    > seal the holes with wood glue using a match stick to ensure that the
                                    > material exposed by the drill is sealed well against moisture. Let it
                                    > soak up as much wood glue as it can. Keep all points of access to the
                                    > cardboard sealed against moisture and the tube will last many years.
                                    > With care, the tube should last decades.
                                    > But then again, the cardboard tubing is very inexpensive, so if
                                    > you don't want to do all that work, just leave it plain and replace
                                    > it when it wears out. Most brands of the stuff have a wax or thin
                                    > plastic coating that helps to seal the major surfaces by default.
                                    > I built a Cassegrain using this tubing in the late 1970's and
                                    > didn't bother to paint it at all. I just had some rubber sheet
                                    > wrapped around the outside held in place with upholstery tacks. It
                                    > lasted about three years before moisture eventually made the tube
                                    > weak.
                                    > Check it out. The stuff should be available almost anywhere in
                                    > the world that concrete is sold...
                                    >
                                    > - Jim S.
                                    >
                                    >
                                    >
                                    > To unsubscribe from this group, send an email to:
                                    > atm_free-unsubscribe@yahoogroups.com
                                    >
                                    >
                                    >
                                    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                                    >
                                    >
                                    >
                                  • scopebuilder.1@juno.com
                                    I would think that that would weaken it. I use glue full strength. the trick is to roughen the surface a bit and clamp. Of course if you cant clamp that may be
                                    Message 17 of 26 , Aug 3 6:37 PM
                                      I would think that that would weaken it. I use glue full strength. the
                                      trick is to roughen the surface a bit and clamp.
                                      Of course if you cant clamp that may be a viable alternitive.

                                      John

                                      On Sun, 3 Aug 2003 18:35:14 -0700 "Richard Schwartz"
                                      <richas@...> writes:
                                      > In sealing wood or sonotube with white glue, dilute the glue with
                                      > water
                                      > about 1 part glue to 2 parts water, so that it will penetrate
                                      > better. Do
                                      > let it dry an extra day.
                                      >
                                      >
                                      > ----- Original Message -----
                                      > From: "planetmanwest" <jsstars@...>
                                      > To: <atm_free@yahoogroups.com>
                                      > Sent: Friday, August 01, 2003 2:55 PM
                                      > Subject: [atm_free] Re: Light materials for telescope tube?
                                      >
                                      >
                                      > > --- In atm_free@yahoogroups.com, "davidgr1200" <Davidgr@b...>
                                      > wrote:
                                      > > > Hi Jim,
                                      > > > How does "Sonotube" cope with moisture?
                                      > >
                                      > > Hello David,
                                      > > If sealed well with some good paint it will give many years
                                      > of
                                      > > service. I have uploaded three photos of the most recent scope I
                                      > made
                                      > > with cardboard tube to the atm_free Yahoo site photo albums. Look
                                      > in
                                      > > the "J&S" album. I built this telescope during the two weeks
                                      > > preceding Christmas 1996 or 1997 for my daughter, and it has seen
                                      > > many many nights of dewing and frosting. Sometimes the frost is so
                                      > > thick the tube is white instead of green. When the sunlight hits
                                      > it
                                      > > the next morning the frost melts and runs off. Now, 6 years later
                                      > it
                                      > > looks as good as the first time out and is just as firm and strong
                                      > > (and light weight) as the day it was made.
                                      > > The first and third photos show the way the tube is put
                                      > together
                                      > > with an internal skeleton of plywood rings and wooden dowels. The
                                      > > third photo is a view down the tube illuminated by sunlight. Look
                                      > > closely to see one of the three dowels. The second photo is a
                                      > closeup
                                      > > of the azimuth circle. You can see one of the three 1/2 inch thick
                                      > > pie-shaped teflon pads under the azimuth disk by reflection.
                                      > > Make your skeleton of plywood rings such that there is one
                                      > flush
                                      > > with the skyward end, another near it by the spider, a couple more
                                      > > mear where the tube will be clamped, and another down near the
                                      > mirror
                                      > > cell. Use at least three 1/4 inch hardwood dowels through holes in
                                      > > the rings to hold them together and glue it to make it strong.
                                      > > When the glue dries, shove the skeleton down into the tube
                                      > with
                                      > > plenty of wood glue to make the skeleton a permanent part of the
                                      > tube.
                                      > > This will make the tube very stiff but still quite light in
                                      > weight.
                                      > > Paint the tube inside and out with oil-based house primer,
                                      > then
                                      > > when dry, finish coat it with 3 or 5 coats of good oil based
                                      > enamel.
                                      > > When holes are drilled into the tube (prior to painting of
                                      > > course), clean off the excess paper burrs with a razor blade, then
                                      > > seal the holes with wood glue using a match stick to ensure that
                                      > the
                                      > > material exposed by the drill is sealed well against moisture. Let
                                      > it
                                      > > soak up as much wood glue as it can. Keep all points of access to
                                      > the
                                      > > cardboard sealed against moisture and the tube will last many
                                      > years.
                                      > > With care, the tube should last decades.
                                      > > But then again, the cardboard tubing is very inexpensive, so
                                      > if
                                      > > you don't want to do all that work, just leave it plain and
                                      > replace
                                      > > it when it wears out. Most brands of the stuff have a wax or thin
                                      > > plastic coating that helps to seal the major surfaces by default.
                                      > > I built a Cassegrain using this tubing in the late 1970's and
                                      > > didn't bother to paint it at all. I just had some rubber sheet
                                      > > wrapped around the outside held in place with upholstery tacks. It
                                      > > lasted about three years before moisture eventually made the tube
                                      > > weak.
                                      > > Check it out. The stuff should be available almost anywhere
                                      > in
                                      > > the world that concrete is sold...
                                      > >
                                      > > - Jim S.
                                      > >
                                      > >
                                      > >
                                      > > To unsubscribe from this group, send an email to:
                                      > > atm_free-unsubscribe@yahoogroups.com
                                      > >
                                      > >
                                      > >
                                      > > Your use of Yahoo! Groups is subject to
                                      > http://docs.yahoo.com/info/terms/
                                      > >
                                      > >
                                      > >
                                      >
                                      >
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                                    • davidgr1200
                                      Thanks to everybody who rplied to my question about lightweight materials for a telescope tube. The consensus seems to be that the Sonotube is the easiest
                                      Message 18 of 26 , Aug 4 12:28 AM
                                        Thanks to everybody who rplied to my question about lightweight
                                        materials for a telescope tube. The consensus seems to be that
                                        the "Sonotube" is the easiest answer. I must admit, when I psoed the
                                        question I was expecting to hear about some sort of lightweight rigid
                                        plastic or carbon fibre type of material but it appears that either
                                        such stuff is not available or it is not suitable for telescopes.

                                        Thanks again

                                        David Griffin
                                        (Sweden)
                                      • Hugues.Laroche@ses-astra.com
                                        Hello David, ... I was expecting to hear about some sort of lightweight rigid plastic or carbon fibre type of material but it appears that either such stuff is
                                        Message 19 of 26 , Aug 4 12:40 AM
                                          Hello David,

                                          >>>
                                          I was expecting to hear about some sort of lightweight rigid
                                          plastic or carbon fibre type of material but it appears that either
                                          such stuff is not available or it is not suitable for telescopes.
                                          <<<

                                          Well, I have made a 155 mm (6") refractor with PVC rainpipe tubing. Works
                                          well in these
                                          dimensions, is waterproof, not expensive, relatively easy to work with and
                                          readily
                                          available but it is @*&^# heavy.
                                          On the other hand, you are right that carbon fibre is expensive, not easily
                                          found in
                                          customised dimensions, difficult to work with, despite its advantages
                                          (probably
                                          marginal for a 6" instrument).

                                          So, again, good luck with the sonotube... should work fine. And after all,
                                          if it does not please
                                          you anymore in some years, you will have to have fun redoing it
                                          another way (because ATMing is fun, isn't it?? :-).

                                          Hugues
                                          Luxembourg
                                          6 deg E, 49 deg N



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                                        • scopebuilder.1@juno.com
                                          have you considered a truss setup? just leave it together all the time though. and if you ever move or take a long trip it has the advantage of being
                                          Message 20 of 26 , Aug 4 2:06 AM
                                            have you considered a truss setup? just leave it together all the time
                                            though. and if you ever move or take a long trip it has the advantage of
                                            being dissasembled for better transport.

                                            John

                                            On Mon, 4 Aug 2003 09:40:03 +0200 Hugues.Laroche@... writes:
                                            >
                                            > Hello David,
                                            >
                                            > >>>
                                            > I was expecting to hear about some sort of lightweight rigid
                                            > plastic or carbon fibre type of material but it appears that either
                                            > such stuff is not available or it is not suitable for telescopes.
                                            > <<<
                                            >
                                            > Well, I have made a 155 mm (6") refractor with PVC rainpipe tubing.
                                            > Works
                                            > well in these
                                            > dimensions, is waterproof, not expensive, relatively easy to work
                                            > with and
                                            > readily
                                            > available but it is @*&^# heavy.
                                            > On the other hand, you are right that carbon fibre is expensive, not
                                            > easily
                                            > found in
                                            > customised dimensions, difficult to work with, despite its
                                            > advantages
                                            > (probably
                                            > marginal for a 6" instrument).
                                            >
                                            > So, again, good luck with the sonotube... should work fine. And
                                            > after all,
                                            > if it does not please
                                            > you anymore in some years, you will have to have fun redoing it
                                            > another way (because ATMing is fun, isn't it?? :-).
                                            >
                                            > Hugues
                                            > Luxembourg
                                            > 6 deg E, 49 deg N
                                            >
                                            >
                                            >
                                            > --
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                                            > This e-mail contains proprietary information some or all of which
                                            > may be
                                            > legally privileged. It is for the intended recipient only. If an
                                            > addressing
                                            > or transmission error has misdirected this e-mail, please notify the
                                            > author
                                            > by replying to this e-mail. If you are not the intended recipient
                                            > you must
                                            > not use, disclose, distribute, copy, print, or rely on this e-mail.
                                            >
                                            >
                                            >
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                                            >
                                            >


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                                          • davidgr1200
                                            I,m not sure about a truss setup, there are a couple of peculiarities about my mount which means I cannot have an open tube, or at least it is pretty
                                            Message 21 of 26 , Aug 4 6:37 AM
                                              I,m not sure about a truss setup, there are a couple of peculiarities
                                              about my mount which means I cannot have an open tube, or at least it
                                              is pretty complicated. I have just received a suggestion from someone
                                              on another list which sounds interesting: use 1cm thick styrofoam
                                              sandwiched between two layers of 3mm birch plywood. I think I will
                                              probably try this first as I can make it the same shape and size as
                                              my current tube.

                                              Thanks for all your help

                                              David Griffin
                                              Sweden

                                              --- In atm_free@yahoogroups.com, scopebuilder.1@j... wrote:
                                              > have you considered a truss setup? just leave it together all the
                                              time
                                              > though. and if you ever move or take a long trip it has the
                                              advantage of
                                              > being dissasembled for better transport.
                                              >
                                              > John
                                              >
                                              > On Mon, 4 Aug 2003 09:40:03 +0200 Hugues.Laroche@s... writes:
                                              > >
                                              > > Hello David,
                                              > >
                                              > > >>>
                                              > > I was expecting to hear about some sort of lightweight rigid
                                              > > plastic or carbon fibre type of material but it appears that
                                              either
                                              > > such stuff is not available or it is not suitable for telescopes.
                                              > > <<<
                                              > >
                                              > > Well, I have made a 155 mm (6") refractor with PVC rainpipe
                                              tubing.
                                              > > Works
                                              > > well in these
                                              > > dimensions, is waterproof, not expensive, relatively easy to work
                                              > > with and
                                              > > readily
                                              > > available but it is @*&^# heavy.
                                              > > On the other hand, you are right that carbon fibre is expensive,
                                              not
                                              > > easily
                                              > > found in
                                              > > customised dimensions, difficult to work with, despite its
                                              > > advantages
                                              > > (probably
                                              > > marginal for a 6" instrument).
                                              > >
                                              > > So, again, good luck with the sonotube... should work fine. And
                                              > > after all,
                                              > > if it does not please
                                              > > you anymore in some years, you will have to have fun redoing it
                                              > > another way (because ATMing is fun, isn't it?? :-).
                                              > >
                                              > > Hugues
                                              > > Luxembourg
                                              > > 6 deg E, 49 deg N
                                            • leftfieldstar@aol.com
                                              In a message dated 8/4/03 9:53:40 AM Eastern Daylight Time, ... There is a material available at artist and stationary suppliers called Gatorboard . It is a
                                              Message 22 of 26 , Aug 4 8:41 AM
                                                In a message dated 8/4/03 9:53:40 AM Eastern Daylight Time,
                                                Davidgr@... writes:

                                                > have just received a suggestion from someone
                                                > on another list which sounds interesting: use 1cm thick styrofoam
                                                > sandwiched between two layers of 3mm birch plywood

                                                There is a material available at artist and stationary suppliers called
                                                'Gatorboard'.
                                                It is a foam cored board sandwiched with a random fiber sheet on both sides.
                                                I made a 6 sided tube for a 6 inch f/4 RFT using this material. Weighs less
                                                than a pound. It comes in single and double core with a middle sheet for extra
                                                stiffness. 1/4 inch and 1/2 inch thick.
                                                This is what I used, there are other makers of this type of sandwiched
                                                construction board.

                                                Dominic DiLeo
                                              • davidgr1200
                                                Hi Dominic, I m not sure if this is available over here in Sweden. I ll have to check out our local builders shop.Is it easy to work with? The tube is
                                                Message 23 of 26 , Aug 5 12:06 AM
                                                  Hi Dominic,
                                                  I'm not sure if this is available over here in Sweden.
                                                  I'll have to check out our local builders shop.Is it easy to work
                                                  with? The tube is currently fixed to the mount with a bolt which goes
                                                  through the side of the tube, would this be OK for "Gatorboard"? Can
                                                  it take screws, bolts etc for fixing the mirror cell to the tube?

                                                  Thanks for the suggestion

                                                  David Griffin
                                                  (Sweden)

                                                  --- In atm_free@yahoogroups.com, leftfieldstar@a... wrote:
                                                  > There is a material available at artist and stationary suppliers
                                                  called
                                                  > 'Gatorboard'.
                                                  > It is a foam cored board sandwiched with a random fiber sheet on
                                                  both sides.
                                                  > I made a 6 sided tube for a 6 inch f/4 RFT using this material.
                                                  Weighs less
                                                  > than a pound. It comes in single and double core with a middle
                                                  sheet for extra
                                                  > stiffness. 1/4 inch and 1/2 inch thick.
                                                  > This is what I used, there are other makers of this type of
                                                  sandwiched
                                                  > construction board.
                                                  >
                                                  > Dominic DiLeo
                                                • leftfieldstar@aol.com
                                                  In a message dated 8/5/03 3:06:58 AM Eastern Daylight Time, ... Hi, David This is not a robust material and will not sustain compression without deforming. You
                                                  Message 24 of 26 , Aug 5 6:12 AM
                                                    In a message dated 8/5/03 3:06:58 AM Eastern Daylight Time,
                                                    Davidgr@... writes:

                                                    > I'm not sure if this is available over here in Sweden.
                                                    > I'll have to check out our local builders shop.Is it easy to work
                                                    > with? The tube is currently fixed to the mount with a bolt which goes
                                                    > through the side of the tube, would this be OK for "Gatorboard"? Can
                                                    > it take screws, bolts etc for fixing the mirror cell to the tube?
                                                    >
                                                    Hi, David

                                                    This is not a robust material and will not sustain compression without
                                                    deforming. You can make an adjustable saddle ring out of a solid material to couple
                                                    the tube to your mount. Hardware can be secured directly to and thru it if
                                                    you take precautions to disperse point loads by using rigid spacers and broad
                                                    washers.

                                                    Why not rebuild the entire scope? You can build a simple and rugged Dob
                                                    moount in a day with a minimum of hand tools. If you want to lighten it
                                                    substantially, a full rebuild is needed. What EXACTLY do you have for a telescope? Type
                                                    of mount, total weight? Need specific and concise information.

                                                    Dominic DiLeo
                                                    In Maine
                                                  • davidgr1200
                                                    Hi Dominic, If you can let me know your e-mai laddress I can send you a foto and some more details. Best wishes David
                                                    Message 25 of 26 , Aug 6 2:04 AM
                                                      Hi Dominic,
                                                      If you can let me know your e-mai laddress I can send you
                                                      a foto and some more details.

                                                      Best wishes

                                                      David

                                                      > What EXACTLY do you have for a telescope? Type
                                                      > of mount, total weight? Need specific and concise information.
                                                      >
                                                      > Dominic DiLeo
                                                      > In Maine
                                                    • leftfieldstar@aol.com
                                                      In a message dated 8/6/03 5:05:41 AM Eastern Daylight Time, ... David, Post your pictures into a folder at the atm_free site and post information to the group
                                                      Message 26 of 26 , Aug 6 6:42 AM
                                                        In a message dated 8/6/03 5:05:41 AM Eastern Daylight Time,
                                                        Davidgr@... writes:

                                                        > If you can let me know your e-mai laddress I can send you
                                                        > a foto and some more details.
                                                        >
                                                        David,

                                                        Post your pictures into a folder at the atm_free site and post information to
                                                        the group that you wish to add. This will allow all members to have a look
                                                        and supply some helpful replies.

                                                        Dominic DiLeo
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