Loading ...
Sorry, an error occurred while loading the content.

kid's atm 2 focii

Expand Messages
  • a
    Hi He is in polishing but notices two focal points, differing by 2 cm. Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
    Message 1 of 10 , Aug 1, 2009
    • 0 Attachment
       
      Hi
       
      He is in polishing but notices two focal points, differing by 2 cm.
       
      Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
       
       
      Thanks and Regards
       
      Ali Khan
      in orange glasses
    • a
      Hi He is in polishing but notices two focal points, differing by 2 cm. Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
      Message 2 of 10 , Aug 1, 2009
      • 0 Attachment
         
        Hi
         
        He is in polishing but notices two focal points, differing by 2 cm.
         
        Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
         
         
        Thanks and Regards
         
        Ali Khan
        in orange glasses
      • Mark Whitaker
        Without seeing the scratches I can t offer any advice on what they may be or how to deal with them. I hope he did a thorough job of fine grinding and
        Message 3 of 10 , Aug 1, 2009
        • 0 Attachment
          Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

          Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

          Mark


          From: a <ak666666@...>
          To: atm_free@yahoogroups.com
          Sent: Saturday, August 1, 2009 9:36:19 AM
          Subject: [atm_free] kid's atm 2 focii

           

           
          Hi
           
          He is in polishing but notices two focal points, differing by 2 cm.
           
          Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
           
           
          Thanks and Regards
           
          Ali Khan
          in orange glasses

        • a
          Hi eight inch mirror 280 cm fl He did pencil test before leaving fine grinding. 4 to 5 hours polishing. He focused on a wire mesh and saw two places where mesh
          Message 4 of 10 , Aug 1, 2009
          • 0 Attachment
             
            Hi
             
            eight inch mirror
            280 cm fl
            He did pencil test before leaving fine grinding.
            4 to 5 hours polishing.
            He focused on a wire mesh and saw two places where mesh focussed. 2 cm apart. Mirror 19mm thick at start.
             
             
             
             
            Thanks and Regards
             
            Ali Khan
            in orange glasses
            ----- Original Message -----
            Sent: Saturday, August 01, 2009 8:53 .
            Subject: Re: [atm_free] kid's atm 2 focii

             

            Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

            Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

            Mark


            From: a <ak666666@hotmail. com>
            To: atm_free@yahoogroup s.com
            Sent: Saturday, August 1, 2009 9:36:19 AM
            Subject: [atm_free] kid's atm 2 focii

             

             
            Hi
             
            He is in polishing but notices two focal points, differing by 2 cm.
             
            Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
             
             
            Thanks and Regards
             
            Ali Khan
            in orange glasses

          • a
            Hi He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of
            Message 5 of 10 , Aug 1, 2009
            • 0 Attachment
               
              Hi
               
              He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of slipping and no friction.
               
              He filtered ceo suspension through a cean cloth.
               
              Thanks and Regards
               
              Ali Khan
              in orange glasses
              ----- Original Message -----
              Sent: Saturday, August 01, 2009 8:53 .
              Subject: Re: [atm_free] kid's atm 2 focii

               

              Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

              Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

              Mark


              From: a <ak666666@hotmail. com>
              To: atm_free@yahoogroup s.com
              Sent: Saturday, August 1, 2009 9:36:19 AM
              Subject: [atm_free] kid's atm 2 focii

               

               
              Hi
               
              He is in polishing but notices two focal points, differing by 2 cm.
               
              Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
               
               
              Thanks and Regards
               
              Ali Khan
              in orange glasses

            • Mark Whitaker
              OK, that s approximately f/11 so I suspect that he is shooting for a spherical mirror with no paraboloid. Texereau says that f/11 for an 8 mirror is more
              Message 6 of 10 , Aug 1, 2009
              • 0 Attachment
                OK, that's approximately f/11 so I suspect that he is shooting for a spherical mirror with no paraboloid.  Texereau says that f/11 for an 8" mirror is more than adequate to satisfy the Rayleigh criteria.

                A good, full polish for an 8" mirror by hand will probably take at least 15 hours.  Polishing compound, pitch, glass type, personal habits and a whole lot of other factors will effect this.  Still, I recommend that he err on the conservative side and go 20 full hours for 8".  Even when a mirror looks polished to the novice, it generally still has small pits or sleeks.  These are often not apparent until the mirror is coated and can't be seen (uncoated) under ordinary lighting.

                I would not worry about the wire mesh trick too much.  I don't think you can really tell what's going on by doing it for a lot of reasons.  Remember, an astronomical mirror will only produce good clean image over a very small area, on the order of a degree or so.  Once you get off axis a small amount, you start getting all the aberrations you would expect from any mirror.  So I suspect he is fretting over nothing.

                Does he plan on any more elaborate testing?  A simple pinhole and KE test will easily show when a sphere has been obtained and does not require any math.  Another option is to use the mirror uncoated on the moon.  In the end, all that matters is that he is satisfied with the images it produces.

                Personally, I would make a simple foucault tester with a pinhole/KE and look at the mirror.  With a mirror as large as 8", it is not easy to obtain a sphere automatically.  Some test feedback and stroke adjustment go a long way to producing a good sphere.

                Mark


                From: a <ak666666@...>
                To: atm_free@yahoogroups.com
                Sent: Saturday, August 1, 2009 11:37:58 AM
                Subject: Re: [atm_free] kid's atm 2 focii

                 

                 
                Hi
                 
                eight inch mirror
                280 cm fl
                He did pencil test before leaving fine grinding.
                4 to 5 hours polishing.
                He focused on a wire mesh and saw two places where mesh focussed. 2 cm apart. Mirror 19mm thick at start.
                 
                 
                 
                 
                Thanks and Regards
                 
                Ali Khan
                in orange glasses
                ----- Original Message -----
                Sent: Saturday, August 01, 2009 8:53 .
                Subject: Re: [atm_free] kid's atm 2 focii

                 

                Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

                Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

                Mark


                From: a <ak666666@hotmail. com>
                To: atm_free@yahoogroup s.com
                Sent: Saturday, August 1, 2009 9:36:19 AM
                Subject: [atm_free] kid's atm 2 focii

                 

                 
                Hi
                 
                He is in polishing but notices two focal points, differing by 2 cm.
                 
                Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
                 
                 
                Thanks and Regards
                 
                Ali Khan
                in orange glasses


              • Mark Whitaker
                What type of pitch is he using? It is a petroleum based pitch (tar) or a pitch based on tree sap? I have no experience with petroleum based pitches and am
                Message 7 of 10 , Aug 1, 2009
                • 0 Attachment
                  What type of pitch is he using?  It is a petroleum based pitch (tar) or a pitch based on tree sap?  I have no experience with petroleum based pitches and am not sure linseed oil would be a good agent with those.

                  In any case, for the amount of pitch you would normally use to polish an 8" mirror, you would normally only need a few milliliters of linseed oil.  So I would say he ruined his pitch.  The thing about linseed oil is that you can't boil it away as you would an excess of turpentine so he will probably need new pitch.

                  For a long focus sphere, you want a harder pitch than you would normally use for faster mirrors or parabolizing.  The harder pitch (with lots of pressing) tends to produce a sphere.

                  Mark


                  From: a <ak666666@...>
                  To: atm_free@yahoogroups.com
                  Sent: Saturday, August 1, 2009 11:42:40 AM
                  Subject: Re: [atm_free] kid's atm 2 focii

                   

                   
                  Hi
                   
                  He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of slipping and no friction.
                   
                  He filtered ceo suspension through a cean cloth.
                   
                  Thanks and Regards
                   
                  Ali Khan
                  in orange glasses
                  ----- Original Message -----
                  Sent: Saturday, August 01, 2009 8:53 .
                  Subject: Re: [atm_free] kid's atm 2 focii

                   

                  Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

                  Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

                  Mark


                  From: a <ak666666@hotmail. com>
                  To: atm_free@yahoogroup s.com
                  Sent: Saturday, August 1, 2009 9:36:19 AM
                  Subject: [atm_free] kid's atm 2 focii

                   

                   
                  Hi
                   
                  He is in polishing but notices two focal points, differing by 2 cm.
                   
                  Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
                   
                   
                  Thanks and Regards
                   
                  Ali Khan
                  in orange glasses


                • a
                  Hi Thanks a million for all your valuable help. Thanks and Regards Ali Khan in orange glasses ... From: Mark Whitaker To: atm_free@yahoogroups.com Sent:
                  Message 8 of 10 , Aug 1, 2009
                  • 0 Attachment
                     
                    Hi
                     
                    Thanks a million for all your valuable help.
                     
                     
                    Thanks and Regards
                     
                    Ali Khan
                    in orange glasses
                    ----- Original Message -----
                    Sent: Saturday, August 01, 2009 11:51 .
                    Subject: Re: [atm_free] kid's atm 2 focii

                     

                    What type of pitch is he using?  It is a petroleum based pitch (tar) or a pitch based on tree sap?  I have no experience with petroleum based pitches and am not sure linseed oil would be a good agent with those.

                    In any case, for the amount of pitch you would normally use to polish an 8" mirror, you would normally only need a few milliliters of linseed oil.  So I would say he ruined his pitch.  The thing about linseed oil is that you can't boil it away as you would an excess of turpentine so he will probably need new pitch.

                    For a long focus sphere, you want a harder pitch than you would normally use for faster mirrors or parabolizing.  The harder pitch (with lots of pressing) tends to produce a sphere.

                    Mark


                    From: a <ak666666@hotmail. com>
                    To: atm_free@yahoogroup s.com
                    Sent: Saturday, August 1, 2009 11:42:40 AM
                    Subject: Re: [atm_free] kid's atm 2 focii

                     

                     
                    Hi
                     
                    He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of slipping and no friction.
                     
                    He filtered ceo suspension through a cean cloth.
                     
                    Thanks and Regards
                     
                    Ali Khan
                    in orange glasses
                    ----- Original Message -----
                    Sent: Saturday, August 01, 2009 8:53 .
                    Subject: Re: [atm_free] kid's atm 2 focii

                     

                    Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

                    Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

                    Mark


                    From: a <ak666666@hotmail. com>
                    To: atm_free@yahoogroup s.com
                    Sent: Saturday, August 1, 2009 9:36:19 AM
                    Subject: [atm_free] kid's atm 2 focii

                     

                     
                    Hi
                     
                    He is in polishing but notices two focal points, differing by 2 cm.
                     
                    Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
                     
                     
                    Thanks and Regards
                     
                    Ali Khan
                    in orange glasses


                  • a
                    Hi Yes tar. Thanks and Regards Ali Khan in orange glasses ... From: Mark Whitaker To: atm_free@yahoogroups.com Sent: Saturday, August 01, 2009 11:51 . Subject:
                    Message 9 of 10 , Aug 1, 2009
                    • 0 Attachment
                       
                      Hi
                       
                      Yes tar.
                       
                       
                      Thanks and Regards
                       
                      Ali Khan
                      in orange glasses
                      ----- Original Message -----
                      Sent: Saturday, August 01, 2009 11:51 .
                      Subject: Re: [atm_free] kid's atm 2 focii

                       

                      What type of pitch is he using?  It is a petroleum based pitch (tar) or a pitch based on tree sap?  I have no experience with petroleum based pitches and am not sure linseed oil would be a good agent with those.

                      In any case, for the amount of pitch you would normally use to polish an 8" mirror, you would normally only need a few milliliters of linseed oil.  So I would say he ruined his pitch.  The thing about linseed oil is that you can't boil it away as you would an excess of turpentine so he will probably need new pitch.

                      For a long focus sphere, you want a harder pitch than you would normally use for faster mirrors or parabolizing.  The harder pitch (with lots of pressing) tends to produce a sphere.

                      Mark


                      From: a <ak666666@hotmail. com>
                      To: atm_free@yahoogroup s.com
                      Sent: Saturday, August 1, 2009 11:42:40 AM
                      Subject: Re: [atm_free] kid's atm 2 focii

                       

                       
                      Hi
                       
                      He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of slipping and no friction.
                       
                      He filtered ceo suspension through a cean cloth.
                       
                      Thanks and Regards
                       
                      Ali Khan
                      in orange glasses
                      ----- Original Message -----
                      Sent: Saturday, August 01, 2009 8:53 .
                      Subject: Re: [atm_free] kid's atm 2 focii

                       

                      Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

                      Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

                      Mark


                      From: a <ak666666@hotmail. com>
                      To: atm_free@yahoogroup s.com
                      Sent: Saturday, August 1, 2009 9:36:19 AM
                      Subject: [atm_free] kid's atm 2 focii

                       

                       
                      Hi
                       
                      He is in polishing but notices two focal points, differing by 2 cm.
                       
                      Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
                       
                       
                      Thanks and Regards
                       
                      Ali Khan
                      in orange glasses


                    • Mark Whitaker
                      I read somewhere that tar can be cut with clean motor oil. Again, I have not worked with tar so I have no experience with it but I know it has been used and a
                      Message 10 of 10 , Aug 2, 2009
                      • 0 Attachment
                        I read somewhere that tar can be cut with clean motor oil.  Again, I have not worked with tar so I have no experience with it but I know it has been used and a company in the US (Cycad) sells a petroleum based optical polishing pitch.

                        Mark


                        From: a <ak666666@...>
                        To: atm_free@yahoogroups.com
                        Sent: Sunday, August 2, 2009 12:18:52 AM
                        Subject: Re: [atm_free] kid's atm 2 focii

                         

                         
                        Hi
                         
                        Yes tar.
                         
                         
                        Thanks and Regards
                         
                        Ali Khan
                        in orange glasses
                        ----- Original Message -----
                        Sent: Saturday, August 01, 2009 11:51 .
                        Subject: Re: [atm_free] kid's atm 2 focii

                         

                        What type of pitch is he using?  It is a petroleum based pitch (tar) or a pitch based on tree sap?  I have no experience with petroleum based pitches and am not sure linseed oil would be a good agent with those.

                        In any case, for the amount of pitch you would normally use to polish an 8" mirror, you would normally only need a few milliliters of linseed oil.  So I would say he ruined his pitch.  The thing about linseed oil is that you can't boil it away as you would an excess of turpentine so he will probably need new pitch.

                        For a long focus sphere, you want a harder pitch than you would normally use for faster mirrors or parabolizing.  The harder pitch (with lots of pressing) tends to produce a sphere.

                        Mark


                        From: a <ak666666@hotmail. com>
                        To: atm_free@yahoogroup s.com
                        Sent: Saturday, August 1, 2009 11:42:40 AM
                        Subject: Re: [atm_free] kid's atm 2 focii

                         

                         
                        Hi
                         
                        He suspects his lap is too soft as he added 4 spoons of linseed oil to the melt. He says the channels show signs of closing up. He says there is lot of slipping and no friction.
                         
                        He filtered ceo suspension through a cean cloth.
                         
                        Thanks and Regards
                         
                        Ali Khan
                        in orange glasses
                        ----- Original Message -----
                        Sent: Saturday, August 01, 2009 8:53 .
                        Subject: Re: [atm_free] kid's atm 2 focii

                         

                        Without seeing the "scratches" I can't offer any advice on what they may be or how to deal with them.  I hope he did a thorough job of fine grinding and smoothing.

                        Remind me, what size mirror is this and what is it's focal length?  How many hours does he have polishing?  What is meant by 2 focii and how is this determined?

                        Mark


                        From: a <ak666666@hotmail. com>
                        To: atm_free@yahoogroup s.com
                        Sent: Saturday, August 1, 2009 9:36:19 AM
                        Subject: [atm_free] kid's atm 2 focii

                         

                         
                        Hi
                         
                        He is in polishing but notices two focal points, differing by 2 cm.
                         
                        Near edges, he sees a bundle of lines, like scratches. Cant see them through magnifier.
                         
                         
                        Thanks and Regards
                         
                        Ali Khan
                        in orange glasses



                      Your message has been successfully submitted and would be delivered to recipients shortly.