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BVC

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  • Greg
    Has anyone in this group used BVC for making a mirror? What is your opinion? I could buy a BVC blank for about 1/3 less than a Pyrex blank.
    Message 1 of 28 , Mar 2 12:01 PM
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      Has anyone in this group used BVC for making a mirror? What is your
      opinion? I could buy a BVC blank for about 1/3 less than a Pyrex blank.
    • Mitchell
      ... blank. ... Mike Lockwood seems to be the only person on the net I can find that posted his findings. Scroll to the bottom of this page for links to each
      Message 2 of 28 , Mar 2 1:06 PM
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        --- In atm_free@yahoogroups.com, "Greg" <starguy@...> wrote:
        >
        > Has anyone in this group used BVC for making a mirror? What is your
        > opinion? I could buy a BVC blank for about 1/3 less than a Pyrex
        blank.
        >

        Mike Lockwood seems to be the only person on the net I can find
        that posted his findings. Scroll to the bottom of this page for links
        to each section of work:

        http://bi-
        staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html

        Mitch
      • mtolb25356@aol.com
        i have heard so many bad things about it that i wont even try it ************************************** AOL now offers free email to everyone.
        Message 3 of 28 , Mar 3 4:14 AM
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          i have heard so many bad things about it that i wont even try it




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        • Mitchell
          ... Yeah. I ve heard so many bad things about school I m not gunna go anymore. Also about taxes, so I won t pay them when i get my own house. I probably won t
          Message 4 of 28 , Mar 3 7:20 AM
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            --- In atm_free@yahoogroups.com, mtolb25356@... wrote:
            >
            > i have heard so many bad things about it that i wont even try it

            Yeah. I've heard so many bad things about school I'm not gunna go
            anymore. Also about taxes, so I won't pay them when i get my own house.
            I probably won't work either ;)

            Those "bad things" could have come from one person who wasn't
            doing things correctly and it just carries by word of mouth. I've heard
            a lot too and the only person who I know has tried it and talks about
            it is Mike. Sometimes things need to be taken with a grain of salt...

            Food for thought,

            mitch
          • David Hakenewerth
            ... OMG RS has been reincarnated. Dave go ... house. ... heard ... about ... salt...
            Message 5 of 28 , Mar 3 8:43 AM
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              --- In atm_free@yahoogroups.com, "Mitchell" <funnybone101@...> wrote:
              >
              > --- In atm_free@yahoogroups.com, mtolb25356@ wrote:



              OMG RS has been reincarnated.

              Dave



              go
              > anymore. Also about taxes, so I won't pay them when i get my own
              house.
              > I probably won't work either ;)
              >
              > Those "bad things" could have come from one person who wasn't
              > doing things correctly and it just carries by word of mouth. I've
              heard
              > a lot too and the only person who I know has tried it and talks
              about
              > it is Mike. Sometimes things need to be taken with a grain of
              salt...
              >
              > Food for thought,
              >
              > mitch
              >
            • leftfieldstar@aol.com
              In a message dated 3/3/07 7:20:53 AM Eastern Standard Time, mtolb25356@aol.com writes: i have heard so many bad things about it that i wont even try it And
              Message 6 of 28 , Mar 3 8:43 AM
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                In a message dated 3/3/07 7:20:53 AM Eastern Standard Time, mtolb25356@... writes:
                i have heard so many bad things about it that i wont even try it
                 And that makes for an authoritative response? It is incredible that you have such a flippant disregard for serious work done by many individuals who have substantiated their efforts and are the only real source of conclusive information. Mike Lockwood has shown much information on his website regarding the 32" BVC based scope of his associate, Bob Holms, who is doing some serious work.
                 Your(TOLB) persistent one line, meatless responses do nothing to clarify a subject and you have been correctly rebuffed before for making previous unsubstantiated statements. The flames are on for you by me because this is a forum of information that attempts to avoid hearsay and empty opinions. Your comments are usually both.
                 
                 
                Dominic DiLeo 




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              • John Abrahamian
                ... I currently have a 25.25 which I ve worked thru fine grinding and smoothing phases. I worked a 21 hydrocal tile tool. It did work a bit faster than
                Message 7 of 28 , Mar 3 10:03 AM
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                  --- In atm_free@yahoogroups.com, "Greg" <starguy@...> wrote:
                  >
                  > Has anyone in this group used BVC for making a mirror? What is your
                  > opinion? I could buy a BVC blank for about 1/3 less than a Pyrex blank.
                  >

                  I currently have a 25.25" which I've worked thru fine grinding and
                  smoothing phases. I worked a 21" hydrocal tile tool. It did work a bit
                  faster than Pyrex-it is a bit softer. I did not have any scratching
                  problems as I use distilled water for all my work. I used a 21"
                  hydrocaltile tool for all the grinding and smoothing. Be sure to check
                  the flatness of
                  the back-I worked down a couple of high spots and it is ok now. There
                  are some bubbles in the
                  subsurface layer(about 1/4" below the surface) but I believe there are
                  also inclusions in other glass as well. They are not near the surface
                  so they don't interfere with the grinding. People are working
                  laminated lightweight blanks which have much larger air pockets in
                  them between the pillars-so I can't see a bubble or two affecting
                  anything to the point where it would affect your telescope views.
                  As soon as I'm finished with my astronomy club's mirror I will be
                  polishing and figuring it. I am using a homebuilt grinding-figuring
                  machine for all the work. Obviously working tool on top for all phases
                  of the project! I am not a BVC promoter-I,like yourself, wanted a
                  large mirror and figured the price was right so I bought one. I will
                  update later on the polishing success. This is an older blank from ASM
                  not AJ's(current owner). I believe it will be much easier to figure
                  than plate glass. And when the Pyrex runs out people will be trying
                  all sorts of new materials so we must not be afraid of
                  a little experimentation. I wouldn't have sent a guy $1000 for
                  something if I thought it wouldn't work. I did find success stories
                  with BVC mirrors on the web.

                  go here:
                  http://www.astrosurf.com/jwisn/20inch.htm
                  http://jhpw.phys.ntu.edu.tw/html/atm.html
                  http://www.dougbraun.com/scope.html
                  http://www.atmlist.net/pipermail/atm/2004-July/002943.html
                  http://www.stargazing.net/aaa/avatm/avatm_atms.htm
                  http://www.cloudynights.com/ubbthreads/showthreaded.php/Cat/0/Number/987596/page/0/view/collapsed/sb/5/o/all/vc/1

                  All these people can't be fools!


                  John Abrahamian
                • Greg Furtman
                  Dave, I think you re right! Scary. Greg Furtman 27426 County Rd H Webster, WI 54893 http://home.centurytel.net/starguy My
                  Message 8 of 28 , Mar 3 5:26 PM
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                    Dave,
                     
                    I think you're right! Scary.
                     
                     
                    Greg Furtman
                    27426 County Rd H
                    Webster, WI 54893
                     
                     
                    "My goal in life is to become the person that my dog thinks I am."
                     


                    From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of David Hakenewerth
                    Sent: Saturday, March 03, 2007 10:44 AM
                    To: atm_free@yahoogroups.com
                    Subject: [atm_free] Re: BVC

                    --- In atm_free@yahoogroup s.com, "Mitchell" <funnybone101@ ...> wrote:

                    >
                    > --- In
                    href="mailto:atm_free%40yahoogroups.com">atm_free@yahoogroup s.com, mtolb25356@ wrote:

                    OMG RS has been reincarnated.

                    Dave

                    go
                    > anymore. Also about taxes, so I won't pay them when i get my own
                    house.
                    > I probably won't work either ;)
                    >
                    > Those "bad
                    things" could have come from one person who wasn't
                    > doing things
                    correctly and it just carries by word of mouth. I've
                    heard
                    > a lot
                    too and the only person who I know has tried it and talks
                    about
                    > it
                    is Mike. Sometimes things need to be taken with a grain of
                    salt...
                    >
                    > Food for thought,
                    >
                    > mitch
                    >

                  • George Anderson
                    The previous owner/manufacturer (and developer) of BVC had some quality control issues which have been discussed ad naseum on the ATM lists. The company was
                    Message 9 of 28 , Mar 3 8:24 PM
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                      The previous owner/manufacturer (and developer) of BVC had some
                      quality control issues which have been discussed ad naseum on the ATM
                      lists. The company was sold to the current owner AJ Telescopes (or
                      something like that) and I have not heard any complaints from people
                      who are using and polishing BVC.
                      Try keeping up to date on the information before commenting.

                      George Anderson
                      Montreal Canada

                      Clear skies and good health


                      --- In atm_free@yahoogroups.com, mtolb25356@... wrote:
                      >
                      > i have heard so many bad things about it that i wont even try it
                      > <BR><BR><BR>**************************************<BR> AOL now
                      offers free
                      > email to everyone. Find out more about what's free from AOL at
                      > http://www.aol.com
                      >
                    • mtolb25356@aol.com
                      sorry once bitten im out i wont risk bvc no chance plate glass is cheaper and works just fine ************************************** AOL now
                      Message 10 of 28 , Mar 4 4:13 AM
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                        sorry once bitten im out i wont risk bvc no chance plate glass is cheaper and works just fine




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                      • mtolb25356@aol.com
                        say what you will i have seen with my own eyes a delaminated bvc blank and photos of mor than one with holes from bubbles the size of a dime. 1 plate is cheap
                        Message 11 of 28 , Mar 4 4:22 AM
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                          say what you will i have seen with my own eyes a delaminated bvc blank and photos of mor than one with holes from bubbles the size of a dime. 1" plate is cheap and easy to find i have made or seen made in my classes over 40 mirrors made from plate.your own snobbish responses wont change my mind.




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                        • Thomas Janstrom
                          Hi Greg, I have a 10 BVC mirror that is now getting on to 7 years old, so it is from his early days, that I m very happy with…… I did find the surface to
                          Message 12 of 28 , Mar 4 4:47 AM
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                            Hi Greg,

                            I have a 10" BVC mirror that is now getting on to 7 years old, so it
                            is from his early days, that I'm very happy with…… I did find the
                            surface to be a bit "rubbery" during figuring, like it would stretch
                            and return a bit as I worked. I don't know if this because the
                            matterial is so soft, or if it's because of the ways it's made...

                            Thomas.


                            --- In atm_free@yahoogroups.com, "Greg" <starguy@...> wrote:
                            >
                            > Has anyone in this group used BVC for making a mirror? What is your
                            > opinion? I could buy a BVC blank for about 1/3 less than a Pyrex
                            blank.
                            >
                          • Greg Furtman
                            Where do you find large (18 - 20 ) plate blanks? Is plate made thicker than 1 ? Greg Furtman 27426 County Road H Webster, WI 54893
                            Message 13 of 28 , Mar 4 5:44 AM
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                              Where do you find large (18" - 20") plate blanks? Is plate made thicker than 1"?
                               
                              Greg Furtman
                              27426 County Road H
                              Webster, WI 54893
                               
                               

                              "My goal in life is to become the person that my dog thinks I am."

                               


                              From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of mtolb25356@...
                              Sent: Sunday, March 04, 2007 6:22 AM
                              To: atm_free@yahoogroups.com
                              Subject: Re: [atm_free] Re: BVC

                              say what you will i have seen with my own eyes a delaminated bvc blank and photos of mor than one with holes from bubbles the size of a dime. 1" plate is cheap and easy to find i have made or seen made in my classes over 40 mirrors made from plate.your own snobbish responses wont change my mind.




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                            • Jerry
                              I was just starting to ask the question What are the so many bad things you have heard about BVC? when this popped in to the mailbox. ... From:
                              Message 14 of 28 , Mar 4 7:14 AM
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                                I was just starting to ask the question “ What are the so many bad things you have heard about BVC?” when this popped in to the mailbox.

                                 

                                -----Original Message-----
                                From: mtolb25356@...
                                 

                                say what you will i have seen with my own eyes a delaminated bvc blank and photos of mor than one with holes from bubbles the size of a dime. 1" plate is cheap and easy to find i have made or seen made in my classes over 40 mirrors made from plate.your own snobbish responses wont change my mind.

                                 

                                 

                                Some of the responses to mtolb’s comment seemed to be as lacking in knowledge of BVC as his comment was lacking in detail.  If his comment was lacking in detail it would seem that the thing to do would be to ask for detail first, and then flame him.

                                 

                                I’m not for or against BVC or whoever is making it. It may be superior to any other material for all I know. Before I spend my money on a blank of BVC or any other material I will let others prove its worth. If only favorable comments are allowed how could we discuss anything but perfect materials or products?

                                 

                                I really liked RS’s (Mitch’s) comments. I was rolling on the floor for a while. First I rolled one way. His response was a perfect circle of reasoning.  And then I rolled the other way. When I was young, I remember people telling me that smoking cigarettes is bad for your health.  I’ve been told that driving drunk kills people.  And I’ve been told that 2 things in life are certain… death and taxes.

                                 

                                Jerry

                                 


                              • Mitchell
                                ... http://home.centurytel.net/starguy ... Behalf ... s.com, ... s.com, ... We ll see how I act in, oh say, 45 years ;) Mitch
                                Message 15 of 28 , Mar 4 9:17 AM
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                                  --- In atm_free@yahoogroups.com, "Greg Furtman" <starguy@...> wrote:
                                  >
                                  > Dave,
                                  >
                                  > I think you're right! Scary.
                                  >
                                  >
                                  > Greg Furtman
                                  > 27426 County Rd H
                                  > Webster, WI 54893
                                  >
                                  > <http://home.centurytel.net/starguy>
                                  http://home.centurytel.net/starguy
                                  >
                                  > "My goal in life is to become the person that my dog thinks I am."
                                  >
                                  >
                                  > _____
                                  >
                                  > From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On
                                  Behalf
                                  > Of David Hakenewerth
                                  > Sent: Saturday, March 03, 2007 10:44 AM
                                  > To: atm_free@yahoogroups.com
                                  > Subject: [atm_free] Re: BVC
                                  >
                                  >
                                  >
                                  > --- In atm_free@yahoogroup <mailto:atm_free%40yahoogroups.com>
                                  s.com,
                                  > "Mitchell" <funnybone101@> wrote:
                                  > >
                                  > > --- In atm_free@yahoogroup <mailto:atm_free%40yahoogroups.com>
                                  s.com,
                                  > mtolb25356@ wrote:
                                  >
                                  > OMG RS has been reincarnated.
                                  >
                                  > Dave

                                  We'll see how I act in, oh say, 45 years ;)

                                  Mitch
                                • John Abrahamian
                                  ... things ... blank and ... 1 plate ... comment was ... . ... Ok- I m working a very large BVC blank at the moment. When can I expect it to delaminate? Was
                                  Message 16 of 28 , Mar 4 10:37 AM
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                                    --- In atm_free@yahoogroups.com, "Jerry" <wa4guu@...> wrote:
                                    >
                                    > I was just starting to ask the question " What are the so many bad
                                    things
                                    > you have heard about BVC?" when this popped in to the mailbox.
                                    >
                                    >
                                    >
                                    > -----Original Message-----
                                    > From: mtolb25356@...
                                    >
                                    >
                                    > say what you will i have seen with my own eyes a delaminated bvc
                                    blank and
                                    > photos of mor than one with holes from bubbles the size of a dime.
                                    1" plate
                                    > is cheap and easy to find i have made or seen made in my classes over 40
                                    > mirrors made from plate.your own snobbish responses wont change my mind.


                                    > Some of the responses to mtolb's comment seemed to be as lacking in
                                    > knowledge of BVC as his comment was lacking in detail. If his
                                    comment was
                                    > lacking in detail it would seem that the thing to do would be to ask for
                                    > detail first, and then flame him.
                                    .
                                    > Jerry
                                    >

                                    Ok- I'm working a very large BVC blank at the moment. When can I
                                    expect it to delaminate? Was it immediately visible? Was the blank
                                    unacceptable upon its delivery to the student for grinding or did this
                                    take place during the process? Did the holes appear at the surface or
                                    were they buried deep inside the blank? How about a little detail?

                                    Why make a blanket statement of criticism WITHOUT adding a little detail?

                                    No one has ever gotten an annealed piece of Pyrex glass or plate glass
                                    which had too much strain in it? I don't seem to be able to find cheap
                                    plate glass at this time-especially at 25".
                                    Just My 2 Cents-John Abrahamian
                                  • leftfieldstar@aol.com
                                    In a message dated 3/4/07 1:37:53 PM Eastern Standard Time, imas1@aol.com ... comment was ... . ... Mitch s response took the high road and was elegantly put.
                                    Message 17 of 28 , Mar 4 12:36 PM
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                                      In a message dated 3/4/07 1:37:53 PM Eastern Standard Time, imas1@... writes:
                                      > Some of the responses to mtolb's comment seemed to be as lacking in
                                      > knowledge of BVC as his comment was lacking in detail.  If his
                                      comment was
                                      > lacking in detail it would seem that the thing to do would be to ask for
                                      > detail first, and then flame him.
                                      .
                                      > Jerry
                                      >
                                       Mitch's response took the high road and was elegantly put. Tolb has a history of one line unsubstantiated comment, even after much prompting to give proof of his sources. I am well aware of the narrow limitation of cyberspace correspondence so a safe position one often takes is to limit negative interaction with such persons. My issue is that this is a forum based on a science promoted honestly. Those of us who are experienced in this art know when someone is less than authentic pertaining to the art. Novices come here to learn the science, not the alchemy and so this forum should be a safe harbor for the truth.
                                       I know from the past that Mr. Tolb has passed off some material as his own when in fact it was the work of Richard Schwartz. He also makes claim to have a cellular mirror that is glued up but has no performance data. I am simply resolved to challenge anyone who makes statements that seem to not click. I am not above eating my words whenever proven wrong.
                                       
                                      Dominic DiLeo




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                                    • Jerry
                                      Hello Dominic I thought mtolb s comment was sufficiently vague to be meaningless. If I had direct knowledge of BVC I may have asked him to elaborate and maybe
                                      Message 18 of 28 , Mar 4 5:36 PM
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                                        Hello Dominic

                                         

                                        I thought mtolb’s comment was sufficiently vague to be meaningless.  If I had direct knowledge of BVC I may have asked him to elaborate and maybe debated his concerns.  And like you, if I had seen more of what I previously perceived as a tendency to make un-warranted malicious statements, I might have just started flaming him right off the bat.  I’m not saying I would be “right” in doing that.  I just know that I am like that.  

                                         

                                        It makes for a cleaner burn when the nature of the differences is clear.

                                         

                                        I have seen examples of someone expressing opinions for or against some product for reasons that have nothing to do with the quality of the product. Maybe they know the producer and have no desire to be negative, or an urge to see them succeed has a stronger influence than the weaknesses of the product. On the other hand, maybe they don’t like the individual, or they or a friend have a competing product and want to see him fail. It works both ways. It is just as unethical to recommend a product to someone for wrong reasons as it is to recommend against that product for wrong reasons. (My opinion.)

                                         

                                        My comment that I would wait until a material is proven before I would spend my money on it should not be taken as a negative comment on BVC.  I’m just as reluctant to spend my money on any product that I’m not sufficiently sure of.  That doesn’t speak to the quality of the product. It speaks to my knowledge of the product. The producer of a product must take some of the responsibility of getting the truth concerning their product out to potential customers.

                                         

                                                    What would be helpful would be more in depth testimonials from mirror makers without imposing a bias in favor of positive comments.  For the most part what I have seen on the web is not very conclusive and sometimes self contradictory. If some professionals would start using them in commercial scopes, that would prove them one way or the other rather quickly.

                                         

                                        As I said, BVC may be superior.  I don’t know.  I hope a reasonably priced supply of all sizes of mirror blanks will be available to ATMs from now until the end of time.  In that sense, I am for the success of the maker of BVC both at making good blanks and in their business. The same goes for all those other blank makers and would be blank makers too.

                                         

                                         

                                        Jerry

                                         

                                         

                                        -----Original Message-----
                                        From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of leftfieldstar@...
                                        Sent: Sunday, March 04, 2007 3:36 PM
                                        To: atm_free@yahoogroups.com
                                        Subject: Re: [atm_free] Re: BVC

                                         

                                        In a message dated 3/4/07 1:37:53 PM Eastern Standard Time, imas1@... writes:

                                        > Some of the responses to mtolb's comment seemed to be as lacking in
                                        > knowledge of BVC as his comment was lacking in detail.  If his
                                        comment was
                                        > lacking in detail it would seem that the thing to do would be to ask for
                                        > detail first, and then flame him.
                                        .
                                        > Jerry
                                        >

                                         Mitch's response took the high road and was elegantly put. Tolb has a history of one line unsubstantiated comment, even after much prompting to give proof of his sources. I am well aware of the narrow limitation of cyberspace correspondence so a safe position one often takes is to limit negative interaction with such persons. My issue is that this is a forum based on a science promoted honestly. Those of us who are experienced in this art know when someone is less than authentic pertaining to the art. Novices come here to learn the science, not the alchemy and so this forum should be a safe harbor for the truth.

                                         I know from the past that Mr. Tolb has passed off some material as his own when in fact it was the work of Richard Schwartz. He also makes claim to have a cellular mirror that is glued up but has no performance data. I am simply resolved to challenge anyone who makes statements that seem to not click. I am not above eating my words whenever proven wrong.

                                         

                                        Dominic DiLeo




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                                      • Greg
                                        Jeez - I didn t mean to open this can of worms. I just wanted some info. Aperture fever is nasty. I m just looking for the least expensive cure I can find
                                        Message 19 of 28 , Mar 4 6:05 PM
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                                          Jeez - I didn't mean to open this can of worms. I just wanted some
                                          info. Aperture fever is nasty. I'm just looking for the least expensive
                                          cure I can find meaning making my own mirror & scope. Champagne tastes,
                                          beer budget.
                                        • George Anderson
                                          ... You just have to go through universtity and finish a Doctorate (IIRC) in physics and then gain RS s experience and you are there! George Clear skies and
                                          Message 20 of 28 , Mar 4 8:09 PM
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                                            > > OMG RS has been reincarnated.
                                            > >
                                            > > Dave
                                            >
                                            > We'll see how I act in, oh say, 45 years ;)
                                            >
                                            > Mitch
                                            >

                                            You just have to go through universtity and finish a Doctorate (IIRC)
                                            in physics and then gain RS's experience and you are there!

                                            George

                                            Clear skies and good health
                                          • mtolb25356@aol.com
                                            In a message dated 3/4/2007 1:38:00 P.M. Eastern Standard Time, imas1@aol.com writes: I don t seem to be able to find cheap plate glass at this
                                            Message 21 of 28 , Mar 5 5:42 AM
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                                              In a message dated 3/4/2007 1:38:00 P.M. Eastern Standard Time, imas1@... writes:
                                              I don't seem to be able to find cheap
                                              plate glass at this time-especially at 25".
                                              i say it all the time swift glass will waterjet you a 25" for under 1000$




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                                            • mtolb25356@aol.com
                                              In a message dated 3/4/2007 8:47:11 A.M. Eastern Standard Time, starguy@centurytel.net writes: Where do you find large (18 - 20 ) plate blanks? Is plate made
                                              Message 22 of 28 , Mar 5 5:45 AM
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                                                In a message dated 3/4/2007 8:47:11 A.M. Eastern Standard Time, starguy@... writes:
                                                Where do you find large (18" - 20") plate blanks? Is plate made thicker than 1"?
                                                 
                                                swift glass or f.j. grey no dosnt come thicker than 1" last price i got 5 months ago was 875$ for a 25" round




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                                              • Hugues.Laroche@ses-astra.com
                                                ... Hi hi hi, I will add just one more worm ;-) ... What size are you on? My monster project is stuck for a while (polishing machine out of service)... the
                                                Message 23 of 28 , Mar 5 6:02 AM
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                                                  >Jeez - I didn't mean to open this can of worms.

                                                  Hi hi hi, I will add just one more worm ;-)

                                                  John Abrahmanian said:

                                                  >Ok- I'm working a very large BVC blank at the moment.

                                                  What size are you on? My monster project is stuck for
                                                  a while (polishing machine out of service)... the blank is
                                                  out of BVC, 44.6" diameter (not a typo). There is no sign
                                                  of delamination after about 4 years that I received it.
                                                  Deep under the surface  there are some light gray patches,
                                                  roughtly concentric to the mirror, that are likely
                                                  flattened bubbles. They do not seem to
                                                  imprint on the Foucault views, but the figure is still
                                                  quite rough so it may not appear yet.
                                                  My only concern with the material is the ease of scracthing.
                                                  Even if it is partly related to the very large size
                                                  and consequent difficulty of storage, dust elimination etc...

                                                  Hugues


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                                                • John Abrahamian
                                                  ... Yours is very large-mine is just large in comparison. 25.25 diameter but very large for me! But-I have the same concentric light gray area. It is
                                                  Message 24 of 28 , Mar 5 10:36 AM
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                                                    --- In atm_free@yahoogroups.com, Hugues.Laroche@... wrote:
                                                    >
                                                    > >Jeez - I didn't mean to open this can of worms.
                                                    >
                                                    > Hi hi hi, I will add just one more worm ;-)
                                                    >
                                                    > John Abrahmanian said:
                                                    >
                                                    > >Ok- I'm working a very large BVC blank at the moment.
                                                    >
                                                    > What size are you on? My monster project is stuck for
                                                    > a while (polishing machine out of service)... the blank is
                                                    > out of BVC, 44.6" diameter (not a typo). There is no sign
                                                    > of delamination after about 4 years that I received it.
                                                    > Deep under the surface there are some light gray patches,
                                                    > roughtly concentric to the mirror, that are likely
                                                    > flattened bubbles. They do not seem to
                                                    > imprint on the Foucault views, but the figure is still
                                                    > quite rough so it may not appear yet.

                                                    Yours is very large-mine is just large in comparison. 25.25" diameter
                                                    but very large for me! But-I have the same concentric light gray area.
                                                    It is concentric and about 1/3rd from the center. It is less than 1/4"
                                                    wide at the widest point and appears to not go all round inside the
                                                    glass. I can't see it really affecting anything as cellular blanks
                                                    have much larger air gaps and people are selling them.

                                                    With the material being soft it might be necessary to go light on the
                                                    weight when polishing-to reduce rough appearance. I'll post when I
                                                    have some results. This blank is 2" thick which should make figuring
                                                    much simpler than 1" plate-I've worked that before. I'm not sure 1"
                                                    plate at 25" is even doable. Fighting astigmatism and thermal
                                                    problems,not to mention strain in plate glass. This is why I chose
                                                    this blank and not plate ALTHOUGH if there was plate glass 1.5" or
                                                    thicker I would've tried it first probably.

                                                    > My only concern with the material is the ease of scratching.
                                                    > Even if it is partly related to the very large size
                                                    > and consequent difficulty of storage, dust elimination etc...

                                                    I am currently making a new sagitta for f/4 and am ready for 320 this
                                                    evening. I'm at .039 at this time. I use distilled water for polishing
                                                    and do not clean up alot when polishing. What lies on the floor or
                                                    table doesn't concern me. Just don't contaminate the blank or tool
                                                    surface. There is a photo of a professional opticians machines working
                                                    2 mirrors-side by side. There is a piece of cardboard separating the
                                                    two turntables(probably 2 feet apart)

                                                    Good Luck-John
                                                  • Mike Lockwood
                                                    Hi, Saw the thread and thought I d update you on Bob Holmes 32 (0.8 meter) telescope performance. He recently imaged a magnitude 23.8 (yes, that s right)
                                                    Message 25 of 28 , Mar 5 2:26 PM
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                                                      Hi,

                                                      Saw the thread and thought I'd update you on Bob Holmes' 32" (0.8
                                                      meter) telescope performance. He recently imaged a magnitude 23.8
                                                      (yes, that's right) asteroid. An image is posted in the images page,
                                                      the link to which can be found on this page (sorry for the long URL):

                                                      http://bi-staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html

                                                      Also check out the faint galaxies in the background of the M51 image,
                                                      and the resolution in the M33 image. Keep in mind, these are not
                                                      heavily processed, stacked images, they are more raw, somewhat like
                                                      the science images he takes, and only a few minutes in duraton. One
                                                      of these days we need to do some serious "pretty picture" photography
                                                      and really get some amazing images that leave those in the dust.

                                                      Bob is only cooling this mirror a small amount, and it's still
                                                      producing excellent images from a less than optimal location in
                                                      Illinois. It's beating out similar-sized scopes located on much
                                                      better observing sites.

                                                      With this standard of performance established, I challenge you to find
                                                      another material that is 2" thick, and that will keep its shape fairly
                                                      well over the course of a night of cooling. BVC has a lower
                                                      coefficient of expansion and less heat capacity than plate, so it
                                                      doesn't deform nearly as much when cooling.

                                                      That said, Pyrex is more homogenous and will have less tendency to go
                                                      astigmatic due to cooling-induced dimensional changes, which is
                                                      something I noted with this blank, both in testing and in actual
                                                      operating conditions in the telescope.

                                                      The prices for BVC also went up quite a bit recently, so it does not
                                                      look as appealing when compared to Pyrex as it did a year ago,
                                                      especially a nicely generated blank. I recently bought two 24" blanks
                                                      from United Lens and the price per blank was quite similar to the
                                                      current price for BVC. UL does an excellent job of generating and
                                                      grinding the back really FLAT, saving me a lot of time.

                                                      So is Pyrex or BVC better? BVC has a practical cooling advantage over
                                                      monolithic Pyrex. However, I suspect Pyrex is a bit more homogenous,
                                                      which is important during polishing/figuring runs that generate heat
                                                      in the glass. (If the glass expands unevenly, you get an uneven
                                                      figure, possibly astigmatic.) Which is more important in a large
                                                      mirror that never really gets to equilibrium over the course of a
                                                      night? I just don't know, and no one has compared well-figured Pyrex
                                                      and BVC mirrors if identical dimensions quantitatively.

                                                      No matter what statements I or other people make, they cannot possibly
                                                      refute the success of this 0.8m telescope.

                                                      Mike Lockwood
                                                    • tomofreno2000
                                                      Very impressive! What does this scope use for a coma corrector? Tom W. ... page, ... staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html ...
                                                      Message 26 of 28 , Mar 5 8:04 PM
                                                      • 0 Attachment
                                                        Very impressive! What does this scope use for a coma corrector?
                                                        Tom W.


                                                        --- In atm_free@yahoogroups.com, "Mike Lockwood" <parabola30@...>
                                                        wrote:
                                                        >
                                                        > Hi,
                                                        >
                                                        > Saw the thread and thought I'd update you on Bob Holmes' 32" (0.8
                                                        > meter) telescope performance. He recently imaged a magnitude 23.8
                                                        > (yes, that's right) asteroid. An image is posted in the images
                                                        page,
                                                        > the link to which can be found on this page (sorry for the long
                                                        URL):
                                                        >
                                                        > http://bi-
                                                        staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html
                                                        >
                                                        > Also check out the faint galaxies in the background of the M51
                                                        image,
                                                        > and the resolution in the M33 image. Keep in mind, these are not
                                                        > heavily processed, stacked images, they are more raw, somewhat like
                                                        > the science images he takes, and only a few minutes in duraton. One
                                                        > of these days we need to do some serious "pretty picture"
                                                        photography
                                                        > and really get some amazing images that leave those in the dust.
                                                        >
                                                        > Bob is only cooling this mirror a small amount, and it's still
                                                        > producing excellent images from a less than optimal location in
                                                        > Illinois. It's beating out similar-sized scopes located on much
                                                        > better observing sites.
                                                        >
                                                        > With this standard of performance established, I challenge you to
                                                        find
                                                        > another material that is 2" thick, and that will keep its shape
                                                        fairly
                                                        > well over the course of a night of cooling. BVC has a lower
                                                        > coefficient of expansion and less heat capacity than plate, so it
                                                        > doesn't deform nearly as much when cooling.
                                                        >
                                                        > That said, Pyrex is more homogenous and will have less tendency to
                                                        go
                                                        > astigmatic due to cooling-induced dimensional changes, which is
                                                        > something I noted with this blank, both in testing and in actual
                                                        > operating conditions in the telescope.
                                                        >
                                                        > The prices for BVC also went up quite a bit recently, so it does not
                                                        > look as appealing when compared to Pyrex as it did a year ago,
                                                        > especially a nicely generated blank. I recently bought two 24"
                                                        blanks
                                                        > from United Lens and the price per blank was quite similar to the
                                                        > current price for BVC. UL does an excellent job of generating and
                                                        > grinding the back really FLAT, saving me a lot of time.
                                                        >
                                                        > So is Pyrex or BVC better? BVC has a practical cooling advantage
                                                        over
                                                        > monolithic Pyrex. However, I suspect Pyrex is a bit more
                                                        homogenous,
                                                        > which is important during polishing/figuring runs that generate heat
                                                        > in the glass. (If the glass expands unevenly, you get an uneven
                                                        > figure, possibly astigmatic.) Which is more important in a large
                                                        > mirror that never really gets to equilibrium over the course of a
                                                        > night? I just don't know, and no one has compared well-figured
                                                        Pyrex
                                                        > and BVC mirrors if identical dimensions quantitatively.
                                                        >
                                                        > No matter what statements I or other people make, they cannot
                                                        possibly
                                                        > refute the success of this 0.8m telescope.
                                                        >
                                                        > Mike Lockwood
                                                        >
                                                      • Mike Lockwood
                                                        Hi, Currently it utilizes the Paracorr that threads onto the SBIG camera. Mike Lockwood
                                                        Message 27 of 28 , Mar 6 8:47 AM
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                                                          Hi,

                                                          Currently it utilizes the Paracorr that threads onto the SBIG camera.

                                                          Mike Lockwood


                                                          --- In atm_free@yahoogroups.com, "tomofreno2000" <tomofreno2000@...>
                                                          wrote:
                                                          > Very impressive! What does this scope use for a coma corrector?
                                                          > Tom W.
                                                        • claudio argandoña
                                                          Hello friends... impressive mirror of Bob Holmes (congratulations!). Where I can find Web pages with information about polish with small tool? Thanks Claudio
                                                          Message 28 of 28 , Mar 6 8:53 AM
                                                          • 0 Attachment
                                                            Hello friends... impressive mirror of Bob Holmes (congratulations!).
                                                            Where I can find Web pages with information about polish with small
                                                            tool?
                                                            Thanks
                                                            Claudio Argandoña, Santiago Chile (sorry for my little english)



                                                            --- In atm_free@yahoogroups.com, "tomofreno2000" <tomofreno2000@...>
                                                            wrote:
                                                            >
                                                            > Very impressive! What does this scope use for a coma corrector?
                                                            > Tom W.
                                                            >
                                                            >
                                                            > --- In atm_free@yahoogroups.com, "Mike Lockwood" <parabola30@>
                                                            > wrote:
                                                            > >
                                                            > > Hi,
                                                            > >
                                                            > > Saw the thread and thought I'd update you on Bob Holmes' 32" (0.8
                                                            > > meter) telescope performance. He recently imaged a magnitude
                                                            23.8
                                                            > > (yes, that's right) asteroid. An image is posted in the images
                                                            > page,
                                                            > > the link to which can be found on this page (sorry for the long
                                                            > URL):
                                                            > >
                                                            > > http://bi-
                                                            > staff.beckman.uiuc.edu/~melockwo/telescopes/holmes32/holmes32.html
                                                            > >
                                                            > > Also check out the faint galaxies in the background of the M51
                                                            > image,
                                                            > > and the resolution in the M33 image. Keep in mind, these are not
                                                            > > heavily processed, stacked images, they are more raw, somewhat
                                                            like
                                                            > > the science images he takes, and only a few minutes in duraton.
                                                            One
                                                            > > of these days we need to do some serious "pretty picture"
                                                            > photography
                                                            > > and really get some amazing images that leave those in the dust.
                                                            > >
                                                            > > Bob is only cooling this mirror a small amount, and it's still
                                                            > > producing excellent images from a less than optimal location in
                                                            > > Illinois. It's beating out similar-sized scopes located on much
                                                            > > better observing sites.
                                                            > >
                                                            > > With this standard of performance established, I challenge you
                                                            to
                                                            > find
                                                            > > another material that is 2" thick, and that will keep its shape
                                                            > fairly
                                                            > > well over the course of a night of cooling. BVC has a lower
                                                            > > coefficient of expansion and less heat capacity than plate, so it
                                                            > > doesn't deform nearly as much when cooling.
                                                            > >
                                                            > > That said, Pyrex is more homogenous and will have less tendency
                                                            to
                                                            > go
                                                            > > astigmatic due to cooling-induced dimensional changes, which is
                                                            > > something I noted with this blank, both in testing and in actual
                                                            > > operating conditions in the telescope.
                                                            > >
                                                            > > The prices for BVC also went up quite a bit recently, so it does
                                                            not
                                                            > > look as appealing when compared to Pyrex as it did a year ago,
                                                            > > especially a nicely generated blank. I recently bought two 24"
                                                            > blanks
                                                            > > from United Lens and the price per blank was quite similar to the
                                                            > > current price for BVC. UL does an excellent job of generating
                                                            and
                                                            > > grinding the back really FLAT, saving me a lot of time.
                                                            > >
                                                            > > So is Pyrex or BVC better? BVC has a practical cooling
                                                            advantage
                                                            > over
                                                            > > monolithic Pyrex. However, I suspect Pyrex is a bit more
                                                            > homogenous,
                                                            > > which is important during polishing/figuring runs that generate
                                                            heat
                                                            > > in the glass. (If the glass expands unevenly, you get an uneven
                                                            > > figure, possibly astigmatic.) Which is more important in a large
                                                            > > mirror that never really gets to equilibrium over the course of a
                                                            > > night? I just don't know, and no one has compared well-figured
                                                            > Pyrex
                                                            > > and BVC mirrors if identical dimensions quantitatively.
                                                            > >
                                                            > > No matter what statements I or other people make, they cannot
                                                            > possibly
                                                            > > refute the success of this 0.8m telescope.
                                                            > >
                                                            > > Mike Lockwood
                                                            > >
                                                            >
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