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Re: [tec-scopes] Extending teh focuser of the TEC140

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  • Bruce MacEvoy
    if i understand the flexure geometry and the T point calculations then you could get a frame of reference by dividing the T point declination error in
    Message 1 of 11 , Aug 23 9:19 AM
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      if i understand the flexure geometry and the T point calculations then you could get a frame of reference by dividing the T point declination error in arcseconds by 206265, then multiplying that number by your focal length in millimeters. that would give the millimeter distance of the flexure from the optical path. the size of that number might resolve whether it is a software, mount or optical path problem. (for example, a 10 mm mechanical flexure seems pretty implausible.)

      why would a mechanical flexure be in the declination? if you track a star whose declination is your latitude below a zenith angle of say 30º, then i'd guess most of the flexure would be in right ascension. are you sure the mount is perfectly level and polar aligned?

      bruce


      From: ferranmazzanti <Ferran.Mazzanti@...>
      To: tec-scopes@yahoogroups.com
      Sent: Thursday, August 22, 2013 4:09 PM
      Subject: [tec-scopes] Extending teh focuser of the TEC140

       
      Hi folks,

      I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.

      I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?

      Thanks a lot for your help,

      Ferran.



    • gjwcac
      Tim, Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn t matter how
      Message 2 of 11 , Aug 23 10:08 AM
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        Tim,

        Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn't matter how tight the focuser or collet is adjusted, this setup will have some droop.

        Jim M.

        --- In tec-scopes@yahoogroups.com, Tim Khan <timkhan@...> wrote:
        >
        > I dont have any issue with my 4535 focuser holding 8 lbs of camera and filter-wheel. I have the older focuser with the button socket screw that you can adjust the pressure against the drawtube and remove any slop.
        >
        > Regarding the mount, do you have data collection for periodic error. Does it drift at a different rate for the first minute then settle immediately after a slew? If so this could be a bearing/housing/preload issue on your dec axis of your mount and may not be attributed to the scope and focuser.
        >
        >
        >
        > ________________________________
        > From: ferranmazzanti <Ferran.Mazzanti@...>
        > To: tec-scopes@yahoogroups.com
        > Sent: Thursday, August 22, 2013 7:09 PM
        > Subject: [tec-scopes] Extending teh focuser of the TEC140
        >
        >
        > Hi folks,
        >
        > I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.
        >
        > I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?
        >
        > Thanks a lot for your help,
        >
        > Ferran.
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >
        >     http://docs.yahoo.com/info/terms/
        >
      • ferranmazzanti
        Hi Jim, it could be as you say, but let me tell you that the filter wheel + ccd is about 1 kg only (less than 2.5 lbs) which should be peanuts for the FT3545
        Message 3 of 11 , Aug 26 1:32 AM
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          Hi Jim,

          it could be as you say, but let me tell you that the filter wheel + ccd is about 1 kg only (less than 2.5 lbs) which should be peanuts for the FT3545 focuser. The TEC has such a large backfocus that I want to think this has already been taken into account when dessigning it... Yuri?

          But of course that could be the source of problems -or not. I'm debugging my whole system, from pier to topmost guiderscope rings, so go figure :(

          Best regards and thanks,

          Ferran.

          --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@...> wrote:
          >
          > Tim,
          >
          > Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn't matter how tight the focuser or collet is adjusted, this setup will have some droop.
          >
          > Jim M.
          >
          > --- In tec-scopes@yahoogroups.com, Tim Khan <timkhan@> wrote:
          > >
          > > I dont have any issue with my 4535 focuser holding 8 lbs of camera and filter-wheel. I have the older focuser with the button socket screw that you can adjust the pressure against the drawtube and remove any slop.
          > >
          > > Regarding the mount, do you have data collection for periodic error. Does it drift at a different rate for the first minute then settle immediately after a slew? If so this could be a bearing/housing/preload issue on your dec axis of your mount and may not be attributed to the scope and focuser.
          > >
          > >
          > >
          > > ________________________________
          > > From: ferranmazzanti <Ferran.Mazzanti@>
          > > To: tec-scopes@yahoogroups.com
          > > Sent: Thursday, August 22, 2013 7:09 PM
          > > Subject: [tec-scopes] Extending teh focuser of the TEC140
          > >
          > >
          > > Hi folks,
          > >
          > > I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.
          > >
          > > I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?
          > >
          > > Thanks a lot for your help,
          > >
          > > Ferran.
          > >
          > >
          > >
          > > ------------------------------------
          > >
          > > Yahoo! Groups Links
          > >
          > >
          > >
          > >     http://docs.yahoo.com/info/terms/
          > >
          >
        • gjwcac
          Ferran, The FT3545 (if adjusted correctly) is not the source of the droop. My guess is the smaller diameter t-extensions (and the three threaded connections)
          Message 4 of 11 , Aug 26 7:54 AM
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            Ferran,

            The FT3545 (if adjusted correctly) is not the source of the droop. My guess is the smaller diameter t-extensions (and the three threaded connections) are bending under the weight of the camera and filter wheel. For a given length and weight, the extensions will bend ~ 17x more than the focuser draw tube, and that number doesn't include any mechanical flex at the threaded joints.

            Jim M.

            --- In tec-scopes@yahoogroups.com, "ferranmazzanti" <Ferran.Mazzanti@...> wrote:
            >
            > Hi Jim,
            >
            > it could be as you say, but let me tell you that the filter wheel + ccd is about 1 kg only (less than 2.5 lbs) which should be peanuts for the FT3545 focuser. The TEC has such a large backfocus that I want to think this has already been taken into account when dessigning it... Yuri?
            >
            > But of course that could be the source of problems -or not. I'm debugging my whole system, from pier to topmost guiderscope rings, so go figure :(
            >
            > Best regards and thanks,
            >
            > Ferran.
            >
            > --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@> wrote:
            > >
            > > Tim,
            > >
            > > Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn't matter how tight the focuser or collet is adjusted, this setup will have some droop.
            > >
            > > Jim M.
            > >
            > > --- In tec-scopes@yahoogroups.com, Tim Khan <timkhan@> wrote:
            > > >
            > > > I dont have any issue with my 4535 focuser holding 8 lbs of camera and filter-wheel. I have the older focuser with the button socket screw that you can adjust the pressure against the drawtube and remove any slop.
            > > >
            > > > Regarding the mount, do you have data collection for periodic error. Does it drift at a different rate for the first minute then settle immediately after a slew? If so this could be a bearing/housing/preload issue on your dec axis of your mount and may not be attributed to the scope and focuser.
            > > >
            > > >
            > > >
            > > > ________________________________
            > > > From: ferranmazzanti <Ferran.Mazzanti@>
            > > > To: tec-scopes@yahoogroups.com
            > > > Sent: Thursday, August 22, 2013 7:09 PM
            > > > Subject: [tec-scopes] Extending teh focuser of the TEC140
            > > >
            > > >
            > > > Hi folks,
            > > >
            > > > I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.
            > > >
            > > > I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?
            > > >
            > > > Thanks a lot for your help,
            > > >
            > > > Ferran.
            > > >
            > > >
            > > >
            > > > ------------------------------------
            > > >
            > > > Yahoo! Groups Links
            > > >
            > > >
            > > >
            > > >     http://docs.yahoo.com/info/terms/
            > > >
            > >
            >
          • topboxman2000
            Maybe this will help: http://starlightinstruments.com/store/index.php?route=product/category&path=44_67 Pretty pricey. Peter
            Message 5 of 11 , Aug 26 8:07 AM
            • 0 Attachment
              Maybe this will help:

              http://starlightinstruments.com/store/index.php?route=product/category&path=44_67

              Pretty pricey.

              Peter

              --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@...> wrote:
              >
              > Ferran,
              >
              > The FT3545 (if adjusted correctly) is not the source of the droop. My guess is the smaller diameter t-extensions (and the three threaded connections) are bending under the weight of the camera and filter wheel. For a given length and weight, the extensions will bend ~ 17x more than the focuser draw tube, and that number doesn't include any mechanical flex at the threaded joints.
              >
              > Jim M.
              >
              > --- In tec-scopes@yahoogroups.com, "ferranmazzanti" <Ferran.Mazzanti@> wrote:
              > >
              > > Hi Jim,
              > >
              > > it could be as you say, but let me tell you that the filter wheel + ccd is about 1 kg only (less than 2.5 lbs) which should be peanuts for the FT3545 focuser. The TEC has such a large backfocus that I want to think this has already been taken into account when dessigning it... Yuri?
              > >
              > > But of course that could be the source of problems -or not. I'm debugging my whole system, from pier to topmost guiderscope rings, so go figure :(
              > >
              > > Best regards and thanks,
              > >
              > > Ferran.
              > >
              > > --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@> wrote:
              > > >
              > > > Tim,
              > > >
              > > > Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn't matter how tight the focuser or collet is adjusted, this setup will have some droop.
              > > >
              > > > Jim M.
              > > >
              > > > --- In tec-scopes@yahoogroups.com, Tim Khan <timkhan@> wrote:
              > > > >
              > > > > I dont have any issue with my 4535 focuser holding 8 lbs of camera and filter-wheel. I have the older focuser with the button socket screw that you can adjust the pressure against the drawtube and remove any slop.
              > > > >
              > > > > Regarding the mount, do you have data collection for periodic error. Does it drift at a different rate for the first minute then settle immediately after a slew? If so this could be a bearing/housing/preload issue on your dec axis of your mount and may not be attributed to the scope and focuser.
              > > > >
              > > > >
              > > > >
              > > > > ________________________________
              > > > > From: ferranmazzanti <Ferran.Mazzanti@>
              > > > > To: tec-scopes@yahoogroups.com
              > > > > Sent: Thursday, August 22, 2013 7:09 PM
              > > > > Subject: [tec-scopes] Extending teh focuser of the TEC140
              > > > >
              > > > >
              > > > > Hi folks,
              > > > >
              > > > > I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.
              > > > >
              > > > > I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?
              > > > >
              > > > > Thanks a lot for your help,
              > > > >
              > > > > Ferran.
              > > > >
              > > > >
              > > > >
              > > > > ------------------------------------
              > > > >
              > > > > Yahoo! Groups Links
              > > > >
              > > > >
              > > > >
              > > > >     http://docs.yahoo.com/info/terms/
              > > > >
              > > >
              > >
              >
            • topboxman2000
              Shorter URL: http://tinyurl.com/FT3545-Extensions Peter
              Message 6 of 11 , Aug 26 9:02 AM
              • 0 Attachment
                Shorter URL:

                http://tinyurl.com/FT3545-Extensions

                Peter

                --- In tec-scopes@yahoogroups.com, "topboxman2000" <pnagy@...> wrote:
                >
                >
                >
                > Maybe this will help:
                >
                > http://starlightinstruments.com/store/index.php?route=product/category&path=44_67
                >
                > Pretty pricey.
                >
                > Peter
                >
                > --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@> wrote:
                > >
                > > Ferran,
                > >
                > > The FT3545 (if adjusted correctly) is not the source of the droop. My guess is the smaller diameter t-extensions (and the three threaded connections) are bending under the weight of the camera and filter wheel. For a given length and weight, the extensions will bend ~ 17x more than the focuser draw tube, and that number doesn't include any mechanical flex at the threaded joints.
                > >
                > > Jim M.
                > >
                > > --- In tec-scopes@yahoogroups.com, "ferranmazzanti" <Ferran.Mazzanti@> wrote:
                > > >
                > > > Hi Jim,
                > > >
                > > > it could be as you say, but let me tell you that the filter wheel + ccd is about 1 kg only (less than 2.5 lbs) which should be peanuts for the FT3545 focuser. The TEC has such a large backfocus that I want to think this has already been taken into account when dessigning it... Yuri?
                > > >
                > > > But of course that could be the source of problems -or not. I'm debugging my whole system, from pier to topmost guiderscope rings, so go figure :(
                > > >
                > > > Best regards and thanks,
                > > >
                > > > Ferran.
                > > >
                > > > --- In tec-scopes@yahoogroups.com, "gjwcac" <trimil@> wrote:
                > > > >
                > > > > Tim,
                > > > >
                > > > > Look at the photo -- Ferran has about four inches of T2 extension tubes between the FT3545 and the heavy filter wheel and camera. It doesn't matter how tight the focuser or collet is adjusted, this setup will have some droop.
                > > > >
                > > > > Jim M.
                > > > >
                > > > > --- In tec-scopes@yahoogroups.com, Tim Khan <timkhan@> wrote:
                > > > > >
                > > > > > I dont have any issue with my 4535 focuser holding 8 lbs of camera and filter-wheel. I have the older focuser with the button socket screw that you can adjust the pressure against the drawtube and remove any slop.
                > > > > >
                > > > > > Regarding the mount, do you have data collection for periodic error. Does it drift at a different rate for the first minute then settle immediately after a slew? If so this could be a bearing/housing/preload issue on your dec axis of your mount and may not be attributed to the scope and focuser.
                > > > > >
                > > > > >
                > > > > >
                > > > > > ________________________________
                > > > > > From: ferranmazzanti <Ferran.Mazzanti@>
                > > > > > To: tec-scopes@yahoogroups.com
                > > > > > Sent: Thursday, August 22, 2013 7:09 PM
                > > > > > Subject: [tec-scopes] Extending teh focuser of the TEC140
                > > > > >
                > > > > >
                > > > > > Hi folks,
                > > > > >
                > > > > > I need some of your wisdom :) The fact is that I have one TEC140 jewel that bought a few years ago, which comes equipped with the FT3545 focuser. The fact is that I pretend to use it with my Paramount MX mount, but so far I feel I'm suffering from flexures in my system as the TPoint models I build have huge declination flex terms. That can be dut to many different things, and consulting the people at Software Bisque, some say I may have flex in my focuser-to-CCD train.
                > > > > >
                > > > > > I have a lightweight Starlight Xpress SXV-H9 camera connected to a manual filter wheel... the whole things can weight around 1 kg, which the focuser should handle flowlesly. But the fact is that, in order to reach focus, I need to rack out the focuser about 80mm, and then add two male-female T-thread extensions of 20mm each, for a total of 120mm. That then connects to the filter wheel+CCD. All the extensors and connectors are screwed to the focuser, so I *think* this is stiff enough not to produce flexure, but since I'm debugging my problems, I don't rule out anything. Then the question I wanted to ask you is: what would be, in your opinion, the most rigid way of doing the connections, from the base of the focuser to the filter wheel, considering the later has a female T-thread connection?
                > > > > >
                > > > > > Thanks a lot for your help,
                > > > > >
                > > > > > Ferran.
                > > > > >
                > > > > >
                > > > > >
                > > > > > ------------------------------------
                > > > > >
                > > > > > Yahoo! Groups Links
                > > > > >
                > > > > >
                > > > > >
                > > > > >     http://docs.yahoo.com/info/terms/
                > > > > >
                > > > >
                > > >
                > >
                >
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