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RE: [Telescopes] Dob to EQ

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  • Christopher Erickson
    1. You could invest in an EQ tracking platform for your Dob. 2. You could pick up a GP-DX and a set of appropriate stationary or rotating tube rings. 3. You
    Message 1 of 15 , Jun 1, 2002
      1. You could invest in an EQ tracking platform for your Dob.

      2. You could pick up a GP-DX and a set of appropriate stationary or rotating tube rings.

      3. You could pick up a University Optics classic GEM EQ mount and put it on a short pier. Once again picking up a set of tube
      rings. You could motorize it with parts from Parks, JMI or Aeroquest Machining.

      http://www.scopecity.com/parks1.htm

      http://www.universityoptics.com

      http://www.jimsmobile.com/

      http://www.aeroquest-machining.com/

      http://users.kricket.net/ken/

      http://home.netcom.com/~tlsystem/

      http://www.atmsite.org/keyword.html

      http://astronomy-mall.com/regular/products/eq_platforms/compact.htm

      http://www.johnsonian.com/

      http://www.saao.ac.za/~wpk/scope/scope.html


      Happy reading!!

      -Christopher Erickson
      Network Design Engineer
      We Byte
      5432 E. Northern Lights Blvd., Suite 529
      Anchorage, AK 99508
      N61° 11.710' W149° 46.723'
      www.data-plumber.com



      -----Original Message-----
      From: Bill [mailto:ke4wkp@...]
      Sent: Friday, May 31, 2002 10:50 PM
      To: telescopes@yahoogroups.com
      Subject: [Telescopes] Dob to EQ


      Hey guys just a quick question. Lets say I purchase an
      Orion XT8 Dob. Then later down the road I want to
      Purchase say a Great Polaris EQ mount. I would be able
      to mount the OTA from the Dob on the GP mount right?
      Or might I need something larger or would it even be
      feasible. I cant decide between the xt8 or the skyview
      deluxe 8 EQ newt I like the SVD8 because of the EQ
      mount and possibility for electronic drive(I have
      decided against Goto but I still like tracking drives)
      & I like the Dob because it is a little faster & cost
      less. So maybe if I get the Dob and Decide later that
      I would like EQ I could just get a mount & if I'm lazy
      just use the dob mount. Decisions Decisions
      Thx Bill
    • Geoff Gaherty
      ... There should be no problem mounting an XT8 tube assembly on an equatorial mount. The same is not true of all Dobsonians, since some have cells which only
      Message 2 of 15 , Jun 1, 2002
        Bill wrote:
        >
        > Hey guys just a quick question. Lets say I purchase an
        > Orion XT8 Dob. Then later down the road I want to
        > Purchase say a Great Polaris EQ mount. I would be able
        > to mount the OTA from the Dob on the GP mount right?
        > Or might I need something larger or would it even be
        > feasible.

        There should be no problem mounting an XT8 tube assembly on an equatorial mount.
        The same is not true of all Dobsonians, since some have cells which only work
        in one orientation, but the XT series is OK in this regard. You will have the
        perennial problem of equatorially mounted Newtonians that the eyepiece and
        finder will end up in awkward positions from time to time, so you need to have
        some means of rotating the tube assembly in its saddle. Parks and Parallax sell
        rotating rings for this purpose.

        However I doubt that a GP mount is large enough to handle the size and weight of
        the XT8 tube assembly. I've been using an SVD8 tube assembly on a GP-DX, which
        seems OK, at least for visual observation, but I'm not sure even it could handle
        the added length and weight of the XT8 tube. You will also need to find some
        alternative to the GP's tripod, which will put the eyepiece awkwardly high. My
        GP-DX is mounted on an 18" pier, which makes for very convenient eyepiece
        heights for a seated observer.

        > I cant decide between the xt8 or the skyview
        > deluxe 8 EQ newt I like the SVD8 because of the EQ
        > mount and possibility for electronic drive(I have
        > decided against Goto but I still like tracking drives)
        > & I like the Dob because it is a little faster & cost
        > less.

        Although the SkyView Deluxe mount is adequate for smaller scopes, it is not
        heavy enough to support the SVD8 tube assembly, which weighs twice as much as
        the SVD6, which is right at the maximum load for this mount. I'm not clear what
        you mean by the Dob being "faster"...if you mean that in the photographic sense,
        it isn't so: the SVD is f/4 while the XT8 is f/6.

        --
        Geoff Gaherty
        Toronto Centre RASC
        geoff@...
      • Bill
        ooopps I meant slower. I understand that the faster svd8 f/4 needs collimation more often and may not be as compatible to some eyepieces as a slower XT8. Maybe
        Message 3 of 15 , Jun 1, 2002
          ooopps I meant slower. I understand that the faster
          svd8 f/4 needs collimation more often and may not be
          as compatible to some eyepieces as a slower XT8. Maybe
          I am just over analyzing all of this too much. I will
          probably just get the XT8 like Phil suggested in the
          first place and start from there.
          My Thanks to this Fine Group for all of your comments
          and suggestions.
          Clear Skies,
          Bill
          --- Geoff Gaherty <ggaherty@...> wrote:
          > Bill wrote:
          > >
          > > Hey guys just a quick question. Lets say I
          > purchase an
          > > Orion XT8 Dob. Then later down the road I want to
          > > Purchase say a Great Polaris EQ mount. I would be
          > able
          > > to mount the OTA from the Dob on the GP mount
          > right?
          > > Or might I need something larger or would it even
          > be
          > > feasible.
          >
          > There should be no problem mounting an XT8 tube
          > assembly on an equatorial mount.
          > The same is not true of all Dobsonians, since some
          > have cells which only work
          > in one orientation, but the XT series is OK in this
          > regard. You will have the
          > perennial problem of equatorially mounted Newtonians
          > that the eyepiece and
          > finder will end up in awkward positions from time to
          > time, so you need to have
          > some means of rotating the tube assembly in its
          > saddle. Parks and Parallax sell
          > rotating rings for this purpose.
          >
          > However I doubt that a GP mount is large enough to
          > handle the size and weight of
          > the XT8 tube assembly. I've been using an SVD8 tube
          > assembly on a GP-DX, which
          > seems OK, at least for visual observation, but I'm
          > not sure even it could handle
          > the added length and weight of the XT8 tube. You
          > will also need to find some
          > alternative to the GP's tripod, which will put the
          > eyepiece awkwardly high. My
          > GP-DX is mounted on an 18" pier, which makes for
          > very convenient eyepiece
          > heights for a seated observer.
          >
          > > I cant decide between the xt8 or the skyview
          > > deluxe 8 EQ newt I like the SVD8 because of the EQ
          > > mount and possibility for electronic drive(I have
          > > decided against Goto but I still like tracking
          > drives)
          > > & I like the Dob because it is a little faster &
          > cost
          > > less.
          >
          > Although the SkyView Deluxe mount is adequate for
          > smaller scopes, it is not
          > heavy enough to support the SVD8 tube assembly,
          > which weighs twice as much as
          > the SVD6, which is right at the maximum load for
          > this mount. I'm not clear what
          > you mean by the Dob being "faster"...if you mean
          > that in the photographic sense,
          > it isn't so: the SVD is f/4 while the XT8 is f/6.
          >
          > --
          > Geoff Gaherty
          > Toronto Centre RASC
          > geoff@...
          >
          > You are subscribed to the "Talking Telescopes"
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          >
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          >
          >


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        • philip_harrington
          Bill, The GP-DX, while a great mount, isn t all that suitable for that type of telescope. It can carry up to 22 pounds, which is also about what the XT-8
          Message 4 of 15 , Jun 1, 2002
            Bill,

            The GP-DX, while a great mount, isn't all that suitable for that type
            of telescope. It can carry up to 22 pounds, which is also about what
            the XT-8 weighs, so I'd be leery about that. But I'd be more
            concerned with the telescope's girth. I have a feeling that the tube
            would hit the tripod legs often, greatly limiting the telescope's
            aiming ability.

            Most reflectors of yore were mounted on pedestals. Their benefit was
            that, thanks to no tripod legs, they could reach anywhere from
            horizon to zenith without hitting the mounting. I'd recommend you
            look into something like that, even if it's used. Mountings for
            Criterion RV-6's are fairly common in the used-equipment arena, so
            consider that (I even have one that I'm selling eventually, but I
            digress). Drawbacks, include the fact that the drives were AC
            powered, not DC, so an inverter will be needed for mobile operation.

            If you're looking for a new mount, one of the Russian-made TAL mounts
            might be a good choice. Take a look at http://www.talscopes.com I
            can't recall what the TAL scopes weigh, but I bet their 6-inch weighs
            more than the XT-8.

            Phil
            -----------------------
            Phil Harrington
            http://www.philharrington.net


            --- In telescopes@y..., Bill <ke4wkp@y...> wrote:
            > Hey guys just a quick question. Lets say I purchase an
            > Orion XT8 Dob. Then later down the road I want to
            > Purchase say a Great Polaris EQ mount. I would be able
            > to mount the OTA from the Dob on the GP mount right?
            > Or might I need something larger or would it even be
            > feasible. I cant decide between the xt8 or the skyview
            > deluxe 8 EQ newt I like the SVD8 because of the EQ
            > mount and possibility for electronic drive(I have
            > decided against Goto but I still like tracking drives)
            > & I like the Dob because it is a little faster & cost
            > less. So maybe if I get the Dob and Decide later that
            > I would like EQ I could just get a mount & if I'm lazy
            > just use the dob mount. Decisions Decisions
            > Thx Bill
          • carboss20
            ... I am in the process of doing this very thing. The rings sold by Parallax while fantastic are very expensive, especially the rotating versions. Hands Optics
            Message 5 of 15 , Jun 1, 2002
              --- In telescopes@y..., Bill <ke4wkp@y...> wrote:
              > Hey guys just a quick question. Lets say I purchase an
              > Orion XT8 Dob. Then later down the road I want to
              > Purchase say a Great Polaris EQ mount. I would be able
              > to mount the OTA from the Dob on the GP mount right?
              >

              I am in the process of doing this very thing. The rings sold by
              Parallax while fantastic are very expensive, especially the rotating
              versions. Hands Optics advertises a set of rings that should work for
              $59.00 U.S.or so.

              If you want to use the tube on both mounts as I am
              attempting you will have to move the center of gravity forward as the
              side bearings are placed where one of the rings should be. I am doing
              this with a much needed tube extension that can be removed easily.
              too much to go into here but I will be posting pics of the completed
              project in a few weeks. One other thing I will be mounting mine on a
              CI700. I will be using pier as soon as I can get one but will be
              using the original tripod at first. I will be the only guy using a
              ladder to look through a 8" F/6 scope :)

              Vern __________________________________________________
              > Do You Yahoo!?
              > Yahoo! - Official partner of 2002 FIFA World Cup
              > http://fifaworldcup.yahoo.com
            • carboss20
              ... I am in the process of doing this very thing. The rings sold by Parallax while fantastic are very expensive, especially the rotating versions. Hands Optics
              Message 6 of 15 , Jun 1, 2002
                --- In telescopes@y..., Bill <ke4wkp@y...> wrote:
                > Hey guys just a quick question. Lets say I purchase an
                > Orion XT8 Dob. Then later down the road I want to
                > Purchase say a Great Polaris EQ mount. I would be able
                > to mount the OTA from the Dob on the GP mount right?
                >

                I am in the process of doing this very thing. The rings sold by
                Parallax while fantastic are very expensive, especially the rotating
                versions. Hands Optics advertises a set of rings that should work for
                $59.00 U.S.or so.

                If you want to use the tube on both mounts as I am
                attempting you will have to move the center of gravity forward as the
                side bearings are placed where one of the rings should be. I am doing
                this with a much needed tube extension that can be removed easily.
                too much to go into here but I will be posting pics of the completed
                project in a few weeks. One other thing I will be mounting mine on a
                CI700. I will be using pier as soon as I can get one but will be
                using the original tripod at first. I will be the only guy using a
                ladder to look through a 8" F/6 scope :)

                Vern __________________________________________________
                > Do You Yahoo!?
                > Yahoo! - Official partner of 2002 FIFA World Cup
                > http://fifaworldcup.yahoo.com
              • Herm
                sure, but not a GP by a long shot.. instead use one of the new chinese EQ6 mounts at about $1k or so.. If you just want tracking then why not get an equatorial
                Message 7 of 15 , Jun 1, 2002
                  sure, but not a GP by a long shot.. instead use one of the new chinese
                  EQ6 mounts at about $1k or so.. If you just want tracking then why not
                  get an equatorial platform?.. even better get an XT10 now! (g).

                  If you want to do photography then that's a totally different
                  question.

                  Bill <ke4wkp@...> wrote:

                  >Hey guys just a quick question. Lets say I purchase an
                  >Orion XT8 Dob. Then later down the road I want to
                  >Purchase say a Great Polaris EQ mount. I would be able
                  >to mount the OTA from the Dob on the GP mount right?

                  Herm
                  Astropics http://home.att.net/~hermperez
                • Geoff Gaherty
                  ... Real rotating rings are expensive because they require a large high-precision bearing surface, which must be really hard to make. I have a set of Parks
                  Message 8 of 15 , Jun 1, 2002
                    carboss20 wrote:
                    >
                    > I am in the process of doing this very thing. The rings sold by
                    > Parallax while fantastic are very expensive, especially the rotating
                    > versions. Hands Optics advertises a set of rings that should work for
                    > $59.00 U.S.or so.

                    Real rotating rings are expensive because they require a large high-precision
                    bearing surface, which must be really hard to make. I have a set of Parks rings
                    on my 8" Cave which are about forty years old but are smooth as silk: they
                    rotate easily without affecting the direction the scope is pointed, yet stay in
                    place the rest of the time. I'm not sure how they do it, since I've never dared
                    to disassemble them, but I suspect a _lot_ of Teflon is involved. (Yes, Teflon
                    as available forty years ago. My 1957 Coast mount used sheet Teflon for thrust bearings.)

                    Most tube rings don't work at all well because they are designed to have a lot
                    of friction. You have to loosen the clamps a lot before the tube will rotate,
                    and then it is very hard to adjust. The _one_ exception I've found for this is
                    the rings in my Intes MN61, which are almost as good as the Park rings. I think
                    there are two factors at work here: the tube is heavy and probably very exactly
                    round, and the material on the inside of the rings is exactly right, whatever it
                    is. I put a large hose clamp on the tube to keep it from slipping when I'm
                    turning the tube. DON'T expect the standard Synta rings to work as well on a
                    thin sheet metal tube. I have Synta rings on several scopes, and they are
                    really hard to adjust.

                    > If you want to use the tube on both mounts as I am
                    > attempting you will have to move the center of gravity forward as the
                    > side bearings are placed where one of the rings should be. I am doing
                    > this with a much needed tube extension that can be removed easily.
                    > too much to go into here but I will be posting pics of the completed
                    > project in a few weeks. One other thing I will be mounting mine on a
                    > CI700. I will be using pier as soon as I can get one but will be
                    > using the original tripod at first. I will be the only guy using a
                    > ladder to look through a 8" F/6 scope :)

                    That was me with my Cave 8" f/7 on Losmandy G-11 until I got shorter tripod
                    legs! Even now, it's strictly a "stand-up" scope while it used to be a
                    "sit-down" scope on my old cast iron boat anchor mount, which has a pedestal
                    base like Phil is talking about.

                    --
                    Geoff Gaherty
                    Toronto Centre RASC
                    geoff@...
                  • Geoff Gaherty
                    ... I just put an image of my Intes 6 f/6 Mak-Newt on GP-DX and Cave 8 f/7 Newt on G-11 side-by-side in the Photos section:
                    Message 9 of 15 , Jun 1, 2002
                      Geoff Gaherty wrote:
                      >
                      > That was me with my Cave 8" f/7 on Losmandy G-11 until I got shorter tripod
                      > legs! Even now, it's strictly a "stand-up" scope while it used to be a
                      > "sit-down" scope on my old cast iron boat anchor mount, which has a pedestal
                      > base like Phil is talking about.

                      I just put an image of my Intes 6" f/6 Mak-Newt on GP-DX and Cave 8" f/7 Newt on
                      G-11 side-by-side in the Photos section:

                      http://photos.groups.yahoo.com/group/telescopes/vwp?.dir=/Telescopes&.src=gr&.dnm=DavidGoliath.jpg&.view=t&.done=http%3a//photos.groups.yahoo.com/group/telescopes/lst%3f%26.dir=/Telescopes%26.src=gr%26.view=t

                      I'm standing up using the LOMO binoviewer on the Cave, and I'm 6'1" tall, to
                      give you an idea of scale. The picture was taken back in October when I was
                      doing a side-by-side comparison of the two scopes on Jupiter. Pretty close to a
                      tie: a little more detail resolved in the Cave, a little more contrast in the Intes.

                      --
                      Geoff Gaherty
                      Toronto Centre RASC
                      geoff@...
                    • carboss20
                      ... have a lot ... will rotate, ... for this is ... rings. I think ... very exactly ... right, whatever it ... when I m ... well on a ... they are ... I too
                      Message 10 of 15 , Jun 1, 2002
                        > Most tube rings don't work at all well because they are designed to
                        have a lot
                        > of friction. You have to loosen the clamps a lot before the tube
                        will rotate,
                        > and then it is very hard to adjust. The _one_ exception I've found
                        for this is
                        > the rings in my Intes MN61, which are almost as good as the Park
                        rings. I think
                        > there are two factors at work here: the tube is heavy and probably
                        very exactly
                        > round, and the material on the inside of the rings is exactly
                        right, whatever it
                        > is. I put a large hose clamp on the tube to keep it from slipping
                        when I'm
                        > turning the tube. DON'T expect the standard Synta rings to work as
                        well on a
                        > thin sheet metal tube. I have Synta rings on several scopes, and
                        they are
                        > really hard to adjust.

                        I too was impressed by the MN61 tube rings. I was surprised as to how
                        easy it is to rotate the mn61 within them. As ras as the Synta rings
                        go you are as usual right on the money. I think I have a way around
                        that but the seam in the tube has me a little concerned. I will
                        surely post my results.

                        Vern
                        >
                        >
                      • faintfuzzyfinder
                        Just make sure you get a dob with a mirror cell that supports or hangs on to the mirror in all orientations. Many dobs have a cell designed only to work in one
                        Message 11 of 15 , Jun 1, 2002
                          Just make sure you get a dob with a mirror cell that
                          supports or hangs on to the mirror in all
                          orientations. Many dobs have a cell designed only to
                          work in one orientation (sling style mounts).

                          Jeff


                          __________________________________________________
                          Do You Yahoo!?
                          Yahoo! - Official partner of 2002 FIFA World Cup
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                        • Geoff Gaherty
                          ... That seems to be a feature of the original John Dobson design which has never been adopted by the mass market Dob makers. Every one I ve seen has a real
                          Message 12 of 15 , Jun 1, 2002
                            faintfuzzyfinder wrote:
                            >
                            > Just make sure you get a dob with a mirror cell that
                            > supports or hangs on to the mirror in all
                            > orientations. Many dobs have a cell designed only to
                            > work in one orientation (sling style mounts).

                            That seems to be a feature of the original John Dobson design which has never
                            been adopted by the mass market Dob makers. Every one I've seen has a "real"
                            mirror cell that holds the mirror firmly (sometimes too firmly) in all orientations.

                            Starmaster seems to be unusual among the big Dob makers in not using a sling.
                            The mirror is supported behind by traditional 3-point or 9-point (or more)
                            supports, and at the edge by two posts at 45° to the center line. Rick's
                            rationale is that this is the kind of mount that all mirror makers use for
                            testing their mirrors. There are two more posts above the mirror at 45° to the
                            center line, with about a millimeter of space to the mirror edge, and all four
                            posts have clips atop them, again with about a millimeter of clearance to the
                            front of the mirror. The mirror can thus travel about a millimeter in any
                            direction, but there's no danger of it flying loose or having pressure put on
                            it. It _is_ a little unnerving, when pointing close to the horizon, to suddenly
                            have the mirror tip forwards against its upper supports with a decided clunk.

                            --
                            Geoff Gaherty
                            Toronto Centre RASC
                            geoff@...
                          • outwest112
                            ... suddenly ... decided clunk. I m glad to hear I m not the only one with this feature. Part of my set up and collimation ritual involves running the scope up
                            Message 13 of 15 , Jun 1, 2002
                              > It _is_ a little unnerving, when pointing close to the horizon, to
                              suddenly
                              > have the mirror tip forwards against its upper supports with a
                              decided clunk.

                              I'm glad to hear I'm not the only one with this feature. Part of my
                              set up and collimation ritual involves running the scope up to the
                              zenith and down to the horizon several times. This helps the mirror
                              find its home for the night after a bumpy car ride. Once its settled
                              it will keep collimation all night.

                              But yeah it's sort of bush league. I tend to chase people away during
                              the setup rather than having to explain it.
                            • Herm
                              Geoff, how do you like this binoviewer?.. how does it compare to its more expensive brothers? ... Herm Astropics http://home.att.net/~hermperez
                              Message 14 of 15 , Jun 1, 2002
                                Geoff, how do you like this binoviewer?.. how does it compare to its
                                more expensive brothers?

                                Geoff Gaherty <ggaherty@...> wrote:

                                >I'm standing up using the LOMO binoviewer on the Cave

                                Herm
                                Astropics http://home.att.net/~hermperez
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