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19110Re: Linear Focuser

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  • gjcaunter
    Dec 10, 2008
    • 0 Attachment
      Hi Anat,

      I found the thumbscrew after a more thorough look (blush), it was
      hidden quite well inside bubble wrap. I also peeled off the quality
      control sticker on the bottom of the focuser to reveal the tension
      adjuster, a 4mm allen screw right where it should be (thanks Timm).

      Regarding backlash, there seemed to be very little initially. I used
      the scope on a couple of nights with no complaint. Since then it seems
      to have loosened in my subjective opinion. Testing it this evening,
      before any adjustment, I found that after a few turns of the fine
      focusing knob in one direction, I could turn it a full 270 degrees in
      the opposite direction before the focuser tube caught. Loosening the
      tension has virtually eliminated this backlash - response is now near
      enough immediate throughout the whole length. There is still some
      backlash after the tube is fully retracted which has to be worked out
      before the tube will begin to extend again, but I will simply leave
      the tube extended a few mm during storage to avoid this.

      It remains to be seen whether this looser arrangement will be
      satisfactory with the diagonal/eyepiece attached for any length of
      time, but the design doesn't seem prone to creep. Perhaps the
      thumbscrew will help in that regard if necessary. I will keep things
      updated but I seem to have achieved my immediate goal.

      Thanks to all,
      Gareth

      --- In William-Optics@yahoogroups.com, "aruangra" <aruangra@...> wrote:
      >
      > Dear Gareth
      >
      > I received the M90 last night. The large thumbscrew on the bottom is
      > provided separately. I was about to contact WO for the missing
      > thumbscrew. But I found it after carefully looking for it. The
      > thumbscrew is used to lock the drawtube. I really like the R&P design
      > of the linear focuser and the lock screw which is essential for
      > photography. I have very very small backlash in my focuser (almost the
      > same amount of backlash as a 3.5" FT focuser).
      >
      > Regards,
      > Anat
      >
      >
      >
      >
      > --- In William-Optics@yahoogroups.com, "gjcaunter" <gjcaunter@> wrote:
      > >
      > > Dear Anat,
      > >
      > > Hi, I'm Gareth and this is my first post on the WO Yahoo group. I was
      > > looking for information about the LinearPower focuser and this
      > > discussion caught my eye.
      > >
      > > I actually have a new WO Megrez 90 APO with the LinearPower focuser in
      > > my hands. Unfortunately there is a lot of backlash which I would like
      > > to try and correct. I had looked though all the documentation
      > > beforehand but found nothing relating to this design.
      > >
      > > Notable differences worth mentioning between the one pictured on the
      > > WO website and my own are: mine lacks the large silver ring (this is
      > > only relevant to SCTs I presume), and the central allen-screw and
      > > large thumb screw on the bottom are absent. There are threaded holes
      > > where both of these are located in the images on the website - the one
      > > that has the allen-screw is covered by a quality-control sticker on my
      > > Megrez. I'm 99% sure I haven't lost any screws (so to speak, you may
      > > disagree).
      > >
      > > Is it too early to ask if you or anyone else has experience with this
      > > focuser? I would appreciate any advice about how to adjust it.
      > >
      > > Best regards,
      > > Gareth
      > >
      > > --- In William-Optics@yahoogroups.com, "aruangra" <aruangra@> wrote:
      > > >
      > > > Hi Timm
      > > >
      > > > Many thanks for the clear description. I am excitedly waiting for
      > > > Megrez 90 with the new linear power focuser.
      > > >
      > > > Regards,
      > > > Anat
      > > >
      > > >
      > > > --- In William-Optics@yahoogroups.com, "Timm Bottoni" <t.bottoni@>
      > > > wrote:
      > > > >
      > > > > Hi Anat,
      > > > >
      > > > > Yes, sort of like a rack and pinion, it has a steel rack and a
      nylon
      > > > > gear that turns with the focuser knobs, but it is different in
      > several
      > > > > ways, more sophisticated compared to the rack and pinions
      focusers I
      > > > > have seen before because the entire weight rides on a steel
      bar with
      > > > > steel ball bearings at all times on both sides of the steel
      bar.
      > > > >
      > > > > Both ends are held in place by three inset screws, so the 2"
      > piece is
      > > > > not threaded.
      > > > >
      > > > > The SCT threads screw onto the back of the C8 directly, and
      that is
      > > > > the silver part you see in pictures. That part is not
      threaded onto
      > > > > the rest of the focuser. There are three inset screws that hold
      > it in
      > > > > place in a channel that allows it to rotate, and these three
      screws
      > > > > are adjustable for tension of the rotation. The focuser is
      > locked in
      > > > > place by a thumbscrew.
      > > > >
      > > > > The end where the diagonal inserts also has three screws that
      allow
      > > > > the end piece to also rotate, but there is no thumb screw, it is
      > held
      > > > > in place and tightened to the tapered flange by the three inset
      > > > > screws. WO stated that a custom adapter could be made to attach to
      > > > > this, but I have not seen any more info on what that might be.
      > > > >
      > > > > Another nice improvement is the dual set screws on the brass
      > retaining
      > > > > ring, rather than only one like my refractor has.
      > > > >
      > > > > Does that answer your questions?
      > > > >
      > > > > Take care,
      > > > >
      > > > > Timm
      > > > >
      > > > > --- In William-Optics@yahoogroups.com, "aruangra" <aruangra@>
      wrote:
      > > > > >
      > > > > > Dear Timm
      > > > > >
      > > > > > Thanks for your review. So it is a rack and pinion focuser.
      > Right?
      > > > > > I see that the 2" adapter can be unscrewed from the 2.5" tube.
      > Could
      > > > > > you tell me the thread size of the 2.5" tube? The thread is very
      > > > > > useful to rigidly fix a camera and accessories with a proper
      > > adapter.
      > > > > >
      > > > > > Best regards,
      > > > > > Anat
      > > > > >
      > > > > >
      > > > > >
      > > > > >
      > > > > > --- In William-Optics@yahoogroups.com, "Timm Bottoni"
      <t.bottoni@>
      > > > > > wrote:
      > > > > > >
      > > > > > > Hi William,
      > > > > > >
      > > > > > > I'll try and explain it without picturesf for now, but will
      > > include
      > > > > > > pictures and details in my upcoming review.
      > > > > > >
      > > > > > > First - DON'T TAKE IT APART if you have one, trust me, I know.
      > > ;-)
      > > > > > >
      > > > > > > The Linear Power focuser uses a rack and pinion design to
      > move the
      > > > > > > focuser forward and back, which is very different from any
      other
      > > > > > > focuser I have seen. The entire focuser tube runs on a
      > steel rail
      > > > > > > that is sandwiched between two sets of ball bearings. I am
      > > not sure
      > > > > > > how the two speed focuser works, if it is on tension or gears,
      > > > but it
      > > > > > > is incredibly smooth.
      > > > > > >
      > > > > > > The tension is adjusted easily using an allen wrench, and is
      > > > locked in
      > > > > > > place using a thumb screw. The ability to adjust the tension
      > > > is very
      > > > > > > forgiving, and allows for easy adjustment to meet your weight
      > > > > > > requirements.
      > > > > > >
      > > > > > > I have never used a FeatherTouch or other brand of crayford or
      > > rack
      > > > > > > and pinion, but this design allows for the travel to stay
      > > incredibly
      > > > > > > smooth at any tension from too loose to too tight.
      > > > > > >
      > > > > > > It is a 2.5" design, and the thread on the SCT end, and the
      > > > inside of
      > > > > > > the draw tube is 2" internal. Everything is ultra flat black
      > > > inside,
      > > > > > > and the SCT is shorter in it's travel than the refractor ones
      > > I see
      > > > > > > pictured on the WO site, which makes sense since the
      travel tube
      > > > must
      > > > > > > stop at the threaded SCT ring, it can't go inside the back
      > like a
      > > > > > > refractor one could.
      > > > > > >
      > > > > > > Based on my testing so far, this design is excellent and
      > > capable of
      > > > > > > handling a much heavier load than the Crayford design of
      the one
      > > > on my
      > > > > > > Megrez 80FD. If WO has a way to make it work on the ZS110, I
      > > think
      > > > > > > it will probably preform very nicely.
      > > > > > >
      > > > > > > I'll post the pictures and full review in the next couple of
      > > weeks.
      > > > > > >
      > > > > > > Timm
      > > > > > >
      > > > > > >
      > > > > > > --- In William-Optics@yahoogroups.com, "William Roy Penney"
      > > > > > > <penneywilliam@> wrote:
      > > > > > > >
      > > > > > > >
      > > > > > > > Hi Tim,
      > > > > > > >
      > > > > > > > Do you or anyone else have any details or information about
      > > > the new
      > > > > > > > linear focuser? Is it another crayford type or rack and
      > pinion?
      > > > > > > > I would like to replace the focusser on my Z110, and
      maybe the
      > > > > linear
      > > > > > > > focuser is the "beefed up focuser" which was supposed to be
      > > > > available
      > > > > > > > soon from WO (several years ago) but did not eventuate.
      > > > > > > >
      > > > > > > > Merry Xmas
      > > > > > > >
      > > > > > > > William
      > > > > > > >
      > > > > > >
      > > > > >
      > > > >
      > > >
      > >
      >
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