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  1. #1
    Fu Manchu's Avatar
    Fu Manchu Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope



    (i pulled this out of another thread as buried my real question in an
    inappropriate thread)

    Now, im posting a link of the back of the telescope.

    http://home.maine.rr.com/benno/Image-08.jpg

    you can see the 3 thumbscrews and 3 phillips head screws. since im
    without a manual for this thing, how is it that i adjust the mirror
    with these? do i loosen the thumbscrews and do fine adjustments with a
    screwdriver to the phillips screw, or vice versa?


    I'd like to take the whole darn thing off as a unit to clean it. Now,
    heres another point in my confusion. how to get the back off. Not
    shown in the pic are three small screws that screw through the red
    tube into the back. to me, these look like they hold the back on, but
    when i take them off, and tug on the back,nothing gives. granted i
    could tug harder, but am reluctant to do so without all the facts.


  2. #2
    Wfoley2's Avatar
    Wfoley2 Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

    I would guess that you would loosen the philips-head screws, collimate using
    the thumbscrews, then tighten the philips-head screws just enough to hold, NOT
    enough to change the collimation. If I had the scope, I would try this first,
    and if that did not work, try the other way.
    I believe that the three screws on the side are the ones you remove to take out
    the cell. However, be sure to MARK one of these screws and the tube where it
    goes in to be sure you get the cell back in the way it was, or you can lose
    your collimation. Also, be sure you have something soft for the cell to fall
    on when you pull it out in case it is difficult and you drop it. This advice
    is from experience.
    Clear, Dark, Steady Skies!
    (And considerate neighbors!!!)



  3. #3
    CLT's Avatar
    CLT Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope


    "Fu Manchu" <fu@nospam.org> wrote in message
    news:0jqkh09jebegju5s99dmu4sb7n602ook0u@4ax.com...

    I have since posted what you need in the earlier thread. If it is still not
    clear, let us know.

    Clear Skies

    Chuck Taylor
    Do you observe the moon?
    Try http://groups.yahoo.com/group/lunar-observing/
    And the Lunar Picture of the Day http://www.lpod.org/
    ************************************






  4. #4
    CLT's Avatar
    CLT Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

    > I believe that the three screws on the side are the ones you remove to
    take out
    it
    lose

    ???? You are going to lose collimation when you remove it. And it probably
    isn't very well collimated currently. He will quickly learn the easy art of
    collimating a newt.

    Clear Skies

    Chuck Taylor
    Do you observe the moon?
    Try http://groups.yahoo.com/group/lunar-observing/
    And the Lunar Picture of the Day http://www.lpod.org/
    ************************************


    advice



  5. #5
    Martin R. Howell's Avatar
    Martin R. Howell Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

    Just a note here. . .from the photograph, it appears that you need to set
    the declination on the scope's mount to match your latitude. Do a Google on
    "using setting circles."

    --
    Martin



  6. #6
    LarryG's Avatar
    LarryG Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

    On Wed, 11 Aug 2004 18:48:46 GMT, Fu Manchu <fu@nospam.org> wrote:



    You are wise to approach this task with caution. Rest assured that no
    aspect of cleaning or collimating your Tasco newtonian involves rocket
    science or similar arcana. To start with, lets define some terms, to
    avoid confusion:

    Mirror Cell Assembly: The mechanism which holds the (primary) mirror,
    secures it to the tube, and allows for alignment and collimation.
    In addition to the mirror, the mirror cell assembly usually consists of:

    The Mirror Cell / Holder / Mounting Plate - The part which actually holds
    the mirror.

    The Back Plate - Connects the Mirror Cell to the tube wall. Sits behind
    the
    mirror cell.

    The Collimation Screws - a set of three or six. Three thumbscrews are used
    to pull the mirror cell toward the Back Plate; springs provide push in the
    opposite direction. Or a set of six screws (three thumbscrews for pull,
    and
    three thrust screws for push) act to point and lock the mirror in
    alignment.

    (Tube) End Ring - usually a plastic reinforcing ring mounted at the ends of
    the tube. Its function is that of a bumper - it keeps the tube-ends from
    getting dented, and protects your walls and shins from getting scraped or
    cut
    by the tube's sharp (metal) edges.


    (These aren't official nomenclature, just a convenience for communication.)

    ====


    In your photo, the large black ring, with six collimations screws showing,
    is
    the back plate. On the other side of the back plate is the mirror cell.

    The "three small screws that screw through the red tube into the back" pose
    something of a problem.
    - If they are long enough to go into the back-plate, then they are what
    holds
    the mirror cell assembly in place.
    - If the screws are just long enough to go into the tube, but not the back
    plate,
    then there may be another set of screws under the end-ring.
    - It is possible that the End Ring and the Back Plate are all part of the
    same piece of plastic.


    In any event, you should NOT have to touch the Collimation Screws to get
    the mirror
    cell assembly out.

    However, before you start, make alignment marks where the end-ring meets
    the tube,
    and where the back plate meets the end-ring. These will help when it comes
    time to
    re-assemble the optical tube assebly, by merely lining up the respective
    alignment
    marks.


    SUGGESTED PROCEDURE
    1. Remove the three small screws from the end ring.
    2. Attempt to rotate the back plate within the end ring.
    This will tell if other screws are holding it in place, or if the
    back plate and the end ring are one integral piece.
    3. If the back plate rotates, try to remove the mirror cell assembly
    by twisting and pulling (very carefully).
    4. If the back plate does not rotate free of the end ring, try to lightly
    push the end ring off the tube.
    5. If additional hardware holds the back plate to the tube, remove it,
    after first making new alignment marks where the tube and back plate
    meet.
    6. The mirror cell should now be easily removed. (Do so with care.)


    Clean the mirror, according to previous instructions.

    Re-assemble by reversing the disassembly process.

    Collimate the telescope. There are any number of good websites which tell
    you
    how to do this. Some advise using specific collimation tools. If you do
    not
    have such tools, I have a site which allows adequate collimation without
    them:
    < http://www.vvm.com/~piscescs/collimat/NoTools2.html >


    Cheers, and good luck,
    Larry G.












  7. #7
    Fu Manchu's Avatar
    Fu Manchu Guest

    Default Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

    Update. Primary and Secondary mirror out sucessfully, but with a
    hitch. The damn backplate on this thing just wouldnt budge!! So i
    carefully loosened up the thumbscrews and regular screws on the
    backplate until the mirror came loose, the carefully reached down the
    tube and pulled the whole assembly out the front, which barely fit
    out. Once the mirror was out, i exerted some more daring in trying to
    remove the backplate, but to no avail. I think possibly that the
    metal in the screws holes on the backplate is somehow snagged on the
    metal in the tube and that happend when they drilled and tapped during
    original construction.

    To my suprise, there were springs loading the mirror assembly against
    the thumbscrews, which actually it turns out are thumbbolts. The
    screws holding the mirror assembly in place are permanently affixed to
    the mirror assembly, and it is to these that the thumbolts are
    attached, so to put it back together and collimate i believe i would
    have to tighten the thumbolts up snug, and then use the regular screws
    to kind of push the mirror assembly against the spring loaded screws
    for alignment.

    http://home.maine.rr.com/benno/Image-08.jpg
    http://home.maine.rr.com/benno/Image-09.jpg
    http://home.maine.rr.com/benno/Image-10.jpg


    Attached are some pics of the primary mirror assembly (which is of
    suprising quality considering the cheap nature of this particular
    telescope), the secondary mirror assembly (notice the fender washers
    which im going to use to help shim the secondary mirror to more
    closely align with the focuser hole instead of driving the alignment
    screws waayy in to help hold it)

    Next task is to clean the primary and secondary mirrors and center
    mark the primary, and order a collimation set up. Here is a question,
    are there any type of magic marker that will damaged the mirror
    coating? Was thinking of marking the center of the primary with some
    washable marker, putting a paper reinforcment ring around the center
    for a nice laser target.

    As far as a collimation setup, thinking of getting the deluxe laser
    collimator from Orion, a .965" to 1.25" adapter assembly for the
    collimator, and a 10mm and 25mm .965" zhummel plossl lenses.

    Kind of ironic actually that this upgrade costs more than the original
    scope probably did back in the 1980s when my parents brought it home.
    But, i figured this is good practice in learing about the guts of a
    telescope without much to lose as far as the scope is concerned, and
    ill pass it along for my kids to play with some day. It will also
    hold me over as i save up enough cash to buy a motorized base and a
    newer scope down the road.

    I think ill paint "chick magnet" on the side and send a picture and my
    rebuild story to http://www.andysshotglass.com/DontDo.html when im
    done, hehe.






    On Thu, 12 Aug 2004 01:39:04 -0500, LarryG <no.return.addr@none.com>
    wrote:



 

 

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