Cleaning, lubricating and centering a Zeiss GFL Pol Scope

  • Hi Bernd,
    unfortunately Zeiss Italy has a lower limit for the order, amounting to about 150 euros, so I should collect many items to reach such amount.
    The strange thing is that when you search the web for a 3.5 metric grub screw you find all measures except this.
    Sometimes I am temped to thread the existing 3.5 holes to a 4.0, which seems so more popular.
    However, coming to my scope, I continued the evaluation and found that the other GFL body formerly bought, has the object revolver also slightly skewed, but in the reverse direction, so it can be useful to interchange them.
    At this point I should dismount the revolver head, since the old was hesvily damaged as I wrote in a past message.
    But I do not know where to buy the tool necessary to unscrew the screw with two holes in the head.
    I have heard from somewhere of the existence of bits which can be turned with an hex key, but I could not find them in the web.
    Can you help me?
    Thanks and best regards,

    Salvatore

  • Hi Bernd and Klaus,
    Thanks for your contribution.
    To day I tried to exchange the scope arm of the two statives, but unfortunately the dovetails seem different.
    The old stative dovetail allows the insertion of the arm of the new scope, maybe with some play, but the new one refuses the insertio of the arm of the old.
    I tried to dismount the rack fixed to the arms, but the screws are too tight and am afraid to ruin the slot in their head.
    So I stopped my cannibalization effort and I continued by evaluating the overall performance of the new, polarizing scope.
    I detected some skewness in the illumination, maybe due to the imperfect centering and alignment of the whole optical system, so my first ideas for correcting the disalignment of the table and the axis of the objective-ocualar seems insufficient, because I must also take care of the condenser.
    In fact the observation of various specimens shows a sort of oblique illumination, and by looking in the tube without the ocular, the maximum of briliance of the source appears when I move the eye from the perpendicular to the right by a couple of degrees.
    I will tell more later.
    Best regards,

    Salvatore

    • Offizieller Beitrag

    Hi Salvatore,

    it is not very clever to change parts from dovetail. These are fited components. For dismount the rack from the arms you neet the matching screwdriver. But in worst case you will have problems with the two pins.
    To control the axis of illumination i have my special tool. Klaus sold this to me as scrap objective without lenses. ^^
    Together with a telescope eyepiece i can look to iris diaphragm and center the position by moving the arm on the base.
    The condenser you can center later. There are centering screws at the carrier.

    Regards
    Bernd

  • Hi,
    after some additional efforts it seems that the condenser can be reasonably centered and aligned to the rotating table, so the only problem remaining is the impefect alignment of the objective revolver.
    To solve this problem I see two ways:
    1) to dismount the revolver head and remount again with some metal sheets between the arm and the revolver to align correctly.
    2) to build a device to be interposed between the revolver and the inermediate tube, which could allow a proper positioning, that is to place the center of rotation of the table near the center of the objective axis.
    According to the first way the system could be aligned and centered, while the second will only take care of the centering.

  • Hi Bernd,
    I agree with you. The second way was imagined only if other ways gave no result.
    Now, to make your test, I think I should:
    a) dismount the condenser to free the way from the revolver to the iris.
    b) build a collimating device, like a pinhole ocular and objective to be placed on the straight tube, to aim at the iris.

    Have you any simpler way to suggest?

    Thanks and regards,
    Salvatore

  • Hi Salvatore,

    exact, the condensor must be dismounted and you need a pinhole objective.
    The iris diaphragm is as reference point not movable.


    Regards
    Bernd

    Hi Bernd,
    to day I finished to buid my primitive collimator and just tested it.
    The collimator is made of a straight tube of Zeiss, where as ocular I put a turned aluminum disc with a 1 mm central hole, and at his ent on a round cavity I placed a turned plexiglas disc with a 2 mm indentation at the center (perhaps too big, but in case, I will do another)
    Looking through the ocular, I saw that the collimator aims at a point about 2 mm on the left of the iris center.
    Since during dismount of the scope arm I noticed some adjustability of it relatively the base plate, I tried to mount the arm in the most favourable position for centering, but this was not sufficient, and still 1.5 mm about were present between the image of the indentation and that of the iris center.

    When playing with the iris I noticed that the illumination seemed skewed as well.
    To test it I placed a foil of paper on the table and oserved in the dark the light coming from the diaphragm.
    It shows a strong inhomogeneity, which I could not completely correct by moving the lamp holder.
    The lamp I use is made by Zeiss and of the type with three lobes. I have recently bought it from ebay, since the lamp holder af the scope needs such a type.
    By substituting the lamp with a bayonet type lamp mounted in another holder, which I have for another scope, the illumination is much more homogeneous, so I start to think that the ebay lamps was not a good buy. But anyhow I plan to buid a led illuminator.

    At this point I think I should dismount the nosepiece and remount it with some metal foils between the nosepiece and the arm to correct the inclination.
    I am going to build a convenient tool for dismounting the nosepiece, unless I can buy it somewhere from somebody... :)

    • Offizieller Beitrag

    Hi Salvatore,

    many thanks for your detailed reporting. The screw of nosepiece is very hard tightended. I made a tool for a client, a very good friend from Klaus, but he was not able to loose this screw. At the end of one's tether he sent the scope to me and five seconds later the screw was solved.
    It is not a joke, it is really happened.

    Regards
    Bernd

  • Hi Bernd,
    probably I also will be unable to unscrew the nosepiece, but I think there is nothing else to do than to try.
    Perhaps the screw is blocked by some sealant which has to be softened before unscrewing.

    Best regards,
    Salvatore

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