The INFINITY XLKTM Collimation Procedure
ALL PICS & ILLUSTRATIONS COMPLIMENTS OF JASON KHADDER
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Central Pupil View INFINITY XLKTM Offset Pupil View
Identification of the four center spot reflections*

*Equal-sized images as illustrated & best results are achieved with the focuser/autocollimator racked in/out appropriately to place the autocollimator mirror at or very near the focal plane.

CENTRAL PUPIL

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  • Reflection "P" is the sharpest and brightest of all the rest.
  • Reflection "1" is oriented like "P" but is typically somewhat fuzzy.
  • Reflection "2" is the sharpest and brightest inverted reflection.
  • Reflection "3" is the dimmest inverted reflection & is somewhat fuzzy.
  • OFFSET PUPIL

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    STEP 1: Assessing Overall Optical Axes Alignment:
    CENTRAL PUPIL

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  • Insert the INFINITY XLKTM in the focuser & examine both pupil views.
  • Axial alignment errors will likey be present as depicted.
  • The objective will be to have only "P" be visible via the CENTRAL PUPIL & and "Perfect" twin hexagrams via the OFFSET PUPIL. Anything else is indicative of axial misalignment.
  • OFFSET PUPIL

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    There are two types of axial alignment errors:

  • FAE (Focuser Axial Error) is the distance between the primary mirror center point and the focuser axis.

  • PAE (Primary Axial Error) is the distance between the primary mirror focal point and the focuser axis.

    Eliminating both errors is the main goal of "axial" collimation. Typically, FAE is eliminated first by adjusting the secondary mirror then PAE is eliminated by adjusting the primary mirror.

  • STEP 2: Assessing FAE
    CENTRAL PUPIL

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    The "Carefully Decollimated Primary (CDP)" protocol was pioneered by Vic Menard
    Using the central pupil only:

  • Intentionally de-collimate the primary mirror by slightly adjusting one of the 3 cell collimation knobs until reflections "1" and "2" are sufficiently separated to clearly see "P" and "3"
  • OFFSET PUPIL

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    STEP 3: Eliminating FAE by adjusting the secondary mirror:
    CENTRAL PUPIL

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    Using the central pupil only:

    Adjust only the secondary mirror until reflections "P" and "3" stack forming a prefect hexagram -- an indication of FAE elimination.

    OFFSET PUPIL

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    Stacking reflections "P" and "3" via the central pupil based on CDP eliminates FAE
    STEP 4: Eliminating PAE by adjusting the primary mirror:
  • Remove the INFINITY XLKTM autocollimator and replace it with the BLACKCAT XLTM Cheshire (or similar PAE alignment tool).

  • Adjust only the primary mirror until Reflection "P" is perfectly centered in the cheshire ring.
  • CHESHIRE VIEW

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    Centering reflection "P" using the Cheshire (or similar PAE alignment tool) eliminates PAE
    STEP 5: Checking for residual errors:
    CENTRAL PUPIL

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  • Re-insert the INFINITY XLKTM and check reflections via both pupils.

  • If your see residual background ghosts via the CENTRAL PUPIL and/or imperfect hexagram via the OFFSET PUPIL then you have residual axial alignment errors.
  • OFFSET PUPIL

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    STEP 6: Correcting potential residual errors:
    CENTRAL PUPIL

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  • Repeat the CDP (step2) with more precision by ensuring reflections "P" and "3" form a perfect hexagram in the CENTRAL pupil and redo steps 3 - 5.

  • After carefully repeating steps 2 - 5, ensure only reflection "P" is visible in the CENTRAL pupil and perfect hexagrams appear in the OFFSET pupil.
  • OFFSET PUPIL

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    Re-check for PAE elimination using the BLACKCAT XLTM Cheshire (or similar PAE alignment tool).

    STEP 7: If errors still persist, try this iterative adjustment approach:
  • Using the CENTRAL pupil, eliminate all inverted background ghost reflections with only "P" remaining by only adjusting THE PRIMARY MIRROR.

  • Using the OFFSET pupil stack reflections "P" and "2" to form a perfect hexagram by only adjusting the THE SECONDARY MIRROR.

  • Iterate back and forth betweeen adjustments of the two mirrors as necessary; usually 4 or less iterations is required.
  • Successful Axial Convergence and What it Means!
    If "all" tools simultaneously yield "textbook" visual queues, optical axes convergence has been accomplished. With sustainment of these adjustment settings, you can be confident that your scope will perform to its maximum image-detail-delivering potential that atmospheric "seeing" will allow.