CATSEYETM 2" Autocollimators

The CATSEYE Collimation web site has been changed to a "Frames" format. If you do not see a split Frame to the left, click: Here

The World's First and Foremost Precision 2" Autocollimators!


2-Inch INFINITY(TM) II Autocollimator
Click for a Closeup


All New 2" 2-Pupil INFINITY XLKP Autocollimator
Click for a Closeup

* Buy One Now! * Attention XLTM & XLKTM Owners! You can have your unit refurbished and upgraded to the new XLKPTM configuration for $45 + S&H. Contact me at: Jim Fly
These are the most discriminating axial alignment assesment tools available ...
For a comprehensive tutorial on AC funtionality, an excellent read is:

"Concise thread about autocollimators+improvements"
by Jason Khadder, 12/31/2009

To meet the demand for the more critical alignment needed in todays' big, fast Newts, CATSEYETM 2" autocollimators have been carefully engineered and assembled to achieve a new benchmark in precision and visual clarity. In a few short years since the introduction of the first INFINITYTM autocollimator and subsequent leap forward with the XLKTM 2-pupil model, the CATSEYETM line of autocollimators are recognized as the definitive "gold standard" by performance-minded astronomers world wide.

While viewing with the 2" INFINITY XLPTM or central pupil of the XLKPTM, 4 images of the reflective triangle are usually seen. Convergence of these multiple images, concurrent with the proper Cheshire view, validates precision alignment of the Primary and focuser axes.

Click Each Image For a Closer View.
If Animations stall, refresh your browser.

Primary Tilt Animation Secondary Tilt/Rotation Animation
Telescope Animation Frames Modeled & Rendered with POV-Ray
2" INFINITY(TM) displaying 4 triangle center-spot images
Click for a Closeup

INFINITYTMAutocollimators Exclusive Features
  • A CATSEYE-exclusive "first-Surface" Mirror that incorporates:
    • Premium optically-flat glass.
    • Guaranteed internal orthoganal mirror registration.
    • SiO2 coated aluminum.
  • Generous 1.625" Aperture for faster off-axis "ghost" image discovery.
  • 1.5" barrel length for maximum drawtube-axis alignment.
  • Precision-Machined "Black" Delrin Eyepiece and 6061-T6 Aluminum "Honed" barrel.

Inherent in the optical design of an astrograph, the Primary's native focal plane is positioned well above the focuser drawtube to facilitate image focus at the camera CCD chip. Consequently, for accurate axial-alignment funtionality using the autocollimator's signature reflections during collimation, a focuser "extension" accessory of appropriate length must be used to position the autocollimator mirror surface at or very near the focal plane. Presently, an extender of suitable length from 3rd-party sources is the recommended solution, but soon, a better mechanical option will be available from CATSEYE with the offering of extended-body configurations integral to the autocollimator itself. Stay tuned for pricing and availability.

The NEW INFINITY XLKPTM Autocollimator
Its predecessor voted #8 in the CN Top 10 Astro Gear of the Year 2010 Reader's Choice Poll

Click for a Closeup

2" INFINITY XLKP(TM), Offset Pupil View w/Perfect Collimation
Click for A Closup

The continued refinement of this amazing tool is the direct result of the "out of the box" thinking and analysis by Ghassan "Jason" Khadder on the Cloudy Nights Astronomy Forum. The "K" in the tool's name is a tribute to Jason's extrodinary insight in facilitating the conversion of his autocollimator modeling theory to reality.

The 2nd "offset" pupil of the INFINITY XLKPTM provides a unique "spit-pair" view of the 4 center spot reflections that facilitates additional axial-error resolution/correction after they have eluded viewing in the central pupil at close reflection convergence.

INFINITY XLKP Central and Offset Pupil Views

The conventional central pupil view on the left shows a single stack of multiple images that "appear" correct while the 2nd offset pupil view on the right reveals that incremental residual errors are actually still present in the axial alignment.

The new INFINITY XLKPTM surpasses the axial alignment capability of its XLKTM legacy with a 21% reduction in pupil diameter for even more axial-error resolution before the central-pupil images disappear during the iterative convergence collimation method.

Additionally, a new novel mirror manufacturing process produces a long-awaited improvement in the consistency and precision of mirror-hole circular definition and spacing to facilitate precision alignment with the tool's eyepiece pupils.

INFINITY "XLK" and "XLKP" Mirrors
Side-by-side look of a typical XLKTM mirror with irregular (approximately 0.125") pupils and the new XLKPTM mirror with "perfect-circle" 0.100 pupils.

* Buy It Now! * Attention XLTM & XLKTM Owners! You can have your unit refurbished and upgraded to the new XLKPTM configuration for $45 + S&H. Note: Legacy autocollimators (such as the "Type II") made prior to the introduction of the XLTM are not eligable for the upgrade; these can be easily identified by a 1-inch barrel length versus a 1-1/2" length for the XLTM and XLKTM. Contact me at: Jim Fly.
2.00" INFINITY "XLK" Pic - Oblique View
Click for a Closeup
2.00" INFINITY "XLK" Pic - Front View
Click for a Closeup
2.00" INFINITY "XLK" Pic - Top View
Click for a Closeup
For a Step-By-Step Pictorial of the INFINITY XLKTM Collimation Procedure:



When "perfect" collimation is "close at hand", 4 center-spot reflections can be seen in the INFINITYTM autocollimator and are the result of multiple reflective interactions between the 3 mirror components of Primary, Secondary and Autocollimator.

In these simulations below, both Primary and Focuser optical axes alignment errors are present resulting in the reflections being spread apart from their "perfect collimation" stacked position.

You might see something like this ....

Autocollimator View Showing 4 Spot Images

or perhaps this ...

Autocollimator View Showing 4 Spot Images

  • Reflection "P" is the "Primary" or "first" reflection and is the direct reflected image of the spot itself via the Diagonal mirror after 1 FL pass. Reflection "P" is what is visible "without" the autocollimator whereas images (#1, #2, & #3) are reflections of "P".

  • Reflection "1" is generated from reflection "P" after an additional reflection back from the A/C mirror, via the diagonal to be reflected off the Primary and back via the diagonal to the eye for a total of 3 FL passes from the original spot. It's sensitivity to Primary axis error is 4X and to Focuser axis error is 2X.

  • Reflection "2" (inverted) is generated from the "real" image response from the (parabolic) Primary mirror at its Center of Curvature (COC at 2 FL's away) from the spot reflection it sees in the Autocollimator mirror (which is 1 FL away). The trick here is that the autocollimator reflects (or "folds") the real image back onto the Primary surface where it is then seen via diagonal reflection by the eye (just like reflection "P") - it is a total of 5 FL passes from the origin.

    The reflection "2" sensitivity to both Primary and Focuser axes errors is 4X each. Total distance between reflections "1" and "2" is the vector sum of the primary mirror and focuser axial errors. When the other axial error has been removed, this distance is either 8X the primary mirror axial error or 6X the focuser axial error.

  • Reflection "3" (inverted) is a reflection of reflection "#2" following a path like that of reflection "#1" (generated from reflection P) for a total of 7 FL passes to the eye from the original spot. When the faintest reflection (#3) is in view, the distance from "P" to "3" represents a sensitivity to focuser axis error of 2X regardless of the Primary axis error.

    It is this unilateral sensitivity to the focuser axial error that allows us to use this reflection to "zero" the focuser axis with Vic Menard's "Carefully Decollimated Primary Mirror" protocol, leaving the primary mirror axial error, magnified 8X, visualized as the distance between reflections 1 and 2.

    The distance and direction between reflections "#2" and "#3" is always equal to that seen between "P" and "1" and between the two A/C pupil reflections; thus, these two spot reflection "pairs" will always be arranged with their centers forming 2 separate parallel lines that are also parallel to the A/C pupil reflections.

*** Many thanks to Vic Menard and Nils Olof Carlin for their insightful contributions and editing assistance ***
Read: Nils Olof Carlin's "The Autocollimator and its Reflections" updated July 2010
Read: Vic Menard's Autocollimator comments:
Click to see Vic's

INFINITY(TM) Image Sequence 3 Movie Clip (57 FRAMES)
Autocollimator Image