Which CATSEYETM Tools Do You Need?
(REVISED 7/26/07)

  • If you only have a 1.25" diameter focuser, then you are limited to the 1.25" CATSEYETM Cheshire options. CATSEYETM does not currently make 1.25" sight tubes or 1.25" autocollimators. For small mass-produced commercial scopes (such as Tasco brand), there is a .965 MINICATTMCheshire.

  • If your Secondary mirror minor axis is smaller than 1.759", the 2" CATSEYETM sight tubes are probably inappropriate; otherwise, a 2" sight tube is a must for centered placement of the Secondary under the focuser and achieving the desired circular presentation to the eye.

  • Regardless of f-ratio, I recommend a complete "comprehensive" set of tools for all collimation functionality - that means a "sight tube", "Cheshire" and "autocollimator". That being said, if your scope is f/6 or slower and your budget is tight, then defer purchasing an autocollimator. Even though theoretical performance tolerance constraints suggest that the resolution capability of the autocollimator is not useful on "slow" scopes, I always use an autocollimator on my 8" f/6 so there's never any doubt that I have achieved axial convergence for maximum scope performance.

  • If you already have a "Barlowed" Laser, it has the same functionality as the Cheshire, so you will only need a sight tube and an autocollimator to round out your needs for complete collimation functionality.

  • If you like the idea of being able to assess both Primary tilt and Secondary presentation/placement under the focuser simultaneously, then the "dual function" TELECATTM Sight tube is the way to go. Even though there is some redundancy in Cheshire functionality with the BLACKCATTM and the TELECATTM included in the PROTM kits, many folks get both for the convenient smaller "pocket" size of the BLACKCATTM in the field and its brighter visibility performance at night.


  • If your Primary Mirror diameter is 15" of less, the 15" Max. Kits and template is for you; otherwise, you'll need the 32" max. size template. I now offer the 15" Max. templates with special 7.75" & 9.75" diameter registration circles for the odd-size "GSO" mirrors found in "Zhumell" scopes and others. Please let me know if you own one of these at the time of order. If you have a need for a Primary template larger than 32", e-mail me for "custom" template work.

  • Choice of spot color is merely a matter of personal preference. I prefer and recommend "Red" for the center spot due to it's nice contrast in color to the "reflective white" ring reflection of the CATSEYETM Cheshire ring. May folks prefer the "white" as touted by Vic Menard for it's reported higher visibility at night in the autocollimator (especially for longer focal length scopes where the spot is illuminated from the front. The new "Reflective White" spots are made from the same media as the Cheshire reflective ring are becoming quite popular as well.

  • "Solid" spots work just fine with all CATSEYETM tools. The "hole" perforation option for spots is primarily for folks who choose to use Lasers in their protocol; The hole size should be slightly larger than the laser beam spot diameter at the Primary mirror. If you are using a "Barlowed" Laser, the 1/4" size has been found to useful as it reportedly provides a symmetrical bright annulus ring around the return screen hole when Primary axial collimation is achieved. Additionally with the hole in the center spot, the collimation tool eyepiece "pupil" of the Cheshire and the Autocollimator can be seen inside the hole reflection as in indicator of having achieved excellent axial collimation. The most popular perforation size in the small spots is 1/8" and in the large spot, 3/16".