Farpoint Primary Mirror Center Marking Kit — Up to 12.5"

Product Overview

The Farpoint Primary Mirror Center Marking Kit puts an accurate centre mark on a Newtonian or Dobsonian primary mirror — the reference point every collimation tool reads against, and the step that comes before collimation can begin. It covers primary mirrors up to 12.5″ in diameter.

The kit holds a precision-cut acetate template for locating the exact centre of the mirror and eight triangle centre-mark targets. The triangles are sized so their edges touch the outside of the illuminated field when viewed through a Cheshire, which removes the guesswork from judging whether the mark is centred in the field.

Who It's For

This is a good match if you have an unmarked primary mirror, or if the existing mark has worn, lifted or been lost to a mirror cleaning, and you already own the collimation tools that read it. It also suits the case where you have collected a laser collimator and a Cheshire separately rather than as a kit, and the marking components were not part of those purchases. With eight targets supplied, there is stock for more than one mirror or for replacing a mark later.

Key Features & Design

• Precision-cut acetate template: locates the exact centre of the primary mirror rather than approximating it by eye or by rule.
• Eight triangle centre-mark targets: enough for several mirrors, or for replacing a mark that has worn.
• Triangle geometry matched to the Cheshire field: the triangle edges touch the outside of the illuminated field seen through a Cheshire, so centring is read directly instead of estimated.
• Covers mirrors up to 12.5″: the standard-size template, which fits most Newtonians and mid-size Dobsonians.
• Works with every collimation method: laser collimators, Cheshire eyepieces and autocollimators all read the same mark.
• Made in the USA: by Farpoint, alongside their collimation tools.

Optical Design

A centre mark is not a decoration on the mirror; it is the datum that turns collimation from an estimate into a measurement. A laser collimator aligns by putting its returned spot back on that mark, and a Cheshire aligns by reading the mark's concentricity within an illuminated field. Where the mark is off-centre, both tools align the telescope faithfully to the wrong point, and neither gives any sign that they have.

The triangle targets in this kit are cut to a specific size for that reason. Through a Cheshire, the primary presents as an illuminated field with a defined outer boundary, and the triangle's edges are dimensioned to touch that boundary when the mark sits centred. The reading therefore becomes a yes-or-no comparison between two edges rather than a judgement of how close a dot is to the middle of a bright circle, which is a much finer thing for the eye to resolve. The acetate template handles the other half of the problem, locating the mirror's true geometric centre so the target lands where it belongs.

Recommended Uses

• Marking a new or newly coated primary: a freshly aluminised mirror comes back without a mark.
• Replacing a worn mark: spots lift over years of cleaning and handling.
• Preparing a mirror-making or upgrade project: a new primary in an existing tube needs its own reference point.
• Completing a set of separately bought tools: a laser and a Cheshire acquired on their own have nothing to align to until the mirror is marked.
• Keeping spare targets on hand: eight are supplied against a future re-mark.

Compatibility and Accessory Notes

• Mirror size: primary mirrors up to 12.5″ in diameter.
• Larger mirrors: the Farpoint LARGE centre-marking kit covers 12″ to 26″ primaries, and we stock it.
• Telescope types: Newtonian and Dobsonian reflectors. Refractors, catadioptric and SCT designs collimate by other means and use no centre mark.
• Tool compatibility: the mark reads the same to a laser collimator, a Cheshire eyepiece and an autocollimator, regardless of brand.
• Already included in the kits: the Farpoint 1.25″ and 2″ Collimation Kits and the Super Collimation Kit each ship with these marking components.
• Tell us your scope and we will confirm the template size for your mirror.

Good to Know Before You Order

• This is the standard template, for mirrors up to 12.5″. A primary from 12″ to 26″ takes the LARGE kit, which we also stock.
• The kit marks the mirror; it does not collimate it. A laser collimator, Cheshire eyepiece or autocollimator does the aligning, reading against the mark this kit places.
• Marking is a one-time job on a mirror in hand. The primary comes out of the tube for it, and the mark then lasts as long as the coating does.
• The triangle targets sit at the centre of the primary. That area lies in the shadow of the secondary mirror, so the target intercepts no light that reaches the eyepiece.
• Eight targets are supplied. That covers several mirrors or several re-marks over the years.
• It applies to reflectors. For a refractor, SCT or Maksutov, tell us what you have and we will point you at the right collimation approach.

Frequently Asked Questions

Is it difficult to install?

No. The primary comes out of its cell, the acetate template locates the mirror's centre, and a triangle target goes on at that point. It is a one-time job and the mark then lasts the life of the coating.

Does a centre mark affect the image?

No. The target sits at the geometric centre of the primary, which is inside the shadow the secondary mirror already casts, so it blocks no light that would otherwise reach the eyepiece.

Why a triangle rather than a ring or a dot?

The triangle's edges are cut to touch the outside of the illuminated field seen through a Cheshire. That turns centring into a comparison of two edges, which the eye judges far more finely than the position of a dot within a bright circle.

My mirror is 16″. Will this kit cover it?

The template here is cut for mirrors up to 12.5″. A 16″ primary takes the Farpoint LARGE centre-marking kit, which covers 12″ to 26″.

Do I need this if I am buying a Farpoint collimation kit?

The 1.25″ and 2″ Collimation Kits and the Super Collimation Kit already include the marking template and triangle spots. This standalone kit is for replacing used targets or for marking a mirror when the collimation tools were bought separately.

Can it be used on an SCT or a refractor?

Those designs collimate by other methods and carry no centre mark, so the kit has no role there. Tell us what you have and we will point you at the right approach.

Bottom Line

In short: a precision-cut acetate template and eight triangle centre-mark targets for Newtonian and Dobsonian primaries up to 12.5″, sized so the triangle edges meet the illuminated field in a Cheshire. It sets the reference point that every laser, Cheshire and autocollimator reads against.