Farpoint Primary Mirror Center Marking Kit — Up to 12.5"

Product Overview

The Farpoint Primary Mirror Center Marking Kit marks the exact centre of a Newtonian or Dobsonian primary mirror — the reference that laser collimators, Cheshire eyepieces and autocollimators all align to. It contains a precision-cut acetate template sized for mirrors up to 12.5" in diameter, together with eight triangle-shaped centre-mark targets.

The triangles are the detail that matters. Their edges touch the boundary of the illuminated field seen through a Cheshire, so the mark reads as aligned or not aligned rather than as roughly centred — which is what removes the ambiguity a round dot leaves.

Who It's For

This is a good match if you own a Newtonian or Dobsonian reflector with an unmarked primary mirror, or one whose existing centre spot has lifted, faded, or was never placed accurately. It is the first step for anyone setting up a collimation routine, whether the end goal is a quick laser check before a visual session or a full laser-Cheshire-autocollimator pass before an imaging run. Mirror makers and anyone who has just had a mirror recoated will need it too, since recoating removes the old mark.

Key Features & Design

• Precision-cut acetate template: sized for primary mirrors up to 12.5" in diameter, so the centre is located geometrically rather than measured by eye.
• Eight triangle centre-mark targets: enough for the job and for the inevitable second attempt, plus spares for other scopes.
• Triangular geometry: the triangle's edges meet the outside of the illuminated field through a Cheshire, which converts a judgement call into a clear read.
• Works with every collimation tool: laser collimators, Cheshire eyepieces and autocollimators all reference the same mark.
• One-time job: once the mirror is marked, the mark lasts until the next recoat.

Why the Centre Mark Comes First

Collimation is the process of bringing the optical axis of the primary, the secondary and the focuser into agreement. Every tool that does it works by comparing something against the centre of the primary mirror — a laser puts its beam there and reads where the return lands, a Cheshire lines up reflected apertures around it, an autocollimator stacks reflections of it. Without a mark, none of them has a reference; the tools still produce a picture, but there is nothing in it to align to, so what looks like collimating is estimating.

Placement accuracy carries through the whole chain. An off-centre mark biases every subsequent adjustment by the same amount, and because the tools are all referencing it, none of them will contradict it — the error is consistent and therefore invisible. That is the reason for a cut template rather than a ruler: it locates the geometric centre of the mirror directly, and the triangle targets then make the resulting alignment readable through a Cheshire.

Recommended Uses

• Marking a new or unmarked primary: many reflectors ship with no centre spot at all.
• After a recoat: recoating strips the old mark, and the mirror needs a new one before it can be collimated.
• Replacing a poor or lifted mark: a spot that has peeled, faded or was placed by eye is worth redoing.
• Setting up a collimation routine: the step that has to happen before a laser or Cheshire is worth owning.
• ATM and mirror-making projects: a finished primary needs marking before first light.

Compatibility and Accessory Notes

• Mirror size: Newtonian and Dobsonian primary mirrors up to 12.5" in diameter.
• Larger mirrors: from 12" to 26", the Farpoint Primary Mirror Center Marking Kit LARGE is the correct template, and we stock it.
• Telescope types: reflectors only. SCTs, Maksutovs, refractors and other catadioptric designs do not use a primary centre mark.
• Works with: Farpoint laser collimators, Cheshire eyepieces and autocollimators, and the collimation tools of any other make — a centre mark is a universal reference.
• Already included with some kits: Farpoint's laser collimators and collimation kits ship with this standard template. This kit is the separate purchase if you bought a tool elsewhere, need a replacement, or have another mirror to mark.

Good to Know Before You Order

• Reflectors only. A primary centre mark is a Newtonian and Dobsonian technique. SCTs, Maksutovs and refractors collimate differently — tell us what you have and we will point you at the right approach.
• Check your mirror diameter. This template covers up to 12.5". At 12" to 26" the LARGE version is the one to order, and the two sizes overlap at 12" so a 12" mirror can use either.
• It marks the mirror; it does not collimate it. The mark is the reference a laser, Cheshire or autocollimator then aligns to, so it is the first purchase rather than the only one.
• The mirror comes out of the tube. Marking means removing and handling the primary, which is straightforward on most reflectors but is worth setting aside a clear, uncluttered table for.
• Take your time on placement. The mark is the reference for every future adjustment, so a careful few minutes here pays back over the life of the mirror.

Frequently Asked Questions

Is it difficult to set up?

No, but it is deliberate work rather than a quick job. The mirror comes out of the tube, the acetate template locates the centre, and a triangle target goes on that spot. The template does the hard part — finding the geometric centre — so what is left is careful placement. Eight targets are supplied, so a first attempt you are not happy with is not a problem. Farpoint also publishes preparation guides and downloadable collimation references if you would like to read the sequence through first.

Why does the centre mark matter?

Every collimation tool aligns against it. A laser reads where its beam returns relative to the mark, a Cheshire lines up reflected apertures around it, an autocollimator stacks reflections of it. Without a mark those tools have no reference, so the alignment is guesswork — and an inaccurately placed mark biases every adjustment by the same amount without ever contradicting itself.

Why triangles rather than a round dot?

Because a triangle gives you edges to read against. Its edges meet the outside of the illuminated field seen through a Cheshire, so you are matching straight lines to a boundary instead of judging whether a circle looks centred inside another circle.

What size mirror does this fit?

Primary mirrors up to 12.5" in diameter. For 12" to 26" mirrors, the LARGE template is the right one and we carry it.

Does the mark affect what I see through the telescope?

No. The centre of the primary sits in the shadow of the secondary mirror, so the marked area is already blocked from contributing to the image.

Do I need this if I bought a Farpoint laser or collimation kit?

Not usually — those ship with this standard template included. This is the separate purchase if you bought your collimation tools elsewhere, if you need a replacement, or if you have a second mirror to mark.

Bottom Line

In short: a precision-cut acetate template and eight triangle centre-mark targets for Newtonian and Dobsonian primary mirrors up to 12.5". It is the step that gives every other collimation tool something to align to, and it only has to be done once.