Anneaux

Sizing and Choosing Tube Rings

Rings are specified by inner diameter and should match the tube closely. Too large and the felt compresses unevenly; too small and they will not close.

• Inner diameter, not aperture: An 80 mm refractor typically has a tube diameter around 90 mm, and dew shields are wider still. Measure the tube where the rings will sit.
• Hinged versus split rings: Hinged rings allow a tube to be dropped in without removing the top half, which is considerably easier in the dark with cold hands.
• Felt and liner material: A proper liner distributes clamping force and protects paint; a hard ring on a bare tube can dent thin aluminium.
• Top accessory holes: Rings with threaded top holes accept a short rail for a guide scope or finder, keeping accessories close to the optical axis and reducing flexure.
• Rotation for framing: Loosening rings to rotate the tube changes camera angle without breaking the imaging train, which preserves spacing.
• Ring spacing on the bar: Rings placed further apart resist flexure better; too close together and a long tube can pivot under load.

Why Choose David Astro for Tube Rings

Ring fit is a measurement problem, and a wrong measurement is an expensive return.

• Model-based sizing: Tell us the telescope model and we will look up the actual tube diameter rather than asking you to estimate it.
• Balance planning: We advise on ring spacing and dovetail length together, since rings positioned to balance a heavy camera can end up too close for good rigidity.
• Accessory mounting considered: If you intend to carry a guide scope, we recommend rings with usable top mounting rather than adding a bracket later.
• Authorized dealer: Genuine hardware with full manufacturer warranty, held in our Canadian warehouse.
• Ships from Canada: No duties or brokerage fees for Canadian buyers.

Tube Rings in Canada — Frequently Asked Questions

How do I measure for tube rings?

Measure the outer diameter of the tube itself at the point where the rings will clamp, not at the dew shield or the focuser end. If you can give us the telescope model we can usually confirm it directly.

Can rings be slightly oversized?

A few millimetres can be taken up with additional liner material, but a significant mismatch causes uneven clamping and can mark the tube. It is better to get the correct size.

How far apart should rings be?

As far as balance allows. Wider spacing resists flexure and rotation better. If a heavy camera forces the rings forward and close together, consider a longer dovetail instead.

Do I need rings if my telescope has a fixed dovetail?

Not necessarily, but rings add the ability to rotate the tube for framing and to mount accessories on top, which a fixed foot does not offer.

Need the right ring size?

Send us your telescope model and we will confirm the diameter. Canadian stock, fast domestic shipping.