SVBONY SV161 1.25″ Double Helical Focuser (M42 / T2)

Product Overview

The SVBONY SV161 is a 1.25″ double helical focuser with M42 x 0.75 (T2) threads on both ends: female on the telescope side, male on the camera side. It provides 10 mm of drawtube travel with 0.05 mm adjustment accuracy, ranging from 43 mm to 53 mm in height, and the drawtube does not rotate as you focus. A clamp screw locks the focus position. It is CNC-machined aerospace aluminium alloy with a frosted anodised finish and weighs 100 g.

Who It's For

This is a good match if you are building or upgrading a guide scope, finder or small lens-based imaging setup and want fine, non-rotating focus for a guide camera or eyepiece, or if a telescope or telephoto lens has a coarse focuser that is hard to set precisely.

Key Features & Design

• Double helical focusing: 10 mm of travel at 0.05 mm adjustment accuracy.
• Non-rotating drawtube: the camera or eyepiece, and the guide star field, keep their orientation while you focus.
• M42 x 0.75 both ends: female telescope side, male camera side, so T2 accessories attach without extra adapters.
• Clamp screw: locks focus for long sessions, with an anti-skid brass screw.
• CNC aerospace aluminium: frosted, anodised housing.

Recommended Uses

• Guide scopes: SVBONY designs it for guide scopes such as its SV165 mini guide scope.
• Finder and guide-camera focusing with a non-rotating field.
• Telephoto lenses and small telescopes with sluggish focusing, used with a camera adapter.

Compatibility and Accessory Notes

• Telescope side: M42 x 0.75 female.
• Camera side: M42 x 0.75 male, for T2 camera adapters such as Canon or Nikon T-rings (sold separately).
• 1.25″ inner diameter for 1.25″ accessories.
• Height: 43 mm minimum, 53 mm maximum, which is the figure to add to a backfocus calculation.

What's in the Box

• 1 x 1.25″ double helical focuser with female T2 thread
• 3 x M3 screws

Good to Know Before You Order

• Travel: 10 mm is designed for fine focusing; the optic needs to be close to focus already.
• Camera adapters sold separately. If you are unsure what your setup needs, send us your guide scope and camera and we will work it out with you.

Frequently Asked Questions

Is it difficult to set up?

No. It threads onto an M42 telescope or guide-scope connection, and the camera or adapter threads onto the top.

Does the camera rotate when I focus?

No. The drawtube keeps a fixed orientation.

Can I lock the focus?

Yes. A clamp screw holds the focus position.

Bottom Line

In short: a 100 g, M42-threaded double helical focuser with 10 mm of non-rotating travel and 0.05 mm accuracy for guide scopes, finders and small imaging optics.