SVBONY SV198 50mm f/4.1 Mini Guide Scope with Dual Helical Focuser

Product Overview

The SVBONY SV198 is a 50 mm f/4.1 achromatic mini guide scope with a 206.6 mm focal length, a dual helical focuser with 12 mm of travel, and a Vixen-standard base. The eyepiece end takes 1.25″ eyepieces or guide cameras and also carries a T2 thread. A 45 mm T2 extension tube is included so insert-style guide cameras can reach focus. The aluminium tube is 55.5 mm in diameter and 234 mm long, and the scope weighs 557 g.

Who It's For

This is a good match if you autoguide a deep-sky imaging rig and want more aperture than a 30 mm mini guider without the weight of a 60 mm scope, or if you want a finder that can double as a guide scope.

Key Features & Design

• 50 mm, f/4.1 achromat: 2-element / 1-group objective, fully multi-coated, with blackened lens edges.
• 206.6 mm focal length: a longer guiding focal length than a 30 mm or 120 mm mini guider.
• Dual helical + telescopic focuser: 12 mm helical travel with a millimetre scale, so you can return to a known focus position.
• 1.25″ and T2 connection: accepts 1.25″ eyepieces and cameras, or threads on via T2.
• Reduced internal reflections: SVBONY's internal design limits stray light for better contrast.
• Vixen-standard base for direct mounting to a Vixen-style shoe.

Optical Design

The SV198 uses a two-element, single-group achromatic objective at f/4.1. For guiding, the relevant figures are aperture and focal length: 50 mm gathers more light than a 30 mm guider, so more guide stars are available in a given field, and 206.6 mm gives finer guiding resolution with a small-pixel guide camera. The millimetre scale on the helical focuser lets you note and return to your guide camera's focus position.

Recommended Uses

• Autoguiding deep-sky imaging rigs with a 1.25″ guide camera such as the SVBONY SV905C or SV305, which SVBONY names as examples.
• Finder use with a standard 1.25″ eyepiece when the extension tube is removed.
• Plate-solving or polar-alignment camera on a portable setup.

Compatibility and Accessory Notes

• Guide cameras: insert 1.25″ guide cameras use the included 45 mm extension tube (M42×0.75 male and female threads), which brings them to focus and, per SVBONY, reduces vignetting.
• Eyepieces: without the extension tube, standard 1.25″ eyepieces reach focus.
• Mounting: Vixen-standard base; dew cap diameter 58 mm.
• Handle bar: SVBONY shows the SV198 seated on the SV211 handle bar, which has an integrated saddle for a guide or finder scope.

If you are pairing it with a different guide camera, send us the camera model and we will confirm the focus position with you.

What's in the Box

• SV198 50 mm f/4.1 mini guide scope
• Lens bracket
• 45 mm T2 extension tube
• 1.25″ dust plug
• Silicone objective lens cover

Good to Know Before You Order

• Guide camera sold separately.
• Backfocus: SVBONY does not publish a backfocus figure; the included 45 mm extension is what brings insert-style guide cameras to focus.
• Weight 557 g: worth including in your mount payload alongside the main telescope and camera.

Frequently Asked Questions

Is it difficult to set up?

No. Mount it on a Vixen-style shoe, insert the guide camera with the 45 mm extension, focus on a bright star with the helical focuser and lock it.

How does it compare with the SV106 and SV165?

SVBONY's comparison lists the SV198 at 50 mm and 206.6 mm (557 g), the SV106 at 60 mm and 240 mm (790 g), and the SV165 at 30 mm and 120 mm (342 g).

Can I use it as a finder?

Yes. Remove the extension tube and use a 1.25″ eyepiece.

Which guide cameras fit?

1.25″ insert-style cameras such as the SVBONY SV905C and SV305, or cameras with a T2 thread.

Bottom Line

In short: a 50 mm f/4.1 guide scope with a 206.6 mm focal length, a scaled dual helical focuser and both 1.25″ and T2 connections, supplied with the 45 mm extension that guide cameras need to reach focus.