SVBONY SV222 1.25″ 45° Correct-Image Prism Diagonal (Metal, FMC)

Product Overview

The SVBONY SV222 45° is a 1.25″ correct-image prism diagonal that gives an erect, non-reversed view at a 45° angle. The BK7 prism is fully multi-coated and phase-coated for contrast, the body is CNC-machined aluminium with black anodizing, and the interior is baffled and matte-blackened against stray light. Clear aperture is 16 mm, optical length about 93 mm, the nosepiece carries an M28.5 x 0.6 filter thread, and the diagonal weighs 167 g (5.87 oz).

Who It's For

This is a good match if you use a refractor for both terrestrial and astronomical viewing and want a metal-bodied correct-image diagonal with phase-coated optics, for example for birding by day and lunar or planetary observing at night.

Key Features & Design

• 45° upright BK7 prism: correct daytime orientation, right-side-up and non-reversed.
• Fully multi-coated plus phase coating: SVBONY specifies high contrast and a bright, clear image.
• CNC aluminium body: black anodized for durability.
• Baffled and matte interior: blackened, baffled light path to suppress internal reflections.
• Brass pressure ring and large chrome thumbscrew: holds the eyepiece firmly without marking it, and is easy to operate with gloves.

Optical Design

A correct-image diagonal uses a roof-type prism to invert and revert the image in the same element that turns the light path, so what you see matches the scene in front of you. Phase coatings on the prism's roof faces counter the phase shift that otherwise softens contrast in roof prisms. The internal baffle and matting keep off-axis light out of the eyepiece.

Recommended Uses

• Terrestrial viewing and birding with a refractor.
• Planetary and deep-sky visual observing, which SVBONY lists for refractors.
• Outreach, where an upright, correctly oriented image helps new observers.

Compatibility and Accessory Notes

SVBONY illustrates the SV222 connected to a telescope, a Barlow lens, an eyepiece and 1.25″ filters:

• Telescope side: 1.25″ barrel with an internal M28.5 x 0.6 thread.
• Barlow lens: a 1.25″ Barlow fits the eyepiece holder.
• Eyepieces: any 1.25″ eyepiece, held by screw clamp and brass ring.
• Filters: standard 1.25″ filters thread into the nosepiece.

What's in the Box

• 1 x SV222 1.25″ 45° metal correct-image prism diagonal
• M4 screws
• 1 x dust cap
• 1 x dust plug

Good to Know Before You Order

• 16 mm clear aperture: as published by SVBONY. If you want to check it against a particular wide-field eyepiece, send us the model and we will look at it with you.
• Refractor use: SVBONY lists it for refractors.

Frequently Asked Questions

Is it difficult to set up?

No. It slides into the 1.25″ focuser and the eyepiece locks in with the large thumbscrew.

How is it different from the SV221 45°?

The SV222 has a CNC aluminium body, a BK7 prism with full multi-coating plus phase coating, and an internally baffled light path; the SV221 has an ABS housing with aluminium barrels and a larger 19 mm aperture.

Can I use filters with it?

Yes, 1.25″ filters thread into the M28.5 x 0.6 nosepiece.

Bottom Line

In short: a metal-bodied 1.25″ 45° correct-image diagonal with a phase-coated BK7 prism and baffled interior for refractors used day and night.