SVBONY SV188P 1.25″ 90° Dielectric Mirror Diagonal

Product Overview

The SVBONY SV188P is a 1.25″ 90° star diagonal with a dielectric-coated mirror rated at 99% reflectivity. The aluminium-alloy body has a 1.25″ nosepiece with an M28.5 x 0.6 filter thread and a 1.25″ eyepiece clamp with a brass compression ring and brass thumbscrew. The mirror is 11 mm thick, and the diagonal weighs 125 g.

Who It's For

This is a good match if you observe through a refractor, Maksutov or SCT and want a comfortable viewing position for objects high in the sky, with a bright, high-reflectivity mirror in the light path.

Key Features & Design

• 99% reflectivity dielectric mirror: bright images with minimal light loss.
• 90° viewing angle: comfortable posture when the telescope points high.
• Brass compression ring and thumbscrew: holds the eyepiece securely without scratching the barrel or letting it rotate.
• M28.5 x 0.6 filter thread on the nosepiece for standard 1.25″ filters.
• Aluminium alloy body with M4 set screws.

Recommended Uses

• Visual observing of the Moon, planets, double stars and deep-sky objects.
• Comfortable high-altitude viewing with refractors and catadioptric telescopes.

Compatibility and Accessory Notes

• Nosepiece: 1.25″ barrel, fits any 1.25″ focuser or visual back.
• Eyepiece side: 1.25″ clamp.
• Filters: M28.5 x 0.6 thread on the nosepiece.
• Maksutov and SCT use: these telescopes need a 1.25″ visual back. The SVBONY MK127 includes its SCT-to-1.25″ adapter, so the SV188P slides straight in.

Good to Know Before You Order

• Image orientation: like all mirror diagonals, the view is upright but reversed left to right, which is standard for astronomical observing.
• Size: this listing is the 1.25″ version. 2″ eyepieces need a 2″ diagonal.

Frequently Asked Questions

Is it difficult to set up?

No. Slide the nosepiece into the focuser or visual back, tighten the set screw, and insert a 1.25″ eyepiece into the brass compression ring.

Why a dielectric mirror?

A dielectric coating reflects 99% of visible light, more than a standard aluminized mirror, which gives a slightly brighter image.

Will it work on a Maksutov such as the MK127?

Yes, through the telescope's SCT-to-1.25″ adapter.

Bottom Line

In short: a 1.25″ 90° diagonal with a 99% reflectivity dielectric mirror and a brass compression clamp, for bright, comfortable visual observing.