Sharpstar Z4 100mm f/5.5 Sextuplet APO Astrograph

Product Overview

The Sharpstar Z4 is a 100mm f/5.5 sextuplet APO astrograph designed for serious deep-sky imaging. Its 550mm focal length, integrated flat-field optical design, and 36mm image circle make it a strong match for APS-C astronomy cameras and DSLR/mirrorless imaging setups.

Unlike many refractors that require a separate flattener and careful spacing calculation, the Z4 is built as a self-flattened astrograph. For imagers, that means a cleaner camera train and fewer backfocus complications.

Who Is This Product Best For?

The Z4 is best for intermediate and advanced astrophotographers who want a dedicated wide-to-medium-field imaging refractor with premium mechanical support. It is ideal for deep-sky imagers using APS-C sensors, cooled astronomy cameras, filter wheels, and guiding setups.

Why Choose This Product?

• 100mm aperture and 550mm focal length for nebulae, galaxies, and larger deep-sky targets.
• Sextuplet fully air-spaced APO design with two ED glass elements.
• Integrated flat-field design with no separate flattener required.
• 36mm image circle suitable for APS-C imaging systems.
• Large 3.4-inch rack-and-pinion focuser with 1:10 fine adjustment.
• 360-degree rotator for framing targets without disturbing focus.
• Includes M86, M68, M54, and M48 adapter options.
• M48 adapter includes internal 2-inch filter thread.
• 300mm Vixen-style dovetail and multifunction handle for easier setup and balancing.

Recommended Uses

• Deep-sky astrophotography with APS-C cameras.
• Nebula, galaxy, star-field, and broadband imaging.
• Portable or semi-permanent imaging rigs.
• Dedicated astrograph setups using filter wheels, OAGs, and cooled cameras.

Compatibility and Accessory Notes

The Z4 includes a rear M48×0.75 male thread and adapter path through M86×1, M68×1, M54×0.75, and M48×0.75. The M48 adapter supports 2-inch filters. It is designed for imaging and works best on a suitable equatorial or strain-wave mount capable of carrying the 4.3kg OTA plus camera, guider, filter wheel, and accessories.

Important Limitations

• Best treated as a dedicated imaging astrograph rather than a beginner visual telescope.
• Designed around a 36mm image circle, so full-frame cameras may show limitations at the corners.
• A suitable mount, guide system, camera spacing setup, and imaging accessories are still required.
• Although the optical system is self-flattened, mechanical spacing and tilt control still matter for best results.

Frequently Asked Questions

Is the Sharpstar Z4 good for beginners?

It is not the first telescope we would normally recommend for a beginner. It is better suited to imagers who already understand polar alignment, guiding, camera spacing, and image calibration.

What is the Z4 best used for?

The Z4 is best used for deep-sky astrophotography with APS-C cameras, especially targets that benefit from a 550mm focal length.

Does it need a separate flattener?

No. The Z4 is designed as a self-flattened astrograph and does not require a separate field flattener.

Can it be used visually?

It is primarily an imaging astrograph. Visual use may be possible depending on adapters, but this is not its main purpose.

What cameras are best matched to it?

APS-C cooled astronomy cameras and APS-C DSLR/mirrorless cameras are the best match for the 36mm image circle.

Our Recommendation

Ontario Telescope recommends the Sharpstar Z4 for astrophotographers who want a compact but serious 100mm imaging astrograph with integrated field correction. Choose it when you want a cleaner imaging train and do not want to add a separate flattener. Do not choose it as a first visual telescope or if your main camera is full-frame and you need fully corrected corners across the entire sensor.