Focal Length Reducer Skywatcher 0.77x for Evostar 150DX ED telescope

The Skywatcher 0.77x focal length reducer for the Evostar 150DX ED telescope is an optical accessory that reduces the effective focal length of the specified Evostar 150DX ED by a factor of 0.77. By shortening the focal length it widens the field of view and effectively produces a faster focal ratio, making the telescope more suitable for wide-field visual observing and shorter-exposure astrophotography with compatible imaging equipment. The reducer is designed for straightforward integration into the Evostar 150DX ED optical train without altering the main optical elements of the telescope.

Advantages

The focal length reducer increases the usable field of view and lowers the effective focal ratio, enabling shorter exposure times for deep-sky imaging and easier framing of extended objects. It preserves the main optical configuration of the Evostar 150DX ED while providing a simple mechanical interface for installation. The accessory is intended to maintain image quality across the reduced focal plane when used with the matching telescope model and suitable cameras or eyepieces.

Suitable for

• Wide-field astrophotography of nebulae, star fields and large galaxies
• Visual observations requiring a wider apparent field with the Evostar 150DX ED
• Reducing exposure time demands for planetary and deep-sky imaging with compatible cameras
• Users who want a simpler setup for framing extended targets without changing primary optics

Key specifications

• Reduction factor: 0.77x (reduces telescope effective focal length to 77% of original)
• Designed optical compatibility: Evostar 150DX ED refractor
• Effect on focal ratio: produces a faster effective focal ratio suited for shorter exposures
• Mechanical interface: fits into the optical train of the specified telescope model for straightforward installation
• Intended use: visual wide-field observing and astrophotography with cameras or eyepieces compatible with the Evostar 150DX ED

How to use

Install the focal length reducer into the Evostar 150DX ED optical path according to the telescope and reducer mechanical interfaces, ensuring secure and correct spacing between the reducer and camera sensor or eyepiece to achieve proper focus. After installation, adjust focus and perform framing and focusing routines with the chosen camera or eyepiece. When imaging, verify backfocus distance and perform test exposures to confirm focus across the field; minor adjustments to camera spacing may be required to optimize field flatness and edge sharpness.

Usage recommendations

Use the reducer with the Evostar 150DX ED only and check camera backfocus requirements before imaging. For best results in astrophotography, pair the reducer with a camera whose sensor size matches the intended field of view and perform flat-field calibration to compensate for any residual vignetting. When switching between visual and imaging setups, confirm mechanical spacing to maintain correct focus and avoid contact between accessories.