GS Series PAPO Apochromatic Guide Scopes
Professional-grade guide scopes designed for precision astrophotography.
Available in two focal length models to match your imaging system:
- GS-250AR / GS-250AC – 250mm focal length | 50mm aperture | f/5
- GS-350AR / GS-350AC – 350mm focal length | 58mm aperture | f/6
Key Benefits: PAPO Precision • High Stability Guiding • Superior Star Quality
Overview
The GS Series uses a proprietary three-element PAPO (Planar Apochromatic with integrated field flattener) optical configuration featuring an ED glass element. This reduces chromatic aberration and preserves accurate star colour. Precision-machined internal threads and broadband multi-layer AR coatings greatly improve contrast and brighten star images, resulting in highly accurate guide corrections for stable deep-sky imaging.
Designed around a flat, corrected 1-inch image circle, the GS Series supports cameras up to the Sony IMX533 sensor size. This makes it suitable not only for guiding but also for visual use, star-hopping, and entry-level deep-sky astrophotography.
Key Features
1. PAPO Apochromatic Optical System
ED glass and integrated field correction deliver sharp, pinpoint stars with minimal chromatic aberration. Suitable for guiding, visual use, or wide-field DSO imaging.
GS-250 Spot Diagram
GS-350 Spot Diagram
2. Anti-Reflection Threading & High Transmission Coatings
Multi-layer broadband AR coatings increase light transmission, while internal anti-reflection baffling suppresses glare and improves contrast.
3. CNC-Machined, Lightweight Metal Construction
Precision CNC machining provides structural rigidity with low weight. The fine matte anodised finish offers durability and a premium tactile feel.
4. Modular Optical Tube Design
Includes a universal M48 extension tube for configuring optical path length for both visual and imaging use.
Note: The GS-250 may not reach focus when using a diagonal.
5. Two Focuser Options
- AC Version: Rackless focuser for smooth manual focusing and lightweight camera setups.
- AR Version: Rack-and-pinion focuser compatible with ToupTek AAF electronic focusers and heavier camera loads.
Compatibility
- Supports guide & planetary cameras up to 1" sensor size
- 1.25" eyepiece interface + external M42×0.75 threads
- Multiple M5 mounting points for accessories
- Dovetail base supports tripods & equatorial mounts
- Modular M48 extension tube for visual & imaging setups
What's in the Box
FAQ
Which guide cameras work best with the GS Series?
Any guide camera or planetary camera with a 1" or smaller sensor is ideal. Popular choices include ToupTek, ZWO ASI120/220/290, Player One guiding cameras, and IMX533 sensors for wide-field imaging.
Can this be used for visual observing?
Yes — simply attach a 1.25" eyepiece. The GS Series functions as a compact wide-field finder scope.