The Sky Rover 70 GPS is a serious little imaging system. Seventy millimeters of Super ED triplet optics delivering 420mm at f/6 and enough speed to grab deep-sky detail in reasonable exposure times. On-axis, the imaging performance is excellent. But like any fast refractor, the triplet's inherent field curvature means that stellar images tighten toward the center while softening toward the edges — a physics limitation that becomes obvious when you examine stars across an APS-C sensor. The SR70GPSFF 1× field flattener is designed to solve exactly that problem.
The flattener threads directly onto the 70 GPS's integrated CAA using the standard M54×0.75 connection. It maintains the native 420mm focal length and f/6 ratio — nothing about the scope's speed or working distance changes. What does change is that the curved focal plane becomes flat, matching the flat surface of your camera sensor. The result: sharp, round stars from the center of the frame to the corners. For a triplet this compact, adding the matched flattener transforms it from a capable grab-and-go refractor into a complete flat-field imaging platform.
Flattener, Not Reducer
This is a 1× flattener — it preserves the native focal length and focal ratio of the 70 GPS. You maintain the full 420mm f/6, unchanged. The field of view, exposure times, and star scale all stay the same as the uncorrected scope — you gain only what matters for imaging: perfectly flat, corrected stars across the entire sensor instead of ones that degrade toward the edges.
Direct CAA Threading
The 70 GPS's integrated CAA features M54×0.75 female threads. The SR70GPSFF threads directly onto those threads — no adapters, no spacers, just a clean one-piece connection between scope and flattener. This integrated design gives you the mechanical simplicity and optical alignment you need for reliable imaging performance.
Camera Connection
The camera side of the flattener connects to your imaging equipment via standard 48mm T-threads. DSLR and mirrorless cameras connect via a T-ring for your specific camera mount (sold separately). Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring.
What's Included
- Sky Rover SR70GPSFF 1× field flattener for 70 GPS
Features
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1× field flattener — no focal reduction. Maintains the 70 GPS's native 420mm f/6. Corrects field curvature for flat, sharp stars across the sensor without changing the imaging characteristics or working distance.
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Dedicated design for the Sky Rover 70 GPS triplet. Matched to the 70 GPS's optical prescription. Purpose-designed for this scope's specific field curvature profile — not a universal accessory.
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Direct M54×0.75 threading onto CAA. The flattener threads directly onto the 70 GPS's camera angle adjuster. No intermediate adapters — just a solid mechanical connection that maintains optical alignment.
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Excellent APS-C format imaging performance. Delivers flat, well-corrected stars across APS-C sensors at the native 420mm f/6. Transforms a fast, portable triplet into a complete imaging system.
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Standard camera-side threading. DSLR and mirrorless bodies connect via a T-ring (sold separately); dedicated CMOS/CCD astronomy cameras attach directly — 48mm T-threads are standard on most.
Frequently Asked Questions
Do I need this flattener for visual observing?
No. Field curvature only affects imaging — your eye naturally accommodates the curved focal plane during visual observation. The flattener is specifically for camera work.
How does this flattener differ from Sky Rover's GPA flatteners?
The GPS flatteners thread directly onto the integrated CAA's M54 output, giving you a dedicated, mechanically optimized system. GPA flatteners use different connection threads. Each Sky Rover model has a matched flattener designed for its specific optical and mechanical design.
Will this fit the 60 GPS or 80 GPS?
No. The SR70GPSFF is designed specifically for the 70 GPS's 420mm focal length, M54×0.75 CAA threading, and optical prescription. The 60 GPS and 80 GPS each have their own matched flatteners.
What cameras does this work with?
DSLR and mirrorless cameras connect via a T-ring for your specific camera mount (sold separately). Dedicated CMOS and CCD astronomy cameras typically have 48mm T-threads built in and connect directly without a T-ring.
What's the back focus distance?
It is the industry standard 55mm. The critical measurement is the distance from the flattener's rear threads to the focal plane — ensure adequate spacing for your camera's back-focus design.
Final Thoughts
The 70 GPS is already an excellent compact imaging refractor. Adding the SR70GPSFF flattener completes the system. You get the triplet's speed and light-gathering, the integrated CAA's precision, and now a flat focal plane matched to your sensor. That's a professional-quality imaging platform in a scope light and portable enough to grab for an evening's work or a weekend at a dark site. It's what the system was designed to do.
