The Sky Rover 155 GPS is the flagship of the Sky Rover lineup — a 155mm Super ED triplet with a 1240mm focal length at f/8. It features a redesigned CAA with a 3.7-inch clear aperture, built to match the optical precision of the scope itself. At 1240mm f/8, this is the serious deep-sky imaging scope — the one you reach for when imaging planetary nebulae, tight star clusters, distant galaxies, and the kind of high-magnification work that separates genuine imaging systems from grab-and-go equipment. But like all refractors, the 155 GPS has inherent field curvature. At the eyepiece, your eye adapts instantly. Behind a camera sensor — especially a full-frame one — it becomes visible: stars in the center are tight and round, while stars at the edges of the frame start to elongate. That’s the optical reality of refractor design — and it’s exactly what the SR155GPSFF 1× field flattener is designed to correct.
The flattener maintains the 155 GPS's native 1240mm focal length and f/8 ratio. It changes nothing about the focal length or speed — it simply flattens the curved focal plane into a flat one that matches your camera sensor. The result is sharp, round stars from center to corners at the full 1240mm focal length. For a scope this capable, the matched flattener is the natural companion: you get the full resolving power of 155mm aperture at native focal length, with corrected stars across the entire sensor — even the widest full-frame frames.
Flattener, Not Reducer
This is a 1× flattener — it preserves the native 1240mm focal length and f/8 ratio of the 155 GPS. If you want the full imaging power of this flagship scope at its native focal length with a corrected field, this is the accessory that makes it possible. The field of view, star size, and exposure times all remain the same — you just get flat, well-corrected stars across the sensor instead of curved, elongated ones at the edges.
If you prefer a shorter focal length and faster system instead, Sky Rover offers the SR155GPSRFF 0.8× reducer, which yields 992mm f/6.4. The choice is yours: native focal length with the flattener for maximum resolving power, or shorter focal length and faster speed with the reducer.
Camera Connection
The camera side of the flattener connects to your imaging equipment via standard 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 SR155GPSFF 1× field flattener for 155 GPS
Features
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1× field flattener — no focal reduction. Maintains the 155 GPS's native 1240mm f/8. Corrects field curvature for flat, sharp stars across the sensor without changing the imaging characteristics.
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Designed for 1240mm flagship imaging. At this focal length, field flatness is critical for the kind of high-precision, high-magnification work that defines flagship refractor performance. The flattener is optimized for the 155 GPS's optical prescription.
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Full-frame sensor coverage. Designed to support full-frame sensors with strong edge performance when properly spaced. The 3.7-inch clear aperture of the 155 GPS's redesigned CAA supports the matched flattener across all formats.
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The flagship deserves a flagship corrector. The 155 GPS's 155mm aperture, 1240mm focal length, and precision engineering are built for serious imaging. The matched flattener gives you flat-field performance at native focal length — exactly what flagship deep-sky imaging demands.
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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.
What's the difference between this flattener and the SR155GPSRFF reducer?
The flattener (this product) preserves the native 1240mm focal length and f/8 ratio while correcting field curvature. Use it if you want the full 1240mm focal length and 155mm resolving power at native speed. The SR155GPSRFF 0.8× reducer shortens the focal length to 992mm and speeds up the system to f/6.4, making exposures faster but reducing magnification. Choose based on your target scale and exposure time preferences.
Will this fit any other Sky Rover scope?
No. The SR155GPSFF is designed specifically for the 155 GPS's optical prescription and mechanical connection. Using it on a different scope will not produce correct results. Each Sky Rover scope has its own matched flattener.
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.
Final Thoughts
The 155 GPS at 1240mm f/8 is built for the kind of deep-sky work that demands excellence: tight star clusters, planetary nebulae, galaxy details, the kind of targets that reward aperture and focal length in equal measure. The matched SR155GPSFF flattener gives you the flat-field performance that matches the scope's optical and mechanical quality. It's the essential accessory for the flagship Sky Rover. That's the pairing that defines 155mm refractor imaging at its best. If you’re imaging at native focal length, this isn’t an upgrade — it’s part of the system.
