Sky-Watcher · Newtonian
SkyWatcher S20204 Quattro Coma Corrector (Black)
Sharp stars edge to edge at f/4: a dedicated coma corrector built for serious Newtonian imaging.
Price updated Mar 22, 2026
Performance Scores
Overview
If you own a Quattro imaging Newtonian or a similar fast f/4 Newtonian reflector, coma is your constant enemy. Stars at the edges of your images stretch and smear into comet-like shapes, and no amount of careful focusing will fix it. That is the problem this corrector is designed to solve. The SkyWatcher Quattro Coma Corrector uses FPL51 ED glass alongside Schott optical glass to minimize coma across a wide field without changing your effective focal length.
Magnification stays the same, so your framing and scale remain predictable between sessions. It requires exactly 55mm of backfocus to function correctly, so you will need to confirm your camera and focuser setup can achieve that distance before purchasing. Canon and Nikon camera adapters are available separately, which adds to the overall cost. It is worth noting that this corrector is optimized specifically for f/4 Quattro-series scopes.
Using it at other focal ratios may reduce its effectiveness. With only seven Amazon reviews and a 3.6 rating, real-world feedback is limited, so researching user experiences on dedicated astronomy forums before committing at this price point is genuinely worthwhile.
At a Glance
f/4
Focal Ratio
Specifications
Key Features
- Corrects coma in fast f/4 Newtonian reflectors, producing sharp stars across the full field of view
- Uses FPL51 ED glass combined with Schott glass for well-corrected, high-contrast images
- Preserves your original focal length, keeping image scale and framing consistent
- Requires 55mm of backfocus, a specific constraint to verify against your existing camera and focuser setup
- Compatible with Canon and Nikon DSLRs via adapters sold separately, adding flexibility for camera pairing
- Optimized specifically for the Quattro imaging Newtonian series, which may limit performance on other telescope designs
- Priced at $490, it targets dedicated imagers who need reliable edge correction rather than casual visual observers
Customer Reviews
7 reviews
While this seemed expensive, as compared to a cheaper, generic coma corrector, there was a distinct improvement when pairing this with my Quattro 250p. Well worth the money for imaging. Stars tight and round to the corners.
I had to return the original coma corrector because it appeared that the box had been opened and the product used, based on scratches it had on the edge of the corrector and the open plastic bag it came in. I purchased another version and it arrived perfectly fine. I know that some products are sold...
While the price tag will give you pause, when it comes to astrophotography… you get what you pay for in many scenarios. The construction of the FF is of good quality, it is threaded on the end to accept 2” filters, and for DSLRs…the M48 Canon or Nikon adapter is required, which Skywatcher has availa...