Every smart-telescope comparison eventually hits the same wall: the specs that sell scopes aren't the specs that matter on a given target. For wide-field nebulae and nearby galaxies, aperture and field of view win the argument. For tiny planetary nebulae and compact galaxy cores — the kind of targets that live inside a 3-arcminute circle — the math flips, and the smaller-looking scope on paper actually turns in the better image.
That's the specific question Reddit threads keep arguing about: on a target like M57 or M1, which Seestar is actually resolving more structure? We ran the numbers and compared stacks from both scopes against the three small targets most people cite — the Ring, the Dumbbell, and the Crab. The answer is unambiguous, with one important caveat about availability.
Quick answer
For small planetary nebulae and compact galaxies, the Seestar S50's 250 mm focal length and 2.39 arcsec/pixel sampling consistently resolve more structure than the S30 Pro at 160 mm and 3.74 arcsec/pixel. The catch: ZWO discontinued the original S50 in early 2026, so new units are clearance only. If you want a current scope and small DSOs are your priority, the S50 Pro is the direct replacement; if you want the S30 Pro's wider framing instead, buy it knowing you're trading small-target resolution for field of view.
ZWO Seestar S50 (discontinued)50 mm f/5 APO, 250 mm FL, IMX462 1920×1080, 2.39"/px sampling — clearance/used only
ZWO Seestar S30 Pro30 mm f/5.3 APO quadruplet, 160 mm FL, IMX585 3840×2160, 3.74"/px — full review
What "small deep-sky objects" actually means
"Small" is doing a lot of work in the question. For practical purposes we mean targets whose apparent size is under about 5 arcminutes along the long axis. That's the regime where the S30 Pro's 4.6° field renders the target as a tiny feature in a sea of surrounding sky, and where the S50's 1.46° diagonal field puts it near the center of the frame with structure actually visible.
Three touchstone targets land squarely here:
- Ring Nebula (M57): approximately 2.5 × 2.0 arcminutes — one of the sky's most compact and classically-featured planetary nebulae
- Dumbbell Nebula (M27): approximately 8 × 5.6 arcminutes — a middle case, roughly on the border of "small"
- Crab Nebula (M1): approximately 6 × 4 arcminutes — the supernova remnant whose filaments only resolve with real angular size
Larger emission nebulae like the Veil, the North America Nebula, or the Heart and Soul complex live in the opposite regime, where the S30 Pro's wider field and mosaic workflow pay off. Our smart telescope buying guide breaks the price tiers by framing need; this piece is specifically about the small end.
The sampling math that decides it
The honest comparison isn't aperture or megapixels — it's arcseconds per pixel. That's the number that tells you how big a target appears on the sensor, and therefore how much detail you can pull out of the stack.
| Spec | ZWO Seestar S50 | ZWO Seestar S30 Pro |
|---|---|---|
| Aperture | 50 mm | 30 mm |
| Focal length | 250 mm | 160 mm |
| Focal ratio | f/5.0 | f/5.3 |
| Main sensor | Sony IMX462, 2.1 MP | Sony IMX585, 8.3 MP |
| Native resolution | 1920 × 1080 | 3840 × 2160 |
| Pixel pitch | 2.9 µm | 2.9 µm |
| Sampling | 2.39 arcsec/pixel | 3.74 arcsec/pixel |
| Field of view | 1.28° × 0.72° (~1.46° diag) | 2.24° × 3.99° (~4.6° diag) |
| Dual-band filter | Built-in | Built-in |
| EQ mode | No | Yes (~60 s subs) |
Two columns matter for this specific question: sampling and field of view. The S50 samples the sky at 2.39 arcsec per pixel, close to Nyquist for typical suburban seeing of 3–4 arcseconds. The S30 Pro at 3.74 arcsec per pixel is noticeably undersampled relative to the same seeing — you're throwing away resolution that the atmosphere was actually giving you. Siril's drizzle integration can partly recover undersampled detail on the S30 Pro's data, and our Siril starter guide covers that workflow, but no amount of processing invents sampling that wasn't captured in the first place.
The megapixel difference is a distraction here. The S30 Pro has four times as many pixels total, but they're spread across a frame that's about 3× wider in area, so for a small target that only occupies a tiny portion of the frame, the per-target pixel count is actually lower on the S30 Pro.
Target by target
M57, the Ring Nebula (~150" × 120"): on the S50, M57 spans roughly 63 × 50 pixels — enough to see the oval ring structure, the central cavity's brightness gradient, and under good conditions the central white dwarf. On the S30 Pro, M57 spans about 40 × 32 pixels; the ring is identifiable but reads as a small, soft donut. Our Ring Nebula target guide has settings tables for both scopes and expected image scale examples.
M27, the Dumbbell (~480" × 336"): this is the fairer fight. At its size, M27 covers around 200 pixels across on the S50 and about 128 on the S30 Pro. The S50 still wins on structural detail — the dumbbell waist and the fainter outer wings resolve better — but the S30 Pro produces a perfectly satisfying image here. If your target list is dominated by M27-sized objects, the comparison tightens. More in the Dumbbell Nebula settings guide.
M1, the Crab (~360" × 240"): the filamentary structure is what people chase on M1, and it's precisely the kind of fine detail that needs real angular size on the sensor. The S50 gives you 150 pixels of target width to work with; the S30 Pro gives you about 96. On a well-processed stack from a dark site, the S50 shows meaningful filament structure. The S30 Pro shows a convincing oval glow with hints of filaments only in the strongest-signal regions. See our Crab Nebula target page for processing specifics.
The availability caveat
Here's where the clean comparison gets complicated. ZWO discontinued the original S50 in early 2026 and launched the Seestar S50 Pro at $999 as the direct successor. New S50 units are now clearance stock at specialty retailers, and Amazon's listings for the original S50 are limited to third-party and open-box inventory with no consistent live offer price. That's why the product card above shows "Check Current Price" rather than a live number.
The S50 Pro keeps the 50 mm aperture (and roughly the same sampling advantage over the S30 Pro) while adding a 4K sensor, a dew heater, a wide-angle second camera, and EQ mode with ~60 s subs. For small-target work it inherits the S50's framing advantage. If you want a current, in-production 50 mm scope and your target list is small planetaries and compact galaxies, the S50 Pro is the honest buy — and that's a separate review we'll link once it's published.
What the S30 Pro trades in exchange
None of this makes the S30 Pro a weak scope. It's trading image scale for everything else: a 3× wider field, EQ-mode tracking that lets it push longer subs than the original S50, a dual-camera chassis for context shots, a modern 4K sensor, and the ASCOM/NINA path for later that no 50 mm Seestar currently offers at a comparable price. For a buyer whose target list leans toward big emission nebulae and nearby galaxies — Andromeda, the Rosette, the North America Nebula, the Heart and Soul mosaic — the S30 Pro is straightforwardly the better tool, and it's priced $300 under the S50 Pro.
The wrong move is forcing a 30 mm scope to do 50 mm work by cropping aggressively in post. You end up with a soft, undersampled image of a small target when a different scope would have given you a sharp one. Pick the scope that matches the frame size of what you actually want to shoot.
Who should buy which
Buy the Seestar S50 if you can still find a new-condition unit at or near its old $549 clearance price, your target list is dominated by small planetary nebulae and compact galaxies, and you don't mind owning a product line that's no longer getting firmware feature updates. It's a legitimately good scope for the specific job of resolving small targets; it just has a definite finish line.
ZWO Seestar S50 (discontinued)50 mm aperture, 250 mm FL, 2.39"/px sampling — clearance/used inventory only
Buy the Seestar S30 Pro if your target list runs wide and medium rather than small, you want the current platform with ongoing firmware support and the eventual ASCOM/NINA path, you need the active dew heater for humid climates, or you want the dual-camera setup for context shots. The S30 Pro at $699 is the better match for most buyers' target lists today — just not the specific one in this article's headline.
ZWO Seestar S30 Pro30 mm dual-camera, equatorial tracking, 4.6° wide-field framing
Our take
The question in the headline has a clean technical answer and a complicated real-world one. On M57, M27, and M1 specifically, the S50's longer focal length and tighter sampling produce visibly better results in stacks from either scope. That's not opinion; it's what Sony's published pixel-pitch specs for the IMX462 and IMX585 imply and what side-by-side community images show.
What's changed in 2026 is that the S50 you'd actually buy to win this fight isn't the one in the headline anymore — it's the S50 Pro. The S30 Pro remains the right choice for most buyers because most target lists lean wide, but if you spent last winter working out the focal-length math on your own and concluded you needed a 50 mm scope for small planetaries, trust that math: just buy the current version.
Last updated October 27, 2026. S30 Pro price verified against Amazon via the Creators API on publish date. S50 availability verified against the Seestar S50 Pro launch announcement.