Camera Comparisons

Real, same-target comparisons between the cameras actually used across this site — not spec-sheet numbers on their own, but real shots of the same object through different gear, and what's actually responsible for the difference. Two live here so far; more will be added as new gear and shots come in.

Iris Nebula: Seestar S50 vs ASI533MC Pro

Same nebula, two cameras, worlds apart in how they got there. This page puts the Seestar S50 next to the ASI533MC Pro — not as a scored review of either (both already have their own full write-ups), but as a straight comparison of what a fully automated smart telescope and a dedicated cooled astro camera actually deliver on the same target, side by side.

The Seestar S50 is a self-contained smart telescope — optics, camera, mount and software all sealed into one unit, aimed and operated entirely from a phone. The ASI533MC Pro is the opposite end of the spectrum: a bare cooled sensor that only becomes a telescope once it's bolted to one — here, an Askar 71F APO refractor, guided and controlled through a ZWO ASIAIR. The spec sheet gap between them explains most of what follows.

The Same Target, Shot on Both

Both shots below are the Iris Nebula (Caldwell 4 / NGC 7023) — faint enough to punish weak optics and short integration, detailed enough to show the difference clearly. One honest caveat before the images: the integration times aren't equal — the ASI533MC Pro stack has roughly twice the total exposure time of the Seestar's. That's a fair reflection of how each system actually gets used in practice, not a controlled scientific test, so read what follows with that in mind.

What the Difference Actually Comes From

The clearest difference is sheer resolution. The Seestar's IMX462 sensor outputs a native 1920×1080 — a little over 2 megapixels — while the ASI533MC Pro's IMX533 is a 3008×3008 square sensor, drizzle-stacked here to 6016×6016. That's roughly four times the pixel count feeding in from a much larger physical sensor, and it shows directly in how much of the nebula's faint outer dust the ASI533MC Pro shot holds onto that the Seestar's output simply doesn't have the resolution to resolve.

None of that is purely a hardware story, either — integration time matters on its own. Signal-to-noise scales with the square root of total exposure time, so the ASI533MC Pro's 150 minutes against the Seestar's 79 minutes is worth roughly 38% more signal-to-noise (√(150/79) ≈ 1.38) before sensor, cooling or aperture ever enter into it. A Seestar left running for the same 150 minutes wouldn't close the whole gap — the hardware differences below are real — but it would close part of it, which is exactly why the caveat above matters: this shows what each system delivers in realistic use, not what either is capable of at matched exposure.

That noise gap is something more time can at least partly close. Resolving power is a different problem, and time can't buy it back at all — aperture sets a hard ceiling on how much fine detail a scope can ever resolve, however long it stacks for. The Rayleigh diffraction limit for a 50mm aperture works out to about 2.8 arcseconds; for the Askar 71F's 71mm, about 1.9. The Seestar physically cannot resolve anything finer than its own limit, no matter the exposure time. In practice, ordinary UK atmospheric seeing (commonly 2–3 arcseconds from a back garden) often blurs both scopes toward a similar practical limit anyway, so this rarely bites as hard as the numbers suggest — but on a good night, the bigger aperture is capturing real detail the Seestar's optics were never going to resolve in the first place, integration time or not.

The ASI533MC Pro's sensor is thermoelectrically cooled to around 35°C below ambient, with no amp glow to correct for (see the full ASI533MC Pro review), which keeps its noise floor low even on 180-second subs. The Seestar has no cooling at all, which is exactly why it leans on many short 10-second subs instead of fewer long ones — it trades noise-per-frame for frame count, and stacks its way to a usable image rather than exposing its way there.

The Askar 71F's 71mm aperture and integrated field flattener (full review) are also simply gathering more light than the Seestar's small built-in 50mm optic, over a longer effective focal length — more photons per second landing on a sensor that's already better at holding onto them.

None of this is really an argument that one camera is "better" in isolation. The Seestar found this target itself, plate-solved, and started stacking without a laptop in sight; the ASI533MC Pro shot meant a mount, a guide scope, a full ASIAIR session, and processing every sub by hand afterwards. That trade-off — convenience against control and ultimate detail — is the real decision, not the resolution numbers on their own.

East Veil Nebula: Seestar S50 vs Nikon D5300 vs ASI533MC Pro

One target, shot three times in a single month, as the setup behind it actually changed. The East Veil Nebula (Caldwell 33 / NGC 6992) went from the Seestar S50's own optics, to an old Nikon D5300 bolted onto a new manual telescope with a T-ring adapter, to that same telescope's camera being upgraded to a dedicated cooled ASI533MC Pro three weeks later. This isn't three cameras picked to compare — it's the real order this site's gear actually arrived in.

Two of these three shots came from the exact same telescope. Only the Seestar has its own separate optics — the D5300 and the ASI533MC Pro were both shot through the same Askar 71F (full review), 486mm and 488mm focal length respectively — near enough identical. That matters: it means the D5300-versus-ASI533MC-Pro pair isolates the camera alone, with the glass held constant, while the Seestar comparison is a genuinely different optical train as well as a different camera.

The Same Target, Three Times

None of these three are equal-length exposures, and they're each processed and cropped as their own finished photo rather than identical test frames — so this is three real results, not a controlled experiment. Seestar: 597 × 10s subs, ≈99 minutes. D5300: 42 × 120s subs, ≈84 minutes. ASI533MC Pro: 40 × 180s subs, ≈120 minutes.

What Actually Changed Between Them

The most visible difference isn't noise or resolution at all — it's colour. The D5300's stock IR-cut filter blocks much of the exact red light the Veil Nebula emits most strongly in (see the full D5300 review), which is why that shot leans hard toward blue and loses most of the nebula's red filaments — a real optical limitation of an un-modified DSLR on this specific kind of target, nothing to do with exposure time or noise.

Aperture sets a hard ceiling on resolving power no matter how long a scope stacks for, as covered above. What's worth noticing here is that the diffraction limit explains the Seestar's shortfall against both of the other two shots, but it says nothing about the difference between the D5300 and the ASI533MC Pro — those two share the exact same 71mm aperture, so whatever separates their results is down to the camera alone.

And what separates them is mainly noise control. The ASI533MC Pro's sensor is thermoelectrically cooled and has no amp glow to correct for; the D5300's sensor has neither, so heat-generated noise builds up more over 120-second subs than it does on the ASI533MC Pro's 180-second ones. The two sensors are physically different sizes too — the D5300's APS-C chip has nearly three times the surface area of the ASI533's 1" sensor, gathering more total light and covering a wider field at the same focal length, which is exactly why it was worth trying before buying anything new.

Which One Should You Actually Buy

If you want to point something at the sky and get a genuinely good image with almost no learning curve, the Seestar S50 is still the easiest and — at around £550 all-in — the cheapest way in; see the full Seestar S50 review. If you already own a DSLR, it's worth bolting onto a telescope before buying anything dedicated at all — a T-ring adapter is a small outlay against a purchase you might not need, and the D5300 review covers what that actually looks like in practice. Once a DSLR's noise floor and stock filter start holding a target back — or you want the resolution and control a dedicated camera brings from the start — the ASI533MC Pro paired with a scope like the Askar 71F is the serious step up. Either way, Your First Telescope is a good place to start if you're still deciding between these paths generally, not just these specific products.