Smart telescope field of view
How much sky each smart telescope actually covers, computed from its focal length and its sensor rather than copied from a specification sheet. The short answer for the impatient: the fields these makers publish are not comparable with each other as printed, because they are not all the same measurement.
Last updated . These instrument specifications are re-checked against the manufacturers monthly.
The trap. ZWO lists the Seestar S30 Pro at 4.6 deg. No edge of that frame is 4.6 degrees. It is the diagonal, and the frame it describes is 4.01 by 2.25 degrees. A diagonal is not something you can photograph: it is the one direction across a rectangle that no target can be aligned along.
The cost is concrete. Read 4.6 as the width and a target three degrees across looks like a comfortable fit; it fits the long edge, but the short edge is only 2.25 degrees, so it does not fit the frame the narrow way and needs a mosaic. On these 16:9 sensors the diagonal overstates the long edge by 15 percent and the short edge by 104 percent.
The same applies across makers. The S30 Pro's 4.6 and the S50's 1.29 are not the same measurement, so they cannot be divided. Like for like, the S30 Pro's long edge is 3.10 times the S50's and it covers 9.6 times the area; the S50 Pro's is 1.91 times the S50's, for 3.6 times the area.
What each maker publishes, and what it means
Of the 6 instruments below, across 3 manufacturers: 2 publish a labelled pair of edge angles, 3 publish a single bare number that turns out to be the diagonal, and 1 publishes a figure rounded so coarsely that it cannot be resolved to an axis at all.
| Model | Long edge | Short edge | Diagonal | Area | Maker publishes | Which is it? |
|---|---|---|---|---|---|---|
| Seestar S30 | 2.13 | 1.20 | 2.44 | 2.54 | 2.46 deg |
diagonal only |
| Seestar S30 Pro | 4.01 | 2.25 | 4.60 | 9.03 | 4.6 deg |
diagonal only |
| Seestar S50 | 1.29 | 0.73 | 1.48 | 0.94 | 0.73 deg x 1.29 deg |
both edges |
| Seestar S50 Pro | 2.46 | 1.38 | 2.82 | 3.40 | 2.8 deg (Portrait) |
diagonal only |
| DWARF 3 | 2.95 | 1.66 | 3.38 | 4.89 | 3 deg |
cannot be toldfits long edge or diagonal |
| Celestron Origin | 1.27 | 0.85 | 1.53 | 1.08 | 1.27 deg x 0.85 deg |
both edges |
Long edge, short edge and diagonal are in degrees; area is in square degrees. Telephoto optics only: the dual-lens models also carry a wide-angle finder (the S30 Pro's is 63 degrees) which is not an imaging field and is not tabulated here.
The specifications this is computed from
| Model | Aperture | Focal length | Ratio | Sensor | Frame | Pixel pitch |
|---|---|---|---|---|---|---|
| Seestar S30 | 30 mm | 150 mm | f/5 | Sony IMX662 | 1920 x 1080 | 2.900 ummaker figure |
| Seestar S30 Pro | 30 mm | 160 mm | f/5.3 | Sony IMX585 | 3840 x 2160 | 2.914 umfrom datasheet |
| Seestar S50 (discontinued) | 50 mm | 250 mm | f/5 | Sony IMX462 | 1920 x 1080 | 2.932 umfrom datasheet |
| Seestar S50 Pro | 50 mm | 260 mm | f/5.2 | OmniVision OS08B10 | 3840 x 2160 | 2.905 umfrom datasheet |
| DWARF 3 | 35 mm | 150 mm | f/4.3 | Sony IMX678 | 3840 x 2160 | 2.011 umfrom datasheet |
| Celestron Origin (discontinued) | 152 mm | 335 mm | f/2.2 | Sony IMX178 | 3096 x 2080 | 2.400 ummaker figure |
The arithmetic
A sensor edge of width w millimetres at focal length f millimetres subtends
angle = 2 x arctan( w / 2f )
The sensor edge is its pixel count times its pixel pitch. One detail matters more than it looks: the pitch a telescope maker prints is rounded, and the rounding is too coarse to reproduce their own published field. Every ZWO model here is listed at 2.9 um. Carry that through the S50 and you get 1.276 degrees against ZWO's published 1.29, a miss of about a percent that reads like a disagreement and is not one. The IMX462's datasheet diagonal of 6.46 mm across its 1920 x 1080 array gives 2.932 um, and that reproduces 1.290 degrees, which is ZWO's figure exactly.
So the active area below is taken from the sensor's own datasheet diagonal wherever one was found, and falls back to the maker's rounded pitch only where none was. Each published figure is then tested against the axis it claims to be, to a tolerance set by its own printed precision: a figure given as 2.46 asserts two decimals, one given as 3 asserts none and admits half a degree either way.
| Model | Active area | Maker says | Computed axis | Difference | Tolerance |
|---|---|---|---|---|---|
| Seestar S30 | 5.568 x 3.132 mm | 2.46 | 2.440 | 0.020 | 0.025 |
| Seestar S30 Pro | 11.191 x 6.295 mm | 4.6 | 4.596 | 0.004 | 0.050 |
| Seestar S50 | 5.630 x 3.167 mm | 1.29 | 1.290 | 0.000 | 0.005 |
| Seestar S50 Pro | 11.156 x 6.275 mm | 2.8 | 2.820 | 0.020 | 0.050 |
| DWARF 3 | 7.722 x 4.344 mm | 3 | 2.949 | 0.051 | 0.500 |
| Celestron Origin | 7.430 x 4.992 mm | 1.27 | 1.271 | 0.001 | 0.013 |
Every published figure lands on a computed axis once the convention is identified. The DWARF 3's single significant figure is the one case where more than one axis fits inside its own rounding, so it is reported as undetermined rather than forced to a guess.
Does it fit in one frame?
A target fits a frame if the frame can be rotated to line the target's long axis up with the frame's long edge and the target's short axis still fits the frame's short edge at that same rotation - checking only one axis against the short edge, as an earlier version of this page did, wrongly called some targets a mosaic that fit perfectly well turned sideways. Angular sizes are read from the same deep-sky catalog the Live Sky Map draws, so they cannot drift from the rest of the site.
Every instrument here mounts alt-azimuth. On an alt-az mount the frame's own rotation on the sky (its parallactic angle) is not something the observer chooses; it drifts as the telescope tracks and can sweep well over a hundred degrees across a single session. "Fits" below means the target fits at some achievable rotation, not that every rotation the mount happens to be at will show it framed.
| Target | S30 | S30 Pro | S50 | S50 Pro | DWARF 3 | Origin |
|---|---|---|---|---|---|---|
| M31Andromeda, 190' x 60' | Mosaic0.7x | Tight1.3x | Mosaic0.4x | Mosaic0.8x | Mosaic0.9x | Mosaic0.4x |
| M45Pleiades, 110' | Mosaic0.7x | Tight1.2x | Mosaic0.4x | Mosaic0.8x | Mosaic0.9x | Mosaic0.5x |
| M8Lagoon Nebula, 90' x 40' | Tight1.4x | Fits2.7x | Mosaic0.9x | Fits1.6x | Fits2.0x | Mosaic0.8x |
| M42Orion Nebula, 66' x 60' | Tight1.2x | Fits2.3x | Mosaic0.7x | Tight1.4x | Fits1.7x | Mosaic0.9x |
| M81Bode's Galaxy, 27' x 14' | Fits4.7x | Fits8.9x | Fits2.9x | Fits5.5x | Fits6.6x | Fits2.8x |
| M51Whirlpool, 11' x 8' | Fits9.0x | Fits16.9x | Fits5.4x | Fits10.4x | Fits12.4x | Fits6.4x |
| M57Ring Nebula, 1' | Fits71.8x | Fits135.2x | Fits43.5x | Fits83.0x | Fits99.5x | Fits51.2x |
Fits: target sits inside the frame, rotated to match, with room to spare. Tight: fits the frame rotated to match, but with less than half a frame of margin. Mosaic: does not fit either edge of the frame at any rotation; needs more than one panel. The multiplier is the short edge divided by the target's major axis, so 2.0x means the frame is twice as tall as the target is wide.
Looking for other makers?
This page stays deliberately narrow: the six instruments above are the original probe, and it stays that size on purpose. The full comparison - all 23 current and recently-discontinued smart telescopes across five makers (ZWO, DwarfLab, Vaonis, Unistellar, Celestron), the same computed-not-transcribed field of view, plus price, weight, and an openness rating no other comparison tracks - is the Smart Telescope Comparison. An earlier version of this note excluded the Vaonis Vespera II over an apparent field-of-view discrepancy; that discrepancy turned out to be a mismatch against a different model's published figure, not a Vespera error, and it is resolved and included there.
Sources
- Seestar S30: optics and sensor read from www.seestar.com on 2026-09-04. No independent sensor diagonal was found for this part, so the telescope maker's own pitch is used and the tolerance below is widened to match.
- Seestar S30 Pro: optics and sensor read from www.seestar.com on 2026-09-04. Pixel pitch corroborated against the sensor's own datasheet diagonal of 12.84 mm, which implies 2.914 um against the 2.9 um the telescope maker prints (+0.5 percent).
- Seestar S50: optics and sensor read from www.seestar.com on 2026-09-04. Pixel pitch corroborated against the sensor's own datasheet diagonal of 6.46 mm, which implies 2.932 um against the 2.9 um the telescope maker prints (+1.1 percent).
- Seestar S50 Pro: optics and sensor read from www.zwoastro.com on 2026-09-04. Pixel pitch corroborated against the sensor's own stated optical format of 12.80 mm, which implies 2.905 um against the 2.9 um the telescope maker prints (+0.2 percent).
- DWARF 3: optics and sensor read from www.dwarflab.com on 2026-09-04. Pixel pitch corroborated against the sensor's own datasheet diagonal of 8.86 mm, which implies 2.011 um against the 2 um the telescope maker prints (+0.5 percent).
- Celestron Origin: optics and sensor read from www.celestron.com on 2026-09-04. No independent sensor diagonal was found for this part, so the telescope maker's own pitch is used and the tolerance below is widened to match.
Sensor datasheet diagonals are from the manufacturers' own published sensor documentation. Deep-sky angular sizes are from the catalog described on the methodology page. CycleCalcs is not affiliated with or endorsed by any telescope manufacturer. Seestar and ZWO are trademarks of Suzhou ZWO Optical Co., Ltd, Celestron is a trademark of Celestron Acquisition LLC, and DWARF is a trademark of DwarfLab. Model names appear here only to identify which instrument a number describes.
Related: the telescope and eyepiece calculator does the same arithmetic for any optic and eyepiece you enter, and the astrophotography exposure calculator covers how long a single frame can run before the stars trail.