FOV Calculator · Master Stellarium

Target and view

Survey

Show OAG FOV / overlays

Manual sky FOV (°)

The overlay reads Aladin’s live viewport scale, so zooming with the mouse keeps every rectangle correctly scaled.

Constellations

Show constellation lines

Show transparent constellation figures

Show constellation names

Figure opacity

Overlay statusOff

Constellation data is loaded once and rendered on a dedicated lightweight canvas. It does not alter the survey image or the camera, OAG, and mosaic overlays.

Sky-image appearance

Exposure Exposure numeric (stops) Contrast Contrast numeric (%) Saturation Saturation numeric (%)

Exposure multiplier1.00×

Current appearance0.0 EV · 100% · 100%

These controls alter only the displayed survey image. Camera, OAG, and mosaic overlays remain unchanged. Exposure uses photographic stops: +1 doubles displayed brightness and −1 halves it.

Telescope and reducer

Telescope Native focal length (mm) Reducer preset Reducer factor Effective focal length (mm)

Seestar S30 / S30 Pro presets select the built-in telephoto camera and native optics automatically. Frames use portrait orientation: S30 ≈ 1.20° × 2.13°; S30 Pro ≈ 2.24° × 3.99°. Compare the two using separate comparison setups.

The Apertura CarbonStar reducing coma corrector is 0.95×. Celestron’s classic SCT reducer is 0.63×; dedicated EdgeHD reducers for the 8, 9.25, 11, and 14 are 0.70×.

Compare imaging setups

Add as many setups as needed. Each has an independent telescope, camera, reducer, and editable effective focal length.

Main imaging cameras

Tick any combination to overlay multiple main-camera FOVs at the same time.

Main rotation (°) Rotation numeric (°)

Guide cameras

Tick any combination to overlay multiple guide-camera FOVs at the same time.

OAG geometry

OAG preset Prism width (mm) Prism height (mm) Prism-center offset (mm) OAG angle (°) Angle numeric (°) Guide sensor rotation (°) Guide rotation numeric (°)

Preset offsets are practical planning estimates. Exact usable field can vary a bit with prism insertion depth and mechanical spacing.

Calculated geometry

Current effective focal length

Largest selected main FOV

Largest selected guide FOV

Prism footprint

Guide-center radius

Current Aladin FOV

Overlay key

Prism-delivered footprint

Path traced by guide-field centre

Mosaic tiles

Important When OAG overlay is turned off, only the selected main imaging camera FOVs remain visible.

Mosaic planner

Show mosaic overlay

Mosaic camera Mosaic telescope Mosaic reducer preset Mosaic reducer factor Mosaic effective focal length (mm)

Columns Rows

Horizontal overlap (%) Horizontal overlap numeric (%) Vertical overlap (%) Vertical overlap numeric (%) Mosaic rotation (°) Mosaic rotation numeric (°)

Use the same overlap on both axes

Number tiles in acquisition order

Tile count—

Single-tile FOV—

Total mosaic span—

Center spacing—

Effective focal length—

The mosaic camera, telescope, reducer, and rotation are independent from the main imaging setup. Both remain visible together for direct comparison. Adjacent tiles overlap by the selected percentages, and numbering uses a snake pattern to minimize slew distance.