/fov
/fov <scope> <camera> <target>
Shows the field of view your saved telescope + camera combination would actually capture, drawn as a rectangle over a real, angularly-calibrated image of the target — the same visual language tools like Telescopius or an ASIAir’s own framing display already use, so you can judge at a glance whether a target fits, is too small, or is too large for your setup, without doing any math yourself.
Usage: /fov scope: [pick from autocomplete] camera: [pick from autocomplete] target: M31 — all three are required.
camera needs a saved resolution (sensor pixel dimensions),
not just pixel pitch — /savecamera with a known
camera_model fills this in automatically; otherwise add it
with /editcamera.
target doesn’t have to be in the catalog: if nothing matches,
it’s tried as a raw RA/Dec coordinate instead — either
standard HMS/DMS notation (5h35m17s, -5°23'28") or plain
decimal degrees (83.82, -5.39). No catalog covers every
object, and this is the way around that rather than a promise
every object will eventually be added.
Also shows the sampling rate (arcseconds per pixel — how much sky each pixel actually covers) and the Rayleigh diffraction limit (the finest detail your aperture can theoretically resolve, regardless of camera) — both genuinely useful numbers for judging whether a setup is well-matched to a target before spending a night on it, not just decoration.
If the target’s size is known, its outline is drawn as a dashed amber ellipse (your camera’s frame stays the solid green rectangle), tilted to the object’s position angle, so you can see how it sits in your frame. A long, thin object is only outlined when its position angle is known — a guess would be worse than no outline — and a raw coordinate has no size to draw.
When the target is long and thin and its orientation is known, a “Suggested rotation” line gives the camera angle (position angle of the image’s up direction, north through east) — handy for an automatic rotator — and the picture is rotated to match, so the green frame shows the suggested framing (a small N/E compass shows where north and east went). If the whole target fits, the angle lays your sensor’s long side along it; if it’s bigger than your frame, the angle is the one that covers the most of it. It’s a suggestion: rotator software differs in how it counts angles.
Without a suggested rotation the image is north up, and the frame is drawn level — there’s no way to know how your camera is actually rotated on the sky from any data this bot has, since that depends entirely on how you mounted it that session.
Background image: DSS2 (color), via hips2fits, a cutout service run by CDS (the Strasbourg astronomical data center behind SIMBAD and Aladin). The Digitized Sky Survey is licensed CC BY-NC-SA 4.0, and the credit under the picture says so.
Coordinates button: the 📋 button replies (only you see it) with the target’s J2000 and JNow coordinates, in hours/minutes/seconds and decimals, ready to copy into mount or planetarium software that wants JNow, plus the suggested rotation when there is one. JNow is for today, by precession alone.
Parameters
| Name | Required | Description |
|---|---|---|
scope | Yes | Your saved telescope profile (see /savescope) |
camera | Yes | Your saved camera profile (see /savecamera) -- needs a saved resolution, not just pixel pitch |
target | Yes | A deep-sky object (M31, NGC 6960, Andromeda Galaxy), or a raw RA/Dec coordinate if it's not in the… |