FramingPanel

The imaging planner's tool: describe a sensor and a focal length, and the panel both states the field in degrees and lays that rectangle on the sky through engine.showFieldOfView(). Composes <ToolPanel>, <Button>, <Field>, <Slider> and <HudReadout>.

Framing

Sensor

36.0 × 24.0 mm

Focal length 200 mm

533

Rotation 0°

Position angle — measured from celestial north, so the frame holds its orientation against the stars rather than against the screen.

Sampling

Pixel pitch

Microns — gives arcsec per pixel

Field

10.29° × 6.87°

Diagonal

12.35°

Scale

—″/px

Enter a pixel pitch to see whether you are sampling well.

Select a deep-sky object to check it against this frame.

Every control is live. The readouts are computed by fieldOfView() and pixelScale() from src/Engine/Observation.ts, which is why they work here with no engine running; only the rectangle on the sky needs the map.

On the map it is one of the tools: the instrument bar opens it.

Worked examples

Rendered at build time by the panel's own maths. The arctangent form matters at wide field: the small-angle approximation everyone quotes puts a full frame at 200 mm nearly a degree and a half wrong.

Sensor	Focal	Field	Diagonal	Scale
Full frame · 36×24 mm	200 mm	10.29° × 6.87°	12.35°	6.13″/px at 5.94 µm
APS-C · 23.5×15.7 mm	200 mm	6.72° × 4.50°	8.08°	3.88″/px at 3.76 µm
Micro 4/3 · 17.3×13 mm	135 mm	7.33° × 5.51°	9.16°	5.74″/px at 3.76 µm
1" · 13.2×8.8 mm	1000 mm	0.76° × 0.50°	0.91°	0.50″/px at 2.4 µm

Activation

The panel is one of the map's tools, so it is inert until the instrument bar opens it: hidden, inert, holding no engine resources and drawing nothing. A page adds it once and pays nothing until the observer asks for it.

---
import FramingPanel from '../design/compositions/FramingPanel.astro';
---
<FramingPanel />

Then any of:

openTool('framing')     // from design/compositions/tool-bus, or the bar's own button
closeTool('framing')
F                       // keyboard, when no field has focus

It no longer announces a state of its own and no longer force-closes the layers list to take the column — InstrumentBar owns which tool is on screen, and this component owns only what the rectangle on the sky does. Escape closes it, like every other tool.

Behaviour

The rectangle is pinned to sky coordinates, so it rides the sky as it turns and stays on the target through a time scrub.
It centres on the current selection — dso:select, star:select — and on the view centre when there is none. Use view centre re-pins it to wherever the camera is looking.
Selecting a deep-sky object compares its catalogued major axis against the frame and says plainly whether it fits, fits only lengthways, or needs a mosaic.
Closing the panel, or navigating to a page without it, removes the annotation — the engine survives navigation and would otherwise keep the rectangle forever.
Optics are remembered in localStorage under whatthestar:optics. Persistence.ts models one fixed progress record and exposes no generic slot, and a camera setting does not justify widening a file three other panels share.

Placement

placement="hud" (the default) docks the card into the map's left tool slot, where the shared <ToolPanel> shell gives it its width, its ceiling and its way out. placement="inline" — used above — leaves it in the page flow for documentation, where the --hud-* layout variables do not exist.