THE CORE LOOP — VOLUME TO FIND · SLICE TO READ
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ORIENT — open VOLUME mode (V). Anything glowing is candidate signal: the default transfer
function already cuts at the noise floor. Use MAX-INT to find faint point sources; stretch
SPECTRAL DEPTH to exaggerate velocity structure — a tilted or twisted feature along the spectral
axis means rotation or outflow.
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LOCK — click a feature. The ray is marched through the cube, the brightest channel along it is
locked, and you land in SLICE mode at that channel.
-
READ — hover anywhere: sky position (α/δ or Galactic ℓ/b), spectral coordinate (frequency,
wavelength, velocity or Faraday depth) and flux are the true file values, not rendered colors. Scrub
←/→ to walk the line profile channel by channel.
-
PROBE — click a pixel to pin a spectrum through that spaxel. The waveform behind the scrubber is
the cube-mean spectrum — jump straight to the lines.
TRUST CONTRACT
SLICE IS QUANTITATIVE — native-resolution float values streamed from the file. Use it
for anything you'd write down.
VOLUME IS QUALITATIVE — spatially/spectrally binned, half-float quantized, and
shaped by your transfer function. Never estimate a flux or a size from it; it exists to tell you where to
point the slice view (and to make the screenshot for your talk).
Both modes share one normalization and stretch — bright agrees with bright; only slice mode says how bright.
USE IT FOR / NOT FOR
- triage — "is there anything in this cube?"
- finding line channels before deeper analysis
- data-quality checks (NaN borders, bad pixels via MAX-INT)
- velocity structure, demos, teaching
- publication photometry
- moment maps & spectral fitting
- arcsecond astrometry on wide fields (SIP ignored)
- anything measured off the volume render
WORKFLOW TIP
Tune WINDOW + STRETCH once in slice mode on a strong channel (ASINH for faint extended
emission · LOG for high dynamic range). Volume mode inherits the same scaling — then shape only the
TRANSFER FUNCTION for the volume look.
KEYS
←/→ channel · ⇧←/→ ×10 · SPACE play · V mode · G guide · R reset
view · double-click fit · wheel zoom · drag pan/orbit · ESC close