Remote imaging, processing pipeline, and observing plans. Merged from itelescope + astro-pipeline.
laurence
4ed23cef96
colour.py assembles a viewable image from whatever a session actually has: LRGB, RGB with a synthetic luminance, SHO in the Hubble palette, HOO, or a single filter as greyscale. Nothing is assumed about which filters exist, which is the whole point - three of the four archived sessions have no luminance channel. The background fit takes the lesson from Centaurus A, where a plane fitted around a large galaxy absorbed 17.9 ADU/px of its halo. The excluded region is now sized from the data: the ellipse grows until it contains most of the flux above sky, so it suits a galaxy filling the frame and a small nebula equally, and only a plane is ever fitted, never a flexible surface. One mask is derived from the deepest channel and applied to all of them, so the fit cannot shift the colour balance. Broadband and narrowband need opposite stretches, which cost a round to discover. Broadband channels share the luminance's midtone, preserving the real brightness ratios that keep star colours honest. Narrowband cannot: the lines differ enormously in strength, so a shared stretch renders the entire nebula in whichever colour Ha was mapped to. Each narrowband channel is now stretched to its own sky target instead. Green suppression is applied to broadband only. On a narrowband palette it would fight the palette, green being a deliberate channel assignment rather than an artefact. Measured rather than eyeballed, because the SHO render looked wrong by eye and was not: both palettes put the sky at 0.098 against a 0.10 target and neutral to within 0.004. What differs is the data. NGC 2030's brightest pixels reach 0.80 to 0.87, the Tarantula's only 0.23 to 0.33, because that session is a single 60 second frame per filter - three minutes in total. A correct pipeline renders nearly empty data as a nearly empty frame. |
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|---|---|---|
| docs | ||
| itelescope | ||
| observing/eclipse-2026-menorca | ||
| pipeline | ||
| state | ||
| .gitignore | ||
| CLAUDE.md | ||
| README.md | ||
astrophotography
Everything to do with taking, processing and understanding astronomical images: the remote telescopes, the code that turns their frames into pictures and measurements, and the plans for observing in person.
Formed by merging the itelescope and astro-pipeline repositories, with the
history of both preserved.
Layout
| Directory | What it is |
|---|---|
| itelescope/ | The iTelescope.net remote telescope network: a review of every scope, a southern-target guide, the observing plans, and the points drain campaign |
| pipeline/ | The processing and analysis code. Calibration, stacking, plate solving, rendering and the science analyses |
| observing/ | Plans for observing in person. Currently the total solar eclipse of 12 August 2026 from Menorca |
| state/ | Project state under the Default Workflow: objective, current work, decisions, working notes |
| docs/ | The Default Workflow itself: branching, commits, documentation policy, cost control |
Start here
- Planning or reviewing a remote imaging run: itelescope/CAMPAIGN.md and itelescope/TELESCOPES.md
- Processing a session's data: pipeline/README.md
- What is happening right now: state/TODO.md
- Why something was done a particular way: state/DECISIONS.md
Where the image data lives
Not in this repository. A single calibrated frame is 61 MB and a session
runs to several gigabytes, so sessions stay on disk and the code finds them
through the ASTRO_SESSION environment variable:
set ASTRO_SESSION=...\NGC5128\20260721
python pipeline/stack.py
Each session directory carries its own METHODS.md describing what was done to
that data and what was found, written for a reader who was not there. The code
lives here; the pixels and the account of them live with the data.
Things learned the hard way
Recorded because each cost real time or real money, and because each is a requirement for anything built next rather than a curiosity:
- Measure whether a core is saturated before buying time to fix it. A foreground star 69 arcsec from Centaurus A's nucleus was mistaken for the galaxy, and a telescope booking was made to solve a problem that did not exist. Filter the stars out of the measurement first.
- Vet moving-object candidates in detector coordinates. Registration holds the sky still, so it drags sensor defects across the frame on perfectly straight, constant-rate tracks. Hot pixels are better-behaved asteroids than real asteroids. One cut took 141 confident spurious detections to zero.
- Never compare an aperture magnitude against a point-source catalogue without checking the source is a point. A resolved object looks exactly like a 2.8 magnitude outburst.
- Never fit a sky background to a field the target fills. A plane fitted around a large galaxy eats its halo, measured at -17.9 ADU/px. Fit the background and a source model together.
- A photographic ND filter is not a solar filter. It passes the infrared that carries the heat.