First stage of the generic pipeline. The existing scripts parse
filenames, expecting calibrated-T32-...-Luminance-BIN2-W-300-001.fit,
which works for exactly one telescope, one binning and one exposure
length. Three of the four archived sessions have no luminance channel at
all, so that approach cannot process them.
session.py opens each frame and reads FILTER, EXPTIME, XBINNING, OBJECT
and DATE-OBS instead. It groups frames by filter, works out which colour
scheme the session supports (LRGB, RGB, SHO, HOO or mono), and writes a
manifest. Filter aliases are mapped, so a header saying H-alpha, Halpha
or HA all resolve to Ha.
Three real defects were found by running it against the archive rather
than by reasoning about it:
Frame counts came out doubled. iTelescope ships every frame twice, as
'calibrated-*' with bias, dark and flat applied and 'raw-*' without, and
extracting both put two copies of each frame into the stack. Only the
calibrated archives are extracted now, with CALSTAT used as a header
level safety net for sessions that were already extracted the old way.
NGC 5128 now scans as 12/4/4/4, exactly matching the session processed
by hand, which makes it a usable regression test.
A re-mirror over the organised tree produced duplicates and mirror
damage. An interrupted segmented download leaves DIRECTORIES named after
the file being fetched - a directory called something.fit - plus
.cyberducksegment parts. Anything that trusts a file extension will try
to open a directory as a frame. Those are now skipped explicitly at
discovery, ingest and scan, and byte-identical copies that a re-mirror
puts back are removed as they are refiled.
Two T20 archives are corrupt and cannot be extracted. That is real data
loss, not a bug: the session has 14 of its 16 frames and the warning is
printed rather than swallowed.
Not yet done: NGC 6744 mixes bin1 luminance at 4096x4096 with bin2
colour at 2048x2048, so registration will need to resample onto a common
grid rather than assuming every frame shares a shape.
