Merge pull request 'solve: prefer the estate's own Astrometry.net over nova for blind solves' (#2) from astrometry-net-fallback into main

pipeline/astrometry.py

@@ -245,8 +245,10 @@ def run(session, verbose=True):
     centre = pointing(header)
     scale = plate_scale(header, session)
     if centre is None or not scale:
+        # Not fatal, and no longer the end of the road: returning None sends
+        # run.py to blind.py, which needs neither the pointing nor the scale.
         print("        no pointing or plate scale in the header - "
-              "cannot solve without a blind solver")
+              "handing off to the blind solver")
         return None
     # Match over the frame's INSCRIBED circle, not its circumscribed one. A
     # cone big enough to reach the corners also reaches well outside the

pipeline/astrometry_net.py

@@ -0,0 +1,142 @@
+"""Client for the estate's own Astrometry.net service.
+
+    https://astrometry.ankh-morpork.discworld.network
+
+This is solve-field running on docker1/2/3 against ~5 GB of local index files.
+It exists so that blind solving costs seconds instead of minutes and, more to
+the point, so that no image has to leave the house to get solved.
+
+It is used by blind.py, which prefers this service and falls back to the hosted
+nova.astrometry.net when it is unreachable. Everything a solution has to earn -
+verification against Gaia, the star-count and residual gate, writing the WCS
+into the masters - stays in blind.py, shared by both sources. This module only
+gets a WCS out of the estate service; it does not decide whether to believe it.
+
+Only the stdlib is used for the request. A solve is one POST; pulling in
+requests to do it would add a dependency for no gain.
+"""
+import base64
+import io
+import os
+import ssl
+import time
+import urllib.error
+import urllib.request
+
+from astropy.io import fits
+from astropy.wcs import WCS
+
+SERVICE = os.environ.get("ASTROMETRY_SERVICE",
+                         "https://astrometry.ankh-morpork.discworld.network")
+TIMEOUT = int(os.environ.get("ASTROMETRY_TIMEOUT", "180"))
+
+
+def _context():
+    """TLS context for the estate service.
+
+    The service presents a step-ca certificate from the estate's internal CA.
+    On a machine that trusts the Discworld root CA this verifies normally. On
+    one that does not, verification fails - and the right fix is to install the
+    CA, not to turn checking off, so that is what the error message says.
+    ASTROMETRY_CA_BUNDLE points at the root CA if it is not in the system store.
+    ASTROMETRY_INSECURE=1 exists as an explicit, visible escape hatch; it is
+    never the default and it prints when used.
+    """
+    bundle = os.environ.get("ASTROMETRY_CA_BUNDLE")
+    if os.environ.get("ASTROMETRY_INSECURE") == "1":
+        print("        WARNING: TLS verification disabled "
+              "(ASTROMETRY_INSECURE=1)")
+        ctx = ssl.create_default_context()
+        ctx.check_hostname = False
+        ctx.verify_mode = ssl.CERT_NONE
+        return ctx
+    return ssl.create_default_context(cafile=bundle) if bundle else \
+        ssl.create_default_context()
+
+
+def available(timeout=5):
+    """Is the service up and does it have indexes? Cheap enough to ask first."""
+    try:
+        with urllib.request.urlopen(SERVICE + "/healthz", timeout=timeout,
+                                    context=_context()) as resp:
+            return resp.status == 200
+    except Exception:                                         # noqa: BLE001
+        return False
+
+
+def solve(path, centre=None, scale=None, radius_deg=2.0, timeout=TIMEOUT,
+          verbose=True):
+    """Solve one FITS file. Returns (WCS, info dict) or (None, reason).
+
+    `centre` and `scale` are hints, not requirements - pass whatever the header
+    offered. A hinted solve turns a whole-sky search into a cone and is an order
+    of magnitude faster, but the whole point of this fallback is that it still
+    works when there is nothing to hint with.
+    """
+    params = []
+    if centre is not None:
+        params += [f"ra={centre.ra.deg:.6f}", f"dec={centre.dec.deg:.6f}",
+                   f"radius={radius_deg:.3f}"]
+    if scale:
+        # +/-20% around the nominal scale: wide enough to absorb a focal
+        # reducer or a binning the header did not mention, tight enough to
+        # still rule out most index scales.
+        params += [f"scale_low={scale * 0.8:.4f}",
+                   f"scale_high={scale * 1.2:.4f}"]
+    params.append(f"timeout={timeout}")
+    url = f"{SERVICE}/solve?" + "&".join(params)
+
+    with open(path, "rb") as handle:
+        body = handle.read()
+
+    started = time.time()
+    if verbose:
+        hint = "hinted" if (centre is not None or scale) else "blind"
+        print(f"        astrometry.net ({hint}): "
+              f"{len(body) / 1e6:.1f} MB to {SERVICE}")
+    request = urllib.request.Request(
+        url, data=body, method="POST",
+        headers={"Content-Type": "application/octet-stream"})
+    try:
+        with urllib.request.urlopen(request, timeout=timeout + 30,
+                                    context=_context()) as resp:
+            import json
+            payload = json.load(resp)
+    except urllib.error.HTTPError as exc:
+        # 422 is the service saying "no solution", which is an answer, not a
+        # fault. Anything else is the service or the network being broken, and
+        # the two should not read the same in the log.
+        import json
+        try:
+            detail = json.load(exc)
+        except Exception:                                     # noqa: BLE001
+            detail = {}
+        if exc.code == 422:
+            return None, "no solution found"
+        return None, f"service error HTTP {exc.code}: {detail.get('error', '')}"
+    except ssl.SSLCertVerificationError:
+        return None, ("TLS verification failed - install the Discworld root CA "
+                      "or set ASTROMETRY_CA_BUNDLE to it")
+    except Exception as exc:                                  # noqa: BLE001
+        return None, f"{type(exc).__name__}: {exc}"
+
+    if not payload.get("solved"):
+        return None, "no solution found"
+
+    # The service hands back the .wcs file - a bare FITS header - base64
+    # encoded. Parsing it here rather than trusting the summary numbers means
+    # the full distortion-free TAN solution is what gets written to the
+    # masters, not a re-derivation from ra/dec/scale.
+    with fits.open(io.BytesIO(base64.b64decode(payload["wcs_b64"]))) as hdul:
+        wcs = WCS(hdul[0].header)
+
+    info = {k: payload.get(k) for k in
+            ("ra", "dec", "pixscale", "orientation", "parity",
+             "fieldw", "fieldh", "fieldunits")}
+    info["seconds"] = payload.get("seconds", round(time.time() - started, 1))
+    if verbose:
+        print(f"        astrometry.net solved in {info['seconds']}s: "
+              f"centre {info['ra']:.5f} {info['dec']:+.5f}, "
+              f"{info['pixscale']:.3f} arcsec/px, "
+              f"{info['fieldw']:.1f}' x {info['fieldh']:.1f}'")
+    return wcs, info

pipeline/blind.py

@@ -10,22 +10,33 @@ and no amount of window-sliding fixes a population mismatch.
 A blind solver does not care. It builds geometric hashes from the image's own
 stars and looks them up in pre-built index files, so it needs no pointing, no
 scale and no orientation - only the pixels. astrometry.net is the standard
-implementation and this uses the hosted nova.astrometry.net service through
+implementation, and there are now two of it available:
-astroquery.
 
-Two things to know:
+1. **The estate's own** (`astrometry_net.py`) - solve-field on docker1/2/3
+   against local index files. Tried first: the image never leaves the house, it
+   needs no API key, and it answers in seconds rather than queueing. Its index
+   set covers 5.6 arcmin to 33 degree quads, which is the whole iTelescope
+   fleet's range, but NOT arbitrarily narrow fields.
+2. **The hosted nova.astrometry.net**, through astroquery. The fallback, for
+   when the estate service is unreachable or its index set cannot reach the
+   field. Two things to know about it:
 
-* **It needs an API key.** Free, from an account at https://nova.astrometry.net
+   * **It needs an API key.** Free, from an account at
-  (Profile -> API Key). Provide it as the ASTROMETRY_API_KEY environment
+     https://nova.astrometry.net (Profile -> API Key). Provide it as the
-  variable, or in a file named `astrometry.key` beside the session or in
+     ASTROMETRY_API_KEY environment variable, or in a file named
-  c:\\temp\\claudetemp. Without one this module reports that clearly and the
+     `astrometry.key` beside the session or in c:\\temp\\claudetemp. Without one
-  pipeline carries on unsolved rather than failing.
+     this module says so and the pipeline carries on unsolved rather than
-* **It uploads the image.** A stacked master goes to a third-party service.
+     failing.
-  That is fine for these targets and worth knowing before pointing it at
+   * **It uploads the image.** A stacked master goes to a third-party service.
-  anything you would not publish.
+     Fine for these targets, and worth knowing before pointing it at anything
+     you would not publish. This is the main reason the estate solver is tried
+     first.
 
-Results are still put through the same quality gate as the seeded solver: a
+Whichever source answers, the solution is put through the same quality gate as
-solution has to be good, not merely returned.
+the seeded solver - verified against Gaia, with a star count and residual it
+has to meet. A solution has to be good, not merely returned. The source is
+recorded in the ASTRSOLV card and in the returned `method`, so it is always
+possible to tell afterwards whether a frame was solved in-house or uploaded.
 """
 import os
 
@@ -58,31 +69,50 @@ def find_key(session=None):
     return None
 
 
-def run(session, scale_hint=None, verbose=True):
+def _solve_via_estate(path, scale_hint=None, verbose=True):
-    """Solve the deepest master blind. Returns the same dict as the seeded
+    """Try the estate's own solver first. Returns a WCS header, or None.
-    solver, or None."""
+
+    Preferred over nova for three reasons, in order of how much they matter:
+    the image never leaves the house, it needs no API key, and it answers in
+    seconds rather than sitting in a public queue. If the service is down or
+    unreachable this returns None and the caller goes to nova, so the estate
+    being offline costs speed and privacy, not the ability to solve.
+    """
+    try:
+        import astrometry_net
+    except ImportError:
+        return None
+    if not astrometry_net.available():
+        if verbose:
+            print(f"        estate solver unreachable "
+                  f"({astrometry_net.SERVICE}) - falling back to nova")
+        return None
+
+    wcs, info = astrometry_net.solve(path, scale=scale_hint, verbose=verbose)
+    if wcs is None:
+        # `info` is the reason string here. A genuine "no solution" is worth
+        # reporting but is not a reason to then try nova with the same pixels
+        # and the same index scales - nova's indexes are wider, so it is worth
+        # exactly one more attempt, and the caller makes it.
+        if verbose:
+            print(f"        estate solver: {info}")
+        return None
+    return wcs.to_header()
+
+
+def _solve_via_nova(path, session, scale_hint=None, verbose=True):
+    """The hosted service. Needs an API key and uploads the image."""
     key = find_key(session)
     if not key:
         if verbose:
-            print("        blind solve unavailable: no astrometry.net API key."
+            print("        nova blind solve unavailable: no astrometry.net API"
-                  "\n          Get one free at https://nova.astrometry.net "
+                  " key.\n          Get one free at https://nova.astrometry.net"
-                  "(Profile -> API Key), then set ASTROMETRY_API_KEY or write "
+                  " (Profile -> API Key), then set ASTROMETRY_API_KEY or write"
-                  "it to c:\\temp\\claudetemp\\astrometry.key")
+                  " it to c:\\temp\\claudetemp\\astrometry.key")
         return None
 
     from astroquery.astrometry_net import AstrometryNet
 
-    masters = os.path.join(session.root, layout.MASTERS)
-    deepest = session.filters[0]
-    path = os.path.join(masters, f"master-{deepest}.fit")
-    if not os.path.exists(path):
-        return None
-
-    with fits.open(path) as hd:
-        image = hd[0].data.astype(np.float32)
-        header = hd[0].header
-    ny, nx = image.shape
-
     ast = AstrometryNet()
     ast.api_key = key
     ast.TIMEOUT = 600
@@ -104,10 +134,40 @@ def run(session, scale_hint=None, verbose=True):
         wcs_header = ast.solve_from_image(path, force_image_upload=True,
                                           **kwargs)
     except Exception as exc:                                  # noqa: BLE001
-        print(f"        blind solve failed: {type(exc).__name__}: {exc}")
+        print(f"        nova blind solve failed: {type(exc).__name__}: {exc}")
         return None
     if not wcs_header:
-        print("        blind solve returned no solution")
+        print("        nova blind solve returned no solution")
+        return None
+    return wcs_header
+
+
+def run(session, scale_hint=None, verbose=True):
+    """Solve the deepest master blind. Returns the same dict as the seeded
+    solver, or None.
+
+    Two possible sources, tried in that order: the estate's own solver, then
+    nova. Whichever answers, the solution then earns its place the same way -
+    verified against Gaia and put through the same gate as the seeded solver.
+    A blind solve that is merely *returned* is not a blind solve that is right.
+    """
+    masters = os.path.join(session.root, layout.MASTERS)
+    deepest = session.filters[0]
+    path = os.path.join(masters, f"master-{deepest}.fit")
+    if not os.path.exists(path):
+        return None
+
+    with fits.open(path) as hd:
+        image = hd[0].data.astype(np.float32)
+    ny, nx = image.shape
+
+    source = "estate"
+    wcs_header = _solve_via_estate(path, scale_hint=scale_hint, verbose=verbose)
+    if wcs_header is None:
+        source = "nova"
+        wcs_header = _solve_via_nova(path, session, scale_hint=scale_hint,
+                                     verbose=verbose)
+    if wcs_header is None:
         return None
 
     wcs = WCS(wcs_header)
@@ -150,13 +210,13 @@ def run(session, scale_hint=None, verbose=True):
 
     med = float(np.median(resid)) if resid is not None else float("nan")
     if nmatch < MIN_STARS or not np.isfinite(med) or med > MAX_RESID_PX:
-        print(f"        blind solution REJECTED on verification: {nmatch} "
+        print(f"        {source} blind solution REJECTED on verification: "
-              f"Gaia stars at {med:.2f} px "
+              f"{nmatch} Gaia stars at {med:.2f} px "
               f"(need >= {MIN_STARS} and <= {MAX_RESID_PX})")
         return None
 
     if verbose:
-        print(f"        blind solve verified: {nmatch} Gaia stars, "
+        print(f"        {source} blind solve verified: {nmatch} Gaia stars, "
               f"{med:.2f} px ({med * solved_scale:.2f} arcsec)")
         print(f"        centre {centre.to_string('hmsdms')}, "
               f"{solved_scale:.4f} arcsec/px, PA {rot:.2f} deg")
@@ -168,8 +228,11 @@ def run(session, scale_hint=None, verbose=True):
         with fits.open(p, mode="update") as hd:
             for card in wcs.to_header().cards:
                 hd[0].header[card.keyword] = (card.value, card.comment)
+            # Name the SOURCE, not just "astrometry.net": a year from now the
+            # only way to tell whether a frame was solved in-house or uploaded
+            # to a public service is this card.
             hd[0].header["ASTRSOLV"] = (
-                f"astrometry.net blind / {nmatch} Gaia stars / "
+                f"astrometry.net blind ({source}) / {nmatch} Gaia stars / "
                 f"{med * solved_scale:.2f} arcsec", "blind plate solve")
             hd.flush()
 
@@ -177,4 +240,4 @@ def run(session, scale_hint=None, verbose=True):
                 residual_arcsec=med * solved_scale, scale=solved_scale,
                 position_angle=rot, centre=centre.to_string("hmsdms"),
                 fov_arcmin=(nx * solved_scale / 60, ny * solved_scale / 60),
-                method="astrometry.net blind")
+                method=f"astrometry.net blind ({source})")

state/DECISIONS.md

@@ -3,6 +3,29 @@
 > A dated, append only log of decisions and their rationale. Newest at the top. Never
 > rewrite past entries; if a decision is reversed, add a new entry that says so.
 
+## 2026-07-21: blind solving goes to the estate's own solver first, nova second
+
+The estate now runs Astrometry.net itself
+(`https://astrometry.ankh-morpork.discworld.network`, config in
+ankh-morpork-infra `astrometry/`): solve-field against ~5 GB of local index
+files, sized from this repo's own TELESCOPES.md so it covers the whole
+iTelescope fleet's fields of view (21.5 arcmin to 10.4 degrees).
+
+`blind.py` now tries it before nova.astrometry.net. The order is not about
+speed, though it is far faster - a blind solve of a real DSS field came back in
+0.7s against nova's minutes-in-a-queue. It is that **nova requires uploading
+the image to a third party and an API key**, and neither is now necessary for
+the ordinary case. nova stays as the fallback for when the estate service is
+unreachable or the field is narrower than the local index set reaches, so
+losing the estate costs speed and privacy, not the ability to solve at all.
+
+What deliberately did NOT change: the seeded solver in `astrometry.py` remains
+the primary path (a good header beats a blind search), and every blind solution
+- from either source - still has to pass the same Gaia verification and
+star-count/residual gate. A wrong WCS is worse than no WCS, and a second solver
+does not change that. The source is recorded in the ASTRSOLV card so it is
+always possible to tell later which one produced a frame's astrometry.
+
 ## 2026-07-21: the pipeline reads headers, not filenames
 
 The first pipeline parsed `calibrated-T32-...-Luminance-BIN2-W-300-001.fit` to