Astrometry (pyobs.images.processors.astrometry)

Astrometry

class Astrometry(**kwargs: Any)

Base class for astrometry processors

AstrometryDotNet

class AstrometryDotNet(url: str, source_count: int = 50, radius: float = 3.0, timeout: int = 10, exceptions: bool = True, **kwargs: Any)

Perform astrometric solving using an astrometry.net-compatible service.

This processor submits sources extracted from a pyobs.images.Image to an astrometry.net service, obtains a WCS solution, and writes it back to the image’s FITS header. The solver endpoint is configured via url and the request content is built by pyobs.images.processors.astrometry._DotNetRequestBuilder.

Parameters:

• url (str) – Base URL of the astrometry.net service endpoint.

• source_count (int) – Number of detected sources to include in the request payload. The source selection strategy is defined by _DotNetRequestBuilder. Default: 50.

• radius (float) – Search radius constraint passed to the request builder. Units and semantics are defined by _DotNetRequestBuilder (commonly degrees for astrometry.net). Default: 3.0.

• timeout (int) – Timeout in seconds for the network call to the astrometry web service. Default: 10.

• exceptions (bool) – Whether to raise exceptions on failure. If True, processing errors are raised (typically as pyobs.images.exceptions.ImageError). If False, errors are handled by marking the image header and returning the original image. Default: True.

• kwargs – Additional keyword arguments forwarded to pyobs.images.processors.astrometry.Astrometry.

Behavior

• Constructs a request from the input image using pyobs.images.processors.astrometry._DotNetRequestBuilder(source_count, radius).

• Logs request metadata via pyobs.images.processors.astrometry._RequestLogger.

• Sends the request to the configured service with request.send(url, timeout).

• On success, receives solver output and writes the resulting WCS into a copy of the input image using pyobs.images.processors.astrometry._ResponseImageWriter.

• Logs the outcome, including WCS information, and returns the result image.

• On failure:

  • If exceptions=True, raises the underlying pyobs.images.exceptions.ImageError.

  • If exceptions=False, sets WCSERR=1 in the FITS header, logs a warning, and returns the original image unchanged.

Input/Output

• Input: pyobs.images.Image

• Output: pyobs.images.Image (copied) with WCS solution written to the FITS header. Pixel data are typically unchanged.

Configuration (YAML)

Minimal local solver:

class: pyobs.images.processors.astrometry.AstrometryDotNet
url: "http://localhost:8080/api"

Handle failures without raising exceptions:

class: pyobs.images.processors.astrometry.AstrometryDotNet
url: "http://localhost:8080/api"
exceptions: false

Notes

• The _DotNetRequestBuilder determines how sources are extracted and how the request is formed (including any unit conventions for radius). Consult its documentation for details.

• WCSERR is used as a failure marker in the FITS header when exceptions=False.