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It is important to set the pixel scale of the image as accurate as possible to increase the
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speed of astrometry.net. From astrometry.net: "Most digital-camera images are at least 10
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degrees wide; most professional-grade telescopes are narrower than 2 degrees."
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Several parameters are available to set the pixel scale.
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``scale_units``
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- Units used by pixel scale variables
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- Possible values:
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* ``arcsecperpix``: arcseconds per pixel
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* ``arcminwidth``: width of the field (in arcminutes)
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* ``degwidth``:width of the field (in degrees)
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* ``focalmm``: focal length of the lens (for 35mm film equivalent sensor)
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``scale_type``
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- Type of scale used
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- Possible values:
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* ``ul``: Set upper and lower bounds. If ``scale_type='ul'`` the parameters
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``scale_upper`` and ``scale_lower`` must be set to the upper and lower bounds
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of the pixel scale respectively
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* ``ev``: Set the estimated value with a given error. If ``scale_type='ev'`` the
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parameters ``scale_est`` and ``scale_err`` must be set to the estiimated value
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(in pix) and error (percentage) of the pixel scale.
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Parity
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------
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Flipping an image reverses its "parity". If you point a digital camera at the sky and
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submit the JPEG, it probably has negative parity. If you have a FITS image, it probably
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has positive parity. Selecting the right parity will make the solving process run faster,
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but if in doubt just try both. ``parity`` can be set to the following values:
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- ``0``: positive parity
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- ``1``: negative parity
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- ``2``: try both
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Star Positional Error
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---------------------
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When we find a matching "landmark", we check to see how many of the stars in your field
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match up with stars we know about. To do this, we need to know how much a star in your
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field could have moved from where it should be.
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The unit for positional error is in pixels and is set by the key ``positional_error``.
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Limits
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------
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In order to narrow down our search, you can supply a field center along with a radius.
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We will only search in indexes which fall within this area.
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To set limits use all of the following parameters:
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``center_ra``: center RA of the field (in degrees)
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``center_dec``: center DEC of the field (in degrees)
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``radius``: how far the actual RA and DEC might be from the estimated values (in degrees)
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Tweak
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-----
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By default we try to compute a SIP polynomial distortion correction with order 2.
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You can disable this by changing the order to 0, or change the polynomial order by setting
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``tweak_order``.
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CRPIX Center
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------------
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By default the reference point (CRPIX) of the WCS we compute can be anywhere in your image,
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but often it's convenient to force it to be the center of the image. This can be set by choosing
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``crpix_center=True``.
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License and Sharing
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-------------------
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The Astrometry.net [website](http://nova.astrometry.net/) allows users to upload images
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as well as catalogs to be used in generating an astrometric solution, so the site gives
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users the choice of licenses for their publically available images. Since the astroquery
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astrometry.net api is only uploading a source catalog the choice of ``public_visibility``,
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``allow_commercial_use``, and ``allow_modifications`` are not really relevant and can be left
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to their defaults, although their settings are described below
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Visibility
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^^^^^^^^^^
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By default all catalogs uploaded are publically available. To change this use the setting
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``publicly_visible='n'``.
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License
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^^^^^^^
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There are two parameters that describe setting a license:
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``allow_commercial_use``:
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Chooses whether or not an image uploaded to astrometry.net is licensed
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for commercial use. This can either be set to ``y``, ``n``, or ``d``, which
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uses the default license associated with the api key.
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``allow_modifications``:
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Whether or not images uploaded to astrometry.net are allowed to be modified by
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other users. This can either be set to ``y``, ``n``, or ``d``, which
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uses the default license associated with the api key.
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"""
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# Licensed under a 3-clause BSD style license - see LICENSE.rst
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#from __future__ import print_function
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@@ -22,17 +158,18 @@
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importtime
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# export all the public classes and methods
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-
__all__= ['Astrometry', 'AstrometryClass']
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__all__= ['AstrometryNet', 'AstrometryNetClass']
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# declare global variables and constants if any
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# Now begin your main class
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# should be decorated with the async_to_sync imported previously
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astrometry_net_url='http://nova.astrometry.net/'
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apiurl='http://nova.astrometry.net/api/'
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@async_to_sync
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classAstrometryClass(BaseQuery):
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classAstrometryNetClass(BaseQuery):
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"""
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Not all the methods below are necessary but these cover most of the common cases, new methods may be added if necessary, follow the guidelines at <http://astroquery.readthedocs.org/en/latest/api.html>
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