You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
There are several "underlying" WCS classes, all from astrometry.util.util -- Tan, Sip, and anwcs_t. Tan and Sip are the "native" astrometry.net implementations. anwcs can wrap either those classes, or Wcslib. These classes all have "pixelxy2radec" and "radec2pixelxy" methods.
At the Tractor level, there are a few options:
-ConstantFitsWcs is probably the easiest -- it opaquely wraps a Tan or Sip object. (maybe anwcs also?)
-WcslibWcs is similar, but uses anwcs (ie, Wcslib via two levels of wrapping... yuck)
-TanWcs wraps a Tan object, also exposing the Tan object's parameters so that they can be optimized by the tractor, if you wanted.
To answer the specific question here, what I don't understand about this code snippet:
is why you need "t" in the first place. :) If you change FitsWcs to ConstantFitsWcs, you're right, it won't have the cd1_1 etc properties, but I don't see why you actually need them... You can get the underlying wcs object by "kswcs.wcs".
cheers,
--dustin
The text was updated successfully, but these errors were encountered:
Attempting to answer dstndstn/astrometry.net#2 (comment)
The WCS situation is fairly confusing.
There are several "underlying" WCS classes, all from astrometry.util.util -- Tan, Sip, and anwcs_t. Tan and Sip are the "native" astrometry.net implementations. anwcs can wrap either those classes, or Wcslib. These classes all have "pixelxy2radec" and "radec2pixelxy" methods.
At the Tractor level, there are a few options:
-ConstantFitsWcs is probably the easiest -- it opaquely wraps a Tan or Sip object. (maybe anwcs also?)
-WcslibWcs is similar, but uses anwcs (ie, Wcslib via two levels of wrapping... yuck)
-TanWcs wraps a Tan object, also exposing the Tan object's parameters so that they can be optimized by the tractor, if you wanted.
To answer the specific question here, what I don't understand about this code snippet:
kswcs=FitsWcs(Tan('xmm_tile3_ks_20141017.fits',1)) . . .
t=Tan()
t.set_cd(kswcs.cd1_1,kswcs.cd2_1,kswcs.cd1_2,kswcs.cd2_2)
is why you need "t" in the first place. :) If you change FitsWcs to ConstantFitsWcs, you're right, it won't have the cd1_1 etc properties, but I don't see why you actually need them... You can get the underlying wcs object by "kswcs.wcs".
cheers,
--dustin
The text was updated successfully, but these errors were encountered: