On Sep 18, 2008, at 12:19 AM, Matthijs H.D. van der Wiel wrote:
> L.S.,
>
> Does anyone know how to rotate an image in GAIA such that the positive
> RA-direction points to the left and positive Declination up?
> GAIA does read out the correct RA and Dec and shows them in the
> "alpha" and "delta" boxes as I hover over the image. Clicking on
> 'image analysis', 'change coordinates', 'built-in coordinates' shows
> that GAIA is already using the Sky Coordinates. Yet, the image is
> still shown in its native (x,y) orientation.
>
> I have a FITS image with proper WCS information. SAOimage DS9
> understands the WCS info in my image and is also able to rotate it to
> RA horizontal / Dec vertical. Can GAIA do the same?
>
GAIA completely understands the WCS in these images but does not
attempt to rotate the image in order to put North at the top. If the
issue is simply 90 degree rotations or flips you can click on the
little flip/rotate arrows at the top of the GAIA display.
I'm surprised that DS9 resamples the image in order to always display
North up.
To regrid an image to align it with it's coordinate system you can use
KAPPA REGRID and provide a null mapping (where null means "!"). This
works for arbitrary rotation angles.
--
Tim Jenness
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