Spiral: Winding direction on UKIDSS image however different than in SDSS!
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zutopian
http://skyserver.sdss3.org/dr8/en/tools/chart/chart.asp?ra=127.13681062&dec=8.7337857Posted
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klmasters
scientist, admin
One of the images is flipped. I will chase down which. You can see that if you match the star patterns...
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vrooje
admin, scientist
As far as I can tell all the UKIDSS images are flipped compared to SDSS, and many of them (but not all, and not all in the same way) are rotated.
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Edd
scientist
SDSS Skyserver images are oriented to put north top and west right (not left, since you look up at the sky, not down as you look at the ground). We take the images as they come straight off the camera to generate the UKIDSS images, so there's some orientation difference naturally there. The inversion rather than rotation is probably a coordinate convention oversight - do you label the origin of the axes at the bottom left or top left? There's no direct specification for which way is right, and in fact I've heard there's apparently something of a split between amateur and professional astronomy equipment in how the data is written out. I neglected to check for this - it didn't occur to me there would be an issue actually - and I wrote the 'simplest' code to generate the image and some bit of it obviously made the wrong assumption!
This shouldn't affect how you classify at least, since we don't ask you about winding direction any more.Posted
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zutopian
The SDSS image is not just flipped, but also rotated compared to the UKIDSS image.
I flipped and rotated the UKIDSS image. Here it is.:Posted
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zutopian
We currently classify also GZ images, which were taken from SDSS DR8. When we look in DR8, it is rotated, but it isn't flipped, as far as I know.
It would have been fine, if the orientation of the GZ images and the images in SDSS was same.Posted
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zutopian
Now I downloaded below image from the UKIDSS server. The orientation is same as in SDSS.:
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