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Full Version: Matching orientation ST vs astrometry.net
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Hi Greg,

A clarification please, I'm not sure where I'm thinking incorrectly.

Last night I took this pic to see if it shows a very distant quasar (HS 1946+7658 and it did). [/url][url=http://nova.astrometry.net/user_images/2963128#annotated]http://nova.astrometry.net/user_images/2963128#annotated. The object is not relevant now, but it is is the orientation reported by astrometry.net: "Up is 311 degrees E of N", so up is 49 degrees west of N.

I visually matched the image with the atlas using those 3 resolved stars, small details match as well. Attached is a screenshot of the Interactive Atlas view. "Up" in the image is towards up-left  My question is about the orientation arrows shown in the lower-left corner. In reference to those arrows, up in the image it between N and E, so it's east of N. I'm sure I'm doing something wrong but don't know what. The flip and mirror buttons are not enabled. I'm also attaching the camera view to show it matches the picture.

And a related question: in the same Interactive Atlas view, when I right click the circle in one corner of the rectangle defining the camera view and enter a rotation angle, the camera rectangle does not rotate. When I had a camera view also open, sometimes (but just sometimes) the camera view will be updated when I entered a new rotation angle. I haven't figured out the pattern, when it was updated and when not. Any insight on this? Am I using it incorrectly? My intended use was to take the rotation angle specified by astrometry.net and enter it there, rather than visually matching the picture with the atlas.

Thanks!

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Hello,

Looking at your screen captures, I can confirm that everything looks right. My question about the astrometry.net result is, which side do they consider up? Their descriptions seems difficult to understand, particularly when it doesn't define up. Could it be that "up" is the long side of the image, the one at the top of the camera view? Then it would seem to make sense.

Regarding changing the change, you really shouldn't be able to rotate the camera view if the camera doesn't have a rotator (as defined in the imaging system set up). That should go for dragging and for entering an angle. It may be that only the setting the angle part is considering whether or not there is a rotator. I will look into it further.
Hi Greg,

Re: astrometry.net: not entirely sure about their understanding of "up". I checked the paper describing the algorithm, but there's no such information there. Interestingly, there was a CloudyNights thread about it and a shorter one on Flickr. 

Re: rotation. I went into the imaging system's Control System screen and checked "Camera Rotator". However, upon entering an explicit rotation angle, the rectangle representing the camera FOV still does not move. I tried repeatedly and I double-checked the above checkbox was enabled. I tried with both the Camera View window closed (right-click on the small circle, enter a particular rotation angle, notice the rectangle was not rotated)  as well as with the window displayed. Same result. The behaviour was correct, however, when I rotated the angle freely by dragging the small circle with the mouse.

This was with 4.0e.

Thanks for looking into it.