Hi,
As far as I understood, the data requested from jsoc is level 1, meaning the solar north-south axis is not aligned with the vertical y-axis.
In level 1.5 axis, this alignment is done.
Is there a procedure to align cutouts?
Or are cutouts already aligned when specifying bottom left and top right in arcsec and setting the frame to helioprojective?
I want to compare own data from specific Sun regions with SDO data and was thinking that requesting cutouts (like in the documentation) already gives me the right region. But the data still is level 1 which confuses me.
Yes, that’s correct. By default, when requesting cutouts from the JSOC, these data are level 1. You can confirm this by checking the scale or rotation_matrix properties of your resulting sunpy map.
When you request the cutouts from the JSOC, there are several additional processing options, including performing sub-pixel registration. You can find more info about that on the export data page. From sunpy, you can set register=True to perform subpixel registration on each cutout. See the API docs for the Cutout object.
Alternatively, you could also co-align all of the data yourself using the reproject_to method of Map by constructing a WCS for your cutout that has a diagonal rotation matrix and an appropriate scale and reference pixel. You can find more information about the reproject_to method on this page, including a list of examples.
Thank you for your response, but I’m still confused.
The ‘helioprojective’-coordinate system only makes sense if the y axis is aligned with the north-south axis of the Sun, right? (and the x-axis is aligned with east-west). But this is not the case with jsoc level 1 data. So why is there a functionality to request cutouts specifying my coordinate system, if the returned data is level 1 and therefore not aligned? Hope this makes my confusion clear.