Recently I generated a night-sky panorama image. I imported several .cr2 images into Lightroom, exported them as .tif without any adjustments and stitched them together in PTGui. The resulting image had a very strong artifact in the sky which looks like a JPEG-induced compression artifact (see picture).
You can see the artifact on the lower left portion of the night sky. The contrast was greatly increased here, but the artifact is also visible without constrast adjustment.
Upon further investigation, this artifact occurs even in the directly imported .cr2 file and is visible directly in Lightroom (see picture).
In the lower third of the night sky you can see the artifact. This confirms that it is not a result of the panoramic stitching routine but a result of some kind of issue with Lightroom.
I would like to know why this happens and if there is any improvement I could make when importing my image, like selecting colorspace/bit-depth?