I use this feature when the object is small, so it can be viewed on a larger scale when hovering over the image.
The instructions are the ones
@Marc Whitsett posted, but there's a detail that needs to be taken into consideration: the images need to have the same size.
To achieve this in PixInsight, I use the crop tool to highlight the interesting part of the image. But before using the crop tool, I note down the size of the original posted image.
After using the crop tool, I employ the resample tool to make the new image the same size as the original image.
Once done, I post it as a new revision. Now, with the same size as the original image, I follow
@Marc Whitsett instructions to set the image from the new revision as the mouse hover image.