Saturn images and mosaics Options

[Bjorn Jonsson]

The two PDS releases for the first six months of 2011 contain lots of images of Saturn, including observations of the great storm. The images obtained in February and March are particularly interesting. Here is a false color image processed to bring out various details and 'color' differences:



This is a composite of MT3, CB2 and MT2 wide angle images displayed as red, green and blue. The images were obtained on March 21, 2011 from a distance of 883500 km from Saturn's center. The images are part of a multifilter sequence covering this area of Saturn's northern hemisphere - mosaicking is not possible though since the sequence did not include coverage further east (otherwise I would have created a mosaic).

[Bjorn Jonsson]

On March 28, 2017 Cassini obtained many wide angle camera images of Saturn's north polar region at close range using various filters. Here is an orthographic mosaic of 8 RGB color composites. It shows the north polar region from directly above. This is processed from calibrated images with minor modifications to the color balance. The effects of the variable solar illumination across the image have been removed.



However, even though the color is approximately correct it is too saturated compared to Saturn's visual appearance. This is all highly subjective though but should nevertheless be pretty obvious to anyone who has ever looked at Saturn through a reasonably big telescope. Here is a version of the above image processed to more closely approximate Saturn's visual appearance by modifying the gamma:



And finally an image where color differences have been greatly exaggerated. This reveals some faint seams between the images. There are also color variations that are probably due to the sun's different elevation at different longitudes; areas with the sun low in Saturn's sky appear redder.



These images are preliminary in the sense that I'm still working on the exact color balance. Any changes there will be minor (if any) though so I'm posting these images now.

[Kevin Gill]

On March 28, 2017 Cassini obtained many wide angle camera images of Saturn's north polar region at close range using various filters. Here is an orthographic mosaic of 8 RGB color composites. It shows the north polar region from directly above. This is processed from calibrated images with minor modifications to the color balance. The effects of the variable solar illumination across the image have been removed.

...

Beautiful! Curious, what is your process for removing the solar illumination in these? That's one process I haven't yet been able to do.


-- Kevin

[Bjorn Jonsson]

Beautiful! Curious, what is your process for removing the solar illumination in these? That's one process I haven't yet been able to do.

I'm using software written by myself for the combined illumination removal and reprojection steps. I know this is possible in ISIS3 too but I don't remember exactly how (possibly by using photomet?).