A-Team does a better job but here is my method:
1.
Download, install and open Fiji (ImageJ with plug-ins)
2. Drag the ascat files into the Fiji console. (start with a small selection, say, 5 days)
3. From the Image menu select Stacks->Images to Stack
4. Click the rectangle or ellipse button, select area of interest then from the Image menu select Crop.
5. From the Image menu select Adjust->Brightness/Contrast. Scroll through the images to view their histograms.
6. In the B&C console I increase the minimum to 41, in winter this doesn't lose too much information. Apply to all slices.
7. From the Image menu select Stack->Label, click the Preview checkbox and play with the numbers.
8. From the Image menu select Stacks->Make Montage. Set Scale Factor to 1 and click OK
9. From the Process menu select Enhance Local Contrast (CLAHE). I use 127,256,5.3 (For me this is usually just below 'too blocky' but A-Team prefers lower. Play with the numbers.
10. From the Image menu select Stacks->Tools->Montage to Stack and click OK.
11. From the Image menu select Stacks->Animation->Animation Options and choose a speed.
12. From the File menu select Save As->Gif
ImageJ has very few 'undo' options and it's easy to lose a lot of changes. Image->Duplicate is your friend.