Nice work Mark
For my composite transit image
http://www.iceinspace.com.au/forum/s...ad.php?t=92098 I selected one set of images near the middle of the transit when the seeing was better as the background sun image. I then copied and pasted the other twelve image sets on top of that background image as individual layers in normal overlay mode. Then working through each layer individually by having only it and the background turned on (the eye symbol), I set the opacity to about 50 percent and lined them up based on the solar disc. Once they where all lined up, I then went through each individual layer again this time at 100% opacity, and using a layer mask on each layer I painted out everything bar a small area around Venus. Once this was done for each layer it leaves just the background image with it's single crisp sunspot regions (and any other features) with Venus "time lapsing" across the disc.
Cheers
Greg