I have always used the default 2000.0 Epoch in Imagesolver and Annotateimage, but when I noticed a bright star falling exactly on an equatorial grid intersection in my annotated image, I compared it to a couple other tools, Stellarium and SkySafariPro 5 and found the annotated coordinates didn't line up with the other two references (which agreed with one another), even when I changed the Imagesolver/Annotateimage epoch setting. In fact changing the epoch setting in Annotateimage appeared to have no effect on its output.
Thanks for your work on this great tool,
Arlo Reeves