I have been using the Google Sky version of the API for many years now at my star finder astronomy site (eg. http://www.starsfree.com/view/91.025/-24.3/M8 http:

I have been using the Google Sky version of the API for many years now at my star finder astronomy site (eg. http://www.starsfree.com/view/91.025/-24.3/M8 http://www.starsfree.com/view/91.025/-24.3/M8 ). I don't know of an alternative. There is a Moon version and a Mars version, too. I don't know if the images for Sky, Moon and Mars are available to create an alternative, but if they were, I would be up to cobbling together a program to replace these.