I wanted to post this here so others with observatories can see this. I am in the process of retrofitting my dome control and one of the things I wanted to do was to put solar panels on the dome to keep the battery that will run the dome shutter up/down. Just saw this design for a solar charging controller this morning on Instructables and this is simply awesome. I'm an electrical engineer and the design, analysis and presentation of this controller is simply over the top. You can build this controller yourself. He has links to get the custom board and all of the instructions on how it works.