I have a question about Deep Cycle Batteries

Hi All,

I'm heading up to Shingletown Star party this coming weekend and I have a
question about the size/capacity of the battery I'll need. I usually image
where I have access to AC power so this has not been an issue for me
previously.

I have a battery that can power my G-11 with no problem. But I have a Canon
20d that I wanted to use the AC adapter for, as well as Laptop and STV
autoguider.

Now I know my small 35amp/hour Gel Cell is not enough for those, so I need
to know how many amp hours I need to get. Is 55 good enough? 80?

I'll be able to charge the batt. during the day from what I understand, but
night time is the issue.

Any suggestions are appreciated.

Thanks

Craig