First question, How do you charge your battery away from the dock? By outboard for example?
If you can use your outboard to charge your battery you should be able to do OK.
If not you are going to be hard pressed to get more than a couple of days of sailing in without killing your battery.
How many amp hours is your battery rated? Take that number and divide it by 2. That is how many amps you can use before needing to recharge. Using more than 50% will shorten the life of your battery greatly.
Your anchor light will use about 8-10 amps per day. Running lights will use about 4 amps per hour of use and any other lights will use 1-2 amps per hour of use. VHF radio in receive mode will use about 1, stereo radio will use 5 amps per hour.
Figure out your total daily amp usage and divide your battery amperage number/2 by that number. That is how many days you can go out without a recharge.
Many small flexible solar panels will put about 8 to 12 amps back in your battery on a good sunny day. So basically a solar panel for your boat would replace the amount of amps used by your anchor light each night.
When I had a small sailboat I added a second deep cycle battery to my boat, which made it possible for me to anchor out for about 3 days without recharging. That may be cheaper than the purchase of a solar panel.
Hope this helps.