I'm not used to paint outdoor scenes, and I was trying today when I notice something: THE SUN MOVES! Ok that was pretty obvious, but there is some tips for me? Should I draw reaaally a fast sketch and finish it later? Should I draw every day in the same hour?
You'll have this problem everytime you paint under natural light conditions. The sun indeed moves.
One thing to cure that would be to have a good plan ready on how to approach your painting. For the initial drawing, for example, it may not be neccessary to have stable light conditions since its all about hitting the angles and proportions and not the values. So, you can work on your line-drawing the whole day without worrying too much. After that, when you paint in values or colours you will face the problem again, one prossibility would be a make photos of your scene for the capture of value and colour (Of course you will have to be aware of the shortcomings of photos and you should make additional studies to make up for that, I mean study the dark darks and such and define a pallette on the spot.) So yeah, it is possible, most paintings are done in the studio, anyway.
Another possibility would be that you really do come back every day at the same time. I means less breaking down in steps of your process but it also means less control. Nobody controls the weather. Even if you're painting a stilllife inside, a bad eather-front can make for a very dark environment all of a sudden.
You can also learn to paint really fast.
All in all, natural light can be a bitch but I prefer looking at it.
The sun doesn't move *that* fast.
What I would do if you're working on studies is take some pictures for later reference, sketch out your scene, and then block in all the shadows first. Then, even if the sun moves a little bit, you know where the shadows are supposed to be, so it's less of a problem.
Paint small so you get more done. When I say small, I'm talking index-card size and below.
Nathan Fowkes shows you what you can do with a half an hour's time, a small sketchbook, and watercolors. Make your kit portable so you can set up quickly to capture what you see before the light changes. He generally general starts off with a pencil sketch, puts down a transparent warm ground over that, then paints the big masses in, and if time allows, moves on to smaller details.
Remember the general rules of thumb:
• General to specific.
• Big to small.
• Dark to light.
• Back to front.
• Thick over thin.
If the weather conditions shift dramatically, no worries! If you got the important parts in, your painting will still read.
Check out his blog for more examples of "less is more":