I'm sorry to hear you had problems. I don't know if this would work with charcoal, but it works with pastels: Go over the too-dark sky with lots of white, smudge it, and then another layer, till you get the lighter shade you want. Sometimes it helps to press rather hard with the white to get it to take, but start out with a medium pressure till you see how it reacts with the dark. Maybe it'll work, and maybe it won't, but at least this is your chance to experiment and see if it does.
Thanks Sandy, I'll try that. I did try a small area of white on it but I didn't smudge it in. It's a big sky though.
Well Voltville I'm bummed. I had my snowy river drawing all sketched in and it was time to do the sky since there would be trees over the sky. Well my usual light vine charcoal came out too dark. I can't figure out why it came out that dark when I was using a pretty smooth paper. I have 1/2 different erasers and it just won't erase. With a dark sky like that it would look wrong with the sun shining on the trees so I'm scraping it and will try it again another time. I'm too bummed to start over now. I'll have to find something else to do.
Sometimes things don't work out the way they are expected. Part of the learning curve. Don't be bummed, be happy Every drawing isn't going to turn out the way you expect which sucks but good for you for deciding to move on to other projects.