After reading your descriptions of the situation it seems obvious that it isNOT ethical to take this shot. It's not a question of legality since you have tags for both sexes. The problem is with making a clean shot and quick recovery. If it is too dark to tell if it has antlers within 20 yards then it is too dark toshoot. Like TeeJay said, how are you going to see exactly where your arrow hits if you can't even see if it has antlers? How will you know which direction it ran after the shot? Many times a deer does not bleed a lot right away and that last visual sighting can be an extremely important part of the recovery. You said that hitting a twig is not an issue but people hit twigs all the timeeven in broad daylight. No one thinks they are going to hit a twig yet it does happen. Those of us who hold the highest level of ethics do absolutely everything in our powers to make the quickest kill and recovery as possible.

You mentioned that you are a new bowhunter and I think that is another reason to wait until you have better light. Shooting an arrow at a live animal can be difficult especially until yougain some experience. To make the most accurate shot possible we need to focus on a small area or "pick a spot" as many people say. Sounds to me like you can barely make out the outline of the deer which again is not helping to make the most humane shot.

Many times I climb down from my treestand 5 to 10 minutes before legal shooting time ends because it is just too dark to make an ethical shot. This year with a full moon in early November I actually felt comfortable sitting until legal shooting time ends more times than normal. I have a hunch that if you are seeing deer that often right before daylight then it should not be that hard to get within range of one after daylight with some strategy and patience.