To see planets close to the horizon just after sunset,
you need to wait until Nautical Twilight
center of the sun is geometrically 12 degrees below the horizon. You
can still make out shapes and outlines, but too dark to walk or drive
without artificial light. You can still see the horizon, esp in west.
Dark enough for old time mariners to make calculations. Viewing planet
near the sun, you may need to wait until nautical twilight for sky
to be dark enough. Mercury or other planets or other planets are more
likely to be visible at Nautical Twilight - don't wait too long, since
they will set very quickly after that.
Distances with Fingers
at arm's length, your pinky finger is about 1 degree wide. Your three
middle fingers, held together, are about 5 degrees wide. If you hold
out your fist, it will measure a 10 degree width of the sky. If you
hold up just your pointer finger and your pinky finger, it will be
about 15 degrees of sky between them. If you spread the thumb and
pinky of one hand as far apart as they will go, it will be about 25
degrees from outside edge to outside edge.
method of finding distance of planets with fingers is similar to Mudras
which are given in Hinduism.