Your edge on galaxy is well done really, but maybe try some softer pencils for the outer "edges" use the harder pencil for the core detail.
A blending stick works well for giving a soft nebulous effect.
Your stars are maybe a tad big, to get sharp round stars, use a hard pencil like a 4H.
Getting the size of stars correct in proportion to their magnitudes and each other,takes a lot of concentration for objects with a lot going on, like the double cluster or the bee hive. I am still working on getting that right myself.
Use the pencil going straight down on the paper , not sideways to avoid rough edges on the stars. Any rough edges can be fixed in Photoshop, but if you are doing an object with a huge amount of stars in it, then is best to be accurate from the start. NGC's and Messier objects are easier in a way than moon sketching as you are not really dealing with constant light changes.
Take a good long time to look at the object before sketching it.
Take a good long look at the stars in the field of view, in relation to the NGC and each other and the circular edge of the fov.
If you do a pencil sketch with the intention of inverting it , you can remove detail using a very edge on eraser, this can give a soft effect in the final inverted image. Hope this is of some use.
Deirdre Kelleghan
Irish Astronomical Society
www.deirdrekelleghan.com
  