The following classifications of the various types of deep-sky sketches are solely my opinion only:   

                 Detailed visual telescope sketching:  Observing an object through a telescope via an eyepiece. Drawing the object on paper or a sketch card “as verbatim” as possible using a pencil, or pencils of various hardness.   

     I’m a visual back yard observer after more than forty years.  All of my sketches are made using a pencil and a 5 x 8 blank note card with a 3-inch circle.   

     Impression sketching:  A sketch made at the eyepiece, using a pencil, charcoal, or chalk and representing what the observer mentally perceives, without a great degree of scale or detail. 

      It’s my opinion that John Mallas of “The Messier Album” used this technique, for the…