Hi Warren;

I often use a deep sky filter for emission nebulas if I do not like the unfiltered image. I do not use a filter for galaxies. The camera needs about 2 minutes initially to build up to a very sensitive state. Then I move from object to object.

The exposures are 3-15 seconds and this allows time to observe a dozen or more objects in a session. An 18 inch mirror gathers enough light for most objects of small angular size and the very small fov helps to overcome urban light pollution.

I enjoy viewing galaxies and have used the following set up for several years;MC extreme x2, 18 inch Dob with tracking and a color analog  Speco monitor. I control the camera with my notebook and adjust images on the monitor. Instead of recording a digital image on the laptop I snap a photo of the monitor w my iPhone. Twisting knobs on the monitor gives a better view for me that dealing with digital signals on the laptop. 

I am able to view multiple objects and display them to the public and myself. The images are not attractive astrophotographs but are in color and easily visualized. The Dob has about a 1/4 degree FOV.