better DIY planetary telescope: 8" or 6" Hey all, I'm starting to design my first home built telescope. I already own a 10" dob which works great but I've decided I would like something more transportable that is easier to take camping or wherever else. So right now I'm leaning towards a 6 or 8" truss dob for simplicity and I'd like to gear it more for planetary and lunar observation as opposed to deep sky. I don't want to go any smaller as I want to retain a some deep sky ability. From what I've read, even though aperture is almost always most important, something with a slower focal ratio (f/10 as opposed to f/5 if I understand it right) is better for planetary of viewing. Using this logic, a 6" scope would be better because a larger f-ratio could be used for the same length of tube. With a desired focal length of around 40 inches I could probably get something around f/7 for a 6" or f/5 for an 8". But this wouldn't be much different than my 10" with is f/4.7. So, my question is essentially even though an 8" mirror has greater aperture, is the 6" with a larger f ratio going to be a better option for planetary viewing? Thanks!