Posted By Markus Ludes
a 175 mm apo offers ultrahigh contrast , excellent choice for douple stars and Planets. Due its smaller aperture and no central obstructionit is also way less effected by seeing turbulences, which means the real good nights with 175 mm aperture will be many more than with larger size.
The SC scopes I know will have zero chance on Planets and douple stars against the Apo. On Deep Sky you may see in the SC a brigher Image but much less contrasty, so the Apo will show you some details in Deep Sky stuff which you will not see in the SC
The classic Newtonian can be optized for everything, but you need to accept to deal with tweaking the collim,ation, always , mirrors which need to be cleaned from time to time and a open tube which also will be effected very much by the seeing many times
Leaves the Mak. A bigger Mak 10" or 12" will be also way more often effected by seeing, but if you buy a very high quality Mak and you get seeing like we have had last year in Florida it will beats the Apo , excapt on widefield observing where the apo offers wider field due its shorter focallenght.
Solution: buy a Apo 175 for everyday use and a 16" Mak for the small faint stuff and best seeing for planets