Hi guys, I've never posted here before and am new so bare with me if I have or haven't posted in the right area. 

I've been following alot on this forum recently and find it really helpful so wanted to be part of it.

I'm looking for my first astrophotography telescope. I've currently got my dslr linked up to my celestron nexstar 6slt and it's been working fine but not really ideal. 

I jave been looking at a few and wondered if which one if any of these two I should choose

SKY-WATCHER EVOSTAR 72ED DS-PRO

Skywatcher Startravel 102 AZ-3

the 102 is f4.9 but is achromatic 

the 72ed is doublet and f5.8

I know a lower f ratio is better but will the extra aperture of the 102 be better? I have been told to stay away from achromatic though. I also noticed the one woth the mount is £50 cheaper which to me says something. Any help would be awsome.

thanks 

George