Beginner Astrophotography Scope

[Kowspot]

Hey all! So from the various articles I've read around here I decided to go with the CG-5 mount from Celestron and that leave me with picking out a scope! I was hoping people with experience would be willing to offer some advice.

I am looking to get into deep-sky astrophotography (nebulas/galaxies/etc..) and I don't wanna go all out on a scope since I'm just starting out. I'd like to stay under $700 if possible but a little higher is permissible So far I've narrowed it down to these selections. If you agree/disagree please give reasons, and if you know of any others I didn't list please let me know!

Stellar Vue 70 ED: SVR70ED

Astro Tech 72 ED: Astronomy Technologies Astro-Tech AT72ED 72mm f/6 ED doublet refractor, black tube

Astro Tech 65 ED Q: Astronomy Technologies Astro-Tech AT65EDQ 65mm f/6.5 ED quadruplet astrograph

A few questions I had.. Apart from light gathering ability, does the aperture difference change anything in AP? Like should I consider a 80mm over 70mm over 65mm etc..

Thanks in advance!