[gregbradley]

The standard answer to this type of question is invest in the mount first.

As pointed out, virtually any scope with excellent mount tracking can produce a nice image.

The other standard answer is if learning go short focal length and do long focal length later on.

Why? Everything is magnified with long focal length including the tracking errors. So until you have balancing your mount/scope, go-tos working well, polar alignment near perect, autoguiding under control with low errors and focus perfect then long focal length makes all these things harder.

Even finding the object in your camera can be very difficult with long focal length without accurate go-tos. That comes from excellent polar alignment and use of the software that controls the mount.

The other thing to consider is work back from the type of image you would like to produce.

Pick out images you see on the net you like and decide what scope that was and use that.

APO127mm can image quite a range of things and is well suited to a DSLR. You'd be busy for ages with one of those before you felt it were time to upgrade.

A 200mm RC adds also the need for collimation skills. Others can tell you more but from what I have read on this site the 127 is good value except for the focuser which can be upgraded. Refractors generally don't need to be collimated.

An Orion EON120 may be another nice choice. Nice Taiwanese manufacturing.

Greg.