Because the night sky rotates around fixed points in the Southern and Northern Hemisphere sky, taking pictures of the night sky gets difficult when you want a long exposure or you want to focus in on a very small part of the sky.
The shots above are taken on a platform with fairly modest lens.
The platform I have used for this is the simplest way to get these types of shots - and involves simply placing a camera mount onto a fairly inexpensive computer driven telescope. The approach is also very mobile - the gear can be moved with little effort.
The only down-side to this approach is the time it takes to align your telescope at the beginning of each session.
I have two other projects in hand. The first is a permanent heavy installation based on a modified equatorial mount and the third is a plan to motorize a 12" Dobsonian.