The first real astrophotography I did was with this wonderful instrument from Vixen. There are some things to know about this telescope:

Vixen advertises this instrument as a aplanatic telescope. However, looking a little bit deeper into it, you can wonder why exactly it's so cheap. It's sometimes called "the poor man's RC".
The answer is that the telescope is in fact a corrected Dall-kirkham. A DK has an eliptic primary and a spherical secondary. Add some corrector lenses and you end up with a nice big flat field.

Making spherical mirrors is easy and cheap. The "secret" about this gem is that the 2 mirrors in the instrument are BOTH spherical.
What Vixen does is they coat and allumize the primary mirror in several layers. Bit thicker and thicker towards the center, so you end up with a elliptical primary mirror with the right specifications to form a Dall-Kirkham.
This is possible because it's only a 20cm mirror.
Only issue is: recoating can only be done in their factory in Japan, since this is a specialized coating process.

Collimation: Some words about the collimation. I spend multiple nights collimating this thing. When good collimated it's a nice astrograph. But you have to know how to do it.
To start, the primary needs to be just right in terms of tension. Not too much, not too light. For this you have to deassemble the scope and adjust mirror cell.
First, the focuser has to be aligned. You can do this with a chesire or better with a laser. Get the secondary out and collimate the focuser on the center hole of the spider.
Second, assemble the secondary and collimate using the returning laser.
Third, collimate the primary using a startest.