One of the big challenges in astrophotography is achieving really accurate focus, easiest and fastest way of doing this is with a Bahtinov Mask. there are amny ways of making your own masks, but a robust, accurate and convenient solution is 3D printing.
See THIS PAGE for details of how to use a Bahtinov Mask.
Here are STL files to allow you to 3D print your own Bahtinov Mask for some popular sizes of lens and telescope:
Mask.stl for 130mm reflectors with a roughly 150mm/6" tube, such as the Skywatcher 130P and 130P-DS.
Small-Mask.stl for telephoto lenses (catadioptric and conventional) with a 76mm end diameter.
Tiny-Mask.stl for short telephoto lenses such as the Zeiss 135mm F.3.5 'Sonnar' which take a 48mm filter and have an external diameter of about 52mm.
The largest mask requires two M6 nylon screws about 30mm long to be threaded into two holes, these allow it to be 'hooked' onto the end of the scope.
The smaller masks have an 8mm collar which is an easy fit over the end of the lens. if your scope/lens is a slightly different size, scale the X and Y dimensions (but not the Z-dimension) of the nearest-size mask to fit.
Masks can be used directly on a scope or on the end of a dew shield. They are not a close fit, they just 'hang there' so as not to disturb the focus/pointing when you lift them off.
These print best with quite a dense fill (30-40%) and thicker outer layers than normal.They don't need to be black, just opaque.
My masks were printed on a Prusa i3.
Don't forget to remove the mask before taking photos!