A good focuser is just as important as the optics. Electronic focus control and precise mechanics are a must, especially for astrophotography. Here you will find a large selection of suitable "hardware".
Starlight EC35-505-3CR---End Cap 3.5" with 3.0" Compression Ring openingThis end cap fits the Feather Touch 3.5" focusers and has a 3.0" compression ring ...
.style1 { border-color: #fefefe; border-width: 0; background-color: #ffffff; } TS Optics - T2 Extension ringLength: 15 mm Accurate manufactured T2 extension ring with an overall length of only 15mm excluding T2 external thread