Mk I Dobsonian 16" f5 pros and cons


  • The bearings work well. Although the altitude bearings are of small diameter, putting the pads at a wide angle increases the frictional force to the optimum. The pressure must be much higher than the 15 psi recommended for Teflon / Ebony Star, but seems fine for whatever the yellow material is.
  • It holds collimation well.
  • It's very solid.


  • It's too heavy to move around and set up easily. The complete tube has to be lifted on and off the altitude bearings. Wheels are then fitted so it can be moved in and out of the house. It's awkward to get through the back door. The rocker / groundboard has to be manhandled.
  • The mirror cell is not ideal. There are not enough suspension points (9) for a thin (30mm = 1 3/8") mirror. There's no sling. The cooling of the mirror is slowed down by a thick aluminium plate.
  • It's difficult to shroud, so I haven't tried.
  • Collimation is difficult, requiring two spanners to adjust each bolt.