Installing a GSO two speed focuser on an Orion 203mm OTA?

[Joanna Sue]

Hello Everyone,

I am about to set out on a task which might be somewhat beyond my skill level but I suppose this is how one learns. I am going to attempt to install a GSO 2 speed focuser on an Orion 203mm OTA. As near as I can determine, having both the scope and focuser in hand, there is a fairly large difference between the mounting hole spacing and the focuser distance from the secondary mirror. It appears to me after measuring a few times that the GSO focuser will need to be spaced away from the tube about half an inch. It is actually slightly over a half inch but I have determined it is better to be low than high on that measurement as it is far easier to shim a spacer than it would be to cut one down that is too thick. How I plan on making the spacer is to get a piece of aluminum bar stock 4 inches wide and half inch thick. They generally sell this by the foot online for slightly under 30 dollars US shipped to my location. Then I propose to get this bar passed through a forming roll to arch the bar to conform to the 9.96 inch (253mm) outside diameter of the OTA. Then to cut at 4" and then bore a hole in the bar with a hole saw that is equal or slightly larger than the hole in the Optical tube assembly from a template made with construction paper or poster board. Then to bore 4 holes that align with the OTA hole spacings. Then to do the same on the other side for to match the GSO focuser. Then thread these holes to a common thread to attach the spacer to the OTA and the focuser to the spacer. Then paint the adaptor to a flat black color after polishing off any rough edges. This will be an on going project as I will be depending upon others for some of the work to be done - hopefully at little cost to me....

= Joanna