mldee
26-12-2011, 02:03 PM
Boxing day and everyone's off to the sales. Peace at last! A great opportunity to start on my C8 mods by opening my OTA up and examining. Pics attached.
My interest is based on Multiweb's (Marc) C11 collimation work recently posted here.
Removal of the C8 mirror assy was pretty straightforward. I used this procedure: http://www.ngc1514.com/Celestron/disassem.htm, as it has a good cutaway pic of a SCT in it.
On evaluation of the focus plate to mirror attachment (see pics) I decided it seemed pretty solid, and was not worth touching for such a small size mirror, and decided to limit any activity to removing the small residual mirror "vagueness" when reversing focussing directions and perhaps a one-bolt focus lock as Marc has described in his thread.
Anyway, before I proceed further I'd like to call on learned opinions on whether I should remove the (very small) potential flex between the focus plate and the mirror, due to the red adhesive being silicone-based and retaining some flexibility. Adding Araldite to more solidly lock the mirror to the plate in the gaps between the red stuff?
My question being: is the red flex adhesive there to allow expansion movement, or just because it was the most suitable manufacturing method? I can't see any need for thermal expansion provision in that assembly. ie, if it was glued on too solidly, maybe the stresses on the mirror would be too high? I really doubt it.
If it was solidly glued, I think the focus-shift would improve, as there is almost zero tolerance between the sliding focus tubes, very well mated.
Finally, As a "pusher", rather than a full focus lock, in order to keep the mirror moving against the focus screw, I was thinking of adding a thick donut of soft foam to the rear of the mirror, so that it gradually compressed as the mirror moved rearwards in focus, thereby "pushing" against the "pull" of the focus rod. Simple and may work. Comments?
The pics are basically just reference stuff, in case someone else wants to disassemble theirs in the future.
More news at 11:D
My interest is based on Multiweb's (Marc) C11 collimation work recently posted here.
Removal of the C8 mirror assy was pretty straightforward. I used this procedure: http://www.ngc1514.com/Celestron/disassem.htm, as it has a good cutaway pic of a SCT in it.
On evaluation of the focus plate to mirror attachment (see pics) I decided it seemed pretty solid, and was not worth touching for such a small size mirror, and decided to limit any activity to removing the small residual mirror "vagueness" when reversing focussing directions and perhaps a one-bolt focus lock as Marc has described in his thread.
Anyway, before I proceed further I'd like to call on learned opinions on whether I should remove the (very small) potential flex between the focus plate and the mirror, due to the red adhesive being silicone-based and retaining some flexibility. Adding Araldite to more solidly lock the mirror to the plate in the gaps between the red stuff?
My question being: is the red flex adhesive there to allow expansion movement, or just because it was the most suitable manufacturing method? I can't see any need for thermal expansion provision in that assembly. ie, if it was glued on too solidly, maybe the stresses on the mirror would be too high? I really doubt it.
If it was solidly glued, I think the focus-shift would improve, as there is almost zero tolerance between the sliding focus tubes, very well mated.
Finally, As a "pusher", rather than a full focus lock, in order to keep the mirror moving against the focus screw, I was thinking of adding a thick donut of soft foam to the rear of the mirror, so that it gradually compressed as the mirror moved rearwards in focus, thereby "pushing" against the "pull" of the focus rod. Simple and may work. Comments?
The pics are basically just reference stuff, in case someone else wants to disassemble theirs in the future.
More news at 11:D