I have a Celestron C6 f/5 Newtonian OTA.
Optically very nice images up to 140X. Not really looking to push the magnification but more to optimize it for wide field/low power deepsky viewing.
It originally came with a 1.25" Rack and Pinion focuser of dubious quality.
I am in the process of doing a major make over.
Removed the original focuser, Vixen style finder bracket, spider/secondary holder with attached
I enlargened the focuser hole to 2.4" to accept a 2" JMI NGF-2 single rate Crayford focuser with 2"-1.25 adapter. Drilled 4 holes to match the 2.75" square hole pattern of the new focuser.
Flocked (Protostar) the first 7" circumference from the front of the optical tube. Renistalled the finder bracket holder. Installed and levelled the new JMI 2" Crayford focuser. Reinstalled the spider/secondary holder/2° mirror. Recollimated the scope. Rechecked daytime focus - requires a 2""extension tube to reach focus with a 2" eyepiece. Have not a chance to access nighttime deepsky viewing.
Just one problem with the focuser:
The C6N tube has an outside diameter of ~ 7" but the curvature on the JMI 2" Crayford is more like 12". There is an ~ 1/2" gap running the length of the focuser on the 2 sides parallel to the length of the OTA. There is also a a progressively increasing gap on the other 2 sides.
When you look into the OTA from the front on an oblique angle, ambient light is visible through the 4 "gaps".
What would be a simple (easily removable, if necessary) fix to fill in the focuser "gap" and still look nice? Paintable caulking comes to mind. Other options?