So the new M68 tilt plate for the front of the ZWO OAG/6200/filter wheel combo arrived. As soon as it showed up, I could see this was going to be an issue. There is no sort of light trap to keep light from leaking in when you apply even the slightest amount of tilt. It is just round flat surface (tilt plate) mounted to another round flat surface (oag). So when you raise one side of the plate to apply tilt adjustment, you are immediately separating the plates all the way to the hinge point, which is the opposite side of the tilt adjustment where the two plates meet. The design is not a good one. It would have benefited from some type of light trap tongue and groove style system, but this would have meant a redesign of the OAG. As this was a last minute offering based on customer feedback, it is what it is.
3-D printing to the rescue!
Fortunately, this problem was easily solved. I designed a simple light baffle that threads in to the unused threads of the OAG. The baffle prevents the light cone from being exposed to the gap created by the tilt application. The outer diameter of the baffle allows it to fit inside of a Baader and Moonlite (probably most others too) M68 extension tube. There is enough clearance between the walls of the two surfaces to allow for sufficient tilt application. Clear aperture of the baffle is approximately 60mm. This should cover just about any light cone used for imaging.
Rockstarbill was able to demonstrate the light leak with his camera and modest tilt inputs. Hopefully he will chime in here with the test frames. It was very bad. We tested this simple baffle print with a significant tilt input and a 5 minute dark frame. There was no detectable light leak, and the frame measured identically to the control frame with no tilt input.
I also designed a M68 dust cap that works with this light baffle installed. You can download the baffle file from Thingverse here:
And the dust cap here:
I printed the dust cap with matte black PLA with I think 30% infill. It does not leak light and is suitable for dark frames. This will depend on the material used and your own print settings.