David:
I'm sure you'll get lots of good advice and suggestions on this forum. Let me suggest that you'll need to do some troubleshooting and supply more information in order to solicit the most helpful advice. Do you have a picture of your optical assembly that you could post? That would help to visualize what may be going on here.
I'll begin with a quick and easy investigation for light leaks that I first do in these circumstances. With the scope in a darkened environment (darkened room, outside at night, etc.), cover or close it up the best you can, but you'll need to keep the optical train uncovered. This may work in daytime, but the test is best done in the dark. Start taking frames with your camera, and move a bright light source (flashlight, headlamp, etc.), closely around all the seams and potential places where light comes in. This is often a good way to pinpoint light leaks.
Watch the images from your camera and look for glowing from light leaks. If you find something, a quick fix is Gaffer's tape (or something like that). Cover the offending area with the tape and then check again. Keep doing this until you are satisfied that no light is infiltrating from the various optics pieces. Some of my oldest hardware is now almost fully entombed in Gaffer's tape but still works reliably.
If that doesn't work, then you will need to continue your troubleshooting. I recommend that you start with this and then post your findings. Otherwise, some others may chime in with other suggestions.
Best Regards,
Ben
