A street light shines down onto the spot where I sometimes observe. An occultation board mounted on a photographic tripod shades the scope from the glare of the light and prevents light from the street light directly entering the top of the scope tube and causing internal reflections that ruin the exposures.
The occultation board is simply constructed with a female photographic thread at the base
The occultation board mounted on a tripod showing the offending street light
The occultation board in action, shading the scope from direct street lighting
If the sky is dark, the main objective is to prevent direct light from the street light from entering the top of the telescope tube at an oblique angle. This is the main problem, whilst other ambient light is much less of a problem. When this photograph was taken, there was also a first quarter Moon low in the sky.