Reflections and FWs

[pmrid (Peter)]

I finally tracked down the source of some reflections I was seeing. I finally tracked it down to my filter wheel. But not what you'would think.


It was in the body of the 7 position 31mm ASI EFW itself rather than the internals. I finally noticed the multiple mounting holes on the back and front of the fw body. They seem to be for mounting an OAG assembly or something similar. Really, I'm blowed if I know what they are there for but there are 4 on one side and 8 on the other.

I tried filling the holes with little grub screws but none of my sets fitted leading me to suspect imperial threads which seems a bit odd.

In the end, a bit of black electricians tape fixed it but I thought others might be experiencing the same - so here you are.

[floyd_2 (Dean)]

Thanks for the heads up Peter. I have a ZWO filter wheel somewhere on my distant horizon and will now sort this issue out before it even becomes an issue. Great info!

[logandc99 (Logan)]

This can be made worse if you have a security camera with infrared leds pointing at your telescope. I found weird reflections in my images and noticed they disappeared when I turned off the infrared of the camera monitoring my telescope. I also used black electrical tape to cover the holes and that solved it

[floyd_2 (Dean)]

That's a great point. I actually have a camera set up to monitor my scope so that I can feel safer with slews from inside my shed. The cam is placed to view the scope from the northern side where I can't point the scope (thanks neighbour for growing 4m high trees along my northern fence line). I was wondering if the IRs would potentially cause issues.

[Camissa (Ecki)]

I use blackboard paint for chalk boards. Mixed with some ordinary flower from the kitchen (to make the surface rough) it is the darkest non reflective paint I have ever seen. I use this to paint over all open metal surfaces, screws etc in the image train.