Not sure Trevor, but what I do know is that they are caused by very bright stars that are just outside the camera field of view. I will know more once I have taken a look this weekend.
I noticed your guidescope extends well beyond the front of your RC and you are probably getting your ghost reflections from light bouncing off the refractor into your light path in the RC. Try putting an extended dew shield over the end of the RC and see if your reflections disappear.
Kane, thats a good thought, although I get the same reflections in my RC and I use self guiding with nothing protruding past the open aperture of the RC.. I am going to be trying out my new dew shield next time I've got my RC out, although I dont think that will fix the reflection it might help a bit with all the lights around my house...
I had similar reflections in my C8 for a while. The problem was due to stray light from the PC and Hand Controller getting into the optical path around the camera adapter. However I was using a bolt on t-adapter which had an opening. Just a thought, but have you checked for any openings around the camera/focuser that may be letting stray light in. As a quick fix, I found placing a towel over the camera fixed the problem.
Paul - I dont think thats the case... I got those same reflections with my SBIG ST9E, and the same again with the ST-10XEi. those cameras dont have a view finder for light to leak in... Maybe the ring between the focuser collimation adjustment plate and the rear cell leaks light? I thought maybe the focuser itself, however you're getting the same problem with the feathertouch.. so that shouldn't be the case...
The reflections are blue, so the most likely source is a blue LED in your equipment leaking light into the optical path. If it was starlight reflection, the reflections would be white.
Rob, Maybe true, however the reflection doesn't appear in every star field you shoot with these scopes, and there are 3 or 4 people getting these reflections, all using very different setups, from dedicated CCDs to DSLR's, different filters, different focusers etc... Something tells me that we dont all have a rogue LED leaking light into the optical path.
I think it is coming off the baffle tube. When you pull the telescope apart and see the reflection of a bright light off the baffle tube I am quite convinced this is the cause.
I haven't seen the extension tubes that attach between the visual back and the focuser but they are big enough diameter that I don't think they come into play.
The fact that the reflections appear when a star is just off the edge of the field indicates that the baffle tube is almost doing its job.
The baffle tube needs that nice fine machined rigde that eats reflections.
I have taken some pictures that show what I mean.
The first is just a digital camera stuck in the back of the focuser while held up to a bright light source.
The second is the nice matt black baffle tube from the outside.
The third is the inside of the baffle tube when pointed to a bright light.
