Help with internal reflection

[traveller (Bo)]

I noticed what looks like some internal reflections in my images. See 47 Tuc sample from last night (ignore the poor focus). There is also what looks like a ghost reflection at the opposite side of the image.
Can someone confirm this is actually an internal reflection?
What is the best way to track down the source of the internal reflection?
Cheers
Bo

[JA]

Hello Bo,

Do you get these markings with both/all your cameras? That would be the first thing to check Vs whichever camera gave you the image you posted. Almost looks like a combination of a water with accumulated dust stain. Which scope gave you the mark - The Meade 10? Then I would look for like carefully for similar shape marks on the mirrors with torch as well as for marks on the imaging sensor of the cameras, etc..

Good hunting

Best
JA

[cometcatcher (Kevin)]

I'm inclined to agree with JA. The white spots are in dust doughnuts. Maybe moisture or something. I would give the sensor window a clean.

[Stonius (Markus)]

Full disclosure; I have not much astrophotography experience, but I wanted to throw this out there;

Is it possible that the offending reflection is from an optically flat surface? It looks like reflections I have had with a UV filter at night shooting into bright lights. You get a reflection off each air/glass boundary (air/glass, glass/air) - therefore, two reflections. The fact that they are both in alignment and the same shape suggests to me the two boundaries are parallel, ie, from an optically flat filter or a 45 mirror that has been coated behind the glass, rather than on top of it...something like that?

Hope it helps

Markus

[traveller (Bo)]

Thanks JA and Kev. I've cleaned the lower part of the imaging set up (reducer, filter, sensor). Will check out the front element of the scope during daylight hours and report back.
Bo