Is This Caused By My Cheap Barlow?

[Steve789]

First light with my recently acquired SW 127 Mak and I noticed a very bright artefact when imaging the moon with my MS LifeCam Studio and cheap SW 2X Barlow. See pic below.

My first thought was some kind of internal reflection causing this and as it's only obvious when using the Barlow this is the prime suspect. I've checked to make sure there's no shiny surfaces inside the barlow and have blacked out any shiny parts inside the webcam (just in case) but the problem persists.

I've read somewhere that cheap barlow lenses can be the cause of such reflections but before I rush out and buy a better one I'd like some reassurance this is the most likely cause. I know very little about Cassegrain scopes so I might be missing something here.

[Carina Lass]

Haven't seen anything like that in my SCT even with a Barlow in. Maybe a light within the cone of the objective.

[kalasinman]

Do you re-focus when using the Barlow? Looks far out.

[Steve789]

Yes I refocus after adding the barlow. I think that actual shot is using a barlow plus an extension tube giving a 3X view which was pushing the power of the scope on that night. I get the same effect with or without the extension tube. I may have defocused a bit to make the artefact more pronounced I can't remember. That image is only a single frame from a webcam though so I wouldn't expect it to look too sharp.