Dirty diagonal

[Trentend]

Dumb/newbie question, but when viewing anything above a certain magnification with a diagonal and binoviewer (probably same for mono) I can see lots of dust that’s sitting on the diagonal mirror and it’s spoiling the view. Not talking floaters here but the diagonal glass itself. I’ve tried a blower to remove items before viewing but there’s always something there. Not so much an issue if looking at DSO but is for lunar with a white background.

Any cures?

[Stu]

Are you sure it’s on the diagonal? The surface sits quite a long way from the focal plane so you shouldn’t see this focused. Have you rotated the eyepieces to check it is not on either of them?

[Alien 13]

As above but if it is the diagonal then increase/decrease the distance between the eyepiece and diagonal so its surface is no longer in focus.

Alan

Edited December 18, 2021 by Alien 13

[Trentend]

Thanks I’ll take a further look

[Astrobits]

Also try rotating the binoviewer as there are lots of surfaces within it.

Nigel

[Trentend]

Will do thanks. Crystal clear views last night with a near full and high moon getting crisp x250 mag but also an eye-full of annoying dust particles!

[newbie alert]

When I used mine and had the same issue I opened it up( 4 screws), blew the dust off with a rocket blower then used baader fluid and a microfiber cloth and it was like brand new.. job done

[PeterW]

Which surfaces were the worst offenders? I’ve had dust issues on sensors when imaging, but never visually… apart from eye floaters.

Peter

[Merlin]

If a Barlow is being used dust could be seen on it