[looking up (Steve)]

Hello chaps
This filter came with my Meade scope many years ago.
And I thought it would be time to try it ???
2 questions
1 Its quite dirty like mould on filter see pic and what would I use to clean it I have some old UHTC cleaner from Bintel or ????
2 Is this Filter good for Nebula or Galaxys
The reason I ask I have never used filters in over 20 years in Astrophotography.
Anyway hope I can some advice.
Kind regards as always.
Cheers Steve