› Forums › Imaging › A ring around a red star › The OIII filter used
19 June 2020 at 2:38 pm
#582662
![](https://britastro.org/wp-content/uploads/2017/05/picture-2119-1494592966-80x80.jpg)
Participant
He’s used a Baader 8.5nm CCD narrow band filter. The graph shows it is fairly transparent beyond 1,050nm.
Alan