A mate traded me a 7nm H-a filter (2"/M48 Optolong) for one of those silly eyepiece things
ANYHOW, I know using an H-a filter OSC is entirely possible (1/4 the pixels at least get something - dithering to the rescue!
), but approx. how much longer an exposure compared to RGB OSC? I currently do 10 minute subs with the FSQ-85 and the LP filter, so what is a good ball-park on acquiring H-a data commensurate to the RGb? 20 min? More? Is it a linear relationship?
And lastly, is it necessary or advisable to use the UV/IR cut filter with the H-a filter? (I stack my filters in a special filter-adaptor I had custom made - see below - the end screws off to reveal internal M48 female threads to mount the filters)