How to use dual band filter with OSC?

[Bluebird181]

I purchased a dual band filter for use with a QHY268C color camera. I haven’t had an opportunity to try it yet, but I understand these filters block most of the light except for two narrow bands, which dims the overall image. How does this affect plate solves? Do I first acquire a target and plate solve then insert the filter and begin stacking? Or can a plate solve be done with the filter in place? Also, any guidance on settings for this camera with a dual band filter? Gain, offset, exposure time? My first target will be the western veil.

[admin]

Hi,

just like using a narrowband filter with a mono camera, you will need to take longer exposures to get the same sort of image brightness compared to 'no filter'. For instance, if your filter is about 4nm bandpass in each band then it will cut out about 95% of the light in the red and the green and almost all of the light in the blue. You will need to set exposures up to 20x longer than you are used to to fully counteract this - in practice that might well end up being longer than your mount/guiding will suppport, so you will need a compromise value. Setting a higher gain will help reduce the exposure increase to some extent.

You should be able to plate solve with the filter in place provided the exposures are long enough to show decent stars.

cheers,

Robin