Thanks for your help. I live in a heavily light polluted area and the filter I was going to use is a Skyglow Imaging Filter, which is just a broadband filter used to filter out skyglow and street light pollution. Im wondering how to calculate the amount of vignetting involved with a sensor of the dimensions I posted. I saw that the clear aperture of the filter is 26mm and the diagonal of my sensor is only 22.5mm, so it should fit without vignetting-- however I think the distance between the sensor and the filter is also of concern, and probably narrows the clear aperture of the light pathway. I just wish I knew the physics involved and could make the calculation myself to determine the amount of vignetting. Im hoping one of the kind folk on here can help