Using astrophotography filters, especially narrowband filters, often results in dim images that can be difficult to focus. The Alpine Astronomical Baader Clear Focusing Filter can be used first to clearly focus the image before adding colored and specialty filters.
This clear filter is parfocal with Baader LRGB imaging filters, so once your camera/telescope is properly focused simply switch it to the color filters, confident that the resulting filtered images will be correctly focused. The precisely layered anti-reflection coatings allow for high throughput across all wavelengths, ensuring bright and clear views for maximum focusing ability. Because of the full throughput, this filter can be used as a dust shield stacked with other filters to prevent dust from settling on the lens during long-exposure photography sessions. This version of the clear focusing filter is offered here as an unmounted 50.4mm round option for custom applications and imaging systems.