What is the main difference between the Baader SLOAN/SDSS set and a standard LRGB filter set?
LRGB filters are designed for creating beautiful, full-color astrophotographs. Their bandpasses are broad and often overlap to produce a natural-looking final image. The Baader SLOAN/SDSS ugriz' set is a scientific tool for photometry. Its bandpasses are precisely defined to match an international standard, allowing you to measure the exact brightness of an object in specific parts of the spectrum. You use LRGB for aesthetics and SLOAN/SDSS for data.
Can I use the Baader ugriz' filters for visual observing?
No, these filters are not intended for visual use. They are designed to pass specific, often narrow, bands of light for measurement by a digital sensor (CCD or CMOS). Visually, they would produce very dim, oddly colored, and uninteresting views. Their purpose is purely for scientific data collection.
How does the Baader SLOAN set help measure the light curve of an exoplanet transit in front of a star like HD 189733b?
To measure an exoplanet transit, you would typically use the Baader SLOAN r' or i' filter, where both the star and your camera sensor are most sensitive. By taking a series of timed exposures before, during, and after the transit of a planet like HD 189733b, you can precisely measure the drop in the star's brightness. The standardized passband of the filter ensures your measurements are consistent and can be compared with data from other observers to confirm the transit's depth and duration.
My observatory is in a light-polluted area. Is the Baader SLOAN/SDSS set effective for photometry from a city?
Yes, photometric filters can be surprisingly effective in light-polluted skies. Because you are measuring a target star relative to nearby, non-variable comparison stars in the same field of view, the background skyglow can be subtracted during data reduction. While pristine dark skies are always better, the precise bandpasses of the Baader SLOAN filters help isolate the starlight from common sources of light pollution, enabling meaningful scientific work even from suburban locations.
Why are there five filters in the Baader ugriz' set? Do I need all of them?
The five filters (u', g', r', i', z') measure an object's brightness across the spectrum. The difference in brightness between filters (e.g., g' minus r') gives you the object's "color index," which relates to its temperature. For many projects, like exoplanet transits, you may only use one filter (often r' or i'). For classifying unknown variable stars or studying asteroids, you would need data from multiple filters to determine their physical properties.
Do I need a monochrome or color camera to use the Baader SLOAN/SDSS filter set?
You absolutely need a monochrome camera for any form of serious photometry. A color camera has its own fixed Bayer matrix (RGB filters) permanently bonded to the sensor, which would interfere with the precise bandpasses of the Baader SLOAN filters. Photometry requires a monochrome sensor and a filter wheel to measure the light from one filter at a time.
