Baader SLOAN/SDSS (ugriz') Filter Set – photometric

Yes, you can use the Baader “Fast Transmission” SLOAN filters directly for photometric measurements within the SDSS system. The calibration process is identical to that used with other Sloan filter sets (classic or fast) and depends on both the filters and your camera’s quantum efficiency (QE).

In practice, you perform standard photometry and solve for a zero point and a small Sloan color term so that your results align with the SDSS ugriz system – exactly as SDSS did when accounting for small passband differences between instruments (SDSS Photometric Equations).

Recommended workflow:

1. Calibrate your images (bias/dark/flat) and measure instrumental magnitudes.
2. Match your field stars with the SDSS catalog.
3. For each filter, solve a simple equation that includes extinction and color terms, e.g. for g:
   g_SDSS = g_inst + ZP + kX + c (g − r)_SDSS
   This accounts for airmass (kX), zero point (ZP), and the color correction (c).

The Baader Fast SLOAN filters share the same central wavelengths and bandwidths as the classic SLOAN filters but have slightly different curve shapes. The small difference is fully compensated by the color term. Only for highly precise (<1%) or non-stellar spectra would an additional “S-correction” be applied — this uses published filter curves together with a reference spectrum.

Measured optical density curves of the filters are available for download on the product page. For further guidance on CCD/CMOS photometry, we recommend the resources of the American Association of Variable Star Observers (AAVSO), especially the AAVSO Guide to CCD/CMOS Photometry.

Please scroll down on the page and click on the "Downloads" tab. There you find the OD logarithmic files for all photometric filters for download after registering.

The actual dimensions are 65mm length on each side with tolerance + 0 / - 0.2mm

For (much) larger DSLR lens sizes up to 100 mm aperture you might consider our 100x100x3 mm square photometric SLOAN-Filters: https://www.baader-planetarium.com/en/filters/photometric-filters.html. Especially for work in UV, the SLOAN-U filter (#2961707U https://www.baader-planetarium.com/en/filters/photometric-filters/sloansdss-u%27-filter-%E2%80%93-photometrisch.html#425=1695) is a viable alternative to our time proven U-Venus-filters (https://www.baader-planetarium.com/en/baader-u-filter-(venus-and-uv---350nm).html") - offering a very similar transmission window but up to 100 mm sq size: https://www.baader-planetarium.com/en/sloansdss-u%27-filter-%E2%80%93-photometrisch.html There even is a clever way to hold that huge size filter in front of most any DSLR-lens by obtaining this holder and doing a minimal change that converts this holder from accepting two filters of 2 mm thickness into accepting just one filter w. 3 mm thickness - with a mere screwdriver (sorry for the german Amazon-link): https://www.amazon.de/dp/B07FL3YNHB?pd_rd_i=B08KVZ8VWT&pf_rd_p=5f9972c1-184d-4e29-822a-e867654f66c0&pf_rd_r=5T5PNXXSSA4JVTRSN3QK&pd_rd_wg=6HR08&pd_rd_w=dE1wF&pd_rd_r=e8cc1e1b-747d-4193-acdf-981d7f2e81e4&th=1

Yes, we have clear glass filters in the same sizes and thickness up until 65x65mm. Only the extra-large 100x100 filters are only available as SLOAN and UBVRI. https://www.baader-planetarium.com/en/filters/l-rgb-cmos-filters/baader-clearglass-filter-(c)-for-focusing--dust-protection.html

The tolerance of thickness is 3mm +/- 0.1 mm