These two-piece filter holders were designed to hold gelatin filter sheets for deep-sky, tricolor photography. Purchase gelatin filter sheets from a camera store, cut into a circle slightly larger than the opening (be sure to allow enough material to secure the edges) and install. We suggest that you purchase a separate filter holder for each color filter that you plan to use.
27GEL2 - Fits all current field flatteners and any shipped after May 1994. Clear aperture of the 2.7" filter is 2.35" (60 mm).
27GEL1 - If you have an earlier model (prior to May 1994), we offer part # 27GEL1 with a slightly different thread.
40GEL1 - 4" version designed to fit 4" Field Flatteners.