Baader AstroSolar OD 3.8 Photo Film is highly precise solar neutral density filter film for photographic use only and is available in sheet form for DIY construction. The size of the sheet is 20 x 30cm.
For more than 25 years on the market, this is the only solar film material which does not degrade the optical wavefront, thus allowing high resolution imaging without reduction in sharpness or contrast. AstroSolar film produces a natural white solar image without false blue or orange colour.
This highest precision film consistently produces Strehl ratios of 94 to 96 percent in interferometric tests – thus it performs optically like a Fluorite Triplet Lens by Carl Zeiss.
The AstroSolar Photo Film is suitable for solar photography and is available in a huge range of sizes to fit almost all telescopes and telephoto lenses. It comes with a handy template with many common telescope diameters, making it easy to create a perfect-fitting filter.
WARNING: Make sure to read the included manual for important safety information before use. Testar does not take responsibility for damage caused by improper use. For more information, check out the AstroSolar website.
Note: As the AstroSolar OD3.8 does not block as much light as their denser OD5 filters, your images may end up being overexposed when using highly sensitive modern DSLRs with certain lenses/telescopes. For example, we tested a Canon R5 with a 150mm F/8 refractor and found that even at a shutter speed of 1/4000 at ISO 100, the resulting image was overexposed. If this happens, an additional neutral density filter or polarizer should be added to system.
I purchased this product to photograph the 2023 hybrid solar eclipse in Exmouth, Western Australia. I was able to fashion two filters for the above lenses with plenty of film to spare. Being the first time I was attempting to photograph a total solar eclipse I did not have high hopes but the images I captured were beyond my expectations. The images below were taken with the 300mm lens on a 1.5 crop DSLR (effectively 450mm). The corona is a stack of 21 shots.