WARNING: The OD 3.8 Photographic filters are to be used ONLY for imaging as they pass much more light than the OD 5 filters, enough to cause permanent eye damage.
Baader AstroSolar Photographic Filters are diffraction limited solar neutral density filters mounted in a temperature-compensated cell. This makes them extremely safe and protected against the normal stresses typical solar films are put under, as well as retaining the excellent optical quality at any temperature, be it -30 to +50C. No astigmatism is introduced during cold winters or hot summers. The OD 3.8 Photographic filters allow high resolution lucky imaging of sunspots are the highest magnifications.
The AstroSolar filters are suitable for safe solar photography with almost all telescopes and long telephoto lenses. They are available in a huge range of sizes to fit telescopes from 80 to 180mm in diameter. Velcro safety straps and pads and large centering bolts with rubber grips are included to secure the filter to your telescope. The bolt slots have printed index scales to allow fast and repeatable adjustment. The white outer ring rejects infrared light and features raised edges along both the inner and outer circumference to protect the film.
The film itself is repeatably cemented onto an injection moulded ring, whereas the substrate of that ring has the same thermal expansion like the Astro Solar Filter material itself. This free floating film-carrier ring is held onto the aluminium frame with the help of an additional holding ring made of fiber reinforced plastic – for maximum security against breaking of the cell.
Included are two sets of 38mm long centering bolts, three with 10mm diameter and three with 20mm diameter, along with three safety straps with glue-on pads.
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.
Click to open Baader's Solar Filter Finder Tool to find the correctly-sized filter for your instrument.
Table showing clamping ranges for each size of AstroSolar filter. Click to enlarge.
How to interpret the filter size table: Astrosolar filters include two sets of rubber cylinders and have two sets of fine positioning slots, allowing you to clamp the filters over a large range. The cylinders can be positioned to clamp on the outside of your telescope tube (distance range in RED above) or on the inside of the tube with opposing force (in GREEN).
The number in the name of the filter (ie. ASTF 80mm) indicates the actual aperture of the filter material, not the diameter of the telescope lens/mirror. For example, if you have an 80mm refractor, you need to measure the outer diameter of the telescope tube at the very front, which will be larger than 80mm. Then you can select the appropriate filter that will fit either on the outside of inside of the tube.