What does Optical Density (OD) 5.1 mean for the AstroSolar® Safety Film?
Optical Density 5.1 is a measure of light reduction and is the certified standard for safe, direct visual observation of the sun through a telescope. It means the film transmits only 1/126,000th of the sun's light, effectively blocking 99.999% of its intensity, including harmful ultraviolet and infrared radiation, to a level that is safe for the human eye.
How many filters can I make from one sheet of AstroSolar® Film?
The number of filters depends on the aperture of your instruments and the sheet size you choose. As a guide:
- One very large filter, e.g. for a 16" (400mm) telescope from the 100x50cm sheet, or for a Dobsonian over 20 inches from the 117x117cm sheet.
- Multiple medium-sized filters, e.g. several 8" (200mm) SCT or Dobsonian filters from the 100x50cm sheet, or approximately four filters for 20-inch (50cm) telescopes from the 117x117cm sheet.
- A large number of small filters for binoculars, finder scopes, and camera lenses.
Always measure the outer diameter of your optical tube before cutting the film.
How is the "ClearWhite" view of this AstroSolar® Film different from other solar films?
The "ClearWhite" designation means this AstroSolar® Film is designed to show the sun in its natural, neutral white color. Many other solar films and filters impart a strong orange or yellow cast to the image. A neutral view can make it easier to discern subtle details in sunspot penumbrae and bright faculae near the solar limb.
Can I use the AstroSolar® ClearWhite Safety Film OD 5.1 for photography?
Yes, you can. The OD 5.1 film is perfectly suitable for solar photography, especially when using high frame rates (lucky imaging) for surface detail. However, because it is visually safe, it requires longer exposures or higher gain than dedicated photographic solar film (like Baader's OD 3.8 Photo Film), which is not safe for visual use.
Do small wrinkles in the AstroSolar® Safety Film affect the image?
No, minor wrinkles or waves in the film do not impact optical quality. In fact, the film should be mounted with slight looseness, not stretched taut like a drumhead. Stretching the film can degrade its optical properties. As long as the film is securely mounted in its cell, small wrinkles will have no effect on the sharpness or contrast of the solar image.
Is this AstroSolar® Film a better choice than a welder's glass filter?
Absolutely. While welder's glass can dim the sun, it is not designed or certified for optical use and often has poor optical quality that will severely degrade the image from a telescope. AstroSolar® Safety Film is a precision optical material made to maintain the sharpness and contrast delivered by your telescope, while providing certified safety for your eyes.
