Helios Glass Off Axis Telescope Filter by Seymour Solar - Solar Eclipse Viewing - Made in The USA (15.25" (387mm). Fits Optical Tube Diameter 14 7/8" (378mm) to 15 1/8" (384mm))

With this premium solar filter, you can safely observe and photograph the sun’s surface and features, such as sunspots and eclipses, when attached to your telescope. This filter has an ND5 rating, which means it blocks 99.999% of the sunlight, protecting your eyes and equipment from the sun’s intense light and radiation. The filter has an off-axis aperture, which reduces the image brightness and improves the visibility of daytime atmospheric turbulence. The aperture is made of Helios Solar Glass, which is a high-quality glass that has a reflective coating on both sides to enhance the contrast and clarity of the sun’s image. The glass is mounted into an aluminum outer cell, which is durable and lightweight. This filter is designed for reflector and catadioptric telescopes, and cannot be used with refractor telescopes. The filter has a slip-on design that allows you to slide it over the sky end of your optical tube securely. The filter is secured and centered to the optical tube with three nylon thumb screws and felt padding. Discover the secrets of the sun with our premium solar filter, which is specially designed for telescopes. You can safely observe and photograph the sun’s surface and features, such as sunspots and eclipses, with our ND5-rated filter that blocks 99.999% of the sunlight. SIZING: You must measure the outside diameter of your optical tube or lens before ordering the solar filter. To measure the diameter, you can use a ruler, tape measure, or caliper. You want to measure the widest distance across the end of your optical tube or lens. Measure from the outside of the casing on one side, across the center, to the outside of the casing on the other side. Order the solar filter size that is just larger than your measurement. You are comparing your measurement with the solar filter’s inside diameter. For example: A measurement of 4" (102mm) across the end of the optical tube would require a solar filter with an inside diameter of 4.25" (114mm) because it is the size just larger than your measurement. With our Helios Glass solar filter, you can enjoy the sun’s beauty and power without any risk or hassle.

• Enjoy the contrast and clarity of the sun’s image with our Helios Solar Glass, which is a high-quality glass that has a reflective coating on both sides. The glass is mounted into an aluminum outer cell, which is durable and lightweight, and fits most telescopes.
• Attach the filter easily and securely to the objective lens of your telescope with our clamp-on design. The filter is secured and centered to the telescope with nylon thumb screw(s) and felt tabs, which prevent any damage or scratches to your telescope.
• Capture the stunning phases of the total solar eclipse with our premium solar filter, which is specially designed for telescopes. You can safely photograph the sun’s partial and annular phases with our ND5-rated filter that blocks 99.999% of the sunlight.
• Experience the thrill of totality with our premium solar filter, which is easy to remove and attach to your telescope. You can quickly take off the filter when the moon completely covers the sun’s bright face, and enjoy the spectacular sight of the corona and the chromosphere. You can also put the filter back on when the sun begins to reappear, and continue to observe the rest of the eclipse.
• **Determining Correct Solar Filter Size**: The solar filter should slip over the sky end of your optical tube. Measure the outside diameter of your optical tube using a ruler, tape measure, or caliper. Measure from the outside of the casing on one side, across the center, to the outside casing on the other side. Order a solar filter with an inside diameter slightly larger than your measurement. For example, if your measurement across the end of your optical tube is 4 inches (102mm), choose a solar filter with an inside diameter of 4.25 inches (114mm)—just larger than your measurement.