Type 3 + Lighter density, 1/100th of 1% (Optical Density 4) for maintaining fast
shutter speeds when using "slow" fine grain films. For photographic use
only. (Visual focusing through the camera viewfinder is safe) Solar image
is yellow-orange. Guaranteed fifteen years.
Frequently Asked Questions
WHICH FILTER IS THE SAFEST? All our filters, except for the lighter density photographic version, are completely safe for
unlimited visual use. If handled with care and common sense, all will last a minimum of 20 years to life.
CAN MY TELESCOPE OPTICS GET HOT OR DAMAGED? No, all the heat and intense light is blocked before it can enter the telescope. Your telescope may get warm from sunlight shining on it, not from the small amount of visual light transmitted through the filter.
WHAT DETAIL CAN I SEE? Sunspots and surface granulation are the two main features. The only detail that cannot be seen with a standard filter are prominence and flares which require our highly specialized H-Alpha filter.
IS FULL APERTURE BETTER THAN OFF-AXIS (REDUCED APERTURE)? For telescopes up to 5" aperture, off-axis is not an advantage. However, larger apertures suffer more from daytime atmospheric turbulence. This turbulence is magnified by the aperture. Perfect daytime "seeing" only occurs about 1% of the time. Off-axis increases the focal length and reduces the turbulent effects. As a rule of thumb, order off-axis if your telescope has a focal ratio f/7 or lower in the 6" to 8" aperture range, or if it's larger than 8" aperture. The solar image is not darker with reduced aperture as we allow for this in the coating density. When viewing through the eyepiece, the field of view is not reduced; it looks the same as full aperture. Reduced center aperture is used for refractors. If full aperture is still preferred, it can be stopped down using a simple mask as conditions dictate.