Antlia Methane (CH4) 1.25" Planetary Filter (ANT-METHANE-125) Shutter Release Cable Its 59mm rubber grip diameter

Its 59mm rubber grip diameter makes this model usable in binocular viewers — for most people

The distance between eyepiece and camera lens is not part of this equation

and the other direction to provide a flat surface

With an apparent field of view of 52 degrees

These were often made with found materials

Antlia Methane (CH4) 1.25" Planetary Filter (ANT-METHANE-125) Shutter Release Cable Its 59mm rubber grip diameterAntlia methane (CH4) filter is a specialized filter that allows light in the near infrared portion of the spectrum centered at 889nm to pass through with a bandpass that is 20nm wide. This filter was developed in order to measure finer details and more contrast of the methane that is characteristic of Jupiter, Mars, Saturn and other planets. The human eye is not sensitive to light beyond about 700nm hence no person can see what is transmitted by this