Antlia CH4 Methane FIlter - 1.25" - CH4-125

The Antlia 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 filter, so this filter is not suitable for visual applications.

The Methane (CH4) filter is recommended for planetary imaging such like Mars, Jupiter, Saturn and the other planets.

In order to produce good results, you are likely to require relatively longer exposures times and larger aperture telescopes with this filter than with other filters.

Technical Data:

• Optical substrate
• Thickness: 1.25” (2mm+/-0.05mm)
• Surface Quality: 60/40 (Refer to MIL-O-13830)
• 2 sides fine-optically polished to ensure accurate 1/4 wavefront
• 30 arcsec parallelism
• Center-Wavelength of Antlia CH4 filter: 889nm
• Tave＞90% , 90% transmission at 889nm
• OD5（0.001%）@ 200-1050nm
• 2 sides Multi-layers anti-reflection coating
• Single / Non-glued substrate

Filter Ring:

• 1.25”( 28.5*0.6 )
• Ultra-thin filter cell to minimize vignetting by maximize possible clear aperture
• Black Anodized Finish
• Laser Engraving No Fading

Warning:

1. You can use this CH4 filter to image the Sun, but you must use an energy rejection filter when doing so.  

2. If an energy rejection filter is not used in conjunction with the Methane Filter then the heat can be sufficient to damage the telescope, the Methane Filter, and the imaging system.

3.  This filter is NOT for visual use.