0.7Å ION filter. Condition certified by DayStar Filters, with Full 5 year warranty. Enjoy precision dedicated tuning control with its thermo electric cooling (or heating) in any climate. ION housings do not tilt the optics. This housing improvement increases contrast and maintains the best bandpass performance of your etalon Vibration-free Mag Lev fans dissipate temperature quickly, but do not disturb your view. Tests indicate they can slightly improve eyepiece stability with a minor gyroscopic effect. Our 20mm clear aperture offers a non-vignetted view on telescopes up to ~75mm of aperture. Larger telescopes than this are fine. They will just have reduced field of view. Smaller etalons mean owners can upgrade to narrower bandpass choices for less investment. 12VDC operation - A 6 foot cord, a 6 foot extension and international power plugs are included. Some users may wish to use battery or solar power. Existing T-scanner Filters may be upgraded to the new ION body style for a fee of $900.00 DayStar Filters stand-alone Filters may be used on a variety of telescopes. Telescopes over 60mm aperture require an energy rejection filter. Check our Energy Rejection Wizard to find the ERF that's right for your telescope. A Daystar Filter also requires that your telescope will operate at about F/30. As no F/30 telescopes exist, owners use a barlow to bring their telescope to ~F/30. An F/6 telescope requires a 5X barlow A F/7 or F/8 telescope requires a 4X barlow A F/11-f/12.5 telescope requires a 2.5X barlow A F/15 telescope requires a 2X barlow. *Any DayStar Filter may be used on any aperture telescope with proper energy rejection.