Used ZWO H-Alpha 1.25" 7nm Filter

Condition:

This is a used ZWO H-Alpha 1.25" filter in excellent condition.  The optics and body are clean.  No box; comes in a ziploc bag.  

Any dust you see in the photos is easily removable - it seems that these filters develop an electrostatic charge such that the dust in the air is just attracted to the filter.  

Description:

ZWO 1.25" H-Alpha, SII, OIII 7nm Filter Set

Narrowband filters are a fantastic astrophotography tool when it comes to imaging during times of high light pollution. When all three filters, the H-alpha, SII, OIII filters, are used in unison, it is perfect for tricolor CCD astrophotography!

While narrowband filters do not eliminate the effects of light pollution, they do enhance the contrast between celestial objects and the night sky. It provides this contrast by reducing the transmission of certain wavelengths of light. These wavelengths come from artificial light, mercury vapor and both high and low pressure sodium vapor lights, and natural light, such as skyglow caused by neutral oxygen emission in the atmosphere. Additionally, each filter is fine-optically polished to ensure an accurate 1/4 wavefront.

ZWO Narrowband 1.25" Filter Set Specifications

• Filter Size: 1.25″

• Mechanical Thickness: 7.5mm (5mm + 2.5mm thread)

• FWHM: 7±0.5nm

• H-Alpha Transmission Rate: About 90% transmission

• Infrared wavelength cut-off: 700-1100nm

• Transmission of off-band: <0.1%, OD3(Optical Density)

ZWO H-alpha 7nm Filter

ZWO H-alpha 7nm filter has a bandpass of 7nm, and it passes light at 656nm wavelength. If you want high contrast astroimaging, then this Hα filter will deliver an excellent performance. The light transmission rate for the filter comes up to 80% and the glass has been fine-optically polished to ensure accurate 1/4 wavefront. So, even in areas of strong light pollution, you can still explore the night sky with your imaging equipment!