Antlia Narrowband Filters Spectral Measurement

Each Antlia Narrowband Filter has been scanned by following spectral measurement.

Parameters setting involved in scan accuracy by Agilent Cary series spectrophotometer

Data interval (数据间隔): 0.1nm

Resolution/slit width (狭缝)：0.2nm

The slit is an entrance that controls how much light enters the spectrometer. The width of the slit affects resolution; the narrower the slit, the higher the resolution. We set the slit to 0.2nm，it means scan data we get is an average number within every 0.2nm. For a narrow band of 3nm, the result is closest to the real performance of the filter. If we set slit to 1nm or 3nm for a FWHM 3nm narrowband filter, the resolution is worse, scan result will deviate seriously from the truth.

Scan result of H-alpha Pro filter T% @656.3nm 92%

Firstly, we ensure that the transmittance at 656.3nm is greater than 88%, secondly, all narrowband filters shift its bandwidth to shorter wavelengths with faster optics, for those filter leaning to left, they will have better performance when imaging deep sky objects as the high transmittance of them was kept. The products are more workable for most optics telescopes in market.

If we use a less precise spectrophotometer or parameters to scan, we get result as below

Data interval (数据间隔): 0.1nm

Resolution/slit width (狭缝)：2.0nm

Scan result of H-alpha Pro filter T% @656.3nm 82%