A new city light pollution filter! Triad Quadband Ultra Filter.

For many amateur astronomers and astrophotographers, light pollution makes things difficult and in some cases impossible when it comes to imaging the night sky. All is not lost though. 

For those astrophotographers using a one-shot-colour (OSC) DSLR or cooled cmos camera to image with, the new Triad Quadband Ultra Filter from OPTcorp.com is a must have.

This extraordinary filter not only cuts through light pollution but it also tunes in four specific wavelengths of light allowing you to capture H-beta, H-alpha, Oxygen III and Sulphur II all at the same time. If you’ve used monochrome cmos or CCD cameras with a filter wheel, you’ll know you have to have a separate filter to capture each light channel. So the Triad Quadband Ultra Filter is quite revolutionary and opens up a new world of astrophotography for those using OSC cameras.

I had the opportunity to test this filter and found it to be amazingly effective and a lot of fun!

Due to weather conditions I haven’t had many opportunities to image with the Triad Quadband Ultra Filter, but the few times I did, I was focused on the Elephant Trunk nebula (IC 1396). This is a good test target for the filter, given it’s low in Bortle 8 light pollution from my location starting just after dark and slowly rises over the coarse of the night.

Since this filter blocks out a lot of light pollution, it easily captured some great details with even a small amount of data acquisition such as just 50min. 

I am using a QHY 168C cooled cmos camera (16mp, APS-C sensor) and a William Optics Zenithstar 71mm ED refractor operating at F4.7. The Triad Quadband Ultra Filter is a 2″ mounted design that threads on in front of the camera, in my case onto the field flattener/reducer. 

As you can see in this graphic the Triad Quadband Ultra Filter acts like an FM radio, tuning in specific channels. In this case wavelengths of light! Due to this, the filter is very capable of blocking out light pollution that can interfere and ruin your images when doing astrophotography from the city.

While the weather hasn’t been very cooperative I did manage to get more data on IC 1396 and collected 4.5 hours in total so far. I did the calibration and alignment of these light frames in Pixinsight. I then did some quick processing of the unstretched stacked image using Pixinsight again. The result of this 4.5 hours of data taken with the Triad Quadband Ultra Filter was jaw dropping! Considering the level of light pollution I contend with from the city and using a OSC camera for this test (the bayer matrix divides the colour channels making it not as sensitive as a monochrome camera would be) I was completely blown away by the image. I’ve had to image much longer than this using other equipment to obtain this level of detail and faint nebulosity.