Since getting an SBIG ST-10XME and a CFW10 with Narrowband (Ha, SII, and OIII) filters, I could not wait to image an emission nebula. I received the new goodies on August 9th, and of course, the conditions were not right to image until August 20th. I had first light with the ST-10XME under a bright full moon so I could only shoot through Hydrogen Alpha filter. Ten days later on August 30th, I was able to shoot with all 3 filters so I chose the Elephant’s Trunk Nebula (IC 1396) as my target.
Learning how to image through Narrowband filters was not as difficult as I imagined. Here are some things I learned along the way:
- Since these types of filters only let in certain wavelengths of light, one of the main differences was the exposure time. I typically take 5 minute subs but I had to increase the time to 10 minutes to get a decent looking sub with lots of detail. Your experience may vary and will depend on the focal length of your telescope and imaging equipment
- I still focus my telescope manually so focusing follows the same routine of looking at the stars Full Half Width Maximum (FHWM) to see if you are in focus. I focus with the Ha filter in a 3×3 bin, with a 1 second continuous exposure
- I have collected data a couple of different ways. When the moon is in the sky, I will collect Ha data. If the Moon is not present, I will collect all 3 types of data (Ha, SII, and OIII)
- With Narrowband imaging, it is all about data data data...