Finally, some more clear nights with an almost moonless night. After my last successful outing on the Pinwheel Galaxy at the end of April, I was keen to complete at least one more LRGB image before we lose astronomical darkness for the summer. I attempted Iris Nebula last summer but a lack of ability along with inclement weather meant I failed badly on it. It is still early in the season for this nebula as it remains low in the north eastern skies, however this allowed me to complete 3 clear runs without meridian flipping so it was worth the gamble.
I imaged over three nights, gathering 6 hours of luminance and 3 hours total of RGB data. The exposures were all on gain 0, offset 10, captured on my QHY163m using Sequence Generator Pro v3.
Lum: 75 x 300 secs
LRGB: 30 x 120 secs per filter
Again, I used Astro Pixel Processor to stack and calibrate the subs. I really love this program now I have got used to it. Its ability to remove light pollution gradients, in particular, is superb. I really must get around to completing a review and tutorial on how I use it.
The stacked and calibrated subs are then moved across into PixInsight for processing and combining. I wanted to try and bring out the dust lanes around the nebula, as well as keep the star and nebula colour vibrant without over-doing them. I think I have found a balance here – one I am happy with at this stage anyway. I started to use more complex methods of bringing out the dust using wavelets layers however I found I need more practice with these before I am competent in using them so I stuck to my usual masked stretches, a wide range of star, nebula and bright object masks, and then little adjustments until I reached the final image.
I am a lot happier now with my LRGB process, especially given the skies I have to deal with. The use of a CLS CCD filter in addition is, to my mind, a sensible step to take in order to block out unwanted light polluting light frequencies before they ever hit the sensor. Others disagree, but that’s half the fun of imaging.
Unless I have more clear nights very soon, it’ll be on to narrowband emission nebula until August when we get astro darkness returning in the UK and, with that, Andromeda!
The Iris Nebula -NGC 7023