IC5148 is a planetary nebula (an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives) in the Grus constellation in the Southern hemisphere. It is approximately 3000 light years from earth and has an angular size of around two arc-minutes. It is of moderate surface brightness (~14.4 mag/arc-min^2) and is brightest in the oxygen (OIII) emission line and lesser so in the hydrogen (H-alpha) emission line.
I was having difficulty getting sufficient signal-to-noise ratio (SNR) in the H-alpha channel with my existing OSC camera (QHY183C) due to very limited observing time in Tasmania in recent months due to cloud, moon, wind and all the other weather obstacles. So, I finally pulled the trigger on upgrading to a monochrome camera with larger pixels to help get more detail in the limited time available. The QHY268M is a beautiful camera to work with and it's nice to not have to deal with amp glow!
Even with limited imaging time and poor seeing, the images reveal the very faint nebulosity that surrounds the main nebula that is approximately 60 times fainter. This is visible in my main image but I haven't over-stretched it to make it more prominent as the SNR was fairly low and not amenable to deconvolution. Below is a highly stretched, inverted-monochrome version of the centre of the main image that highlights this outer nebulosity that is almost entirely in the OIII channel.
This is discussed in the beautiful 25/02/2021 Image of the Day by
@Stan Volskiy at
https://www.astrobin.com/iokfgl/ and in the scientific paper that he referenced (
https://arxiv.org/pdf/1810.01350.pdf). Unfortunately, us mere mortals who don't have a 1-metre telescope, have to spend many more hours of imaging time to get good detail in this region! Perhaps, when the moon and weather are right, I will return to this object and give it some more imaging time.
Until then, enjoy!
Philip.
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