Figure 1: NGC6946, the Fireworks Galaxy (imaged October 22, 2022)
Figure 2: NGC6946, the Fireworks Galaxy (imaged October 22, 2022). Cropped.
The Fireworks Galaxy is justifiably famous. It played a significant role in our understanding of the universe as a whole because of the novae found in it back in the 1920s. There are plenty of fireworks in this galaxy, as it is a prodigious birthplace of stars.
Conveniently it is located in our northern skies, and it reasonably easy to image. I have posted images on Facebook of this galaxy in the past, and I have a very nice image from September 2021. This 2022 image was more of a test, to see if my narrowband Hydrogen-alpha imaging might improve things or bring out more features of the galaxy.
In the foreground, within our Milky Way galaxy, is a small open cluster, NGC6939. I include this in the frame of Figure 1. The galaxy and cluster are not associated with each other, other than being in the same line of sight. The cluster is approximately 4000 light-years away, and the galaxy is 25 million light-years away.
This cluster is quite interesting on its own. The stars are quite old, over a billion years old, and it is located a bit away from the Milky Way's disk, which is unusual for open clusters. As the stars are older, they have more Hydrogen/Helium gas and fewer heavy elements. Also, since the cluster is old no stars are particularly bright: The brightest stars do not live very long.
The Fireworks galaxy is relatively close to our Milky Way, but it is not part of the local group. It is believed to contain roughly half the number of stars as the Milky Way and the apparent size is roughly 10 minutes of arc across, much smaller than the moon (diameter 30 arcmin).
In retrospect I must admit that the year-old version of this is quite good (see below). The processing was done a bit differently and the colour balance seems different. The addition of Hydrogen-alpha data does allow me to bring out the nebulae better and there is a slight improvement in the sharpness of the new image.
Figure 2: NGC6946, the Fireworks Galaxy (imaged September 2021)
Fireworks Galaxy, imaged at Lac Teeples on October 22, 2022 (RGB channels) and Hydrogen-alpha on September 1, 2022. Roughly one hour of data in each of the RGB channels and two hours of Hydrogen-alpha. The telescope was the RASA-11 with the ZWO ASI-6200MM mono camera.
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