Supernova Remnant NGC2018
Why was I out imaging on Christmas Eve? Well, why not? It was a clear night with dark (for a suburban location) skies and the visibility was as good as it ever gets. I was also keeping an eye out for a fat guy dressed in a red suit and piloting a sleigh across the skies. No, I didn’t see him.
NGC2018 is a supernova remnant - the expanding cloud of highly energised debris ejected when a star reaches the final stage of it’s life and explodes in a massive explosion.
I picked NGC2018 because it looked interesting. I was wandering through a list of observable objects and thought I’d try my luck at it. It’s not an easy target, having a magnitude (brightness) of just over 10. (The higher the number, the less bright the object is.) I generally limit myself to magnitude 7 or 8 objects simply because of light pollution swamping the data.
With more data, preferably from a dark sky site, this image would be even better.
I’ve had issues with the new camera and horizontal bands through the images. It’s strange, as they weren’t present before - although I simply may not have been recognising them - and there’s been no major changes to the rig. I tried routing the cables away from the main camera, with no effect.
I’ve mostly been able to remove them during post-processing, but I’d rather they weren’t present at all…
Oddly enough, when I increased the gain from 50 to 110 and compared two sets of test images, the bands decreased significantly. I then selected the exposure that gave the best balance between signal and light pollution and kicked off the imaging sequence. I think I manage to over-expose these, as there was a lot (and I mean a LOT) of noise in the stacked image. I’m thinking I should try and keep the individual frames below 20 seconds.
I’m wary of increasing the gain too much, as this decreases the dynamic range of the sensor, as well as reducing the depth of the electron wells (making it easier for an individual pixel to over-expose to pure white). Not exactly what you want.
Image details:
- Gain: 110
- Offset: 10
- Temperature: 0 degrees C
- Exposure: 30 seconds
- Lights: 180
- Darks: 25
- Flats: 25
- Dark Flats (Bias): 25
- Stacked in Siril and proc’d in Affinity Photo
