Eta Carina and the new filters

We had two clear nights in a row here, and although it was the full moon I got very lucky - the moon was so low in the sky that it didn’t rise over the house next door! Talk about “lucky imaging”…

Even then, I had to wait until after midnight before I could start imaging because the roof of my house was in the way. I guess I can’t win them all…

Anyway, the first night out I captured an hour of the Eta Carina nebula with the L-Enhance dual-band filter. This filter does fantastic work in bringing out the rich, deep reds of the Ha spectrum. (Eta Carina doesn’t seem to have much Oiii signal as there’s little blue or green in there.)

Conversely, the UV/IR-Cut filter does just that - it chops out the UV and IR wavelengths, leaving only the visible spectrum. Doing so apparently helps to reduce chromatic aberration and ‘blooming’ in stars.

Of course, it wouldn’t be astrophotography if something didn’t go according to plan. I managed to change my camera alignment between the two nights (which is why the L-Enhance image is in portrait mode) because I was trying to debug an issue with the filter holder. I didn’t find this out until I was doing the post-processing and trying to merge the two data sets. I will be very damned careful not to do it again.

Suffice to say, I got there in the end by some very careful rotating and scaling of the L-Enhance image until the stars all aligned with the UV/IR-Cut image. It wasn’t a fun process, and I ended up cropping the image heavily to avoid the very obvious overlap between the two images.

I’m still having troubles with getting the Flat and DarkFlat calibration frames correct, so ended up not adding them to the mix. This is the area I’ll be concentrating on next, as the key to good images is to have all the correct calibration data.

L-Enhance Image details:

  • Gain: 80
  • Offset: 10
  • Temperature: 0 degrees C
  • Exposure: 20 seconds
  • Lights: 180 (1 hour of data)
  • Darks: 25
  • Flats: 0
  • Dark Flats (Bias): 0
  • Stacked and proc’d in Affinity Photo

UV/IR-Cut Image details:

  • Gain: 50
  • Offset: 10
  • Temperature: 0 degrees C
  • Exposure: 15 seconds
  • Lights: 360 (1.5 hours of data)
  • Darks: 25
  • Flats: 0
  • Dark Flats (Bias): 0
  • Stacked and proc’d in Affinity Photo

Final image created with Affinity Photo

Eta Carina - L-Enhance filter

Eta Carina - UV/IR Cut filter

Eta Carina - Final image