An inconveniently placed tree made getting an image of this comet difficult. On 24-10-25 I only got 3 subframes that were of any use. However, this did serve as a good learning curve for the following night when I decided to have another attempt. The equipment used was a Skywatcher 150P and ZWO ASI 294MC-Pro OSC. FOV is 2.13 x 1.45 degrees at 1.85 arcsec/pixel.
Starting a little earlier I plate solved on Vega to align my mount and entered the RA and Dec of C/2025 A6 Lemmon from The Sky Live website and, there it was, right in the centre of the field. I still had the tree leaves issue but I took 100x30s images of which 47 were used and the rest discarded. The following was the processing sequence:
- StarNet2 to remove the stars from the 47 comet images (it took a while)
- PixInsight (PI) Comet Alignment used to create 47 frames with the comet head centred
- Weighted Batch Preprocessing (WBPP) was used to attempt stacking but proved less than satisfactory, however, the debayered images were used from this process
- PI Image Integration was used to stack the debayered images from the WBPP run
- GraXpert Background Extraction
- GraXpert denoise
- PI STF and Histogram Transformation was used to stretch the image
- Splitting the image into RGB channels the green and blue channels with slightly enhanced (‘S’ curve) using PI curves transform and the channels recombined
- SetiAstro FAME mask was used to remove residual surrounding background created by the tree leaves (!). A PI curves transform was run on the masked image
- Finally the ‘best’ image was used to extract the stars and PI PixelMath used to recombine the comet and stars images
Here is the Astrometry of where this image was taken (between Corona Borealis, Bootes and Serpens):
