Comet 12P/Pons-Brooks is a Halley-type periodic comet that was first discovered by Jean-Louis Pons on July 12, 1812 and then independently rediscovered by William Robert Brooks in 1883.¹

It was already suspected at that time that the circulation was between 65 and 70 years.² Later, Johann Franz Encke determined the final orbit with an orbital period of 70.68 years. In 1882 they searched for the comet in vain. In 1883 it was discovered by chance by William Robert Brooks and only later identified as the same comet. The comet was seen again in 1954. Imaging was done around its passage of April 21, 2024.

Two days after the previous image of the comet 12P/Pons-Brooks, there was a longer opportunity to photograph it, this time leaving enough time to do a full LRGB run. At the time, the comet was just south of Hamal (just not in the image) in the constellation Aries.

I started with 20 subs of 15 seconds per channel in RGB, followed by 60 subs of 15s luminance. Adjacent image shows a sections of the sky of approximately 2.5 x 2 degrees and was taken between 19:35UTC and 20:08UTC using a ZWO ASI1600MM Pro Cool and ZWO RGB filters behind the SkyWatcher Esprit 80ED.

Stacked in APP 2.0.0 beta 17, post-processing in Topaz and PSP.

Click here for the full image.

Almost exactly a week after my previous image of the comet 12P/Pons-Brooks, there was another brief opportunity to photograph it last night. Around a quarter past eight the sky began to clear and Jupiter and the brightest stars could be seen. At the time, the comet was just north of Hamal, the brightest star (magnitude 2) in the constellation Aries (the brightest star in the photo).

Half an hour later the thin cloud had finally left and the recording could begin. Just like last time, to be on the safe side, I started with 20 subs of 15 seconds per channel in RGB, with the intention of then shooting 60 subs of 15s luminance. Of course, that didn't work: just when the recordings with the blue filter started, fog started to form. Fortunately, I am more than 7 meters above ground level, so it didn't bother me right away. But when the captures with the luminance filter started, it quickly became clear that the fog was rising above InFINNity Deck. To make matters worse, I had forgotten to reset my sequence, so after the 15^th sub, NINA decided it was enough (I had shot 45 luminance subs the first time) and the mount was parked.

Adjacent image shows a sections of the sky of approximately 2.5 x 2 degrees and was taken between 19:45UTC and 20:00UTC using a ZWO ASI1600MM Pro Cool and ZWO RGB filters behind the SkyWatcher Esprit 80ED.

Stacked in APP 2.0.0 beta 17, post-processing in Topaz and PSP, where the blue channel was used as extra luminance.

Click here for the full image.

In March 2024 this comet got high enough in the sky to be imaged in the evening. This evening the comet was in between Pisces and Triangulum at a distance of about 1.6AU (242 million kilometres) from Earth.

The weather, however, was not very cooperative. The first attempt, a week before and shown below, was only done in luminance as the gap in between the cloud-cover was too short for serious imaging. During the second attempt, shown here, the weather was again not cooperative with 4-5Bft winds and 80% cloud cover.

Still I managed to image the comet in RGB using both the SkyWatcher Esprit 80ED and SkyWatcher Esprit 150ED, but the wind caused shaking of the telescopes with oval stars as result.

Adjacent image shows a sections of the sky of approximately 2.5 x 2 degrees and was taken between 19:35UTC and 19:54UTC using a ZWO ASI1600MM Pro Cool and ZWO RGB filters (due to upcoming cloud cover there was no time for luminance).

Stacked in APP 2.0.0 beta 17, post-processing in Topaz and PSP.

Click here for the full image.

First a stack was made on the comet (plate 1), then another stacked on the stars (plate 2). A starless version of the last one was made (plate 3) to remove the comet from plate 2 (plate 3 subtracted from plate 2, this resulted in plate 4). Due to the almost stationary movement of the comet, I was unable to get plate 1 starless, so I manually removed the stars using a clone brush. Then removed the noise from the plates in Topaz and combined plates 4 and 1 in PSP with plate 1 above plate 4 as an Exclusion layer.

It then turned out that the clouds had caused wide bands of varying colours in the combined plate, so I loaded that plate back into APP and ran the Light Pollution Filter on it again.

Of all recordings, those from the blue channel were the best. I made a star-less stack of this channel in APP, then passed it through the light pollution filter and finally used it in PSP as a Screen-layer, so that it works as extra luminance. Final editing was done in Topaz and PSP.

My first attempt in 12/P-Pons-Brooks was on 18 March 2024. Only a few small gaps were present in the cloud cover, but at least we had some gaps (the weather had been terrible for weeks again). So an LRGB-sequence was started in NINA, only the luminance of which gave some results. In total 17 subs of 15s were captured and processed while registering on the stars.

Captured with the SkyWatcher Esprit 80ED, ZWO EFW, ZWO luminance filter and ZWO ASI1600MM Pro Cool.

Click here for the full image.