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Saturday, April 13, 2024


Imaging 12P-Pons_Brooks challenge 14-30 April, 2024.

Printable Black and White chart for locating Comet 12P 10April-10 May. Click to embiggen and print. Use with a red light torch (or a standard torch with red cellophane over it) to preserve your night vision.
Printable Black and White Binocular chart for locating Comet 12P. The circle represents the approximate field of view of 10x50 binoculars.Click to embiggen and print. Use with a red light torch (or a standard torch with red cellophane over it) to preserve your night vision.
Photo realistic view of the evening sky simulated in Stellarium for Sunday, April 14 as seen from Adelaide at 18:48 ACST (60 minutes after sunset, click to embiggen). Jupiter is very low above the north-western horizon and within binocular distance of Uranus and the comet 12P (the inset is the approximate binocular view of the trio).Photo realistic view of the evening sky on Sunday, April 21 as seen from Adelaide at 18:39 ACST (60 minutes after sunset, click to embiggen). Jupiter is almost lost above the north-western horizon. Comet 12P is close to the pair of Xi and omicron Tau (the inset is the approximate binocular view of the trio).

Comet 12P Pons-Brooks has been subject to a little bit of hype ("the Devil Comet" because at one stage its U shaped Coma could be interpreted, if you squinted hard, as devils horns), but it is truly a beautiful little comet.  While we have seen some gorgeous images coming from the northern hemisphere, most of them require serious kit. Nonetheless even simple camera/mobile phone may get some nice images.

While the comet is a reasonably bright magnitude 4.5, about as bright as the star Taygeta (19 Tau) in the Pleiades, it is so low to the horizon that you will be difficult to see it through the horizon murk over the next week or so. You will definitely need binoculars, even if you can see the brighter stars of the nearby Pleiades clearly. While the comet is much brighter than Vesta in the Vesta challenge, it is lower in the horizon murk and a more extended object, making it more of a challenge.

On the 14th  the comet will be within binocular distance of Jupiter. Although the comet is magnitude 4.5 at this time and theoretically dimly visible to the unaided eye, atmospheric extinction will mean it is more like magnitude 6. The comet will look like a faint fuzzy dot.

At nautical twilight (an hour after sunset) it will be around three finger-widths above the horizon (and you will need a level, unobstructed horizon to see it). You may have better success looking a bit earlier, when it will be higher despite the brighter twilight sky. Terry Lovejoy was successful in capturing the comet with 7x 1 second exposures at 100 ASA using a Sony A7iii.

Using a more ordinary camera, try zooming in around 3x and using mutiple1 second 100 ISO imaging (you WILL need a tripod for this). Higher ISO (ASA) values will make the sky brighter as well as the comet, so will not be as effective. You may wish to play around with the settings if you have time before the comet sets. 

UPDATE: forget everything I said about imaging. I have been able to get it with 1 second ISO 3200 and 3x zoom, but nothing below ISO 1600. (I have also done 2 and 4 second exposures, but I have an S24, so that’s cheating). I have yet to try stacking, there may be too few stars visible to stack reliably. 

12P Pons-Brooks will climb higher and brighten as it rises (not much though). It should be more or less easily located in binoculars by sweeping up from Jupiter (see printable charts and maps above).

On the 21st the comet will be at it's brightest (unless it undergoes another outburst, it has had nights where it was substantially brighter) at magnitude 4.4 (although atmospheric extinction means it is more like magnitude 5.3 at astronomical twilight, an hour after sunset). At this time it will be nearly two hand-spans above the horizon, almost on top of the two stars Xi and omicron Tau (both around magnitude 3 and readily visible, see charts above). If you can't readily see the pair locate the rather obvious Aldebaran (and the Hyades) and sweep down an to the west by about three binocular widths and the pair should be obvious.

Again, you may wish to look earlier when the comet is higher, and the twilight brighter. While the comet will still look like a fuzzy dot in binoculars, you may be able to see a short tail. 

For imaging try zooming in so the pair of Xi and omicron Tau take up a decent proportion of the field of view (not too  much as the resolution of most point and click cameras and mobile phones degrade severely on zoom) and take multiple 1 second images (I use between 10-20 images), you may try higher ISOs to try and capture more comet detail. Stack the images with an appropriate stacking software. Free Stacking software includes Deep Sky Stacker and Autostakkert for Windows,  and StarStaX for macOS. 

After this 12P Pons-Brooks begins to fade, but still remains "bright", sweeping your binoculars up from Xi and omicron Tau should pick it up. on the 29th it is within binocular distance of nu Tau (see charts, sweep west of Aldebaran for around two binocular widths). At this time, at nautical twilight is over two hand-spans from the horizon and magnitude 4.5 and another good opportunity for imaging.

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