Comet Hunting!!

There’s been quite a buzz over the past few weeks over Comet C/2022 E3 (ZTF). It’s currently in the Northern sky 24 hours a day, barely visible with the naked eye (if at all) and they didn’t even give it a name.

E3, as I like to call it, was last here 50,000 years ago so and it’s certainly not as impressive as Hale-Bopp in the mid-90s, which I remember being one of the brightest objects in the sky, nor Neowise which whilst only just visible only needed a few seconds photographic exposure to be clear.

A few days ago, I decided to go hunting for E3 at about 1am on a very cold, but clear night. It wasn’t easy – I did a lot of checking through apps such as Stellarium and Sky Tonight, but as E3 wasn’t very close to any ‘major’ stars, it was guesswork trying to find it, and of course I didn’t know exactly how it would appear on the camera screen. After a couple of hours I gave up – there was nothing that looked remotely like a comet, just loads of really nice sharp in-focus stars! But it did JUST appear right at the edge of one frame. So, more research the next day, and I used some online software called Astrometry.net to identify what the objects were in that shot. This is called ‘Plate Solving’. You can just see E3 at the left hand edge about 1/5th of the way up.

So using the Plate Solved image, I set up well ahead of time that night and started searching again, but now had a couple of objects that were close to E3 (IC4567 was the closest) and whilst this star wasn’t actually visible, I was able to use the Goto Mount to slew round to it. I took some test shots for focus and exposure, and slewed the camera a few more degrees then suddenly, there it was – a slightly dim blur amongst all the sharp stars, just underneath a neighbour’s TV ariel! EUREKA!!

I ended up with 2 hours of data (30 second exposures), snapped the necessary calibration frames, imported it all into Deep Sky Stacker, set it going and went to bed.

And that was the next set of problems – naively, I hadn’t taken into account that the comet moves at a different speed so that has to be taken into account in the stacking process! So several hours and four stacking attempts later, I finally had an OK image to process! Not the most amazing, but the trail is clearly visible, so I’ll settle on that for now. Unfortunately it seems that DSS isn’t the best option for Comet stacking, so there are some blurry star trails, but hey-ho, learning a new stacking program can wait for another time!!

With the knowledge that now it is nearing its maximum brightness, I thought I’d have another go last night. I was a bit complacent in setting up and assumed I’d be able to find it easily. It’s now pretty well circling Polaris, so should be a breeze to find. WRONG!!!

Problem is, it’s difficult to judge the effective diameter of its orbit from the apps like Stellarium. So after about an hour and a half of effectively throwing a dart blindfolded, I finally found it – but the camera setup was rushed and I needed to re-calibrate to get decent tracking. Then having done that, starting snapping 30 secs frames and the cloud came in!!

This is just one frame, uncropped, with just a bit of processing; the best of just a handful. The comet is now much brighter, although still not visible with the naked eye. A few clear hours forecast for tonight, so hopefully will get some really good frames to stack. Watch this space …