2022 departs with bad weather and 2023 arrives with even worse weather, bringing hurricanes across North America. Sometimes bad weather offers photo opportunities of interesting atmospheric sights, but on balance, as an astrophotographer, I’d rather see the skies clear!
C/2022 E3 (ZTF)
One of the exciting astronomical things that early 2023 will bring us are comets C/2022 E3 (ZTF). Without any surprises, I would rate this comet as “pretty good”, as opposed to hype headlines declaring this comet a “rare blue comet not seen in 50,000 years.” .
It is true that this comet has a green halo, but that is not unusual for comets traveling near the sun, where frozen gases are vaporized and ionized. Compounds of carbon, nitrogen and oxygen are responsible for this.
It is also not uncommon for comets to have orbits so long that they only approach the sun after thousands of years. It is also not a rare comet in terms of its predicted maximum luminosity (magnitude 4.7 according to some optimistic predictions). I would rate it as uncommon, as many comets are not so bright that they can be seen with the naked eye, but they are not rare. This comet will not be visible in urban skies, and even in the countryside, you may have to deliberately look for it.
However, C/2022 E3 (ZTF) will be a good photographic challenge for observers in the Northern Hemisphere as it will be positioned in a favorable position, high in the northeast sky after passing. The Sun is getting closer and closer to the Earth. Besides the green coma, recent photos show a distinct blue ionized tail as well as a white or yellow dusty tail.
The dust tail consists of uncharged dust — particles released when the comet ice melts. As the comet moves in its orbit, some of the comet’s dust balls (think Pigpen from the cartoon Peanuts) are left behind. This layer of dust tends to outline the comet’s orbit until the solar wind blows the smaller particles away from the sun, giving it a rooster tail shape.
The blue ionization tail consists of the frozen gases of the comet that not only melt, but also ionize. Once ionized, the charged particles are strongly affected by the charged particles in the solar wind, and so these particles tend to blow directly off the comet’s head, away from the sun.
A lucky situation for this comet is that it will be visible for weeks from the Northern Hemisphere, even past our closest approach, which will occur on February 2. At its closest. , it would be less than a third of Earth’s distance from the sun. The comet will probably be the most photogenic when it comes close to us, but you should be aware that it will move about half the moon diameter per hour relative to the stars, so a short exposure will be needed if you’re following. follow the stars. If you have a computerized stand capable of self-tracking the comet, then you can make longer exposures, but of course with the stars being dragged.
If you choose a shorter exposure, modern astronomical stacking software such as Deep sky stacker capable of superimposing the stars and creating a second stack on top of the comet, creating a composite image of both sharp comets and sharp stars. Personally, I prefer star trails that show comet motion if only the stars are visible, but if other objects such as galaxies and nebulae can be seen, a composite image is suitable. I.
Even after the closest approach, it’s still worth seeing and photographing as it recedes from us. If it were a “normal” comet, as it receded, it would gradually fade, lose its tail, and disappear into the darkness. However, comets have been known to have outbursts (perhaps a pocket of dust emitting gas), causing sudden flares. This was the case for Comet 17P/Holmes in 2007, when this non-specific, periodic re-appearance (orbital period ~6.9 years) went from magnitude 17 fading to 2, 8, easy to see with the naked eye. This illumination occurred within 42 hours (see Wikipedia article)! Luckily, this happened as it was receding from us and flying high in the northern sky, offering some great photo opportunities for weeks as it passed by deep sky objects. .
In the set of images above, taken over the course of a month, many of the 20-minute images can be stacked because the comet is receding from us and not moving much relative to the stars. These shots were taken at a focal length of 350mm on medium format Ektachrom 200 film (6×9), pushed up to ISO 640.
For tracking Comet C/2022 E3 (ZTF), a good tool is star. The current position of the comet has been highlighted in the free and paid versions of the Android app. But getting the comet to show up on the (free) desktop tool takes a bit of work! Here is the procedure:
- From the left-side pop-up menu, choose Configuration
- In the Configuration menu, select additional navigation.
- On the left side, scroll down Solar system editorthen click configure.
- Select the Solar System tab and click Import the orbital element in MPC format…
- From the next pop-up, select list tab and click:
- Download list of objects from internet
- Select source: List of observable comets of MPC
- Click Get Orbital Elements
- The list of comets will be downloaded and the Import Data window will open. Click Add new and update existing objectsthen press Add object.
Now you are done! All configuration windows can be closed and now, if you enter the comet symbol in the search engine, the comet will appear on the sky map (if it is above the horizon). From my location in southern California, this is the scene at midnight on consecutive nights from mid-January to early February.
Incidentally, the MPC refers to the Minor Planet Center, run by Harvard University, which maintains a database of orbital parameters for minor planets (asteroids) and comets. The ZTF designation in the comet name refers to the automated search project (Zwicky Temporary Facility) that discovered the comet in 2022.
Given the unpredictability of sky conditions and comet growth, it’s hard to say which instrument to use. In general, you should get a fast telephoto lens on any standard DSLR or mirrorless camera (preferably full-frame). Having said that, however, wide-angle shots (e.g. 24mm lens) have shown the comet to be large and bright enough to appear in a relatively short single-frame landscape shot. recent photos shows a fuzzy ion tail several degrees long. Because there can be a long and faint tail, in narrow shots be sure to offset the comet head in your frame. You may not see the entire tail in your framed photos.
A retrograde telescope will be required if you want to track the comet for several weeks. One star tracking should at least be used for tracking stars, as exposures may need to be over a period of several minutes. The interesting thing about photographing a receding comet is that it will move less relative to the background stars.
Good comet hunt! May the clouds part for all of us.