October 2024 is the month when we may or may not see comet C/2023 A3 Tsuchinshan–ATLAS, depending on whether it survives perihelion on 27 September, when it passes within 58.6 million kilometres of the Sun.
Assuming it survives, it should become visible after 11 October, an evening comet visible in darkening twilight.
Here we’ll take a look at the best ways to photograph comet C/2023 A3 Tsuchinshan–ATLAS.
Read our guide on how to photograph a comet and observing Comet C/2023 A3 in November.
What to expect from Comet C/2023 A3 in October
If long period comet C/2023 A3 performs as predicted, its coma and adjacent tail stub should become visible as twilight darkens, but its full glory won’t be realised until true darkness falls.
Of course, as is often the case with comets, near the peak of C/2023 A3’s brightness, as we wait for true darkness the comet will lose what little altitude it has and consequently the view won’t improve much.
In the early period of evening visibility, say 11–15 October, the best strategy will simply be to go for broke and capture as soon as you can find the comet.
The nature of that capture will depend on the apparent size of C/2023 A3 and how bright it gets.
For more info, read our beginner's guide to Comet C/2023 A3, discover the 10 greatest comets of recent times and find out what comets and asteroids are in the sky tonight
Kit and technique
Ideally, a wide- to mid-angle lens on a DSLR or similar camera is a great option for photographing C/2023 A3 Tsuchinshan–ATLAS.
That will give you a lot of flexibility and allow you to capture some foreground for context too.
It pays to keep your ear to the ground and gather as much live, up-to-the-minute comet information as you can.
There will no doubt be lots of photos of the comet online, but if important details like date, time, image scale or equipment details are missing – as is often the case – it can take a bit of sleuthing to work out what’s what.
See the best images of comet C/2023 A3 Tsuchinshan-ATLAS
If it’s possible to work out the size of the tail, this can really help save time choosing your lens/telescope setup.
If C/2023 A3 Tsuchinshan–ATLAS gets as bright as predicted, it could also fall within range of smartphones, so everyone should be prepared to grab a photograph.
Again, when you share your images, letting people know what phone you used for the shot could save a lot of time for others hoping to grab their own photographs too.
Smart telescopes should be able to get decent images of the comet, although if the tail becomes too long some models won’t be able to contain it all in a single frame.
The big advantage of a smart telescope is that it can be very time-efficient.
You can be imaging the comet in minutes, which is helpful if the weather’s being difficult.
Having said this, smart scopes use plate solving to work out where they are pointing and for this to work, stars must be visible to them.
This can prove problematic if an object’s altitude is very low.
If the comet is as bright as predicted, it may also be captured using planetary imaging setups, such as those that use high-frame-rate cameras for lucky imaging.
This technique is good for grabbing detail in the head of the comet, such as jet structures.
These can appear as bright features emanating from the nucleus region, sometimes exhibiting spiral patterns caused by the jets venting as the nucleus rotates.
As long as comet C/2023 A3 Tsuchinshan–ATLAS doesn’t evaporate, and the clouds stay away, October evenings are set to be exciting and rather busy!
Equipment
- Any camera capable of imaging the night sky
- Smartphones, DSLRs or similar
- Smart scopes
- High-frame-rate planetary cameras
Photograph comet C/2023 A3 Tsuchinshan–ATLAS, step by step
Step 1
A low-altitude comet presents many issues, with added jeopardy from the Moon. Being diffuse, both natural and artificial light pollution will make the comet harder to see. For views from 11 October on, under daylight conditions find somewhere with a flat, low and clear west to west-southwest horizon.
Step 2
For early shots (11–17 October), we recommend a wide to mid-angle setup. Make frequent adjustments for twilight. For navigation, use bright star Arcturus, then identify Gemma in Corona Borealis. Spin the Arcturus–Gemma line 90° counter-clockwise; the free end points roughly where the comet will be mid-month.
Step 3
If you have a smartphone with a night shooting mode, select it, make sure that focus is good and take the exposure. Some phones offer longer exposure times if the phone is held still. An inexpensive tripod phone holder is ideal for this. Some models have detachable Bluetooth shutter-activation buttons so you can avoid touching your phone when taking the shot.
Step 4
If you have a smart scope that live stacks, limit your capture sessions to 5–10 minutes (left) to avoid the nucleus smearing into a line (right). If you plan to process the scope’s captures yourself, using PixInsight, for example, you’ll be able to exceed this limit by using comet-specific workflows.
Step 5
For DSLRs or similar, from 11 October exposure times will be limited by twilight. Use a low to mid ISO and a few seconds exposure. Don’t burn out the region containing the comet. Use Arcturus to focus as accurately as possible. Framing low-altitude shots with foreground objects (right) gives context to your image.
Step 6
If the comet’s bright enough, a planetary imaging setup can be used to image its core. Bring the saturation up to 70–80 per cent, take lots of frames and process with, for example, AutoStakkert! Processes such as the Larson–Sekanina rotational gradient filter can help bring out jet detail as shown here for comet 17P/Holmes.
If you capture an photo of comet C/2023 A3 Tsuchinshan–ATLAS, don't forget to send us your images.
