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 shutteractivation 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.