Essentials for imaging a fast-rotating, low-altitude planet
Successful planetary imaging requires unique astro photographic skills and fast-rotating planets such as Jupiter, Mars and Saturn add extra pressure because motion blur can take place if the capture time is too long.
On top of this, the effect of high speed local atmospheric wobbles (seeing) deteriorates results. High-frame-rate cameras lessen the impact to a degree by taking many still images in rapid succession, which are then processed by registration stacking software like RegiStax or AutoStakkert. The automatic process involves sorting by frame quality, registering the best frames to one another and averaging these into a single image. Sensitive and fast cameras are essential because what you’re attempting to do is sample across the fleeting periods of good seeing which should occur during the capture session. Maximum recording times shorter than 60s or even 30s are recommended so high capture frame rates are very desirable. Software such as WinJUPOS offers the facility to undo many minutes of rotation via a de-rotation function.
Jupiter’s visibility from 2018-2023 is further complicated by its low altitude as viewed from the UK. The planet’s decreasing height above the horizon makes it more likely that images will exhibit colour fringing from atmospheric dispersion. This can be countered reasonably effectively by using an optical device known as an atmospheric dispersion corrector (ADC) fitted between the camera and the telescope.
An ADC will allow a colour camera to be used on Jupiter at low altitude. Mono cameras will need an RGB filter set to produce colour images. Using an infrared pass filter as well often helps obtain higher contrast results, while taking advantage of the fact that longer wavelengths are less affected by poor seeing. A methane (CH4, 890nm) filter can also be used to good effect on methane-rich Jupiter. This requires a camera with a good response in the near infrared part of the spectrum.
The movie sequences recorded by high frame rate cameras are good candidates on which to carry out impact flash searches. Software such as DeTeCt (www.astrosurf.com// planetessaf/ doc/dtc/doc/dtc_ tuto_en.htm) looks for the bright transient flashes that may appear on Jupiter’s disc as signs of meteors vaporising in its atmosphere.
Software such as DeTeCt can analyse your capture files, looking for impact flashes – evidence of rare, meteoric events within Jupiter’s atmosphere
A high-frame-rate camera is essential for modern high-resolution planetary imaging
A typical atmospheric dispersion corrector (ADC) contains two counter rotating prisms