My name is Charles Smith and I am a final year Astrophysics Student at
the University of Hertfordshire. As part of my final year, I am
undertaking an investigation entitled 'On the Frequency of Impacts on
Jupiter' and included in that is a Social Study on Amateur Astronomers
in relation their views on monitoring Jupiter. If you could, would it
possible to ask the following questions to your members and provide me
with feedback including a few individual quotes?

1) Are you aware of the 2009 collision with Jupiter captured by an
amateur astronomer, Wesley? If so, what are your views on it?

2) Do your members actively look at Jupiter, be it on their own or as
part of a society?

3) Would it be feasible to monitor Jupiter (regularly) from an amateur
astronomy society such as this one?

Thank you very much for taking the time to read through my email and I
am very grateful for any aid you can provide in relation to my
project.

Many Thanks,

Charles

I use an 8” aperture f/10 SCT for planetary imaging, fitted with an old Philips TouCam webcam and a Barlow-lens magnifier to achieve an effective focal-length of around 7m. At this magnification the Jovian disk fills a fair proportion of the camera sensor, so even with 640x480 pixels resolution I can achieve a reasonable resolution. But in practice, it’s atmospheric turbulence which limits the ultimate image quality, particularly when the planet is low in the sky. And in addition to the prevailing meteorological conditions, thermal air-currents rising from nearby buildings can severely perturb the “seeing” locally.
In addition to local air-turbulence, convection-currents within the telescope tube can also be significant, so the ‘scope must reach thermal equilibrium before it can capture its best images. If like me, you have to carry out the ‘scope from indoors for each imaging session, then it can take more than an hour to cool down ready for use.

Aside from the transient disturbances caused by turbulence, the Earth’s atmosphere also causes spectral dispersion which smears the image vertically: this effect is more severe the lower the planet is in the sky. The large professional observatories use Atmospheric Dispersion-Correctors to counteract this effect, but very few amateurs have these.

Of course there is only a limited period each year when a particular planet is visible from a given latitude, but then this window of opportunity is further constrained from amateur back-garden observatories by the obstructions of nearby houses and trees. And adding the weather to these other constraints, there may be only a few nights per year when high-quality images of a particular planet can be acquired.

My own procedure when imaging is to capture a series of 5fps video streams at 15-minute intervals through the evening, for subsequent processing (using the RegiStax software) to extract a set of reasonably sharp images from each 500-1000 frames of wobbly raw data. Normally the last one of these is the best (when the planet is highest in the sky and the scope has cooled down properly), but if I have a particularly good set one night, I edit them all into a time-lapse video showing Jupiter’s rotation and the movement of the Gallilean satellites. But even if my data-set did happen to include a brief transient such as an impact, I may not see it, since the post-processing would treat it like just another atmospheric perturbation and average it out when forming the final smoothed image.

So what would be the ideal set-up for capturing an impact event on Jupiter? Perhaps the most important prerequisite would be a good location: somewhere close to the equator, with good weather, clear air and well away from other buildings – this would give the best chance of capturing high-quality raw images. The telescope-mount would need to be accurate enough to keep track of the planet at high magnification all through the night, and something like a 14” SCT would be a suitable telescope, fitted with an imaging camera capable of >60 frames per second and linked to a computer capable of storing all this data. Then some software would be needed to sift through each night’s data looking for transient events, and presenting them for further assessment by a human eye. This ideal is far above what most amateurs could aspire to, but perhaps not beyond the reach of a commited enthusiast - and we’ve seen in recent years some notable successes in detecting supernovae and comets by dedicated amateurs with relatively modest equipment.