Occultation of saturn by the full moon tomorrow night (14th May 2014)

Written by Gary on May 13th, 2014

UPDATE: Here is a shot from tonight using the Olympus E-M5 with Olympus 45mm f/1.8 lens and eyepiece projection via a 10″ Newtonian telescope. Seeing was not great but at least the clouds were less than earlier.

saturn occultation May 2014

Those lucky people in Australia with access to a camera and a telescope (or at least a telephoto lens with around 1000mm or more focal length in 35mm terms) will be able to attempt to photograph saturn with its rings going behind the full moon (this is called an occultation) tomorrow night.

Times in the various cities can be found on Ian Musgrave’s web blog post here.

For those of use in Melbourne where the forecast is for nice clear skies (hopefully), saturn will disappear behind the moon at ~ 8.50pm local time and then reappear around 10pm.

You will not need to go to a dark rural site as light pollution will not be as much of a problem other than preventing accurate polar alignment – but this is not really needed either given the short exposures of well less than 1 second. More of an issue is atmospheric disturbances so, a site above grassed land or over water and away from houses is preferred – but then you will have to deal with standing on wet, dew affected grass. For best seeing, elevated sites away from urban areas may be best – but these are colder.

You will need to have everything set up by about 8pm to ensure it is all working for you, and the telescope has had a chance to cool down so your seeing conditions are better.

You will need to manually focus on the moon or saturn well before the crucial events occur as you will be too busy taking shots in the couple of minutes or so each event itself will last.

Ideally you will control your camera remotely so you don’t shake the telescope, and ideally you won’t be using a SLR but a mirrorless camera so the mirror doesn’t shake the telescope.

An ideal camera for this is the new Micro Four Thirds cameras such as the Olympus E-M10 or Olympus E-M1 as these are not only mirrorless cameras which can shoot at rather fast burst speeds of around 10fps for brief bursts (you need rapid shots as atmospheric seeing changes rapidly within each second so sharp images may only be seen on a few frames out of 10 shots), but you get a great compromise in having the most telephoto effect for a large sensor camera while still having good image quality at ISO 1600-3200 (and you will probably be needing ISO 3200).

Better still, these 2 cameras allow you to wirelessly tether to a smartphone so you can see what you are imaging on your smartphone BEFORE you take it and remotely release the camera shutter without shaking the camera. Very nice indeed – my Olympus E-M5 does not have this feature so I will be using a TriggerTrap accessory and iPhone app to trigger the camera by cable.

Manual focus is made more accurate by being able to magnify the image in the electronic viewfinder.

Here is a previous blog post of mine demonstrating what can be achived using the Olympus E-M5 with the TriggerTrap accessory to photograph the occultation of Jupiter by the moon.

Tomorrow night’s event will be a little tougher as saturn is much less bright than jupiter, but it will be higher in the sky so hopefully there will be less atmospheric disturbance and less atmospheric extinction.

Here is one of my images from the Jupiter occultation:

Jupiter

Good luck and have fun.

For those without the above, a pair of binoculars will be useful.

More on astrophotography here, and more on lunar occultations here.

 

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