Photographing Jupiter and her Moons

A brief ‘How to’ on the subject of solar system photography with limited equipment. More specifically the combining of techniques to photograph Jupiter & her 4 Galilean moons.

Beyond the Sun & the Moon  , some of the brightest objects in the skies are a few of our fellow planets. It is quite reasonable & fun to set out on an adventure photographing them from your own back yard. The photograph below demonstrates how this can be done with a standard camera setup.

 

The photograph was taken on a 35mm camera with only a 200mm lens attached. Tripod mounted, 1/15sec f2.8 ISO1250 it shows our moon and Venus  bottom left and Jupiter in the top right.

But what if we’d like to be a little more ambitious, perhaps we would like to focus on planet Jupiter and include some of her moons in the photograph. That too can be achieved without much complication. Within reason you’ll need a lens with a bit more focal length for this one, a 35mm equivalent of 300mm should suffice but more would be better. Again tripod mount for stability and shoot away. The next is a crop from a picture that was taken at 700mm focal length on a Canon 300D using an exposure of 2 seconds at ISO 400 f5.6.

 

To my taste, one of the problems with this is that Jupiter is over exposed and so we see no details on her. But if we reduce the exposure by much then her moons will just fade away into the dark night sky.

So if we want to show details on Jupiter and show her 4 Galilean moons  in the same image, we’ll need to find a workaround.

The simplest solution is to capture 2 separate photographs one exposed for the Galilean Moons and one exposed for the planet Jupiter herself. However to capture some worthwhile planetary details we really need to up our focal length & our light gathering capability. This is where we ideally need to jump to a telescope and I’d suggest 150mm (6 inches) of aperture is the minimum. An aperture of 150mm is indeed what I shall work with here; in the guise of a small Celestron Schmidt-Cassegrain  telescope.

To further complicate the matter we’ll be trying to focus & photograph at an imaging scale that is greatly affected by movements & density changes in our atmosphere. This ‘seeing’ will vary moment by moment like the heat haze that you see above objects on a summer’s day. A solution to this is to take many individual images, or more simply, to video the scene and process the best frames in a computer afterwards. This allows us to seize the best moments of seeing and to discard the rest. So let’s check what we’ll need:

  • Telescope with at least 150mm aperture, more is better
  • Equatorial mount to counteract Earth’s rotation (otherwise the planet may move out of our video frame)
  • Some sort of video recording camera
  • A way of magnifying the image
  • A computer to save the video on to

To record the video many people use a modified webcam or a purpose built planetary imaging camera. These cameras simply slot in where the telescope eyepiece would go and so a standard Barlow lens can be added to provide some further magnification of the scene. The modified webcam route is a very affordable option & can yield some good results.

However, in this instance I am going to use a different technique. An excellent piece of software called EOS Movie Record has been developed. This freeware will allow you to record the LiveView image from a Canon EOS DSLR direct to computer and critically for this occasion it can be recorded whilst the x5 zoom is invoked. So I shall be using my 5D MkII with a x2 extender attached to the back of the scope with an adapter. This will provide 3000mm focal length and the resulting image will be recorded at x5mag on to a laptop PC.

Now that we’re all setup the first thing to do is to record a short piece of video with the exposure bright enough to capture the 4 Galilean moons.

Next we want to reduce the exposure sufficiently to see details in Jupiter’s atmosphere. It is important that we only change exposure, any other changes could alter the relative positions of the moons in the previous video to the position & orientation of Jupiter in this video. Once happy with the exposure, record a video of the scene, perhaps 30s – 90s of video.

Assuming that both video recordings have succeeded, we now need to process our captured data. For the high exposure video with moons, I simply captured a good clean frame to still image. For the lower exposure detailed Jupiter video, we need a piece of software to select and stack the best frames from the video. Registax is a freeware program that will do just that for us.

After stacking the best 500 frames of a 4000 frame video, the image below is what can be seen of Jupiter; the seeing was not particularly good but there are still sufficient details to work with.

Best 500 frames of 4000, stacked & drizzled with wavelet enhancement.

 

Now we need to combine this image with our high exposure frame capture, to include the Galilean Moons.

Any decent image editing program that features ‘layers’ will do for this job, I use Adobe Photoshop. Open both images and copy one into the other as a new layer. Make sure that your imaging scale & orientation are consistent at all times, so that the moons are in the correct  positions. Align the two Jupiters up and then use layer blending & masks to achieve the best result for your image. Apply any final tweaks such as local contrast adjustment and save the final image.

The last thing to do is to identify which moon is which. There are various programs available on the internet, one specifically for this job is JupSat95.

Below is the final image:

The planet Jupiter and her four Galilean Moons; from left to right Callisto, Europa, Io, Ganymede. As at 19:00 GMT 19/01/2011 – Imaging details: FL 3metres C6SCT x2 extender Canon 5DMkII x5 liveview 4000frames (more details on blog)

 

After all our capture & processing work we now have a detailed picture of planet Jupiter and her 4 Galilean Moons. In this particular photograph we have, from left to right Callisto, Europa, Jupiter, Io, Ganymede.

If you have access to a larger telescope such as an 11 or 14 inch SCT then the planetary details available to you will be significantly greater than those shown above; but I hope that I’ve demonstrated that even a relatively small 6 inch telescope can yield a worthwhile Jupiter image that can be processed to give an interesting scene.

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