Photographing Jupiter with her 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.

Moon & Venus Conjunction plus Jupiter

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 picture was taken at 700mm focal length on a Canon 300D using an exposure of 2 seconds at ISO 400 f5.6.

Jupiter @ 700mm

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 4Galilean 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.

Planet Jupiter

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:

Jupiter's Moons

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.

Shooting Stars, Meteors and the Perseids

The recent meteor shower  was a great celestial occasion for both viewing and photography. In this post I hope to explain what causes the ‘shooting star’ displays and illustrate how they appear to radiate from a particular point in the night sky.

I’ve been waiting for a clear sky on the peak night of the Perseids  for several years and this year provided me with the closest yet, almost 2 hours of clear sky with patchy moving cloud. So let’s start with a close-up picture of a shooting star.

A Perseid Meteor 40s f4 24mm ISO1600

Shooting star is a colloquial name for the trail of a meteoroid as it passes through our planet’s atmosphere. At this point it is more correctly called a meteor, if any fragment manages to meet the ground it will then be called a meteorite. Meteoroids are solid chunks of material moving through space with a size ranging from a spec of dust up to 10 meters across. When such an object enters Earth’s atmosphere, at speeds up to 40 miles per second, it heats up and usually disintegrates at about 30 miles of altitude. This fiery death happens in a mere second and is what we see from the ground. The colours seen in this display, can give scientists a clue about the composition of the meteor. In the picture above the blue/green suggests copper and the yellow/orange suggests sodium. If the brightness of a meteor in our skies is greater than that of the planets, then it is considered a fireball or bolide. We were lucky to see one such fireball last night, high in the north-east, above Dyfi Forest.

Perseid and Andromeda click image for a larger view …

The picture above shows a wider field of view, the Perseid meteor can be seen top left, whilst one of our neighbouring galaxies, Andromeda, may be seen in the bottom right. These images were taken using a Canon 5DMkII & 24-105L lens on a normal photographic tripod. With an exposure time of 40 seconds, this is long enough for the Earth’s motion to cause star trails, which are indeed very evident. To avoid this one could mount the camera on a German equatorial mount, as per the picture at the bottom of this blog post.

A meteor shower is said to happen when many meteors are seen in the sky over a short period of time and they all appear to radiate from the same point. This is caused by a stream of cosmic material colliding with Earth’s atmosphere. The Perseids are just one such stream of material. The comet Swift-Tuttle  travels through our solar system on a 130 year orbit, occasionally it loses matter and this is left as a stream of cosmic debris that our planet passes through in the fist half of august each year.

So why do the meteors in a shower appear to radiate from the same point and can we illustrate it?

Having been dropped by a speeding comet, all these cosmic dust particles are travelling in parallel with each other and at very similar velocities, perspective  vision demands that they appear to originate from the same point. For example, imagine you are standing in the middle of a long straight road. Far in the distance 2 motorbikes appear from the same point. In truth one is on the left of the road & one is on the right. As the motorbikes approach you, they will appear to diverge away from the same starting point and eventually one will pass one side of you and the other will pass the other side of you. The motorbikes have never moved apart, yet they appeared to originate from the same point. This is how it is with the meteors but on a much larger, cosmic scale.

The Perseids appear to radiate from a point in the constellation  of Perseus, hence the meteor shower’s name. To illustrate this I took the picture below:

Perseid Radiant click on image to view a larger version …

This was taken with a Canon 40D and 15mm f2.8 fisheye lens, mounted on an equatorial mount to avoid field rotation and star trailing. A series of 170 35-40 second images were taken sequentially. Satellite & aircraft trails were filtered out, as were cloud laden exposures. The remaining exposures were further filtered for meteor activity and then composited to form the above image. Six meteors can be seen streaking across the night sky. To the left one can see the Plough (Big Dipper) asterism ; to the right the constellations of Cassiopeia & Perseus can be seen. Each of the six meteors’ paths can be traced back to within the constellation of Perseus.

The orientation of the above image is looking directly north, over southern Snowdonia. Bottom left is Foel Crochan, Aberllefenni, with some cloud cover.

I hope you saw some meteors, if not, better luck next time. If you are hoping to photograph meteors, remember that the burst of light is typically only 1 second long and that’s what you’re trying to image. So use a fast lens and maximise the light gathering potential of your camera. Expose for long enough that the sky appears slightly brighter than black. Use a focal length of your choice, wider gives you more chance of catching one, longer may give you more detail.

Have fun.