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I have the Canon PowerShot SX410 IS. Last year with some help, I was able to photograph Jupiter and its moons. Now, in the coming Spring, I want to make a photo of Saturn's moons.

I know Saturn's moons reflect less light than Jupiter's. I think I can compensate this using a slower shutter.

On the following photo, you can see the picture I took from Jupiter with its moons and a small star at the bottom.

Jupiter

Can I make a similar picture of Saturn's moons ?

Olivier
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Ruslan
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3 Answers3

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In short: you might have a shot !

Light

I'm not an astrophotography expert, but here are some facts (I hope I interpreted them correctly):

  • Jupiter is in average about 780 millions of kilometers from the Sun. Compared to Saturn and its 1400 millions, it will receive about 4 times less light per unit of surface from the sun. The same is true for their moons.
  • Currently (info from The Sky Live), Jupiter if about 5 AU from Earth and Saturn is about 10 AU from the Earth. The light coming from Saturn will be reduced by another factor 4 before reaching Earth.

If the exact same moons were orbiting Jupiter and Saturn, the intensity of light coming from the one orbiting Saturn will be diminished by a factor 16 compared to the one coming from Jupiter's. If you want to receive the same amount of light, you will need to increase your shutter time by 16.

Now considering the real moons, Io (Jupiter) has a diameter of about 3600 km with an albedo of 0.6 and Titan (Saturn) is about 2500 km wide with an albedo of 0.2. All thing being equals, Io will reflect about 6 times more light than Titan. Titan is about 100 times less luminous than Io !

As a side note, Jupiter and Saturn have about the same diameter (143 vs 120 thousand kilometers) and about the same Bond albedo.

Distance

Considering distance, using the same lens, your camera's sensor will perceive Saturn as being about 2 times less "big" than it did with Jupiter, so you will have 4 times fewer pixels to resolve it. Considering the moons, it should be about the same.

Results

Given those informations, you should be able to judge if you can get a good image of Saturn and its moons, given the image you got from Jupiter.

Comparaison to telescope

For information, this website indicates that you need a 90-millimeter telescope to see the brightest moons of Saturn (90 millimeters being the telescope aperture). This kind of telescope is usually associated with a focal length of about 600 or 700mm (so about a f/7 600mm lens). As your Canon PowerShot SX410 IS is equivalent to a 960mm focal length with a f/5.6 aperture, you might have a shot :)

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Olivier
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  • Thank you! Although probability is small I will try in the spring. Maybe my camera can it. I hope when Saturn will the most close to the Earth I will reach dream from my childhood))). – Ruslan Jan 30 '17 at 19:12
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    @Ruslan Saturn will only be about 15% closer this summer than the farthest it ever gets in 2017. If you have a good night with good seeing just go for it - don't wait until it's a little closer. Good vs bad seeing will be your limitation. – uhoh Jan 31 '17 at 04:50
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You might have a better chance of getting a good image if you take several images and use a photo stacking application to combine them. This allows you to stack many photos together to produce an image with less noise and more detail. There's a free application named StarStaX that allows you to do this sort of thing. It's available for macOS, Windows, and Linux. There are probably others you can find if you want more options.

user1118321
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If you don't have a star-tracking tracking mount on a tripod, it's very "maybe".

Using a Pentax K100D, a 500mm F/8 lens, and a 1.5x teleconverter, I took the following picture of Saturn using ISO 3200 and a 1/60 second exposure.

enter image description here

Your camera isn't quite as capable as mine: the long end of the zoom range isn't quite as long, and maximum ISO is only 1600 (and is somewhat noisier). On the plus side, your camera has a wider aperture at full zoom which compensates for the lower ISO. It's certainly worth trying. Make sure you know where Titan will be so you can pick it out from the sensor noise, and don't drop the shutter speed too slow -- my 1/60 is about as slow as I could go without losing detail to motion blur from the Earth's rotation.

If you do have a tracking mount, it's a definite "yes". Just point the camera at Saturn and keep increasing the exposure time until you see Titan.

Mark
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  • Looking at the overly-blurred photos from that batch, I think one of my 1/30 shots has Titan: there's a grey pixel in about the right place that's significantly brighter than the sensor noise. – Mark Feb 02 '17 at 04:51