{"id":35975,"date":"2022-08-31T11:00:16","date_gmt":"2022-08-31T11:00:16","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=111544"},"modified":"2022-08-31T11:11:16","modified_gmt":"2022-08-31T11:11:16","slug":"how-to-make-a-planetary-animation-of-jupiter","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-make-a-planetary-animation-of-jupiter\/","title":{"rendered":"How to make a planetary animation of Jupiter"},"content":{"rendered":"

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By Pete Lawrence\n \t\t<\/p>

Published: Wednesday, 31 August 2022 at 12:00 am<\/p>

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By photographing the planet Jupiter with a high-frame-rate camera, it\u2019s possible to record the state of the gas giant\u2019s atmosphere.<\/span><\/p>\n

But you can also stitch together sequences of these images, creating planetary animations showing how the gas giant rotates.<\/span><\/p>\n

These can be used to clarify atmospheric details as they turn with the planet, or reveal the orbital dance of the four bright Galilean moons<\/a>.<\/span><\/p>\n

Creating an animation of Jupiter isn\u2019t that much harder than generating a single image, it\u2019s just more processing-intensive, requiring steps that you\u2019ll need to repeat several times.<\/p>\n

Once you\u2019ve built your first animation, the results will hopefully encourage you to have another go.<\/p>\n

Don\u2019t be afraid to experiment, perhaps refining your technique to produce a smoother result.<\/p>\n

Here we\u2019ll look at the techniques to make your own Jovian animations, from capture through to the final build.<\/span><\/p>\n

For more advice, read our guides on how to photograph planets<\/a> and astrophotography image processing<\/a>.<\/strong><\/em><\/p>\n

Capturing your planetary images<\/strong><\/h2>\n

Consider the weather<\/strong><\/h3>\n
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The altitude of Jupiter is an important factor in how clear a view you\u2019ll get, with lower altitudes generally giving the worst view. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Jupiter is at its best when the atmosphere it\u2019s viewed through is stable.<\/p>\n

Atmospheric stability is affected by the weather, altitude of the object and the presence of the jetstream.<\/p>\n

You can determine when the most promising conditions are due from meteorological forecasts. For more on this, read our guide to weather forecasting for astronomy<\/a>.<\/p>\n

Active fronts and deep low-pressure systems tend to cause instability, while high pressure tends to produce the most stable conditions.<\/p>\n

Weather dominated by high pressure with an absence of an overhead jetstream typically produces the best conditions, and websites such as Netweather<\/a> provide jetstream forecasts for this.<\/p>\n

It is when Jupiter is positioned due south that it\u2019s highest in the sky and above the thickest, most turbulent part of the atmosphere.<\/p>\n

If you work out how long you want to image for, you can time your session so the planet is due south at the mid-point.<\/p>\n

Jupiter moves a fair bit over a long session, so make sure it won\u2019t disappear behind any foreground objects.<\/span>\u00a0<\/span><\/p>\n

Photographing your target<\/strong><\/h3>\n
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Lucky imaging requires effort, but the results are often significantly better. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

\u2018Still imaging\u2019 \u2013 taking a single frame of a target \u2013 tends to produce poor results with planets.<\/p>\n

A stills camera, such as a DSLR, captures a snapshot, frozen in time, which is typically heavily distorted by the atmosphere.<\/p>\n

\u2018Lucky imaging\u2019 is a better solution: taking many images in quick succession, harvesting the best and combining them into a single image.<\/p>\n

Often resulting in thousands of images, the results are analysed and organised by quality, aligned and averaged to reduce noise.<\/p>\n

Known as registration-stacking, this laborious process is largely automated by freeware programs such as RegiStax<\/a> and AutoStakkert!<\/a>.<\/p>\n

The final image these generate should be robust enough for post-capture tweaking.\u00a0<\/span><\/p>\n

Low-altitude bright targets suffer from chromatic dispersion, creating colour fringes around their north and south edges. <\/span><\/p>\n

With a colour camera, an atmospheric dispersion corrector<\/a> can reduce this, and a filtered mono camera can diminish the problem too.<\/span><\/p>\n

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Once one RGB set has been completed, each subsequent filtered capture can be used to complete a new full-colour image. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Capturing individual red (R), green (G) and blue (B) frames is an excellent way to get high-quality results.<\/span><\/p>\n

Taking multiple filter sequences means you have a choice of frames to combine.<\/span><\/p>\n

For example, by taking two RGB sequences you can create an image with the RGB from the first set, but also an image with R from the second set, and G and B from the first, and so on.<\/span><\/p>\n

An infrared-sensitive camera with an IR-pass filter will produce high-contrast results that will animate well, and wavelengths at the red end of the spectrum tend to be less affected by atmospheric instability.<\/span><\/p>\n

Create an animation of Jupiter\u2019s Galilean moons<\/strong><\/h2>\n
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Jupiter\u2019s four bright Galilean moons appear in a line, shining like stars near to the planet. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

Jupiter\u2019s four largest, Galilean moons, Io, Europa, Ganymede and Callisto, are bright enough to be recorded with a conventional stills camera.<\/p>\n

With a large enough image scale, they can be shown clearly as separate entities to the planet and, over time, their movement around Jupiter can be recorded.\u00a0<\/span><\/p>\n

There are several ways to accomplish this. One is to ignore the planet\u2019s disc entirely and simply adjust the exposure so the moons record as bright points of light.<\/p>\n

It pays to maintain a reasonably short exposure time here: too long an exposure can produce issues such as each moon \u2018dot\u2019 \u2018wiggling\u2019 at high frequency, due to instabilities in our atmosphere.<\/p>\n

If the telescope\u2019s mount isn\u2019t accurately polar-aligned, extended exposures will also result in the moons appearing as short lines rather than points.\u00a0<\/span><\/p>\n

Lucky imaging can help overcome many of the vagaries introduced by our unstable atmosphere.<\/p>\n

If imaging simply to record a moon as a bright dot, you may still end up with a moon\u2019s image looking larger than it should, but it\u2019ll be tighter than it would be using a stills camera with a long exposure.\u00a0<\/span><\/p>\n

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How long it takes each Galilean moon to travel the apparent diameter of Jupiter, based on their orbits when closest to Earth. Credit: Pete Lawrence<\/span><\/figcaption><\/div>\n

The Galilean moons orbit Jupiter at different periods according to their distance from the planet.<\/p>\n