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Jupiter at 1600mm (03Jan2016)

Jupiter at 800mm x2 Jupiter at 800mm x2 ©2015 Frederick Steiling
Target Information
Main Target Designation(s) Jupiter
Additional Images
Published image Full resolution
Exposures
Unfiltered monochrome 2053 x 50ms
Video source 80% of 2' video
Date(s) of acquisition 03Jan2016
Location Defiance, MO
Equipment
Imager ZWO ASI120MM
Telescope/Lens Orion 8" f/3.9 Astrograph
Mount Celestron CGEM
Focuser Moonlite 2" Newtonian CR
Accessories
Coma Corrector None
Collimator 2" Howie Glatter @ 650nm
Focusing Moonlite Mini V2 High-res Controller
Magnifiers Orion 2x "Shorty" Barlow
Software
Acquisition FireCapture 2.4
Guiding None
Processing AutoStakkert 2, Registax 6, PixInsight 1.8

With the recent and sporadically maddening night skies in the area along with some in-progress maintenance and testing of my deep-space imaging train, it seemed like a great opportunity to aim toward a smaller but much closer target.  What better way to give first-light to my new ASI120MM camera than to point it toward our largest neighbor for my first planetary photo -- Jupiter!

Seen in surprising (albeit moderate) detail considering my a relatively short planetary focal length (1600mm after 2x magnification via a Barlow lens) are the gas giant's bands of clouds composed of ammonia crystals.  The lighter "zones" of these rich atmospheric formations contrast both visually and physically with the darker "belts," the intersections of which can create turbulence upwards of 360 km/h (220 mph)!

And the clouds aren't the only speed demons at play: Jupiter's astounding rotational speed, the result of which is a Jovian day that lasts less than 10 hours, combined with its huge size results in an equitorial radius that is nearly 5,000 km (3100 miles) larger than its polar radius.  In other words, Jupiter is bulging considerably at its midsection because it's spinning like a top... a really, really big top.

This remarkable spin has a considerable effect on the data acquisition for this monochrome photo.  The incredible rate of rotation means that over the course of a single night (if Jupiter is visible for the entire night), we may be able to witness nearly a full rotation of the planet.  In turn, in order to obtain a still photo, exposures need to be taken in very quick succession over a short period of time in order to prevent rotational blurring as the planet spins under the frames.  Here, I took about 2500 frames in 2 minutes to minimize this effect.

Casual observers of my deep space photos may wonder how galaxies, which sometimes are 300 million light years away, can be seen in greater detail than this planet that is, by comparison, practically on top of us.  The reason is a testament to how much larger galaxies are than planets, and how different the techniques for photo acquisition are between the two.  Take, for example, my photo of IC342:  Despite its distance of roughly 10 million light years, its apparent size in our sky is a staggering 21 arcminutes, roughly 60% the size of a full moon, though its apparent magnitude of 9.1 makes it invisible to the naked eye.  By comparison, Jupiter presents itself at an average apparent size in our sky of 45 arcseconds, 2% the size of IC342 and 2.5% the size of a full moon, though it is often the third brightest object in the night sky (after the moon and Venus) at an average apparent magnitude of -2.25.  What this means is that galaxies typically need very long exposures to compensate for their dimness, but often modest focal lengths (small magnifications).  By contrast, planets can use very short exposures because they are so bright, but really benefit from extremely long focal lengths (high magnifications).  Because I used my "galaxy" focal length here, it proved quite difficult to get substantial detail in this "tiny" object.

This was a nice way to get my new monochrome planetary camera some exposure in the field.  The next steps will be to hook it up to a telescope with a much larger focal length so that we can pull out some greater gas band detail, then to obtain filtered images so we can present this beautiful dot in the sky with the rich color it deserves.

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