Imaging the Gas Giants

 The Gas Giant planets are Jupiter, Saturn, Uranus, and Neptune.  I recently decided to take a try at capturing images of Jupiter and Saturn.  How hard could it be?  Pretty hard, it turns out.

The problem with high-resolution imaging is that air currents are constantly shifting the image of the object under study.  When we view an object through an eyepiece our brain tends to filter out the small movements and we learn to perceive detail in spite of the motion.  A camera is not so forgiving.  A single exposure captures the image at one moment in time when things might be in rapid motion and therefore blurred.  The solution is to record video and then select the sharpest frames and add them together to get an integrated picture using only the best data obtained.  So that is what I did, after watching many online videos to benefit from the experience of others.

For these images I used a Celestron C8 SCT (Schmidt-Cassegrain Telescope).  The video camera was a ZWO ASI178MC astro camera, which has 0.0024 mm pixels.  With this pixel size and the 2032 mm (approximate) focal length of the telescope, the image scale was 0.24 arcsec per pixel.  An 8" scope has a resolution of about 0.6 arcsec, so this is probably an adequate amount of oversampling.

The video clips (each less than one minute long) were processed with a program called AutoStakkert.  The sorted and stacked images were then further processed with a program called RegiStax.  The results are shown below.

Saturn, 04 Nov 2023.  Celestron C8 + ASI178MC.

Jupiter, 04 Nov 2023.  Celestron C8 + ASI178MC.

As a first try (ignoring earlier non-video attempts) I am pleased with the results.  However, these images are not so great on an absolute scale.  On a quality scale of 1-10, where "1" represents a blurry image from a cellphone hand-held up to the eyepiece, and "10" represents Hubble-esque images from 11-14" scopes produced by skilled practitioners, these rank at about a "3" (maybe 4, but definitely no higher).  There is much room for improvement.  Will I continue?  I don't know - these kind of images require a lot of computer processing and storage and are really a lot of work.  I think I would rather spend my time fishing, biking, or skiing rather than sitting in front of a computer monitor.

As a counterpoint, I also captured a wide-angle image of Uranus which was a single 60 sec exposure at an image scale too large to see the planet's disc.  This one-and-done type of imaging is more to my liking.

Uranus, 04 Nov 23.  E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2° field.