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Mars featuring prominent volcanoes (2018Aug02)

Mars on 2018Aug02 Mars on 2018Aug02 © Frederick Steiling
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Target Information
Main Target Designation(s) Mars
Companion Object(s) Olympus Mons, Arsia Mons, Pavonis Mons, Arcraeus Mons, Solis Lacus
All Exposures
Date(s) of acquisition 2018Aug02 at 05:31UT
Location Defiance, MO
Capture resolution 456x432
Target Altitude 25.3°
IR Exposures (as Luminance)
Total capture 9014 x 26.4ms at 50% gain
Stack source 30% of 240" video at 37 fps (avg)
Red Exposures
Total capture 19079 x 12.5ms at 50% gain
Stack source 30% frames of 240" video at 79 fps (avg)
Green Exposures
Total capture 8469 x 28.29ms at 50% gain
Stack source 30% frames of 240" video at 35 fps (avg)
Blue Exposures
Total capture 6416 x 37.37ms at 50% gain
Stack source 30% of 450" video at 26 fps (avg)
Imager ZWO ASI174MM
Filters ZWO 1.25" RGB, Astronomik IR 742nm
Telescope/Lens Celestron C14 XLT SCT
Magnifiers Tele Vue 2x Powermate
Correctors ZWO Atmospheric Dispersion Corrector
Effective Focal Length 7820mm (f/22)
Mount Celestron CGE Pro
Focuser Moonlite 2.5" CSL
Acquisition FireCapture 2.5
Guiding None
Processing AutoStakkert 3, Registax 6, WinJUPOS 10, PixInsight 1.8

This has been both an exciting and frustrating apparition for Mars.  Mars is the closest it's been in more than a decade, which means even at its low overall altitude in my northern hemisphere skies, we get a very large apparent diameter in the sky and thus our best chance at high resolution imaging in more than a decade.  However, a poorly timed global dust storm had other plans to obfuscate the surface details and leave us with an otherwise cloudy sphere.

In this attempt, I've probably hit the ideal combination of settling of the storm, apparent size (with the opposition happening only 5 days prior), and good local sky conditions.  The result: My best Martian photo of the year!

In this IRRGB combination, I've taken a different approach to filter combination to try to get the best of the IR detail and the "trueness" of the straight RGB color and polar detail.  The IR filter does a stupendous job cutting through our atmosphere to glean excellent surface detail, but as you might expect, it excels only in the redder areas.  While this is the dominating feature of Mars, it often kills the southern polar cap and northern polar hood, amazing features which would otherwise stand proudly with prominence in the blue channel.  As a compromise, I've used masking to add the IR luminance only over the red surface areas, have left the polar hood untouched from the RGB combination, and have blended IR to the southern cap so achieve a balance between detail and color.

In addition to the timing and conditions of this photo being very good, I also lucked out on the current rotation of the planet, which was such that 4 of the volcanic Martian mountains are clearly evident (see the annotated image here).  The largest of the volcanoes, Olympus Mons, stands at an extraordinary 25 km (72,000 ft), more than 2.5x the elevation of Mount Everest above sea level.  At the ground surface to the southeast of the volcanoes sits the dark feature Solis Lacus, a Martian area well-known for its constantly changing appearance.  Here we see it after emerging from the global dust storm in what is most certainly an altered view from just a month ago.  With piqued interest, I plan to compare its appearance across the many Martian data sets I've taken this year to demonstrate its ever-changing look.

It might be known as the Red Planet, but Mars certainly has much more to offer when its weather cooperates and gives us a look at some of the fascinating features on its surface.

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