Tycho's Craterlets
"Tycho's Craterlets"
Last night a friend posted a shot of the gorgeous ray system of Tycho. It reminded me of this image that I had forgotten about in my image drive. This shot illustrates another aspect of ray systems, the myriad secondary impact craters created when ejected material falls back to the Moon.
Rays are created when a large meteor or an asteroid hits the Moon. The meteor or asteroid usually does so at tens of thousands of miles per hour. They scatter surface material at high speed when they hit, then they penetrate deep below the surface. Their kinetic energy is converted to heat, which vaporizes the meteor/asteroid and much of the moon-stuff around them. That all expands in a catastrophic blast upward and outward from the impact point. The material blown outward is everything from county-sized chunks, to glassy dust, to incandescent gas. The gas may escape the Moon altogether, or cool and condense on the Moon’s surface. The dust blows outward in streaks across the face of the moon, sometimes for thousands of miles, creating the rays my friend captured. The chunks usually fall back onto the moon, blasting craters of their own, or they may scour the surface, cutting radial valleys through mountains and leaving scars as they skip over the surface. That is a sequence of events you do not want to witness up close.
This picture is my best effort to show the effects of those big chunks that fall back onto the moon. Tycho crater is a young crater, so these effects are more clearly seen in its case. Tycho is the crater above center and a little right, the one with a brightly-lit western interior rim, a deeply shadowed eastern floor and a brightly illuminated central peak. Once you find it, look at the craters to the east (right) of Tycho. Look at their insides. Their floors are riddled with tiny craters. Some are arranged in lines stretching away from Tycho, like the rays. My photograph can resolve craterlets down to a little under two kilometers wide. There are hundreds, maybe thousands of them visible in this image. They are most densely packed near Tycho, but they can be spotted all the way to the right edge of the frame. For every one visible here there are many smaller ones below resolution. They have to await a bigger ‘scope.
I used an 8" aperture, 2032 mm focal length f/10 telescope as my lens (Celestron EdgeHD8). A monochrome planetary video camera (ZWO ASI 290MM) was used to collect 2086 video frames at 69 frames per second. This camera has a tiny sensor, with a crop factor of 6.7, so it can only see a tiny part of the Moon.
Of those 2086 video frames, the best 25% (522) were stacked into a single image. This procedure, called "Lucky Imaging" maximizes image sharpness and minimizes image noise and atmospheric blurring. AutoStakkert!3 software did the actual stacking.
The stacked image received wavelets processing in Registax 6 to help pull details from the remaining image noise.
Final processing was completed with Photoshop CC2020.
Tycho's Craterlets
"Tycho's Craterlets"
Last night a friend posted a shot of the gorgeous ray system of Tycho. It reminded me of this image that I had forgotten about in my image drive. This shot illustrates another aspect of ray systems, the myriad secondary impact craters created when ejected material falls back to the Moon.
Rays are created when a large meteor or an asteroid hits the Moon. The meteor or asteroid usually does so at tens of thousands of miles per hour. They scatter surface material at high speed when they hit, then they penetrate deep below the surface. Their kinetic energy is converted to heat, which vaporizes the meteor/asteroid and much of the moon-stuff around them. That all expands in a catastrophic blast upward and outward from the impact point. The material blown outward is everything from county-sized chunks, to glassy dust, to incandescent gas. The gas may escape the Moon altogether, or cool and condense on the Moon’s surface. The dust blows outward in streaks across the face of the moon, sometimes for thousands of miles, creating the rays my friend captured. The chunks usually fall back onto the moon, blasting craters of their own, or they may scour the surface, cutting radial valleys through mountains and leaving scars as they skip over the surface. That is a sequence of events you do not want to witness up close.
This picture is my best effort to show the effects of those big chunks that fall back onto the moon. Tycho crater is a young crater, so these effects are more clearly seen in its case. Tycho is the crater above center and a little right, the one with a brightly-lit western interior rim, a deeply shadowed eastern floor and a brightly illuminated central peak. Once you find it, look at the craters to the east (right) of Tycho. Look at their insides. Their floors are riddled with tiny craters. Some are arranged in lines stretching away from Tycho, like the rays. My photograph can resolve craterlets down to a little under two kilometers wide. There are hundreds, maybe thousands of them visible in this image. They are most densely packed near Tycho, but they can be spotted all the way to the right edge of the frame. For every one visible here there are many smaller ones below resolution. They have to await a bigger ‘scope.
I used an 8" aperture, 2032 mm focal length f/10 telescope as my lens (Celestron EdgeHD8). A monochrome planetary video camera (ZWO ASI 290MM) was used to collect 2086 video frames at 69 frames per second. This camera has a tiny sensor, with a crop factor of 6.7, so it can only see a tiny part of the Moon.
Of those 2086 video frames, the best 25% (522) were stacked into a single image. This procedure, called "Lucky Imaging" maximizes image sharpness and minimizes image noise and atmospheric blurring. AutoStakkert!3 software did the actual stacking.
The stacked image received wavelets processing in Registax 6 to help pull details from the remaining image noise.
Final processing was completed with Photoshop CC2020.