A trio of craters
Continuing with the colored-infrared images…
This time I’m focusing on a well-known trio of craters: Ptolemaeus, Alphonsus and Arzachel.
Again, the technical data and processing technique are the same as for Tycho.
But this time I’ve also reprocessed an image from September 26, 2013 to better compare the colored-IR image with a low-Sun one.
The technical details for that image: C 11@F/25, 2.5x Powermate, ASI 120MM, IR-pass 685nm filter. 4 image mosaic, each a 3000 frame stack. Seeing 7/10.
The newly processed IR image, together with some named craters:
I’ve marked also the more contrasted “small rays” from Tycho, since they fill the frame. They all have a yellowish-orange color towards the top of the frame, while at the bottom they present a yellowish-green tint. There is also a ray (named “ray X”) in the upper right corner of the image which seems to have no visible source, even on wider field images. The normally dark patches inside Alphonsus appear also dark in infrared, as is a small elongated dark patch on the northern rim of Arzachel. These patches are all marked with white circles/ellipses in the black-and-white image. What is immediately visible in the color image is that the three largest craters and some of the smaller ones have parts of their rims of a different color compared to their surroundings; for example the inner walls of Arzachel are light-blue, as are those of Alphonsus. The only part of Ptolemaeus that also has this color is the North-Western rim. There is also a blue halo around Herschel, more easily visible to the East part of the crater. Birt and Thebit A have a yellowish color, as does Ptolemaeus G, the apparent starting point of Catena Davy. Some reddish-haloed craters are also present in the frame.
I’m still figuring out just how much information can I extract from this colored-infrared images, so for each newly processed area I’m comparing the results with the Clementine “color-ratio” images.
Below, the left image presents the area under low-Sun conditions, the middle image shows the colored-infrared image, while the third image presents the Clementine “color-ratio” data.
Even if the colors in the colored-infrared and Clementine images do not match, the variations in color seem to be rather similar. This is proof (again) that this acquisition and processing technique can show more data compared to normal black-and-white lunar images.
The left-most image in the above sequence is better viewed at full-resolution below:
While processing and comparing the images with the Clementine data, I’ve also started to look for the smallest details in my images. So, using the LRO Quickmap I’ve started measuring some of the smallest craters and rimae visible in the above image:
The results, shown in each of the three last images from the above sequence, are encouraging: some of the details are as small as 700meters (!) even less.
There are indeed some World-class astrophotographers (like Damian Peach, Wes Higgins, Thierry Legault, Mike Wirths and others) that can capture details as small as 300-400 meters, in very good seeing conditions, with slightly larger apertures and of course with more knowledge in image acquisition and processing.
This can only motivate me in getting more experience in learning better processing techniques and getting a larger scope 🙂
(March 10, 2014)