I took it through the 9×50 finderscope on my big telescope. Despite the title of this post, I didn’t take this photo through binoculars. Farther north along the terminator, the flat-floored crater Endymion is a black pool of shadow.Ī final confession. Just north of Mare Crisium is the ancient crater Cleomedes, which you might easily pass over when it is less dramatically lit. Like all of the maria or lunar seas, Mare Crisium is an impact basin that was flooded with basalt unlike most of the other maria, Crisium actually looks like a giant, flooded crater. I decided to take this picture because I was really blown away by the sharpness of the features along the terminator, especially Mare Crisium and the nearby craters.
A big part of one’s growth as an observer is learning to see, which largely means cultivating the patience that it takes for your eyes to suss out the subtle details present in whatever you’re observing. Experience counts, and the more experience you have, the more you realize that it counts.
Nevertheless, the camera couldn’t capture detail that wasn’t there, so all of this was at the eyepiece, and how much you might get would depend on your visual acuity and level of experience. The digital images are magnified by the camera and blown up to a convenient size on your screen, so you can pick out a LOT more detail from these pictures than you would out in the dark with the binoculars alone, even if they were mounted. Now here I have to confess that looking at these photographs is cheating, a bit. So what have we got? Well, first of all, there are dozens of craters in view. This lets you selectively brighten and darken pixels of different values, and I use it on almost everything. Here’s the final version of the image, in which I tweaked the brightness and contrast using the “Curves” function in GIMP. You can knock down the CA to unnoticeable levels by using combinations of very expensive glass in the lenses, as in apochromatic refractors or APOs, or with anti-fringing filters, but it can never be completely eliminated. In telescopes and binoculars, the out-of-focus wavelengths at either end of the spectrum make yellowish and purplish halos around bright objects, even in daytime. The problem is that different wavelengths of light have different refractive properties, so a lens can never bring all of the wavelengths to focus at the same point. That’s chromatic aberration or CA, which is present in any optical system that uses lenses to collect light. Then converted to grayscale, which gets rid of the annoying coloration on the limb. The same image, cropped and lightly sharpened using “unsharp mask” in GIMP. Here’s a raw, completely unretouched image I took on the evening of January 2nd. I’m always saying that you can see craters on the moon with binoculars, but I suspect that many people don’t believe me.
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