Phantastic shot of a creepy creature. A Wow experience for me. Did you have enough natural light? The nice diffuse light adds very much to the shot. How much "real stop" is f/16 with "several" extensions?
It has been several years since I took the shot, but I believe it was a typical overcast Florida morning, lots and lots of diffuse light. I've never done any calculations to see what the "real" stop is. The extensions are all of different lengths and can be used alone or can be stacked to give various degrees of image magnification. My usual procedure is to guess as to which extension or extensions I need and then to proceed by trial and error until I have a good image size. I may still have the package insert and it may speak to the effect of the extensions on f stop. If it does, I'll post the information for you. Thank you for your very kind comment. I've always liked the image myself, but I never thought of the moth as creepy, to me it looks more like a kid's plush toy. Perhaps that's because my friend who raises them told me most moths, unlike mothra, don't have mouth parts and so couldn't bite even if they were so inclined.
Edit: The nice thing about photographing moths as opposed to butterflies is that moths are inclined to stay in one place, especially during daylight hours. So, it is easy to get nice, clear images and there's usually no concern over exposure time, since they won't move unless they are really poked. Butterflies are much more difficult to shoot because they are in constant motion. Also, the good colors are usually on just one side of the wing, so they present a double challenge. When I shoot butterflies, I like to use off camera flash and usually shoot at 1/250 of a second and use auto-iso. There would almost never be a situation where 1/13 second would work as an exposure time for butterflies.