After a recent serious family event, I finally have found some time to put a number of things into some order. Among those, I ran across a picture (on photo paper) which I had developed, from a film I had also developed, both in what was then my darkroom. In those days (in the sixties) it was possible to have a chemical darkroom in your house. Digital processing technology did not exist then. Nowadays, chemical processing is tightly controlled, and what limited photography I pursue now is all of digital nature.
The image of the Moon below was taken fairly soon after I bought the used 3" refractor in 1964. I have mentioned this telescope before, shown here on the left. The Moon photo is an afocal image, taken through an eyepiece attached to that telescope.
3" telescope. The Apennines,
Caucasus and Alps on the Moon
(from the bottom up)
The afocal method can be used on any telescope with an eyepiece inserted for visual observation. The trick is to align and mount the camera to be used in such a way that the "optical centres" for all the lenses, both in telescope and camera involved, align precisely. For instance, anyone who has tried to use a smartphone to take a picture by holding it behind the eyepiece of a telescope pointed at the Moon, will have found out that a good, undistorted image is mostly a matter of luck. I've heard that there are smart-phone-to-telescope adaptors available. Personally I haven't seen one, but they should be available at reputable telescope dealers.
Another requirement is an accurate alignment of the telescope mount with the North Pole in the sky. Exposure time may vary, depending on what is being photographed. If the mount is misaligned, and the magnifying power used is high (i.e. a short-focus eyepiece) tracking errors could result in a "smeared" image.
As an aside, there is evidence of the Moon's curvature visible in the photo. You may notice that the crater Eratosthenes at the very bottom is perfectly round. That implies that we are looking straight down on it. The shape of the other craters placed successively higher, i.e. the large one in the centre (Archimedes) looks more oval. Plato, the large crater at the top, even more so, We are looking from increasing angles at them.
That shows the Moon's surface is dropping more and more away from our point of view. For anyone of average height standing on a level surface of the Moon it means that the horizon is about 2.4 km away. This is also shown by the increasingly darker surface curving westward (to the left) on the Moon. The Sun rises in the East on the Moon, just as on Earth, therefore the East is the brightest area on the right.
I think that it is obvious that I like my 3". Occasionally, you may see it on these pages again.
