[8] The subtle colour of the Moon brought out by image processing.
[9] Live view focusing.[10] Earthshine captured using a DSLR camera.
[11] A planetary camera mosaic image of the crescent Moon.Things start to get interesting with larger telephoto lenses of 500–1000mm
focal length; the longer the focal length, the easier it will be to make out more
lunar features such as mountain ranges and craters. It’s advisable to mount
the camera and lens on a sturdy tripod to keep everything still during the
exposure. A remote shutter release is also highly recommended.Using a Telescope as a Lens
A telescope can be used as a lens for your camera. The way to achieve
this depends on the nature of your camera. Fixed-lens cameras must be
"connected" afocally, a term that basically describes the act of pointing the
camera down the eyepiece. DSLR cameras can be connected at prime focus
(the focal point of the primary mirror or objective lens), essentially direct-
coupling the camera to the telescope. A description of these techniques is
given in chapter 2. The settings you’ll need to capture the Moon properly will
depend on many factors, including the brightness of the background sky,
the clarity of the sky and the focal length of the lens you’re using. As a rule of
thumb, if you’re imaging using a photographic lens, set it a couple of stops
back from being fully open (e.g. if a lens has a maximum aperture of f/2.8,
knock it back to around f/5.6). Keep the ISO low initially too. Accurate focus
is very important and can make or break the shot. For a telescope, focus as
accurately as you can through the viewfinder. If your camera has a live focus
capability which allows you to see what the sensor can see while focusing,
use that. For a normal photographic auto-focus lens, turn the auto-focus
on, point the camera at the Moon and half press the shutter button. If you’re
successful, the lens will have auto-focused on the Moon. When done, turn
auto-focus off and be careful not to subsequently change the focus. Take
your shot and review the result. If the Moon looks dark and underwhelming,
increase the exposure. If necessary, increase the ISO as well but try to keep it
below 400 to keep the noise levels down.that impressive to you. Assuming it’s exposed correctly and in focus, a
typical camera lens delivers a Moon disc which appears tiny on the
image frame.
Despite its dominance when visible in the night sky, the Moon’s disc isn’t
actually that big, with an apparent diameter of 0.5°. Put another way, hold
your little finger up at arm’s length and it’ll easily cover the Moon’s disc! The
Moon’s diameter in mm on a 35mm frame is given by dividing the focal
length of the lens you’re using by 109. If you’re using a non-35mm-frame
camera, as most are, the image will appear slightly bigger than this. So for
a 200mm-focal-length lens, on a 35mm frame, the Moon’s disc will appear
just 2mm across! A 300mm or larger telephoto lens will allow detail such
as the lunar seas to be recorded but even at this length, the Moon’s disc still
appears rather small.89Astronomer Book